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I? ~’ 1 ‘ '— ‘w ‘C‘ . 75:?" -...__.:5 ..L‘. 5 ~ ' - . 1:” «2?: :31“: t 7" 1 ‘. . ‘7: ,~ ‘,.5.- _ , , 5: 5.1.5... _. - ,vr- . . .5. =11. . . .5-5‘,‘ .‘P. 5. 5‘..55 .-4-'fl'b:“ . .Q 5 Eggs” _"‘.‘&"‘t y.-. “r 37, .3735.“- ' . -5. @ .... ‘ (5-. - 5 55,3. 3;;fiik 5-- {‘5 . *1, -3§ 5.—" g.-. - THESN. ”A LIBRARY Michigan State , University - This is to certify that the thesis entitled A CONCEPTUAL FRAMEWORK FOR ECOSYSTEM PLANNING AND MANAGEMENT presented by Michae1 Robert Thomas has been accepted towardslfulfillment of the requirements for Doctor of PhiIOSOEhZ degreein Resource Development firmer-rt Major professor Date 2a “5% (‘180 0-7639 * MM\ljflfifluluTflflTflTHTW " TWP - L_:J'" 1 €NT9§6 OVERDUE FINES: 25¢ per day per item RETURNING LIBRARY MATERIALS : Place in book return to remove charge from circulation records JUN 041999 5"» 85:22.7 EA! 1 5 3031 A CONCEPTUAL FRAMEWORK FOR ECOSYSTEM PLANNING AND MANAGEMENT By Michael Robert Thomas A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Resource Development 1980 i %Q&\\ Q ABSTRACT A CONCEPTUAL FRAMEWORK FOR ECOSYSTEM PLANNING AND MANAGEMENT By Michael Robert Thomas Most of the earth's ecosystems have been significantly altered by human activities - either by direct and indirect exploitation of natural resources or by waste products of industrial, agricultural, or domestic processes. In addition, an increasing world population will require more extensive and intensive use of ecological systems to satisfy its future needs. There is concern that continued and uncontrolled develop- ment of natural ecosystems will result in irreversible damage to those systems and their dependent life forms and, ultimately, human systems. A holistic and systematic ecosystems approach to land use planning and management is advocated to direct the renewal and maintenance of natural and human ecosystems, thus ensuring long-term availability of resources and quality living environments. The ecosystem concept is fundamental to this process. An ecosystem is the geographical location where living organisms interact with each other and with their nonliving environment. The impacts of any human modification or manipulation on various ecosystem components can be studied, quantified, or monitored at the ecosystem level. Thus, the ecosystem concept becomes a working principle with tremendous potential for addressing environmental Michael Robert Thomas problems, planning the renewal and maintenance of essential ecosystems, and providing a basis for responsible and intelligent interactions be- tween humans and their environment. Decisions on the use of ecosystems - particularly land and land resources - are influenced by a variety of factors depending on identi- fied or perceived needs of human systems or institutions. Differences in the expertise, philosophies, and problem-solving approaches of de- cision makers representing the interests of social, political, legal, economic, and technological institutions require a planning and manage- ment framework which provides a common communications base and organiz- ing structure. A review of state-of-the-art literature in environmental planning, resource management, systems science, and ecological theory reveals that an ecologically sound land use planning and management methodology can be developed to serve this purpose. Such an ecologically sound planning and management methodology is an organization of information, both factual and theoretical, provided by the various disciplines; a careful simulation and testing of ideas and strategies for resource development and use; and an advocacy of environmental quality. Ecological theory provides the conceptual frame- work which ties this methodology together. Chapters Two through Four have been organized to provide a concep- tual framework describing the value of ecological theory in planning land uses. The value of this is threefold. First, ecological theory provides a systematic organization of the complex interconnections and interdependencies found within living ecosystems. Orienting information within a systems structure will assist decision makers in solving prob- lems through an understanding of ecosystem structures and functions. Michael Robert Thomas Secondly, a study of ecology provides a focus for planning and manage- ment that is based on ecological principles or constraints. This focus can lead to planning strategies (further described in Chapter Five) that efficiently collect and utilize information to adequately assess envi- ronmental constraints, opportunities, and impacts. Finally, ecological theory can provide the understanding that humans are integral parts of ecosystems and, thus, are bound by the same laws that govern all natural ecosystems despite the increasing ability and opportunity to modify nature. Chapter Six shows that management programs can be established which are closely attuned to ecological principles and philosophies of long-term, constructive interactions between human and natural systems. @ Copyright by MICHAEL ROBERT THOMAS 1980 ACKNOWLEDGMENTS I would like to take this opportunity to express my appreciation for the assistance, helpful criticism, and advice given to me by the members of my guidance committee, Dr. Ronald L. Shelton, Dr. Clifford R. Humphrys, Dr. Sanford S. Farness, and Dr. Harold A. Winters. Their dedication and professionalism helped instill in me the desire to see this project through. Dr. Ronald L. Shelton, my major professor, de- serves special thanks for taking the time out of his varied and busy schedule to lend extra and much-needed help in the organization and execution of my research efforts and their written results. I would also like to thank the professional staff of the Department of Resource Development. Ms. Janine Jurcak assisted in the typing of the first draft and Mr. J. Paul Schneider helped with the graphics. Thanks also must go to those unsung heroes in any graduate school experience - one's fellow graduate students. The numerous academic and social interactions allowed an exchange of thoughts and ideas which could only help a research effort. Valuable assistance and friendship were given by Gary P. Friday, Phillip B. Davis, and Linda S. Wennerburg, to name only a few. Happily, most of these colleagues have gone on to their deserved reward (a job) and will lend their special qualities in those environments. My wife Rosemary deserves a special note of thanks for her love, understanding and, especially, patience during my academic career. Her ii contribution does not end there, however, as she edited, typed, and helped greatly in organizing this manuscript. For that, and for many other things, she has my very fond and proud gratitude. TABLE OF CONTENTS LIST OF FIGURES .......................... CHAPTER ONE: INTRODUCTION .................... Problem Statement ...................... Study Objectives ....................... Past Work .......................... CHAPTER TWO: ECOSYSTEM FUNDAMENTALS ............... Introduction ......................... Systems Classification .................... System Definition .................... System Types ...................... Open Systems ...................... System Structure .................... The Black Box Principle ................. Ecosystems .......................... Ecosystem Components .................. Trophic Structure .................... Populations ....................... Communities ............... . . ...... Habitat . ........................ Conclusion .......................... CHAPTER THREE: ECOLOGICAL PRINCIPLES . . . . . . . ........ Introduction ......................... Explanation of Ecosystem Cycles . . . . ........... Energy-Matter Cycle ..................... Population Cycle ....................... Community Cycle ....................... Abiotic-Biotic Cycle ........... . . ........ Summary ........................... Modeling the Ecosystem .................... Conclusion: Understanding Ecosystems ............ CHAPTER FOUR: HUMAN OCCUPANCE 0F ECOSYSTEMS ........... Introduction: Why Study Ecology and Ecosystem Theory? . . . . Classification of Human Ecosystems . . . . .......... Human Use of Ecosystems: An Historical Perspective ..... iv CHAPTER FOUR (Continued) Human Impact on Ecosystems ............ Vegetation ................. Animal Life ................. Surface and Subsurface Waters ........ Soil Fertility and Utility ......... Landforms .................. Atmosphere and Air Quality ......... Planning the Use of Ecosystems: Man and Nature . CHAPTER FIVE: PLANNING FOR THE RENEWAL AND MAINTENANCE OF ECOSYSTEMS ............ Problem Definition ................ Information Base ................. Ecosystem Classification ............. Ecological Inventories and Descriptors ...... Application of Environmental Information ..... l. Identification of Constraints ...... 2. Discovery of Environmental Opportunities 3. Projection of Environmental Impacts . . . Ecologically Based Land Use Planning ....... Plan Design and Implementation .......... Multidisciplinary and Interdisciplinary Planning . Holling Workshop Approach ............ Conclusion .................... CHAPTER SIX: PRINCIPLES OF ECOSYSTEM MANAGEMENT . . . Introduction: Ecosystem Management as a Process . . Concepts of Ecosystem Management ......... Working Within Ecosystem Constraints . . . . Adopting and Maintaining a Long-Term Carrying ...... 000000 ...... . O ...... ...... ...... Capacity Approach in Resource Management . . Prevention of Irreversible Change ...... Protection of Critical Environments . . . . . A Philosophy for Ecosystem Management . Environmental Decision Making ........ Nature-Human Interdependence ........ Developing an Ecosystem Management Methodology . . Problem Definition ............. Information Base .............. Strategy Selection . . . . . . . ...... CHAPTER SEVEN: SUMMARY AND CONCLUSIONS ........ LIST OF REFERENCES .................. ...... O O 95 103 104 106 107 108 112 113 114 117 120 120 123 124 128 131 134 138 138 141 143 143 145 146 149 157 Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 10. 11. 12. 13. LIST OF FIGURES Simple System . . . . Simple System With Feedback Loop ...... The Hierarchy of Physical Systems . The Basic Ecosystem - general interconnection between abiotic components (the habitat) and biotic components (communities) in any geographical location ....... . . . . . The Basic Community - all populations of organisms make up a community and are linked together through the trophic structure (or food chain); the mechanism by which they obtain nutrients and energy determines whether they are producers, consumers, or decomposers . ...... . Relationships Between Trophic Levels and Energy and Matter Use - energy flows through the system with loss of utility and efficiency while matter is continually cycling . . . The Cycling of Energy and Matter Within the Ecosystem . Population Cycle Community Cycle . . . Abiotic—Biotic Cycle - the interaction between organisms and the environment in which the availability of energy and matter is limiting A Combination and Simplification of the Individual Cycles From Figures 7 Through l0 - a diagrammatic version of the cyclic nature of interactions occurring within any ecosystem . . . Conceptual Model of a Complete Ecosystem An Expanded Model for Ecosystem Manipulation - relationships between resource availability and population dynamics . . . . . vi 00000 14 17 19 20 22 23 39 42 44 51 55 58 59 Figure 14. Two Examples of Model Food Webs Used to Interpret Trophic Relationships .............. 98 Figure l5. Examples of Natural and Artificial Constraints Classed Into Three Groups . . . ..... . . . . 105 CHAPTER ONE INTRODUCTION Problem Statement It is an obvious fact that the human populations of the United States and the world are continuing to increase. With such increases there will be a growing demand for more extensive and intensive uses of land and land resources. While it is assumed that more land will be brought into food, mineral, and fiber production to meet society's needs, there is also concern that the ecological systems that must be managed and manipulated to meet human requirements may not be able to continue functioning under the increased stresses of waste assimilation, removal of biomass, soil and mineral depletion, or uncontrolled urban— ization. During the l960$ and early l970s, warnings of impending ecological disaster began to be heeded, and political, social, and environmental activists pressed for changes in policies and in planning and manage- ment activities which were concerned with land use. The Congress of the United States passed laws requiring cleaner air and water, protect- ing wilderness and scenic rivers and, ultimately, a National Environ- mental Policy Act (NEPA; PL 91-190 of 1969). On a global scale, the United Nations established guiding principles for the preservation and enhancement of the human environment (United Nations General Assembly, l972). The passage of NEPA was important in that, for the first time, a national policy was set forth whose purposes were to (l) encourage a productive and enjoyable harmony between humans and their environment by (2) stimulating health and welfare while preventing or eliminating environmental damage and to (3) enrich the understanding of the ecolog- ical systems and natural resources important to the nation (NEPA, op. cit.). In Section 102C, NEPA required that federally funded projects had to submit environmental impact statements (EIS) for the public rec- ord. The EIS contained a description of the proposed activity or pro- gram and its possible alternatives, an assessment of probable impacts on the environment, and a warning of possible environmental damages be- fore they occurred. Many states followed suit with passage of similar legislation concerning state-owned land or large municipal projects. In the decade since the passage of NEPA, there have been hundreds of major EISs submitted on a wide range of subjects. Unfortunately, decisions concerning the environment were not always made with the three major purposes of NEPA in mind. While many impact statements were drafted that enhanced the welfare of society and prevented environmental damage, a study of the documents reveals that a majority of them do little to enrich our knowledge of ecosystems and the natural resources provided by ecosystems on which human systems depend. In addition, im- pact statements were criticized as obstructing progress and leading to unemployment because they did not adequately examine as many alterna- tives as possible and, thus, tended to be economically oriented. The EIS was rarely a document which contained adequate descriptions and evaluations of ecological systems affected by the project; basically, ecological parameters were presented as exhaustive lists and inventories of organisms present within the affected area (Davis, 1979). This pointed to a problem with environmental analysis and impact assess- ment methodologies which has been addressed by authors who are seeking to promote a more accurate and meaningful process in dealing with the environment. Authors such as Odum (1975), Holling and Clark (1975), Hopkins, et. a1. (1973), Andrews (1978), and others have argued that, due to its deficiencies, the EIS methodology should either be modified to reflect more ecologically oriented principles or relegated to the status of just one of many decision-making tools in environmental planning and management processes. They advocate a reevaluation of the planning and management methodologies to alter the way humans perceive and interact with their environment. Ecological constraints and principles should be placed co-equally with economic, political, technological, and so- cial requirements in the decision-making process. This reorientation of priorities is logical in that without healthy, positively function- ing ecosystems, the dependent cultural ecosystems and human institutions would ultimately fail. Because the environment is composed of complex systems working and existing together, study in environmental areas is multidisciplinary. Each discipline, whether based on natural science, social science, or systems science, has different interpretations of its area of interest pertaining to the environment. In order for ecosystems to provide long- term benefit to both natural and human populations, decisions as to the use, management, protection, or preservation of such systems must be based on an integration of information from the various disciplines. Therefore, for proper planning and management of ecosystems, there must be meaningful communication among decision makers in land use policy, economics, business, social organizations, government, industry, and ecology. There must also be active communication between decision makers and individuals affected by decisions. This communication needs a common ground on which questions, methods, or ideas can be placed in the perspective of the solutions being sought. In terms of natural resource management, pollution control, waste disposal, wildlife and vegetation management, urban planning, environ— mental engineering, recreation, and so on, the ecosystems concept can provide the focus for integration of information; communication among decision makers, planners, and managers; and coordination of human ac- tivities in the environment. The ecosystem, with its systematic inter- connections of components (both living and nonliving) and processes, is the logical physical unit on the earth's surface within which manage- ment activities can be implemented and analyzed with respect to their impacts on living and nonliving subsystems. StudyAObjectives The primary objective of this research effort is to develop a con- ceptual framework which can provide the foundation for an ecologically based land use planning and management methodology. The ecosystem ap- proach to the management of natural resources has been presented by Odum (1959), Watt (1968), and Van Dyne (1969) on the argument that ecological management of living systems (including humans) demands a comprehensive understanding of the ecological constraints which guide those living systems. Harris and Williams (1975) and Holling and Clark (op. cit.) call for the formulation of an ecologically based conceptual framework which will provide researchers, systems analysts, planners, and policy makers with a basic understanding of ecology and of the ecological principles which must be considered when gathering information to plan and manage ecosystems. It is an important planning goal to strive for a system which functions as naturally as possible since natural eco- systems (not merely rural ecosystems) fulfill the basic conditions for human life and are ecologically balanced (Glikson, 1971). To achieve the primary objective, five secondary objectives were established, and these subsequently became the five major subdivisions or chapters of the study. These objectives are as follows: (1) To provide an understanding of fundamental ecological theory along with definitions of ecosystem components and functions which are systematically interconnected in living ecosystems. A systems approach in presenting fundamental concepts pro- vides the most direct means of translating ecological theory for decision makers with backgrounds in social, systems, and natural sciences. The chapter also introduces several con- ceptual models which illustrate ecosystem components and how they relate to each other. (2) To describe the complex ecological principles by which all ecosystems, whether they are natural or human-influenced, are governed. An understanding of such principles as carrying capacity, diversity, stability (homeostasis), and resilience is necessary in providing decision makers with measures of the overall health of an ecosystem and to allow projection of what the system may do under various impacts. Several models of ecological processes are constructed and described. They culminated in the development of a general model of an eco- system which serves to (a) provide a basic review of ecosys- tems and subsystems and their interconnections and (b) allow ecosystem managers to project impacts according to their in- fluence on the ecosystem components or processes affected. To reestablish the concept that humans and their systems are integral with the processes and functions of natural systems. This concept is necessary in redirecting the planning and man- agement of ecosystems which have been transformed from more natural states by past uses and abuses. The decision makers must temper the desires and needs of their constituents with- in the perspective of ecological constraints to ensure long- term benefits to both natural and cultural ecosystems. To develop a planning strategy which efficiently gathers and integrates the most useful information in classifying, inven- torying, and analyzing the environment to provide the planner with an identification of ecological constraints, opportuni- ties, and impacts of planning efforts. The major planning objective is to develop a strategy which is flexible enough to adapt to changes in policies or in ecosystems. To develop a management program which is cognizant of ecolog- ical principles and based on a philosophy of (a) providing a decision-making path least environmentally destructive to nature, humans, and their interactions and (b) integrating human processes as parts of evolving nature as opposed to in- trusions upon it. Past Work A review of the literature reveals that there have been few compre- hensive attempts to establish an ecosystem planning and management meth- odology. With the exception of C. S. Hollings' Adaptive Environmental Assessment and Management (1978), which is an innovative approach to ecologically based planning and management, environmental literature is just beginning to depart from the familiar formats of prediction of doom and gloom with few practical solutions and so-called ”cookbook” approaches for conducting environmental impact statements. There is a clear and present need for research efforts which can organize and in— tegrate the information necessary to adequately describe ecosystems, their components, their functions, and their important interactions. It is also necessary to provide a decision—making tool which will allow constructive communications and interactions among decision makers. There is a considerable number of studies which had to be analyzed for this conceptual research study. These included classical studies in ecology, methodologies for conducting environmental impact assess- ments, texts on the human use of ecosystems, and pioneer efforts by physical and environmental planners and managers in developing ecologi— cally based methodologies. CHAPTER TWO ECOSYSTEM FUNDAMENTALS Introduction The study of ecosystems, their forms and functions, has been ap- proached in a number of ways. These approaches have included the gen- eral disciplines of natural science, systems science, and resource management, with each area of study further subdivided into more spe- cialized fields. Such study has led to a greater understanding of dis- crete parts of ecosystems under the general heading of "ecology" (the study of the relationships of living organisms with their environment). The initial purpose of ecological study is to conceptually and system- atically place the parts into a proper and understandable whole. Eco- logical systems or ecosystems are the "wholes” which we seek to under- stand and, ultimately, manipulate for human purposes. Any human acti- vity is therefore the result of some form of ecosystem management or manipulation. The study of ecology was formalized only a little over a century ago, yet there have been many titles and definitions of ecosystems. According to Odum (1971), the term ”ecosystem" was first proposed by Tansley in 1935 while the terms ”microcosm" (Forbes, 1887), ”holocoen" (Friederichs, 1930), ”biosystem" (Thienemann, 1939), and "bioinert body” (Vernadsky, 1944) have also been used. Tyler (1975) has defined an eco- system (or ecological system) as an open system with respect to material 8 and energy flow, comprised of abiotic and biotic components in a geo- graphical locale, whose interrelationships are such as to form a dynamic, self-perpetuating complex. He goes on to say that all ecosystems are bounded by and have interfaces with other ecosystems; each has inputs from and outputs to other ecosystems. It is difficult for one not familiar with the sum total of every- thing written about ecology to understand the overall scheme of things. It often becomes necessary to stand back and view the concept of an eco- system as a whole in order to understand exactly what is being studied. Since the study of ecology first began, various methodologies have been advocated and widely practiced in the description, study, and manipula- tion of ecosystems. As with any discipline which can be approached from various angles, each methodology has its advantages and shortcomings. Each contributes its unique viewpoints and discoveries which further the knowledge of a subject. On the other hand, researchers and teachers have tended to view their areas of expertise as all-important and fail to adequately communicate and integrate their knowledge to others where it could be most helpful. The natural science approach to ecosystem study is based primarily upon the scientific method of observation, experimentation, and hypoth- esis formulation and testing. The majority of what is known about eco- systems comes from this approach. However, much of the "natural science” or ”field” observation is being replaced by ”laboratory" re- search in which many new facts are being uncovered. Investigators are not always able or willing to transcribe their findings into lay lan- guage or into projections of value to human systems. Many natural science texts present each ecological concept separately. A lack of 10 communication between ecologists and the public has led to both a criti- cism of popularized ecological journalism as being unscientific and a failure of large portions of the public to take ecologists seriously. As a result, the fundamental ecosystem is rarely utilized as a unifying concept. Systems scientists have recently begun to formulate ecosystem models written in computer language for the express purpose of quantify- ing and systematizing simple ecosystem interrelationships. The value of computer models of ecosystems has been demonstrated in organizing, sum- marizing and presenting a large amount of information about specific ecological factors gathered through observation, experimentation and re- search (Patten, 1972). On the other hand, the vast amounts of informa- tion generated by complex ecosystem models have led to overconfidence in and, sometimes, misinterpretation of the results; the quality of the results is obviously dependent on the validity of the inputs. Also, computer models are costly in terms of money and information. Simple ecosystem models may be relatively inexpensive but they lack the sophis- tication necessary to accurately predict ecosystem responses. Propo- nents of the systems approach to ecosystem study point out that, as the competence of research increases, so will the accuracy and validity of ecosystem modeling (Rapoport, 1972; Rosen, 1972). From a strictly scientific standpoint, it is relatively simple to quantify and judge the importance of ecological fundamentals, but the significance of such fundamentals to human systems is difficult to com- prehend. Therefore, the most specific methodology in need of assistance from both systems and natural science is ecosystem planning and manage- ment. For millenia, humans have been modifying, changing and, often, 11 destroying natural ecosystems for their own benefit. For the most part, those doing the "management“ were least qualified to do so. In more re- cent times, management has taken on a new and more dynamic meaning; eco- system managers, whether they are foresters, road builders, or directors of nature centers, have begun to seek information and guidance through a closer interaction with systems scientists and natural scientists. The inherent strengths and weaknesses of each discipline have become magnified when put into actual practice by ecosystem managers. What is needed, therefore, is a better understanding of what eco- systems are and why they are important as a basic unit for studying nat- ural and human environments. By taking the fundamental concepts from systems science, natural science, and management, and by rearranging these concepts into an ecosystem framework, more rational decisions can be made pertaining to the use and protection of environments. This chapter examines basic systems theory and how it can be used in describing ecosystems. It then proceeds into a general discussion of the components of typical ecosystems from an ecological perspective. Chapter Two, therefore, is a study of ecology from a blending of systems science and natural science. Once this framework has been introduced, certain ecological principles can be analyzed and evaluated based on natural and human ecosystem perspectives. This analysis and evaluation of ecological principles is done in Chapter Three. Systems Classification Ludwig von Bertalanffy is recognized as one of the pioneers in de- veloping systems theory for biological study (Kramer and de Smit, 1977). His argument is that investigation of single parts and processes cannot 12 provide a total understanding or explanation of living phenomena, the coordination of their parts and processes, or the laws governing such living systems (von Bertalanffy, 1928, 1934). This statement became accepted as the foundation for general systems theory. Thus, biological organisms, ecosystems, social groups, technological devices, and other organized entities can be organized and studied according to this thought process. The concept of systems has been utilized to accurately describe and study ecosystems using both systems science and natural science ap- proaches. Every ecosystem, whether as large as the biosphere or as small as an ephemeral rainwater pond on a forest floor, is either (1) a complete system, or (2) made up of smaller subsystems and tends to be- have as a system. It is helpful to discuss systems theory before pro- ceeding to an understanding of living and complex ecosystems. System Definition A system is defined as a complex unit, aggregation, or assemblage of objects joined in a regular interaction or interdependence, subject to a common plan or serving a common purpose (von Bertalanffy, 1969; Klir, 1969, 1972; Miles, 1973; Sutton and Harmon, 1973). Most people are familiar with social, educational, governmental, and mechanical sys- tems by how these systems function for them and by the way people func- tion as a part of such systems. Systems are discrete only with respect to the interface between their arbitrary boundaries and the surrounding environment. No matter how large a system is in the number of its dif- ferent parts or components and in the function it performs, it is im- portant to remember that systems always behave as wholes (Laszlo, l972). 13 Each system is a separate entity, and all other systems are part of the environment. For example, communication and transportation (though they have many similarities), as systems, are separate from each other. The function of communication is to convey thoughts, ideas, or other forms of social intercourse, while transportation moves people or their re- sources from place to place. On the other hand, if transportation and communication are combined into the larger system of social institutions, they become subsystems and contribute to the holistic functioning of the larger system. System Types Different types of systems have been classified based on their in- teractions with the environment. A system is known as an open system if activities or resources outside of the system are able to cross the sys- tem boundaries to affect the inner workings of the system. The system may then modify such inputs or stimuli to produce outputs or responses. A system whose boundary is impervious to inputs or stimuli or is other- wise not affected by what occurs in the environment is a closed system. (Such closed systems are totally dependent on the Second Law of Thermo- dynamics - as resources are used and degraded, the system becomes less organized and able to do work.) Both open and closed systems may be able to produce outputs or responses, but only open systems can utilize resources from the environment. Closed system outputs are the results of activities Carried out by finite resources inherent to the system. Well-known examples of closed systems include fossil fuels and the earth itself (von Bertalanffy, 1956; op. cit., pp. 32, 47, 102). 14 Open Systems Open systems (Figure 1) can be further subdivided into natural and artificial systems. Natural systems are made up of physical, chemical, and biological components (of which humans may or may not be a naturally occurring part), interacting and evolving together without direct human intervention (Patten, 1959; Chorley, 1964; Laszlo, op. cit.). Common examples of natural systems are forests, fields, oceans, rivers, and so on. INPUT SYSTEM ——>0UTPUT FIGURE 1. SIMPLE SYSTEM. Artificial systems, on the other hand, have been formed by humans or human institutions to achieve a particular purpose and function. Usually, the formation of an artificial system requires the expenditure or transformation of energy and resources. Such systems are rarely com- patible with the natural systems that they replace or are contemporane- ous with. Artificial systems depend entirely upon natural systems for their form and function. For example, before humans developed the tech- nology to transform basic resources into building materials such as pre- stressed concrete or steel, their structures reflected more closely the natural origins of the resources from which they were derived. 15 Architecture was limited by the ability of humans to modify logs, stone, or mud. In addition, artificial systems depend on natural systems for the energy needed for their construction and operation. Cities and other urban areas are, largely, artificial systems and would quickly perish without the constant flow of raw materials, food, and energy pro- vided directly by natural systems or those artificial systems (e.g., agriculture) in a closer interface with natural systems. System_Structure Von Bertalanffy (op. cit.) describes a system as a collection of parts coordinated to accomplish a set of goals. It is bounded by the environment, which provides constraints to the system. The boundary sets the system apart from its general environment, while the objective or performance of the system defines it. The components of the system accomplish the activities or goals of the system. These components may be discrete subsystems which function independently of each other, or the components may be arranged in a hierarchical series of subsystems which require some type of collective interaction to perform a function (Young, 1964). Every system has resources which are used by its compo- nents in their functions which come from within the system itself (closed system) or from the environment across the system's boundary (open system). Finally, management of the system (cybernetics) is pro- vided by the relationships among the various components during their interactions. Such relationships may include cause and effect and feed- back (Weiner, 1948; Ashby, 1956). Studying the system as a whole tells the observer what the system does; examining the parts of a system will provide an understanding of 16 how the system works (Laszlo, op. cit.). In all systems, the whole is usually more than the sum of its parts (Aristotelian dictum); the system (especially if it is natural) has properties no individual subsystem has. A good example of this is the telephone. Most people understand the function of a telephone and have little trouble using it. But the telephone is made up of such a complex of circuitry that it is a black box to all but electrical engineers. All the parts of the telephone must be connected and working properly in order for the telephone to operate as a communication device. It is essential to know how subsystems and systems are intercon- nected in order to understand inputs and feedback which help determine system operation and stability. Feedback (Figure 2) occurs when any portion of the output is reapplied or "fed back” into the system. The state of a system is the condition or function of the system at any par- ticular point in time, as if a photograph were taken of the system as a record (Ackoff, 1971). The system is said to be in a "set state" after output or response occurs. During feedback, part of the output reenters the system as input and modifies (either positively or nega- tively) the state of the system. Negative feedback is defined as that feedback which tends to maintain the stability of the system, while pos- itive feedback usually causes the system to become unstable and self- destructive. Human population growth is an example of feedback. In primitive societies, negative feedback in the form of high birth and death rates decreases while births continue to remain constant, causing an exploding growth rate or positive feedback. Unless factors are in- troduced to lower the birth rate, the system may eventually self- destruct. 17 INPUT SYSTEM ~> OUTPUT FEEDBACK FIGURE 2. SIMPLE SYSTEM WITH FEEDBACK LOOP. The Black Box Principle Before proceeding to a discussion of ecosystems, it is helpful to examine a systems science concept called the Black Box Principle (Sutton and Harmon, op. cit.; Kramer and de Smit, op. cit.). A black box is an open system which responds to inputs as any open system would; however, what is inside the system performing the modifications is unknown. Be— ginning students in systems science operate a computer program in which a black box mathematically manipulates numerical inputs. The students then must predict what is happening within the black box. For example, if the number 4 is entered into the program and the output is 6, some- thing in the black box may have added 2 to the input or may have multi- plied the input by 1—%. If the output is 16, the input may have been squared or multiplied by 4; if the output is 2, the square root of the input may have been taken or the input may have been halved; and so on. The student may have some idea of what was happening within the black 18 box, but he or she would not know the actual mechanism that was perform- ing the manipulation. That mechanism would be called a subsystem of the black box. Ecosystems Ecosystems are the fundamental units in which the complex interac- tions between living things and their environment take place. Of all the categories in the hierarchy of physical systems, from universe to atom (Tansley, op. cit.), the ecosystem is the level at which those re- lationships can be described and studied directly. Figure 3 shows a general representation of the hierarchy of physical systems. It can be seen from the diagram that levels above the ecosystem (e.g., biosphere, planets, etc.) become increasingly more general while levels below the ecosystem (e.g., community, population, organism, etc.) are not only more specific, they do not include the biotic-abiotic interface found in ecosystems. Because ecosystems are open, natural systems, they re- quire energy inputs via sunlight and chemical bonds. The'interconnec- tions between living things and their environment feature the necessary exchange of resources for growth and reproduction. These interrela- tionships form a dynamic, self-perpetuating complex (Tyler, op. cit.). Ecosystems may be conceived and studied in various sizes as long as the major components are present and operate together to achieve some sort of functional stability for any time interval (Odum, op. cit.). 19 UNIVERSE PLANET EARTH BIOSPHERE ECOSYSTEM COMMUNITY POPULATION ORGANISM MACROBIOLOGY _________ __ ECOLOGY MICROBIOLOGY ORGAN SYSTEM ORGAN TISSUE CELL ORGANELLE ORGANIC COMPOUNDS MOLECULE ATOM SUBATOMIC PARTICLE FIGURE 3. THE HIERARCHY OF PHYSICAL SYSTEMS (AFTER TANSLEY, 1935). 20 Ecosystem Components The major functional components of ecosystems are abiotic (non- living) and biotic. Abiotic components are basic inorganic and organic compounds of the environment which are the resources necessary for life. Life can exist only within the earth‘s biosphere, or that portion of the air, water, or land where conditions are favorable for life. If the earth were represented by an apple, the biosphere would be as thin as the skin. Figure 4 is an illustration of the abiotic and biotic components as they are arranged within any ecosystem. Biotic compo- nents make up all of the communities Of living things which interact with the nonliving habitats of the biosphere. ECOSYSTEN COMMUNITY COMMUNITY (BIOTIC) (BIOTIC) HABITAT (ABIOTIC) COMMUNITY COMMUNITY (BIOTIC) (BIOTIC) FIGURE 4. THE BASIC ECOSYSTEM - GENERAL INTERCONNECTION BETWEEN ABIOTIC COMPONENTS (THE HABITAT) AND BIOTIC COMPONENTS (COMMUNITIES) IN ANY GEO- GRAPHICAL LOCATION. 21 The populations of living things - plants, animals, bacteria, and fungi - are collectively arranged within communities, the biotic portion of ecosystems. Populations within a community are classified or ar- ranged according to the trophic structure, which functions to distribute energy and nutrients from the habitat to all living things. These structural components are actually nested subsystems within the overall ecological system. Interconnections between the subsystems provide con- trol and maintenance (these will be examined in more detail in Chapter Three). Figure 5 shows a further breakdown of any community as seen in the previous figure (Figure 4). Each community is composed Of popu- lations of producers, consumers, and decomposers arranged around the trophic structure. The trophic structure is examined in greater detail in the next figure (Figure 6), which shows the basic pathways of energy and matter as they are being utilized by living things (Thomas, et. al.; 1978; p. 24). Biotic components of communities are either autotrophic or hetero— trophic organisms. Autotrophs are the producers - the plants which fix light energy, use simple inorganic compounds and build complex organic substances through the process of photosynthesis. The sun is the basic lifegiver to the earth; only green plants are able to convert solar energy into primary biomass, which can then be used by heterotrophs. The general photosynthetic process is: 6C02 + 12H20 -—> C6H1206 + 602 + 61120 carbon dioxide + water organic sugars + oxygen + water Heterotrophs, including both consumers and decomposers, do not have the ability to utilize sunlight for anything but heat and light. They must 22 COMMUNITY POPULATION OF CONSUMERS POPULATION OF PRODUCERS POPULATION OF PRODUCERS TROPHIC STRUCTURE POPULATION OF DECOMPOSERS POPULATION OF CONSUMERS POPULATION OF PRODUCERS POPULATION OF DECOMPOSERS POPULATION OF CONSUMERS FIGURE 5. THE BASIC COMMUNITY - ALL POPULATIONS OF ORGA- NISMS MAKE UP A COMMUNITY AND ARE LINKED TOGETHER THROUGH THE TROPHIC STRUCTURE (OR FOOD CHAIN); THE MECHANISM BY WHICH THEY OBTAIN NUTRIENTS AND ENERGY DETERMINES WHETHER THEY ARE PRODUCERS, CONSUMERS. OR DECOMPOSERS. 23 ENERGY FLOW HEAT [TOP CARNIVORE] TCARN IVORE OMNIVORES MATTER CYCLE SECONDARY AND TERTIARY ‘7' CONSUMERS :2'3 :33 5:; WASTE MATERIALS, (HETEROTROPHS) 53:; DEAD BODIES COMPLETIZORGANIC ”5‘7 MOLiQULES IHERBIVORESI IOMNIVORESI [BACTERIA] [FUNGIj [CONSUMERS] PRIMARY CONSUMERS """"""""" '23; SPECIFIC AND GENERAL IHETEROTROPHS) ,2. (3;; DECOMPOSERS -BB« 5. I? (HETEROTROPHS) CHEM/CAL 33;; i5? HEAT " :52} 3333 ' :3:1 LAND AQUATIC BACTERIA 3:3 PLANTS PLANTS 3;}: ;:;: :~:-:-:-:-:':-:.:-:-:3:1 SIMPLE INORGANIC PRODUCERS MOLECULES IAUTOTROPHS) 3* REFLECTION HEAT MATTER (“41444 (LIGHT) NUTRIENTS ............................................................................ RESOURCES FIGURE 6. RELATIONSHIPS BETWEEN TROPHIC LEVELS AND ENERGY AND MATTER USE - ENERGY FLOWS THROUGH THE SYSTEM WITH LOSS OF UTILITY AND EFFICIENCY WHILE MATTER IS CONTINUALLY CYCLING (THOMAS, ET. AL., 1978; P. 24). 24 depend on plants to provide food, energy, and oxygen. When plant mate- rials are ingested by primary consumers, the energy from the Chemical bonds in the organic compounds becomes available to the organism. This energy, along with oxygen, helps recombine the nutrients from the food into new compounds that the organism needs for its life processes. If the primary consumer is, in turn, eaten by a secondary or higher-order consumer, its structural components are available for use by the subse- quent consumer. Waste products from respiration or digestion and dead plant and animal remains are fed upon by decomposers (usually smaller organisms which break down the complex organic compounds into their in- organic components). Thus, the cycle has returned to its starting point, with raw materials again available for primary productivity. The amount of food or nutrients available as the result of primary and secondary productivity is termed biomass. Biomass is usually con- sidered to be the standing crop, which is the amount of living organic material present in the ecosystem at any particular point in time. In the black box model of the ecosystem, inputs Of energy and matter cross the system boundary and are converted by productivity (photosynthesis) to create the output Of biomass. (It is understood that one of the sub- systems Of the ecosystem is the activity Of green plants.) Biomass, be- cause of its potential for future nutrients, operates as part Of a feed- back lOOp. There are other ecosystem responses of importance under the general heading of homeostasis, or dynamic eguilibrium (Cannon, 1939). Homeo- stasis is the so-called ”balance Of nature” in which negative feedback allows an ecosystem to maintain stability over long periods of time. In a general sense, there is usually enough plant food produced yearly 25 to allow consumer growth and reproduction, predators to cull surplus organisms, and conditions for decomposition to return sufficient nutri- ents for plant growth. The presence of homeostasis and other ecological processes keeps the living portion of the ecosystem in balance or equilibrium with the constraints Of the environment. Under natural con- ditions, there is usually sufficient output (biomass), living space, and abiotic raw materials to maintain maximum populations of all pro- ducers, consumers and decomposers. This is called carrying capacity, an important concept for managing both natural and man-made systems. Carrying capacity is one of the more influential feedback mechanisms in ecosystems. The interactions between biotic and abiotic factors within the ecosystem occur among the nested subsystems. There are four general (and complex) subsystems of any ecosystem: (l) trophic structure, (2) populations of organisms, (3) communities, and (4) habitat. Each subsystem is specifically identified in the general definition of an ecosystem: an open system with respect to material and energy flow (trophic structure) comprised Of abiotic and biotic components (popu- lations of organisms) in a geographical locale (habitat) whose inter- relationships (community) are such as to form a dynamic, self-perpetu- ating complex. As in all systems, the lower level of resolution (sub- system) explains how the system works. By examining the actions and interactions of each subsystem in greater detail, the functioning of the complete ecosystem can be understood. 26 Trophic Structure Trophic structure (Figure 6) supplies the means by which energy and matter are dispersed throughout the ecosystem and utilized by all biotic components. Basically, this is done within the food Chain. Light energy is fixed by green plants into the organic material form— ing their structure. Herbivores, or plant-eating animals, feed directly upon plants and utilize the stored Chemical energy and organic material for their metabolism. Herbivores are known as primary consumers because they must depend on plants for their food. Secondary, tertiary and higher-order consumers are carnivores because they feed upon herbivores or other carnivores by capturing and killing them. Omnivores are less specialized in their eating habits, having the ability to utilize both plant and animal material. Finally, decomposers - both general (any consumer which breaks complex organic compounds into simpler ones; i.e., most consumers) and specific (consumers which break organic compounds into their inorganic components; usually bacteria and fungi) - complete the cycle. Each link of the food chain comprises a trophic level. A food web, usually the result of several interlocking food chains, is established when there are several representatives of each trophic level present in a given ecological situation. The food web contains more individual organisms in each trophic level than a food Chain to allow for more efficient use of the available energy. The division of matter and energy relationships into set trophic levels is by no means rigid. Whittaker (1975) points out that many animals take food that is suitable in size range and other Characteristics and, con- sequently, food is taken from more than one trophic level. 27 The amount of energy and matter available to the ecosystem is de- pendent upon the rate at which plants are able to transform light energy into biomass, or the amount of food material needed to support a popu- lation. This energy storage is accomplished through primary and second- ary productivity. There is, however, a loss of available energy through each successive trophic level. This inefficiency of energy transfer is due to the first and second laws of thermodynamics: energy cannot be created nor destroyed but may be transformed from one form to another and only if it is degraded or dispersed. Only 2 percent of the light radiated by the sun is absorbed by the leaves of green plants; the rest is reflected back into space. Half of the absorbed light is used dur- ing photosynthesis, making the process only 50 percent efficient. The remaining energy is used during plant respiration and given Off as heat. Therefore, only 1 percent of the total solar energy reaching the earth is available to consumers. From there, only 1/10 Of the total energy available to each trophic level is utilized while the excess is lost as heat during respiration. The higher in the trophic structure (further away from the primary productivity of green plants) an organism is, the less energy is available to that organism. Thinking in terms of bio— mass, it would take 100 pounds of plant material to produce 10 pounds Of a primary consumer or herbivore. That 10 pounds would convert to only 1 pound of a secondary consumer (in this case, a carnivore). If a larger or top carnivore ate the lower-order carnivore, it would be able to add only 1/10 of a pound to its body weight. An omnivore, on the other hand, has the ability to utilize both plant and animal pro- tein, although it is utilizing the stored energy more efficiently when it eats plant material. 28 The study of trophic levels is useful in understanding the food relationships in communities. The availability of suitable food sources is one of the more important factors in determining the ability of a habitat to support populations of organisms. A highly productive eco- system (such as a salt marsh, an estuary, or a deciduous forest) will usually have a large and diverse animal population associated with it. Such an ecosystem will also tend to support a wide variety of niches (or the specialization of a species in relation to other species). Low-productivity areas (such as deserts with less than five inches of rainfall or the infertile open ocean) will have relatively few species of animals and plants associated with them. Populations A population of organisms (Figure 5) consists of all the individ- uals of one species occupying a portion of an ecosystem at any one time. This could include all of the bluebirds living in an orchard, all of the bass in a lake, or all of the dandelions in a neighborhood. This is in contrast to a community which includes every individual of every species which exist in an area. There are many factors which determine why a population is present within an ecosystem, what its size is, and whether its numbers are static, increasing, or declining. Krebs (1972) lists dispersal (acces- sibility Of an area), behavior (habitat selection), the influence of other species, and physical and Chemical factors as major determinants Of a Species' presence in any particular area. The quality of the en- vironment, specifically carrying capacity, will determine the density, relative abundance, and change over time of a population. 29 Populations of organisms are found on the various levels of a food Chain. They help determine how energy will flow through the system and at what rate matter will be cycled. In turn, organisms are dependent on the environment for the energy and nutrients necessary for growth, metabolism and reproduction. The environment provides the flighg, which is the functional status of an organism within its ecosystem due to the morphology, physiology, and behavior of the organism. Niche refers to the specialization of a population within the community, and each species has its distinctive niche area. Much of the occupation of an organism is in search of food; therefore, a niche is often identified via the food relationship. The density, distribution and adaptability of a population will depend to a great extent on the availability of its niches and the vari- ety and abundance of other requirements such as shelter, water, sites for reproduction, and so on. The presence or lack of the requirements for life will determine the population size and whether that population is healthy or failing. Population dynamics is represented by a simple formula that the rate of population increase is determined by the amount Of new individ- uals added to the population (natality + immigration) minus those which leave the population (mortality + emigration). Due to its biotic po- tential, a population will increase as long as there are resources available for its survival. The upper limit of resource availability is the carrying capacity, which is determined by the rate of productiv- ity, amount of biomass, available niches, and habitat or living space. The size of a stable population in any one area will be determined by its ability to stay within the carrying capacity. If the local 3O abundance of a population exceeds the carrying capacity, it must be lowered by reducing the population size. In natural systems, this is done by an increasing death rate or decreasing density through dis- persal. In artificial systems, man has increased his supply of food and other resources with the hope of continually raising the carrying capacity. Inflation and increasing shortages of food, energy, and materials may be an indication that human systems are approaching or even exceeding carrying capacity. Communities Communities (Figures 4 and 5) are the living parts of ecosystems and are made up of all the populations and individuals living in a phys- ical habitat. Some communities are large enough to produce their own food and, therefore, are independent of other communities. Most commu- nities, however, are dependent Upon interactions with adjoining commu— nities. Whittaker (op. cit.) defines a natural community as an assem- blage of populations of plants, animals, bacteria, and fungi that live in an environment and interact with one another, forming a distinctive living system with its own composition, structure, environmental rela- tions, development, and function. An oak forest community may contain oak and other species of trees, shrubs, low-growing herbaceous plants, birds, mammals, insects, microorganisms, and many other living things held together by their interactions with each other and with the envi- ronment. In the above example, the community was named an oak forest because oak trees were the most dominant species observed in that locale. Al- though there are usually many more species of plants and animals present 31 in a community, identification and Classification of a community is simplified by naming the community after the species most common, abun- dant, or conspicuous. In most cases, this is the dominant plant species. Other attributes for Classifying communities have included geomorphic characteristics, Climatic factors, and functional relationships. Ex- amples include tall-grass prairie, tropical rainforest, tidepool, and fertile agriculture. There are two major concepts relating to community ecology. The first deals with interspecific relationships and interdependence of the organisms found in a community. The second pertains to community dyna- mics and, specifically, succession or orderly Change over time. Because of the constraints and limitations on the transfer of energy and matter by the trophic structure and the physical environment, organisms must compete with each other for the materials or space essen- tial for life. Interactions which ultimately influence the growth and survival Of populations are the result of organisms interfering with each other (such as competition, predation, or parasitism), assisting each other (symbiosis), or having no observable effect. Competition, predation, and parasitism are designated as negative species interactions. Competition between species or populations is due to limitations in carrying capacity, available niches, and natural selection. The species which is able to compete most successfully for essential life requirements will do so at the expense of other species. Likewise, predation and parasitism are negative interactions in that one species is destroyed to benefit another. Positive interaction, or symbiosis, occurs when either one or both species of a relationship benefits through the association, but not at the other's expense. 32 Symbiosis includes commensalism (when one species benefits), protoco- operation (when both species benefit), and mutualism (occurring when both species benefit and are actually dependent on each other). Community dynamics is a concept which examines the overall struc- ture and function of a community or of all of the populations existing together. It looks at how communities form and Change over time. Egg; logical succession is the orderly process of community Change. A com- munity will form in an area depending on physical factors such as soil (or substrate) and Climate. Succession is directional; once a community has established itself, it rarely remains unchanged unless physical con- ditions prevent the replacement Of present populations with subsequent ones. An established community can actually modify its environment by altering the soil composition or microclimate in such a way that new species are able to exist in the area. Eventually, the new species will dominate the community, and so on. Each change in community composition is called a seral stage and each seral stage has its associated popula- tions of producers, consumers, and decomposers. Eventually, a community will reach equilibrium with its environment, succession will become sta- bilized, and the community will tend to replace itself over time. A self-perpetuating or ultimate community has reached the climax stage and will remain as such until there is a physical change in the environ- ment which the community cannot adapt to. The climax stage will tend to have the most stable trophic structure, provide the most niches, be the most energy- and material-efficient, and be most resistant to dis- ruptive Change. 33 Habitat Just as the niche describes how a species utilizes its environment, the abiotic habitat (Figure 4) describes where a species is normally found in the environment. There are three general habitats within the biosphere: marine, freshwater, and terrestrial. An organism's living area is that specific portion of the habitat which contains its niche. All trees are terrestrial, but each species of tree has certain require- ments for soil, moisture, temperature, and sunlight which limit where that tree can exist. Therefore, plants are dependent largely on the abiotic portion of the ecosystem as their habitat. This generalization also holds for consumers, but since consumers ultimately depend on plants for food and energy, plants must be considered part of the con- sumer's habitat. Not only does habitat provide the energy and nutrients necessary for life, it also supplies the shelter which organisms need for daily and seasonal movement, secure Sites for rearing Offspring, and protec- tion from predators. Limitations in the habitat will place limits on the carrying capacity, species and population interactions, and commu- nity succession. Habitat also influences the diversity of organisms which, in turn, tends to stabilize the ecosystem. Diversity differences within a given habitat-type reflect the partitioning of available niche space within habitats (Pianka, 1978). Basically, more niche partition- ing allows for a greater variety of organisms and a greater amount of variability in niche utilization within each trophic level. A rich and varied habitat will allow utilization of its niches during daily and seasonal periods and at different levels of space within the habi- tat. For example, nocturnal and diurnal animals may occupy the same 34 niche, although at different times; certain species of birds will occupy niches at different heights of a tree. Organisms which can control their habitat to any degree have the ability to alter community succession which will determine how, and by what species, a habitat will be utilized. During any particular suc- cessional stage, there will be dominant species of plants utilizing the nutrients provided by the soil and producing food at a rate determined by the sunlight available to the habitat. If physical conditions remain constant, the plants will add humus to the soil, provide shade, modify humidity and temperature, and reduce wind velocity. These plants will provide food and shelter for animal and additional plant species. Un- less the community is at Climax or physical conditions Change, succes- sion generally proceeds according to prediction. Animals have also been known to affect habitat, specifically in those instances where there is over-utilization and subsequent reduction of plant species. For exam- ple, overgrazing in short-grass prairies of the American Southwest has led to the loss of such habitats in favor of desert vegetation. Conclusion The purpose Of Chapter Two was to present a general model of eco- logical systems (Or ecosystems) from a consolidation of systems theory, ecological concepts, and basic premises of natural science. Although the study of ecosystems is only a small part of the overall discipline of ecology, the ecosystem level of natural and artificial systems is an important one from the standpoint that both abiotic and biotic com- ponents are accessible for both study and management at the ecosystem level. By adapting a systems approach throughout the Chapter, the 35 complex components of ecosystems could then be isolated and defined. Once the structures and functions of an ecosystem are understood, the interconnections and interactions between them become more readily ap- parent, and the origin and mechanism of such activities can be seen and studied as they actually occur. The intention of every ecologist or student of the environmental sciences is to formulate and test an ecosystem model which conforms with reality. Advances in ecological research have given scientists a good idea of what is already happening in the environment; an accurate eco— system model will give scientists and decision makers the ability to predict what will happen in any future interaction. Specific ecosystem models have become standardized, but complete and comprehensive models are still being hypothesized. A continued combination of the systems and natural sciences will be invaluable in the formulation of workable models with valid predictive powers for use in ecosystem monitoring, evaluation, and management. Chapter Three describes the complex ecological principles by which all ecosystems, whether they are natural or human-influenced, are gov- erned. Ecologists are able to use ecological principles in the formu- lation of models which are of value in studying and predicting ecologi- cal processes. The principles are arranged according to naturally OC- Curring cycles, and models of these cycles are illustrated. A gener- alized ecosystem model has been created to Show the complex interactions which occur within any ecosystem. CHAPTER THREE ECOLOGICAL PRINCIPLES Introduction Ecologists describe and study the components and interactions with- in ecosystems for the purpose of formulating an accurate predictive model. Criteria of such a model includes the development, analysis, and evaluation of ecological hypotheses based on field work and research. In addition to gaining knowledge, the major purpose of establishing cri- teria is to develop the ability to manage and manipulate natural ecosys- tems for their intrinsic value as well as for the resources they provide to functioning human systems. Specifically, understanding ecological criteria in ecosystem management is important in land type and use Clas- sification; resource development and planning; protection and preserva- tion Of ecosystem types; and the control of environmental degradation. The interpretation, analysis, and evaluation of ecological criteria or hypotheses can be approached by examining each process as part of a series of principles. In other words, there are certain "ground rules” which have become established through ecological study. Although most of the principles have yet to achieve the status of scientific law, they are inherently vital to any human interaction with natural ecosystems. Such principles must be understood and generally accounted for in order to study, understand, and manage ecosystems. 36 37 Explanation of Ecosystem Cycles Ecosystems contain fundamentally Circular processes and are subject to numerous feedback effects (Commoner, 1970). Their responses to envi- ronmental effects (or human perturbations) will tend to remain Circular, or homeostatic, as long as feedback continues to be negative. Described in this Chapter are four models of Circular processes - energy-matter, population, community, and abiotic-biOtic - which are governed by eco- logical principles and which occur within all ecosystems. Each cycle represents certain ecosystem subsystems and their associated interac- tions. The interactions between ecosystem components and processes pro- ceed until homeostasis, or dynamic equilibrium, is attained. Equilibri- um within ecosystems over a relatively long period of time will provide an appearance of stability, although most ecosystems are not static. The four ecosystem processes, therefore, represent four homeostatic cycles. These cycles will remain cyclic or Circular as long as inter- actions between components and processes contain negative feedback. All ecosystems have a disruptive threshold where homeostasis can be destabi- lized through natural or human disturbance, although system responses will remain Circular. These homeostatic cycles include energy and mat- ter, habitat, community, and population. The cycles were formulated by taking ecosystem processes and components introduced in Chapter Two and arranging them in appropriate order to demonstrate what occurs in the interactions between living things and their environment. The arrows represent interactions which occur allowing the system to proceed toward dynamic equilibrium. Each box represents an important process which must occur before the next process can proceed; or it may represent a reaction of a component to a preceding environmental 38 constraint. For purposes of clarity, the component which is symbolized by a box in each figure will be underlined in the text. The description will provide an understanding of how each component is affected by a preceding process and how it, in turn, affects those processes which follow it. The complete cycle is homeostatic and enduring. In addi- tion, when all of the cycles are combined, it can be demonstrated that there are no ecosystem processes or activities which occur independent- 1y of each other - everything tends to affect everything else. By carefully studying the cycles within ecosystems, an understand- ing of the interrelationships present in all ecosystems can be achieved and used in establishing ground rules for ecosystem management. Each cycle will be examined individually to obtain a set of ecological prin- ciples which can be applicable to ecosystem planning and management. Energy-Matter Cycle Before proceeding into a discussion of the Energy-Matter Cycle in Figure 7, it must be noted that, in functioning ecosystems, energy does not cycle in the same sense as matter does. ‘Egergy flows through the system: entering as light, being transferred through the trophic struc- ture in Chemical bonds, and leaving the system as waste heat from respi- ration. Energy is included with matter in the ecological cycle because the two represent a combination of available resources which all living things require for survival (refer to Figure 6 in the preceding chapter). Matter continually moves or cycles through the ecosystem in biogeo- Chemical cycles, which include the hydrologic, nitrogen, phosphorus, and carbon cycles. Inorganic and organic compounds continually circulate between living things and the environment in the form of nutrients, 39 food, and waste materials. Some compounds may be held for long periods of time in the bodies of organisms, within rocks or soil, or deep in the ocean, while others, like carbon, are rapidly turned over during processes such as photosynthesis. These materials provide the reguire- ments for survival (of all the known elements which occur naturally, nearly forty are required by organisms), and all are used as they be- come available, either through the food chain or directly from the en- vironment. Therefore, the presence or absence of the minimum quantity of any material essential for life becomes a limiting factor. If a material is present and in usable form, life can occur in that particu- lar habitat. ‘///,» HABITAT’~\\\\\ ENVIRONMENTAL AVAILABLE QUALITY RESOURCES I ‘I OPTIMUM ENERGY-MATTER ENERGY“ POPULATION MATTER \ f CARRYING REQUIREMENTS CAPACITY FOR SURVIVAL NICHE ,/’//, FIGURE 7. THE CYCLING OF ENERGY AND MATTER WITHIN THE ECOSYSTEM. 40 Each of the resources provided by the habitat can be limiting. These include food, water, shelter, and proximity to other members of each species, which is necessary for reproduction. A sufficient quan- tity of resources for a particular species in a habitat will, in turn, provide that species with a flighe, or a position within the ecosystem. Although conditions favorable toward establishment of a niche do not ensure that the niche will be occupied, competition among organisms for resources will tend to fill available niches. The niche available to large herbivores in the tall-grass prairies of the American Midwest was largely vacated through reduction of the vast herds of bison, only to be refilled by domestic beef cattle as a result of human manipulation. The level of carrying capacity is directly proportional to the overall health (relative abundance of resources) of the habitat. As more abiotic and biotic resources are available, a greater variety of niches becomes attainable which will enhance carrying capacity (in this case, distribution of materials and energy) of a particular habitat. Carrying capacity, in turn, limits the ability of a habitat to support an gptimum population. A population will change or fluctuate according to the carrying capacity of the habitat. As resources become available in greater amounts, populations will increase to utilize them through increases in natality (birth rate) or immigration. The opposite (mor- tality and out-migration) occurs as population numbers exceed the abil- ity of the habitat to make resources available for use. Optimum popu- lation levels become established when there is a balance between produc- tion and assimilation Of food materials and when the variety Of niches is filled. 41 Reasons for and why a population is Changing are indications of environmental quality. Under natural conditions, a growing population may demonstrate that the carrying capacity limit has not been reached, while a decreasing population could be an indication that carrying ca- pacity has been exceeded. 0n the other hand, either change could also be symptommatic of a population fluctuating around the carrying capac4 ity or that serious ecological problems may be present within the sys- tem. An oft-quoted example is that of algal blooms in eutrophic lakes. An overabundance of phosphate will lead to a population explosion of algae. As the algae grow and die, oxygen is required in the decomposi- tion of the organic detritus. The percentage of dissolved oxygen in eutrophic lakes is usually low (less than 7 parts per million), and this low percentage of oxygen is rapidly used up during decomposition. Anaerobic decomposition, performed by bacteria which do not require oxy- gen, then takes over, usually with the production of waste materials which may be either noxious or toxic to other organisms. Other parameters of population change due to environmental quality include age distribution and population dispersal. A population with a relatively large number of young individuals will exhibit an increas- ing birth rate and subsequent demand on materials and energy. As the carrying capacity is approached or exceeded, the demands on the envi— ronment will cause a reduction in environmental quality. Population decrease, either through high mortality rates, decrease in birth rates, or dispersal Of the population to other areas, will allow the environ- ment to recover. Completing the circle, the quality of the environment is determined by population demand for materials, energy, living space, 42 and so on, which determine the overall health or carrying capacity of the habitat to support those populations. Population Cycle As Shown in the discussion of the Energy-Matter Cycle, the presence and quality of populations of organisms is dependent upon resources provided by the habitat and, ultimately, upon the carrying capacity. The availability of resources is one of three factors which determine both population density and development; the other two are biotic po- tential and environmental resistance. Environmental resistance will be discussed later in this section. The Population Cycle in Figure 8 is connected to the Energy-Matter Cycle at the carrying capacity component box. BIOTIC l/////” POTENTIAL POPULATION CARRYING DENSITY’ CAPACITY ABUNDANCE NICHE POPULATION ENVIRONMENTAL UTILIZATION RESISTANCE POPULATION INTERACTION COMMUNITY EVOLUTION FIGURE 8. POPULATION CYCLE. 43 According to Odum (1959, 1971), biotic potential in organisms is achieved when the growth rate (population growth rate per individual) becomes constant and maximum for the existing microclimatic conditions. Theoretically, this can occur only when the environmental carrying ca- pacity and other factors (space, food, lack of competition for resourc— es, etc.) are unlimited. Factors contributing to the calculation of biotic potential are the age distribution and the growth rate of each age group. Actually, the term "reproductive potential” would be a more descriptive term because "biotic potential" has been widely used to describe true population increase within carrying capacity constraints, although this is not the case since carrying capacity nearly always prevents a population from ever achieving its true biotic potential. Biotic potential will determine the population density in an eco- system by filling it with new individuals. A portion of an ecosystem which contains the right kinds and amounts of resources will tend to have a more dense population. In those areas, therefore, there will be a higher relative abundance of both individuals and populations. In areas of nutrient richness, such as marine upwellings and estuaries, there will also be concentrations of many species of both producers (phytoplankton) and consumers (zooplankton, fish, marine mammals, etc.). Such areas are not only important feeding grounds, they also tend to be the breeding centers of many species. Populations are both abundant and dense in such areas, and the true biotic potential is most closely realized. In areas where populations or species are widely dispersed as a result of resource or space limitations in the carrying capacity, biotic potential may be more severely limited as well. 44 Communitinycle ' Figure 9 models what occurs when pgpulation interaction and physi- cal processes (abiotic factors) interact to cause successional changes within a habitat and its associated communities. A major kind of com- munity on a given continent is a biome. A biome is a grouping of ter- restrial ecosystems that are similar in vegetation structure, in the major features of environment to which this structure is a response (specifically mean annual rainfall and temperature), and in some char- acteristics of their animal communities (Whittaker, 1975). Local vari- ations within each biome—type are generally dependent upon microclimatic conditions and the influencing effect of individual populations. These two factors work together to bring about environmental modification, which leads to sequential population and community Change known as succession. ‘://,SUCCESSIONrK\\\\\ SELF-REGULATION; POPULATION AND DIVERSITY; COMMUNITY STABILITY CHANGE '1 l ‘ '1 ENVIRONMENTAL ' (ABIOTIc-BIOTIC) COMMUNITY [ENUDIFIUETIONI EQUILIBRIUM - I. f _ CLIMAx PHYSICAL PROCESSES; STAGE POPULATION INTERACTION \\\\\.[HABITATl’//}' FIGURE 9. COMMUNITY CYCLE. 45 The presence and abundance of populations in a habitat will also influence niche utilization and community evolution or succession. A dense and abundant population will usually fill nearly every available niche in its efforts to survive. Competition for niche space can be- come fierce in crowded situations. 0n the other hand, dispersed popu- lations have a surplus of niches to fill, and such niches may become available to adaptable individuals of other species. Ecologically dom- inant species or populations can exert a controlling influence upon communities by their size, numbers, or activities. If certain herbi- vores have increased their numbers enough to defoliate and kill plants they utilize for food, conditions may change sufficiently to allow the growth of different species of plants. This has happened during insect infestations when the dense leaf canopy was removed long enough to al- low light penetration on the forest floor and release lower-story vege- tation. Natural succession in ponds and lakes, or eutrophication, has been accelerated when aquatic plants experience rapid growth due to in- creases in nutrient input. Rapid accumulation of organic detritus will contribute to the natural filling of those bodies of water. Much Of this community evolution depends on associated interactions of abiotic factors, such as Changes in Climate or available sunlight, and a sufficient amount of time. Under natural conditions, the unbal- ancing effect of large populations is usually mitigated over time. Community evolution is normally a very slow process where change is in dynamic equilibrium with stability. Human activities, on the other hand, have Often contributed to more rapid change without the inherent stability of natural systems. Manipulation of population density and abundance has led to changes in both community structure and biotic 46 potential. The classic example is the elimination of a predator species from its niche of controlling an excess population of herbivores. The previously mentioned example of insect infestations and subsequent com- munity change is Often the result of such manipulations. As a community evolves, there is a parallel evolution within the available niches with a subsequent modification of population interac- tjgg, Former niches are eliminated as new ones are created; adaptive species replace those which cannot tolerate the new conditions. Popu— lation interaction is a form of environmental resistance, or the sum total of environmental limiting factors which prevent the biotic poten- tial from being realized (Chapman, 1928; Odum, op. cit.). Environmen- tal resistance limits the carrying capacity by placing restraints on utilization of resources by organisms. Forms of population interac- tions which lead to environmental resistance and ultimately affect bi- otic potential can result in positive and negative interspecific inter- action. Positive interactions occur when two species live together without harming one another; this is known as symbiosis. Symbiosis includes (1) protocooperation (both species benefit by "cooperating" with each other in Obtaining food or protection), for example, small birds picking the teeth Of crocodiles; (2) mutualism (both species are completely de- pendent upon the relationship and would not survive without the other) such as that found in lichens, consisting of an alga which provides food and a fungus which lends supportive structure; and (3) commensalism (one species benefits while the other is unaffected), for example, cattle egrets which feed on insects and amphibians disturbed by grazing cattle, although the birds do not benefit the cattle by ridding them directly of 47 parasites. Community change or manipulation which eliminates one spe- cies of a symbiotic relationship may cause the extinction of the other. Examples of negative interactions, where one species benefits at the expense of the other, are readily observed and widely studied. Al- though a complete understanding Of the mechanisms of interaction has not been achieved, there is little question of the importance of compe- tition and predation as factors of environmental resistance. Competi- tion occurs when two or more species must use the same limited resourc- es; it can be direct, as in aggression, or indirect by elimination of necessary resources. Because energy is expended in competing for re- sources, it is more advantageous for species to avoid direct confronta- tion. This has evolutionary importance by leading to niche separation, specialization, and diversification (Pianka, 1978). Predation, on the other hand, usually occurs between trophic lev- els. A first-order carnivore captures and eats an herbivore while a higher-order carnivore preys upon both herbivores and other carnivores. The action of culling individuals from a population through predation has had an Obvious effect on the biotic potential, although the effect is usually minimal where the interacting populations have had a common evolutionary history in a relatively stable environment (Odum, op. cit.). Natural selection assists both members of the relationship by favoring predators who are more successful at capturing prey and favor- ing prey species more adept at escaping or hiding from predators. Such positive traits tend to be incorporated into the genetic structure of each species, although the carrying capacity is the ultimate variable in population cycles as can be seen in Figure 8. 48 Community evolution, in which populations and niches change over time, was discussed in the previous section; however, a more complete description of the mechanism of succession is necessary here. Each time the environment (soil and microclimate) is modified by the inter- play between the physical processes and an ecologically dominant popu- lation, a position is established for a second dominant population which eventually replaces the first, and so on. Whittaker (op. cit.) outlines a number of trends or progressive developments which underlie most successional processes. As each trend is listed, an explanation will be given using examples from sand dune succession along the shores of Lake Michigan (after Cowles, 1899; Odum, Op. cit.). (1) There is usually progressive development of the soil, with in- creasing depth, organic content, and differentiation of hori- zons toward the mature soil of the final community. Primary succession on sand dunes begins in a relatively harsh environ- ment with strong sunlight and winds and nearly sterile sands. Plants, such as grasses which are tolerant to those severe conditions, become established from wind- or animal-trans- ported seeds. Their roots tend to hold and stabilize the shifting, wind-blown sand; as the plants grow, reproduce, and die, the organic material is held in the stabilized zone and continues to accumulate throughout succession. (2) The height, massiveness, and differentiation into strata of the plant community increase. With the establishment Of early successional stages, modification of the microclimate Occurs; rooted plants break the force of the wind and provide Shade. (5) 49 This provides more favorable climatic conditions for less tol- erant species which eventually replace the pioneer species. 0n the dunes, grasses give way to shrubs which, in succession, are replaced by cottonwoods; oaks and pines; and maples, beeches, and hemlocks. The beech-maple climax forest has the most well-developed stratification of any of the preceding seral stages. Productivity increases with increasing development of the soil and community structure and increasing utilization by the com- munity of environmental resources. As the soil becomes deeper and richer, more plants are able to extract nutrients for growth; each seral stage becomes more productive. Increasing utilization of productivity by consumers will accelerate the turnover Of nutrients through the trophic structure. As height and density of the plant cover increase, the species diversity increases from simple communities of early succession to the richer communities of later succession. Because of the harsh conditions found in early successional stages, there are relatively few organisms which can adapt to such conditions. Through succession and community change, such conditions are tempered with the decrease of direct sunlight and strong winds, the presence of more food (abundance of niches), higher humid- ity, and narrower temperature fluctuations. Organism diversity and stability increase as a result. Populations rise and fall and replace one another along a time gradient; the rate of this replacement slows through the course of succession as smaller and shorter-lived species are replaced 50 by larger and longer-lived ones. Although succession on sand dunes takes many years, the most rapid changes occur within the first successional stages. Plant species tend to be annu- als and are characterized by a rapid turnover of their organic material, high productivity (but less utilization), rapidly growing populations, and higher vulnerability to sudden change. This leads to higher organism metabolism which requires smaller body size; the carrying capacity of that environment can sup- port only the smaller organisms in any trophic level. (6) Relative community stability increases; early stages contain populations which rapidly replace one another, while the compo- sition of the final (or Climax) community is self-regulating. The succession of beach communities along Lake Michigan has been proceeding for roughly 10,000 years. It may be assumed that present beech-maple Climax forests have existed, rela- tively unchanged, for a large portion of those years and will continue to replace themselves into the future as long as cli- matic conditions prevail. Each earlier seral stage was present for a lesser amount of time along the 10,000-year continuum. When a community and its processes have reached equilibrium with the environment, it has reached the final community or climax stage. A climax stage is self-perpetuating and tends to maintain such a state until physical conditions become permanently altered. The climax com- munity will be the most stable and have the most population diversity due to its diversity of niches and complexity of its food web. In looking at the community cycle from a human point of View, there are many places where the cycle can be and has been manipulated. 51 Environmental modification, whether physical, chemical, or biological, has caused changes in community succession. Agriculture reduces vast areas to early successional stages. Reducing species diversity through farming, forestry, and animal husbandry has led to instability as well as an elimination of natural communities. Upsetting environmental equilibrium and carrying capacity has limited the capacity of ecosystems to support populations of organisms. Abiotic-Biotic Cycle The processes taking place in the interplay between living things and their nonliving environment comprise the Abiotic-Biotic Cycle (Figure 10). Technically, these processes are important segments of the previously described cycles, but, due to their importance, a sepa— rate (though interconnected) cycle is proposed to examine the processes in more detail. CARRYING CAPACITY ASSIMILATION RESOURCES (UTILIZATION OF RESOURCES) i 1 , LIMITING ABIOTIC-BIOTIC POPULATION FACTORS FORM .__1 1 ENVIRONMENTAL RESISTANCE I TOLERANCE V FIGURE 10. ABIOTIc-BIOTIC CYCLE - THE INTERACTION BETWEEN ORGANISMS AND THE ENVIRONMENT IN WHICH THE AVAILABILITY OF ENERGY AND MATTER IS LIMITING. 52 The habitat provides resources necessary for life. However, these resources (in this case, abiotic) may or may not be available in usable form or in sufficient quantities to permit the growth and reproduction of organisms. The presence or absence of environmental resources thus becomes a part Of the limiting factors of environmental resistance to population growth, density, and distribution. There are two ecological principles pertaining to limiting factors: Liebig's "law of limiting factors" (1840) and Shelford's "law of toler- ance" (1913). The principle of limiting factors states that, to occur and thrive in a given situation, an organism must have essential mate- rials necessary for growth and reproduction; the material amount most closely approaching the critical minimum tends to be limiting. Odum (1959; pp. 104-143) lists the following physical factors which may be limiting to organisms in an ecosystem: (1) temperature; (2) light radiation; (3) water; (4) temperature plus moisture (the role of Climatic extremes); (5) atmospheric gases (mostly in aquatic environments); (6) macro and micro nutrients, such as organic material and trace elements; ) currents and pressures; (8) soil; ) fire; and ) microenvironment, which can be a combination Of all limiting factors exerted on a population or individual organism spe— cifically where it is found. 53 The principle of tolerance states that the distribution and abun- dance of an organism can be controlled by factors exceeding the maximum or minimum levels of endurance for that organism. In other words, an organism's ability to tolerate limiting factors not only determines where it will be found but also how successful it will be in coping with the conditiOns (and resistance) of its environment. The chief limiting factor of most desert vegetation is the presence of water. Such vegeta- tion is able to tolerate other conditions (temperature extremes, wind, soil salinity, etc.) and grow because it has adapted to drier condi- tions. Likewise, lack of direct sunlight may be limiting to species of plants in a forest understory. In this case, successful species are able to tolerate the limitations and are prepared to take advantage of increased sunlight when a canopy species dies. Because of their complex interactions and inherent stability, eco- systems usually have more resilient tolerance levels than those Of indi- vidual organisms. The effects of ecosystem manipulation are not always readily apparent, often not until the damage done represents irrevers- ible change. Therefore, the study of indicator organisms can be impor— tant in understanding the context between manipulation and tolerance. Organisms with relatively narrow tolerance ranges to specific environ- mental factors make good indicator organisms. Inventory and monitoring of bird life has been proposed as an indicator of environmental quality. The presence or absence of certain species of aquatic life at measurable distances downstream of a sewage outfall has been used as an indication of both the stream's ability to assimilate organic waste materials and its overall water quality. 54 The population form of an ecosystem is dependent upon the ability of a species to tolerate environmental resistance and physical limiting factors. Population form includes those populations present, their age distribution, their density, and their rate of resource utilization or assimilation. Assimilation is the ability of a trophic level to con- vert energy and materials to biomass. This has a direct effect upon establishing the carrying capacity Of an ecosystem. Carrying capacity is then a measure of the amount of resources available for use by liv- ing things. However, whether the biomass is produced and, ultimately, carrying capacity established are a direct measure of the ability of organisms to tolerate various environmental limiting factors and exist and grow in a particular environment. Summary Figure 11 is a simplified diagrammatic version of the complex in- teractions which occur in ecosystems. The cyclical interactions of Energy and Matter (Figure 7), Populations (Figure 8), Communities (Fig- ure 9), and Abiotic-Biotic Processes (Figure 10) have been generalized and placed together to illustrate the inner workings of an ecosystem. Each combination of cycles was arbitrarily chosen because Of commonly shared processes or components. In the diagram, carrying capacity is a component which is shared by the Energy-Matter and Population Cycles; habitat is shared by Energy-Matter and Community Cycles; and available resources is common to Energy-Matter and Abiotic-Biotic Cycles. Closer inspection of each individual cycle will Show that there are other components which are commonly found in a number of cycles. This indicates that there can be several cyclic combinations which are 55 SUCCESSION COMMUNITY HABITAT ENERGY-MATTER CARRYING CAPACITY POPULATION AVAILABLE RESOURCES ABIOTIC-BIOTIC POPULATION INTERACTION ASSIMILATION FIGURE 11. A COMBINATION AND SIMPLIFICATION OF THE INDI- VIDUAL CYCLES FROM FIGURES 7 THROUGH 10 - A DIAGRAMMATIC VERSION OF THE CYCLIC NATURE OF INTERACTIONS OCCURRING WITHIN ANY ECOSYSTEM. 56 achieved by simply moving each cycle model about. In living ecosystems, each process or interaction is so closely interconnected with others that to model such a system would prove difficult. For general, de— scriptive purposes, the next section of this chapter is an attempt to formulate a model of an ecosystem. An understanding of the cyclical nature Of ecological processes and the closeness of the interactions among such processes will help validate an ecological model. Modeling the Ecosystem Various types of models have been used to describe, understand, and manipulate ecosystems. These include conceptual, diagrammatic, mathematical, and computer models (which are derivations of mathematical models). Tyler (1975) defines a model as a representation of a set Of Objects, attributes of objects, and the interrelationships existing among such Objects and attributes, to a level of resolution, accuracy, and precision assignable by the modeler. Because all models exhibit varying degrees of abstractness, the modeler must decide the proper balance between realism and abstraction relative to the purpose of the model. In order to be effective and valuable, an ecosystem model must have a combination of attributes including generality, precision, re- ality, utility, and wholeness. Developing a general conceptual model with a high degree of likeness to the real world will allow the model to be applicable in any ecosystem, whether large or small. The general nature will also yield a high degree of precision because the results of studying at an ecosystem level would be consistent and repeatable. It must be noted that this is not referring to mathematical precision; 57 it is practically mathematically impossible to include all ecosystem variables with any degree of precision. Most mathematical ecosystem models have to be limited to either small (and very general) ecosystems or to the interactions Of a limited number of components. Such models, nevertheless, have been valuable research tools with a high degree Of utility in Serving their intended purpose. The value of a state-of-the-art ecosystem model is in its reality and wholeness. An ecosystem is a real and important part of both natu- ral and artificial systems. A model which includes a high measure of likeness to the real world and incorporates the essential variables responsible for creating the significant dynamics Of the actual system has obvious attractiveness. Chapters Two and Three have presented a series Of conceptual and diagrammatic models which represent general ecosystems and their sub- systems with increasing model complexity. Included are models of eco- system components and trophic structure in Chapter Two and the Popula- tion, Abiotic-Biotic, Community, and Energy-Matter Cycles in the first part of Chapter Three. Each model has been designed to provide an un- derstanding Of ecosystem concepts and the principles governing ecologi- cal activities, interactions, and interrelationships pertinent to func- tioning ecosystems. Figures 12 and 13 diagram the overall conceptual model by placing ecosyStem components and interactions in a double di- agrammatic format. Figure 12 is a state-Of-the-art systems diagram of a complete eco- system which includes feedback loops and interrelationships in some de- tail. It was developed from a combination of component models from Chapter Two and cyclic models from Chapter Three. The model itself is 83 Jacobs (1975; pp. 203-206) generalizes the major effects of human activities on ecosystems by examining their influences on ecosystem diversity, stability, and maturity. These effects include: (1) transient perturbations, such as oil spills, Chemical defoli- ants, fires, or poisonous spills in rivers, which cause short-term effects by resetting the succession clock; (2) Chronic shifts in environmental conditions including persis- tent toxic substances, Cities, pavement, or dams, in which long-term or even permanent conditions are set forcing en- tirely new ecosystems; (3) energy-nutrient relations represented by import into the sys- tem from outside (fertilizers, pollution, agricultural or technological management) or by export to other systems; in either case, the ecosystem must adapt to the net gain or loss; and I (4) manipulation of species, either accidentally or intentionally by importation, extermination, or habitat alteration. Planning_the Use of Ecosystems: Man and Nature The purpose of this chapter has been to add the human element to the concept Of ecosystem by recognizing that humans are integral to the inner workings of even the most remote and uninhabitable regions on earth. It is also recognized that even the least natural human eco- system is still subject to the same ecological principles that govern natural systems. The idea here is that, because humans are part of the environment, they, their activities, and their artifacts must be con- sidered in the planning and management of any ecosystem. Ecological 58 .2mpm>moum whmaazou < Go ammo: D<3Hamozou .IH mmsomm wag—waxy»... ..:uq .muwmuuoua l:m»mo: 10:30.. ddv.:aau loom 30:1.5‘05 $19.: lat—.30 n no: u Sou—sou I. II. .9233; :tdcudo— jo:4.a<_w 30:33:: 3:153; II II II 5:23 p _ 2.33:0... | 2:2le- 8 20:33:: I I I wu_lda»o o u< w.— .. 193550.. 9!. — .I. .— :22: .o .5. 533 I~ mIO:<.58¢ no m—uiu! 3:33.33 4:51.853: mzozoéfif Zigzzflg 29:33 Day; alfldoco 41:929.. £85: 9305 mlo.:4=to¢ on. Isausa _ 535:2: 3.303.. IIHI paw-85>IUOCU; 5|-Il .535... E $3.22. 4.8 3:...3 :- u... :3 3:33 =29:th :3 3:95.- 533. .323 :5... 53...? U33 3:- 332:3: 32::- .o H H H Empisi 3:13.; Tat-8::— _u:.._..u_ £33323. 73.35—73.35— 3.35 .9332: I- 5.35032. 33...: on:_13 mummwuomq 4483.3 mach”: 8.8.04 mu._.l:llou mug-=3 3.22; W32; .2:- _ L EIIIITESSD 25:0: 5-qu “and: acpo. 59 ECOSYSTEM —----1 NATURAL SELECTION I ABIOTICI IBIOTICI BIOGEOCHEMICAL I YCLES l IMITING HABITAT OMMUNITIES IMITING ACTORS CLIMATE ‘, OPULATIONS ACTORS ORGANISMS RESOURCES A 1 PRODU TION OF OOD _ W DEATH 8 CONSUEPTION DECOMPOSI- OF OOD TION g? ASSIMILATION OLERANCE OF ENERGY & —J“‘< DAPTATION NUTRIENTS 9 GROWTH 8 EVOLUTION REPRODUCTION F J EEOUGH NOT ENOUGH COMMUNITY OOD FOOD CHANGE D NCREASING ECREASING OPULATION OPULATION O DL W MODIFICATION INCREASING ECREASING OF DEMAND FOR EMAND FOR ENVIRONMENT RESOURCES RESOURCES 6* fi- CARRYING GREATER "—‘SUCCESSION CAPACITY L_.POTENTIAL LIMITATIONS CARRYING é CAPACITY~ DECLINE IN , POPULATION SIZE } ADJUSTMENT EXTINCTION T8 CARRYING APACITY FIGURE 13. AN EXPANDED MODEL FOR ECOSYSTEM MANIPULATION - RELATIONSHIPS BETWEEN RESOURCE AVAILABILITY AND POPULATION DYNAMICS. 60 a series of hierarchical interactions between subsystems of the abiotic and biotic portions of an ecosystem. Physical or abiotic subsystems include limiting factors and biogeochemical cycles, while biotic sub- systems include environmental modification, impacts on populations, and selection of habitat. Interactions within the physical sector deter- mine physical carrying capacity; likewise, biotic interactions deter- mine biological carrying capacity. Carrying capacity, because of its overall importance in establishing and maintaining the ability of an environment to support a given population of organisms is, therefore, used as a major connector between physical and biological components of the model. Connections are also provided between the individual subsystems to illustrate the close interrelationships found in all eco- systems. The flow nature of subsystem activities, such as community succession, are illustrated by minor cycles within subsystems; the cyclic nature of subsystem activities over a relatively long period of time are provided by minor feedback loops. The purpose of developing a generalized ecosystem model is twofold. First, such a model can provide a basic review of the major components of ecosystems and how they are organized and interconnected. Second, a person studying or manipulating any ecosystem will have the ability to enter the system at any point, visualize the processes affecting that position, and predict possible effects that manipulation of that position would have on subsequent positions. By judiciously selecting entry points, an ecosystem manager can maximize the effects of manipula- tion while minimizing adverse impacts. Figure l3 is an illustration of this procedure. By examining the relationships between resource avail- ability and population dynamics, a separate model can be constructed to 6l demonstrate the feedback effect of carrying capacity on the success of a population in a given area. It can be seen that the availability of food is dependent on the size and growth of a population of organisms. If the population exceeds carrying capacity, it either adjusts its growth rate or becomes extinct. Associated processes such as community change and environmental modification are also affected by the flow diagram of food-population as shown in the model. Conclusion: Understanding Ecosystems A formulation and thorough understanding of ecological principles is essential to all people, whether they function as ecosystem managers or not. All of us are an integral part of natural and artificial eco- systems and therefore are governed by the same principles which control where and how a tree grows or why a fox preys upon a rabbit. Ignorance (intentional or otherwise) of ecological principles leads to several unfortunate occurrences: (l) It causes and intensifies ecological degradation and destruc- tion; (2) It prevents us from understanding natural ecosystems and their intrinsic value; and (3) It limits our ability to design human systems which are com- patible with the environment. The procedure which has been followed in the study of ecology be- gins with adherence to the scientific method of observation, hypothesis, and experimentation. This allows the systematization of ecological components andtheir interconnections and the ultimate formulation of predictive models. The accuracy and effectiveness of such models in 62 the study, manipulation and, when necessary, preservation of ecosystems depends on the use of ecological principles in the model-building proc-' 853. In conclusion, a reiteration of general ecological principles may be helpful: (I) POPULATIONS: All living things are part of the physical system. Their den— sity, abundance, development, and form are dependent upon bi- otic potential, environmental resistance, and the availability of ecological resources which are functions of the carrying capacity. Each species has a specific role (its niche) to play in the environment; eliminating a niche will eliminate the organism. Individuals of a particular species are present in any ecosystem due to dispersal, behavior, impacts from other species, and the combination of physical and chemical factors (Krebs, l972). AVAILABLE RESOURCES: Because of the laws of thermodynamics, energy flows through an ecosystem in only one direction and only by way of decreas- ing utility. Matter, on the other hand, cycles through the system and can be reused by living things. This is limited by the efficiency of the trophic structure and biogeochemical cycles. CARRYING CAPACITY: The habitat provides organisms with their basic requirements for survival; the amount and availability of such resources determine the carrying capacity. Overuse of the habitat by 63 populations of organisms lowers the potential carrying capac- ity which, in turn, limits the ability of the habitat to sup- port a maximum and quality population. (4) SUCCESSION AND STABILITY: Communities change and evolve over time through the responses of organisms to the physical environment and to each other. Organisms which are better able to adapt to changing condi- tions eventually succeed each other by optimizing their niches as such niches change. This tends to increase the diversity of living things in a community and, in many cases, also increases the stability of such systems. All ecosystems are in varying stages of stability or dynamic equilibrium with their physical environment. (5) SYSTEMATIC HOLISM: Everything tends to affect everything else. Ecosystems have the ability to perform a certain amount of self-regulation within limits; if the limits are exceeded (as when a toxic substance is introduced), a species may be eliminated. If any other physical or biological factor is grossly disturbed, an ecosystem may no longer be able to function and may ex- perience various patterns of change, injury, or breakdown (Southwick, l976). Because of their activities, needs, and wants, human beings are an integral and essential part of all ecosystems. Up to this point, how- ever, human-designed and influenced ecosystems have not been examined in this paper because of the necessity to outline basic ecosystem con- cepts and fundamentals. The next chapter, titled "Land Use: Human 64 Occupance of Ecosystems,‘ re-places humans into ecosystems by describ— ing the uses, modifications, and impacts of people upon ecosystems. CHAPTER FOUR LAND USE: HUMAN OCCUPANCE OF ECOSYSTEMS Introduction: Why Study Ecology and Ecosystem Theory? The major premise of Chapters Two and Three is that ecosystems represent the basic units for studying and understanding ecology. Chap- ter Two began with a description of ecosystem fundamentals from natural and systems science standpoints. The chapter introduced the concept of ecosystem, and defined it as an open system of living and nonliving things in any physical space, its interactions and interrelationships being closely bound together in a dynamic equilibrium. The flow of energy, cycling of materials, production and consumption of food, life and death, growth, reproduction, and evolution are all subsystems of each ecological system, or ecosystem. All ecosystems interact with each other to form the biosphere, which is the very limited region of the earth whose conditions permit the existence of life. The myriad of food chains and food webs; population structure, den- sity, and distribution; and all of the other interactions which take place between living organisms and their environment rely on the compli- cated and rather rigid ecological principles described in Chapter Three. Because interactions within ecosystems are generally cyclical as opposed to linear (with the exception of energy flow), ecologists look at eco- systems as dynamic, ever-changing entities and have hypothesized various principles by which ecosystems are governed. Single populations of 65 66 organisms and groups of populations, called communities, are constantly growing and changing in response to their environment. At the same time, the environment is being modified by the living things within it. Carrying capacity, the availability of natural resources for growth and reproduction, and the succession of one community by another are closely dependent on physical aspects of the environment such as energy and nutrient availability, climatic state, and other limiting factors. Ecologists, ecosystem managers, and environmental planners can study ecosystems and ecological principles and construct accurate, pre- dictive models. Graphic, mathematical and computer models have been described and represent a wide range of ecological functions - from a single predator-prey relationship to the complex input-output studies of large ecosystems. Despite our efforts to the contrary, human beings are an integral part of ecosystems. Each natural ecosystem varies with the amount of human interaction and, it may be argued, no ecosystem on earth has es- caped the human touch. From the human use standpoint, the study and understanding of ecosystems is important both intrinsically and practi- cally. By its very nature, the ecosystem is the physical level at which-' living things and their interactions with each other and with the non- living environment can best be observed and comprehended. The systems view provides a perspective for viewing man and nature and of organiz— ing research and planning efforts in reference to the concept of systems and their properties and relationships. It is in the attempt to simpli- fy the complex interrelationships that the ecosystem concept is most meaningful (Laszlo, l972). In order for human systems to properly in- teract with natural systems, the complexities of ecosystems must be 67 known to such an extent that the impacts of human activities may be predicted and, if necessary, mitigated. The practical importance of understanding ecosystems is in direct- ing the planning and management of human activities which use and trans- form ecosystems and their components. The ecosystem ultimately pro- vides natural resources which must be properly managed to provide suf- ficient and long-term benefits. Planning land uses determines how and at what rate ecosystem resources are extracted, modified, conserved, or preserved. Energy, materials, food, living space, recreation, and even employment opportunities are provided, in part, by ecosystem man- agement. The ecosystem, therefore, is the bridge between ecological theory and land use planning. Understanding and applying ecological principles to our uses of land and land resources ensures ecologically based land use planning. Classification of Human Ecosystems A continuum exists between the purest form of natural environment, usually pictured as a wilderness completely untouched by human influ- ence, and the purest form of cultural environment: a large urban cen- ter which is completely artificial or man-made (Farness, l979). The vast array of human land uses exists between the two extremes, each type of land use having a distinctive and proportional mix of natural and artificial components, values, and meanings. The continuum of land uses can be interpreted as a method of classifying human ecosystems. The mix of natural and cultural components determines the degree of human presence and utility of each system. Because current economic structures and technological capabilities have given humans both the 68 desire and means to shape any natural system to fit the required ends, there is no ecosystem on earth which cannot be potentially altered. Therefore, the human presence in natural ecosystems is a factor which must be considered in any classification system regardless of geographi- cal location or apparent lack of human presence. To illustrate this continuum of human ecosystems, a list is provided below which briefly describes (l) (3) various benchmarks along the continuum. This list includes: Pure Cultural Systems - such as the inner city which is an almost totally artificial combination of subsystems; natural components have been completely transformed to fit human needs and have to be imported into the city from outside; the only direct natural influences are from climate; Suburban Systems - primarily human artifacts with natural components, such as vegetation and animal life, modified for aesthetic fitness to the human environment; Exurban Systems - the mix of human and natural components are still heavily weighted toward the cultural environment al- though more natural areas are desired, such as city parks, greenbelts, larger estates or former farms which are primarily open space; Agribusiness Systems - this system has less direct human par- ticipation except for massive influences of technologys how- ever, it is more dependent on natural inputs and constraints than previous systems; Subsistence Agricultural Systems - small, family-owned and operated farms which have not been modified greatly by inputs of technology and which produce food and fiber for personal 69 use; a wide range of uses is included in this category in- cluding slash-and-burn in forest ecosystems, terraced hill- sides, and organic farming; (6) Parks and Natural Areas - these systems are among the first along the continuum to recognize the importance of providing humans with opportunities for direct association with natural ecosystems, although such interaction is usually controlled and not mandatory (i.e., humans within these systems are only partially dependent on the nonhuman aspects - no one is forced to live in that environment); (7) Natural Preserve Systems - areas either set aside because of their intrinsic values (limited-access sanctuaries) or their economic value to other human systems (hunting or fishing pre- serves); human use of such systems is limited and most natu- ral processes are only slightly modified by human management; (8) Pure Natural Systems (so-called wilderness areas) - there is some question as to whether purely natural systems which have never (or rarely) felt human influence exist; however, human activities are extremely limited and generally dependent on natural laws and principles - few humans could interact with such systems without large amounts of artificial support mechanisms. While the preceding list is far from complete due to the other forms of land use, one can easily see how the varying mix of natural and cultural features can provide clues as to how each human ecosystem is structured and how it interacts with its environment. Other forms of land use (such as extraction of natural resources, transportation 70 facilities, water resource use, and so on) can be placed along the con- tinuum once its natural-cultural mix is known. Identifying the land use identifies the ecosystem (e.g., agriculture, urban, transportation, mineral extraction, farm woodlot, etc.), and it is at the ecosystem level that each land use is most adequately comprehended. The energy and material needs, productivity, the mix or diversity of living things, population and community dynamics, carrying capacity, and system sta- bility can all be quantified and understood by considering each land use as a distinct natural and cultural combination. This philosophy is in direct contrast to the more traditional clas- sifications of ecosystems which generally presented such systems as biome-types or ecoclines described by various ecologists (Whittaker, l975; Odum, l959, l97l; Krebs, l972; MacArthur, l972; and many others). From an ecological point of view, the traditional classification is use- ful in describing each natural system, whether that system is a tundra, tropical rainforest, taiga, or steppe. Important components used to define each system include climate, soils, dominant vegetation and ani- mal life, and successional stage (usually the climax stage for simplic- ity). Adding man to the picture tends to complicate things and, until recently, human interactions with natural ecosystems were literally ig— nored by ecologists. The second edition of Odum's Fundamentals of Eco- logy_(l959) was one of the initial efforts to reverse this trend by the inclusion of chapters on man in natural ecosystems. The authors of more recent texts have also begun to realize this need, if only to report examples of human perturbation of natural systems. On the other side of the spectrum are the multitude of environmen- tal texts which tend to classify ecosystems from a land use impact 7l orientation. Whether it is agriculture, urbanization, forestry, or recreation (to name a few), each land use is defined in human terms with little reference to natural or ecological principles. For ex- ample, carrying capacity is described according to socio-economic measurements in which a land area or resource can support only a lim- ited quantity of people for a finite period of time (Gotschalk, l974, l975; and others). Human carrying capacity is only one form of car- rying capacity which must be understood in order to classify each individual ecosystem. In essence, environmental texts classify eco- systems largely from a human use and perturbation orientation and tend to devote only a small portion (perhaps as little as a single chapter) to a description of ecosystems from an ecological standpoint. Because of this shortcoming, such classifications are just the opposite of disciplinarian ecology texts. Each group tends to criticize the other for failing to properly list all aspects needed to understand an eco- system. Ecologists leave out the human component and write their texts in ecological jargon with little real-world applicability, while environmentalists fail to adequately describe natural components of ecosystems and tend to deal in the negative aspects of man-nature in- teractions. The next two sections of this chapter examine (l) human interac- tions within ecosystems from an historical standpoint and (2) the im- pacts of such uses on various natural parameters. Since various au- thors have contributed well-written publications describing the impacts of humans on ecosystems (Dasmann, l975; Foin, l976; Sutton and Harmon, l973; and others), the sections are intended to review and reinforce 72 the need to classify and study ecosystems by considering their natural and their cultural components. Human Use of Ecosystems: An Historical Perspective Excellent histories of human interactions with natural ecosystems have been described by Miller (l975), Dasmann (op. cit., l976), Bennett (l973), Southwick (1976), and Rodgers and Kerstetter (l974). There are three basic forms of man-nature interactions in history, and all three - man in nature, man versus nature, and man and nature - coexist even to- day (Miller, op. cit.). The first of these, ”man in nature,‘ represents individuals and their societies as integral parts of natural ecosystems. In other words, primitive humans were completely dependent on the environment for survival. Early and advanced hunter-gatherer societies had to ob- tain food, shelter, and other needs directly from plants, animals, or nonliving substances occurring naturally in the ecosystem in which they lived. Until the widespread use of fire and the technological advances of tool-making, humans were completely vulnerable to the environmental constraints of carrying capacity and environmental resistance. Early populations of humans were little different from populations of any other organism: they could increase their numbers only if there were sufficient quantities of food or a lack of competitors for resourc- es. Humans learned which animals were capable of being captured and which plants could be eaten without ill effects. Humans also had to find shelter from adverse climatic effects and predators. These early populations maintained stability through high infant mortality and short lifespans, and it must be realized that the human species represented a 73 single component contributing to the dynamic equilibrium of the total ecosystem. l'Man versus nature" represents the activities of human groups which influenced, transformed, or subjugated natural systems for their own use and benefit. In reality, this is what land use is all about. Humans have practiced land use from the simplest slash-and-burn agrarian systems to the most complex transformations of energy and matter of modern technologies. From the time man first used a stick tool to dig a hole for the planting of a tuber or seed, he has been a modifier of natural systems. His crops were vulnerable to changes in weather, soil impoverishment and erosion, or depradations from other organisms which were naturally occurring results of environmental modification. He has had to continually and increasingly add inputs of energy and technology to his efforts to overcome ecological constraints. Early nomadic grazing and shifting agricultural practices resembled hunter-gatherer systems in that they followed the available resources and seasons. However, once areas that could support year-round activity were found, people tended to cease their movements and form settlements. Fewer individuals were needed to work the fields and tend the herds and, with increasing technology, crop surpluses were obtained to support a population removed from the land. This led to more specialization, class distinction and, unfortunately, social and environmental dysfunc- tion. Warfare, slavery, overcrowding, disease, famine, and, ultimately, resource depletion and environmental degradation occurred. Poor or ig- norant land use practices contributed to the decline and downfall of many civilizations throughout history (Dasmann, op. cit.). 74 The most serious manifestations of man versus nature would have to date from the beginnings of the Industrial Revolution to the present. In the last 200 years, cultural and natural resources that fit the in? dustrial—technological institution were used in increasing amounts. More production meant larger populations of consumers who demanded more land and more land resources. Such "progress" was almost always at the expense of the natural environment: land grab, pollution and degrada- tion of the commons, resource depletion, more land clearing for food production, extinction of species, and even extermination of societies still in a "man in nature" form of existence. The cultural environment was also being transformed concurrently with natural systems. Indus- trialized nations, in their thirst for new sources of energy and mate- rials, subjugated large portions of the earth to fill their needs at the expense of other people who were less technologically advanced. As the grip of colonialism was released, the less developed countries sought to raise their standard of living to reflect the standard of liv- ing enjoyed in advanced nations. These people, representing the major- ity of the world's population, are just beginning to make their demands felt. The next section of this chapter, ”Human Impact on Ecosystems," will examine the effects of land use patterns represented by ”man versus nature" in greater detail. The adoption of the ecosystem concept is necessary to implement a shift from "man versus nature” to "man and nature,‘ in which human ac- tivities are planned and carried out to best fit the requirements of each ecosystem type. Mutual cooperation of all people working under ecological constraints is the only way to ensure survival of all forms of life - including humans. In order for it to function properly, any 75 natural system is constantly striving toward equilibrium with its envi- ronment and toward stability in which production roughly equals con- sumption; the factors causing population increases are balanced by those favoring population decrease; and living things grow, reproduce, and die within the natural limits of carrying capacity. "Man and na- ture" requires the same type of equilibrium between human uses of eco- systems and the basic governing forces found in nature. Human con- flicts, aggression, resource exploitation, and overpopulation must be overcome, based on an understanding of the relationships between living things and their environment. In summation, this section has been a description of the continuum of time and cultural meanings and values of human land use patterns. Historically, human social groups have gone from being a relatively small part of natural ecosystems to attaining the ability to control and alter those same systems through massive inputs of energy and mate- rial transformation. To advocate a return to simpler, nontechnological lifestyles would be both foolish and unrealistic. While some isolated social groups such as communes have successfully adopted a simpler lifestyle, the majority of humans lack the ability to readjust, and in— tensive use of agricultural ecosystems will remain necessary to feed the growing populations. Instead, it is recommended that we continue to develop an evolutionary path away from centralized control and ex- ploitation of natural systems to a healthy coexistence with those sys- tems. 76 Human Impact on Ecosystems This section addresses environmental and land use problems at the ecosystem level by examining past and present land use practices in re- lation to their ecological impacts. In order to understand man's place within ecosystems, it is necessary to examine how he has interacted with ecosystem components and ecological principles. Throughout their evolution, humans have increased their ability to manipulate, modify, and alter natural ecosystems. During the last 200 years, however, this ability has caused the most widespread and damaging changes. Most eco- system alteration has been accomplished for the benefit of human popu- lations and, while not all changes have been at the expense of natural ecosystems, it is unfortunate that the majority of them have. Land use practices generally affect ecosystems by altering the diversity and stability of natural plant and animal communities, the quality and quantity of surface and subsurface waters, soil fertility and utility, presence and configuration of land forms or topography, and air quality (Bennett, op. cit.). Each of these areas will be ex- amined in greater detail from an ecological standpoint. Vegetation Since the advent of agricultural practices, natural vegetation has largely been viewed as an obstruction to human needs. Generally, any plant that was not edible or otherwise economically valuable was re- placed by species that were. Natural patterns of vegetation have been altered by fire as in slash—and-burn subsistence farming, removed by logging (and not reforested), modified by plow agriculture and selec- tive grazing, and used for fuel. For example, it is difficult to find 77 unaltered prairie vegetation in the American Midwest since the intro- duction of cattle grazing and farming in the last lOO years. This ma- nipulation has led to an artificial selection in which man has selected against the original grass types in favor of corn or wheat crops. Modern agricultural practices rely on maintaining plant communi- ties in an early successional stage characterized by high productivity, rapidly growing populations, and lower species diversity. Unfortun- ately, this also leads to less stability and specialization in communi- ties and populations, making the crops vulnerable to sudden ecological changes caused by the climate or insect pests. This, in turn, requires proportionately greater economic and technological inputs to maintain the necessary productivity required to grow the crops. The introduction of exotic plant species has also led to various problems with internal ecological checks and balances. Introduced spe- cies such as tropical fruits and ornamentals have proven to be failures when they could not adapt to new conditions. Generally, however, in- troduced plants have become too successful. Due to lack of natural enemies or better adaptability, exotic plants have been able to out- compete with natural vegetation as any gardener would know. Animal Life As methods for hunting and domesticating wild animals became more efficient, humans were able to widen their mastery over larger numbers of species and also choose those species of value. ”Good” species were either domesticated and bred for species enhancement (artificial selec- tion) or they were managed in the wild for food or pleasure. I'Bad" species were designated as such because they directly competed with 78 humans for food (or made humans part of their diet). Attempts to erad- icate these competing or dangerous ”bad” species remain in practice. The use of chemical pesticides has increased to serve this end. Be- cause of biomagnification through the food chain, the cumulative ef- fects of chemicals may not be ascertained for many years. Major impacts on wildlife have occurred through market hunting, habitat destruction, and the introduction of exotic species. Commer- cial hunting practices have caused the extinction of numerous species (passenger pigeon, dodo, great auk, heath hen, etc.) and the widespread disappearance of others (the great whales, wolves, birds of prey, etc.). Habitat destruction has had, and will continue to have, the greatest impact on distribution and abundance of animal species. Reducing the amount and quality of native habitats directly affects the carrying ca- pacity of each ecosystem to maintain an animal population. The dis- appearance of the ivory-billed woodpecker is a good example of the neg- ative aspects of habitat destruction. The introduction of exotic spe- cies presents the same problems to animal populations as it did to plants: exotic species may carry diseases to which native populations have no natural resistance; they may be able to outcompete native spe- cies (as in the starling, house sparrow, and Norway rat) or they may lack natural enemies and become economic pests (e.g., the Japanese beetle, European corn borer, or Dutch elm disease). Surface and Subsurface Waters Water resources have been engineered - and polluted - to meet human needs. Because water is so essential to life, its presence or absence from an area is a determining factor in carrying capacity. 79 Therefore, water supplies have been dammed, canalled, diverted, and pumped from areas with surplus water to those lacking it. Impoundments and diversions have resulted in the loss of wild, free-flowing rivers while the quality of the water itself has usually decreased as a result of such manipulation. Flowing water has a higher concentration of oxy- gen and is generally cooler than still water, while the sediments car- ried by flowing water tend to settle out when the velocity is decreased. This has led to changes in plant and animal succession, diversity, and density; lowering the water quality; and causing engineering problems such as siltation. Areas without surface water sources have had to rely on pumping underground water. As long as recharge was adequate, long-term avail- ability was not seriously altered. However, increasing demands have lowered water tables to the extent that underground water (in reality, a nonrenewable resource) is now being mined in many areas. Other prob- lems associated with pumping subsurface water have included land sub- sidence and salt water intrusion. Water sources have also been used as sinks for human, industrial, and agricultural wastes. Clean, flowing water has the natural ability to assimilate organic wastes through oxidation and trophic utilization. However, large amounts of sewage, toxic substances, fertilizers, and heated water seriously reduce the capacity of natural waters to purify themselves. In natural ecosystems, this results in early eutrophica- tion (succession); changes of species diversity, carrying capacity, dis- tribution, abundance, and even the presence of organisms; and decrease in usability for future human needs. 80 Soil Fertility and Utility Poor land use practices and ignorance have led to soil erosion and impoverishment. Soil erosion results from stripping the natural vege- tation from the land through fire, logging, agricultural practices, or overgrazing and neglecting to replace the natural vegetation with other plants (as in clearcutting) or planting new species which inadequately anchor the soil. The exposed soil is subject to natural weathering by wind and water until the most fertile upper horizons are no longer available for either natural or human use. Examples of widespread soil erosion have occurred in the Dust Bowl of the Great Plains and in the desertification in northern Africa. On the other hand, irrigation projects in arid regions and good soil conservation practices have re- sulted in maintaining both soil fertility and quantity for long periods of time. Soil impoverishment has resulted from a combination of human prac- tices (changes due to massive applications of pesticides and fertiliz- ers) and natural causes (nutrient leaching in tropical lateritic soils cleared for agriculture). Inputs of artificial substances to enhance crop growth may also kill soil microorganisms which, if left alone, act as soil builders by decomposing organic material. The buildup of chem- icals may become toxic to larger forms of life, including man. Landforms Man has been altering the surface configuration of the earth in varying degrees since he began extracting minerals from the earth and building temples to his gods. When human numbers and needs were rela- tively few, natural landforms presented limitations to movement, 8l resource procurement, and settlement patterns. Today, a mountain in the way is moved, a flooding stream is dammed, or a valuable resource is mined after removing hundreds of feet of overburden. Mining (whether open pit, placer, hardrock, or strip) and land sculpting (for roads, railroads, streets or building sites) are feasible in nearly any environment due to advanced technological tools and the economic incentives for their application. However, in the process of topographical alteration, the physical components of ecosystems are also altered, directly impacting the living organisms associated with and dependent on them. After a mineral is extracted, hardrock spoils from mining operations present an extremely hostile environment to plant and animal recolonization. Sealed surfaces from buildings or pavement take the soil out of production (for natural as well as human use) and prevent natural percolation of water into ground strata. Loss of habitat has already been mentioned as a detrimental impact which di- rectly affects natural ecosystems. Atmosphere and Air Quality Human impacts on the atmosphere are perhaps the least understood aspects of human interactions within ecosystems. It is relatively well- known what types of activities are causing what forms of air pollution, but the long-term effects on both human and natural systems are less clear. The major source of air pollution (excluding volcanoes) is from the burning of fossil fuels for transportation and power generation. The proportions of gaseous materials and particulates from combustion are well-known, although potential toxicity of such materials on living things is still being studied. 82 Potentially damaging substances include oxides of carbon, nitrogen, and sulfur; ozone; fly ash; soot; and heavy metals such as lead, cad- mium, and zinc. Most of these substances occur naturally within the matter cycles and can be assimilated in small amounts by living things. However, large portions can kill organisms and cause environmental mod- ification and succession to certain species that are less desirable to most humans. Other atmospheric impacts include radioactivity from nuclear weap- ons testing and climatic alteration from weather modification inten- tional and incidental to other land uses. Long-term impacts from radi- ation may include environmental diseases such as cancer or even an ac- celeration of natural selection due to increased mutation. Affecting the weather may increase desirable weather patterns in one region at the expense of other areas. For example, enhancing rainfall to one ag- ricultural region may "dry up” some regions and cause disastrous floods in others. Impacts on local climates have resulted from large water impoundments, airports, and cities. A debate is currently raging concerning the long-term effects of particulates in the atmosphere, particularly carbon dioxide. The pres- ence of microscopic particles affect the amount of solar reflectivity - if more of the sun's rays are reflected back into space, the overall climate of the earth may cool, possibly triggering a new ice age. 0n the other hand, a dense particulate canopy may act as a layer of insula— tion preventing heat from escaping the earth. A resultant rise in tem- perature may induce melting of the polar ice caps and subsequent sub- mergence of the major population centers. 84 principles contribute to achieving a mature balance between natural and cultural systems because they form the basis for developing dynamic land use policies and management techniques in addition to traditional economic, political, and technological inputs. The next two chapters will first look at ecosystem planning and then at management with the intention of (l) limiting negative human interactions with the environment, and (2) developing a methodology which will promote the man-and-nature perspective introduced in this chapter. Any one of the preceding problems, whether it is land, air, or water degradation; loss of plant or animal species; or a reduction in resource quality, if unchecked, may result in seriously limiting the ability of the environment to support human populations at even the subsistence level. It is therefore necessary to observe, study, plan, and manage the environment with the philosophy that such use must be ecologically sound. Use of the ecosystem concept, introduced and developed in Chapters Two and Three and adapted to a human land use orientation in this chap- ter, will become the focus in developing a planning and management meth- odology in the next two chapters. CHAPTER FIVE PLANNING FOR THE RENEWAL AND MAINTENANCE OF ECOSYSTEMS Problem Definition A plan is a proposed method of achieving a desired end. While there are various forms of planning strategies, certain functions seem common to most plans. Plans are usually goal-oriented; i.e., problems are identified and a systematic procedure is required for their solu- tion; and they are administrative tools. Data must be gathered and integrated into a meaningful and usable form; an official document is produced which usually lists and examines alternative solutions before choosing the most appr0priate one; and the plan is implemented and ad- ministered according to its particular application. In addition, a plan and the planning process must be somewhat flexible to accommodate new information or needs, and the duration of its effect must be long enough to justify the expenses incurred. Since planning is problem-oriented and goal-directed, it is neces- sary to examine how planning fits within an ecological perspective and vice versa. Poor planning with respect to the environment and its var- ious ecosystems has led to such overwhelming problems that only a total reorientation of current planning efforts will remedy the situation. Pollution, resource depletion, the extinction of various organisms, and human overpopulation are notable examples of poor planning. Obviously, the goal of ecologically based planning is to reverse the above trends 85 86 and establish a better quality of life. Renewal and maintenance of eco- systems regardless of their present state of quality is also a basic goal because all humans depend on the functioning of ecosystems for their survival. This leads to another problem which must be addressed in the plan- ning effort: bridging the gap between ecological theory and land use planning. There are natural ecosystems and somewhat less-natural human ecosystems. It should be the intention of planners, resource managers, educators, and so on, to study and understand natural ecosystems so that the evolution and design of human ecosystems can imitate the func- tioning, efficiency, and fitness of more natural ones. Planners and managers who make decisions — answering the questions of how, where, _ and in what quantities natural and human resources are used - must ap- ply ecological principles and accommodate ecological constraints to en- sure that environmental decision makers deal with living and nonliving resources. An understanding of the structure and function of ecosystem components, their interactions, and the collective ”whole” is also nec- essary. This understanding requires a careful selection and combination of elements from various sources of information which form the set of practices and idea systems needed to plan and manage ecosystems and the resources they provide. While it is important to indicate that ecologically based planning is necessary from the standpoint that, for the most part, such efforts have been inadequate or totally lacking, it is also necessary to define those areas and select decision makers that should be part of the proc- ess. Appropriate planning functions include the renewal and mainte- nance of ecosystems in virgin lands, recently exploited lands, and 87 lands which have been used on a long-term basis. To be truly inclusive, the list should contain aquatic ecosystems as well, particularly in oceanic and estuarine areas which have been projected as necessary for providing food to a starving world. Obviously, every land and water area on the earth will be included at one time or another. The utiliza- tion of any land area or land resource (for purposes of simplification, the inclusion of aquatic ecosystems will be assumed) requires an under- standing of that resource, how that resource is connected with other ecosystem components, and the long-term consequences of such use. For example, a decision to develop a new energy-using technology may re- quire an intensive search for future energy supplies. If it is found that adequate supplies are present in a previously protected area, pressure to extract that resource will increase, and the functioning ecosystem in the area will be affected. This is a value judgment which might have more far-reaching ramifications than the resource planners originally thought. Rare species might become endangered ones. In ad- dition, certain biophysical processes which are vital to human well- being (such as air or water purification, the amelioration of toxic substances, or the production of future foods or medicines) could also be threatened. The list of ecosystems which require renewal and main- tenance includes intensively used land areas such as prime agricultural and other food- and fiber-producing areas. Constant use of biocidal and fertilizing chemicals, the elimination of natural checks and bal- ances (such as beneficial insects), and urbanization may seriously af- fect the long-term productivity and availability of such important areas . 88 The list of people who should plan their activities around ecolog- ical principles includes everyone - from the suburbanite who waters, fertilizes, and mows his lawn to the chairman of a multinational energy- producing corporation. In other words, everyone's life depends upon transformed ecosystem components (resources) and the ecosystems from which they come. The efficient and optimal extraction and use of such resources depends on properly orienting the planning function, not only to provide economic and social goods, but to protect and enhance the » biophysical support functions which allow the continued provision of such goods. Poor planning may cause environmental disasters and enor- mous costs to correct the situation. There are three general classes of resources which require the in- put of ecological information to enhance their manipulation and use. These classes include (l) nonrenewable resources, and (2) renewable re- sources - the so-called fund and flow resources - and (3) other land areas which could be designated for either of the above uses but, be- cause they are used for living space or wildlife refuges (for example), are not (Barlowe, l972). A planner, such as a coal-mining engineer, is dealing with a nonrenewable resource, and is concerned with the most efficient, safe, and cost—effective extraction of coal from a surface mine. His planning efforts should also include sufficient information to minimize environmental disturbance and pollution. He must be able to plan the proper reclamation of the landscape after the coal has been mined. His resource use affects local ecological conditions and may, through runoff and machinery exhaust, have some farther-reaching conse— quences in more distant parts of those ecosystems as well. 89 Planners of renewable resources, such as farmers and foresters, must be aware of the potential impacts of the chemicals (such as pesti- cides and fertilizers) used in their operations and also in any land— clearing activities. Research and careful planning are needed to as- sess the impacts which may affect the proper functioning and interac- tions of physical (air, water, soils) and biological (plants, animals, and humans) components of local ecosystems. The all-too-familiar case of high pesticide residues in Great Lakes salmon and lake trout exem- plifies this very well. Through biological magnification within the food chain, relatively nonbiodegradable pesticides such as DDT and Dieldrin began to concentrate in the fatty tissues of such fish. Health officials expressed concern that such high levels might become toxic to the fish and to the people who ate them. Proper planning, development, and use of degradable pesticides of natural origin may have less long- term ecological impacts on components and functions of ecosystems which were not meant to be affected (Odum, 1975). The final area of land use and resource planning includes those ecosystems which, although not designated for production as in the pre- ceding cases, are suffering from increasing development pressures. Land areas experiencing rapid urbanization are often out of balance with both the cultural and natural ecosystems (Stearns and Montag, 1974). The flow of food and water and the provision of shelter (housing), safety, environmental quality, and aesthetically pleasing surroundings are in- terrupted in the process. Building on floodplains or recharge areas, siting power plants in geologically unstable areas, and conversion of functioning natural ecosystems to disrupted ones are only a few examples of planning efforts which have had disastrous results. 90 It is helpful to reiterate the goal orientation of ecologically based land use planning and how it assists in the planning effort. First, ecosystem planning is based on the fact that the ecosystem is the most suitable location for planning human interactions with the biophysical world. Second, ecosystem planning provides an understand- ing of components, structures, functions, and interconnections which no listing or inventory could approach. This understanding helps ex- plain the natural constraints which govern all ecosystems from the sim- plest natural systems to complex, cultural (less natural) human eco- systems. Finally, ecosystem planning allows a holistic, systems approach to human endeavors in which activities can be planned and properly imple- mented with a view toward the functioning and maintenance of the bio- sphere as a whole. Ecological problems can be sorted and classified according to their impacts on both human and natural systems, and solu- tions can be found and implemented with a philosophy of environmental fitness and appropriateness. Information Base Once problems have been identified and goals established, the next step in the planning process is implemented: gathering, organizing, and combining information into the formulation of a plan or course of action with regard to identifying and using resources, planning future developments, or addressing environmental problems. In the study of ecosystems, it is necessary to establish a meaningful information base. This is an important remedy to the problem of gathering copious amounts of data with the hope that everything necessary to properly plan 9T ecosystems will somehow be obtained in the process. Holling and Clark (1975) speak of the need to establish a sound information system based on (l) the conceptual framework of ecological theory which explains ecosystem structure and function, (2) simplified simulation models and management programs which can be integrated to explain or solve environ- mental problems, and (3) extensive and intensive empirical studies which describe causal relationships. The conceptual framework provided by ecological theory has been discussed in Chapters Two and Three of this paper while the solutions to environmental problems will be examined in the next chapter on eco- system management. This section will describe the information systems necessary to inventory, describe, analyze, and classify ecosystems to provide a usable information base for ecosystem planning. Such an in- formation system must be oriented according to an ecological classifica- tion (see below) and have both natural history and cultural information as major components. Ecosystem Classification The purpose of ecosystem classification is to provide a standard- ized and meaningful organization of all of the data gathered on ecosys- tem components, subsystems, structures, functions, and interactions which are necessary to plan and manage such systems. Such a classifica- tion will provide a common starting point for the interactions of ecol- ogists, systems analysts, planners, managers, and other decision makers. The proposed method of ecosystem classification (described in Chapter Four) is based on an evaluation of (l) the spatial extent of a particu- lar ecosystem in question (after it has been defined according to type - 92 usually vegetation, soils, and climate) and (2) the degree of natural- ness, or the combination of relative amounts of cultural (man-made) and natural influences or components. This method is an integration of land use classification (in its many forms) and ecological classifica- tion, which is exemplified by several phytosociological or wildland classification schemes (Driscoll and Spencer, l972; Corliss, et. al., l973; Michigan Department of Natural Resources, l975; Brady, et. al., l979). Defining the spatial or geographical dimension is one of the more difficult problems in ecosystem planning simply from the standpoint of setting meaningful boundaries. Discrete geographical entities such as watersheds or regions of homogeneous patterns of vegetation (biomes) have been suggested as possible foci of planning efforts. However, such large land areas usually cross political boundaries such as state or county lines, and jurisdictional disputes are often the result in large- scale regional planning. It may be necessary to begin with small-scale operations — neighborhoods, private lands, urban centers, parks, and so on - to gain the experience, confidence, and support to plan in region- al ecosystems. Regardless of spatial extent, definable ecosystems will be present in any land area chosen for classification, study, or devel- opment. Land use classifications are not new; many states began inventory- ing their agricultural and forest lands during the early 19005 (Barlowe, 0p. cit.). Such classification schemes were not based on natural land units; rather they were laid out according to the rectangular land sur- veys. Thus, political units such as counties delineated the spatial orientation for such natural classifications (soils) as those developed 93 by the U.S. Soil Conservation Service. Other countries, such as Canada, Australia, and Mexico, have improved this resource classification scheme by carefully describing the interactions of soils, hydrology, landforms, and climate as components of a production function. The Food and Agricultural Organization of the United Nations has developed a system-based land evaluation for agricultural production which is be- ing advocated for developing countries (FAO, 1976). However, such classification schemes still tend to be administered according to po- litical rather than ecological boundaries. Ecologically based classifications have largely originated in Western European countries (most notably in The Netherlands and Great Britain) and in Canada. In Canada, Angus Hills (1961, 1970, 1976) has proposed a total site classification which approaches an ecosystem classification; his system is based on a description of natural charac- teristics such as surface relief, geological materials, climate, and soils. His method is one of the first to look at natural systems holis- tically and attach ecological significance to the components used in the description. Hills' classification is directed at the evaluation of the capability, suitability, and feasibility of ecosystems for all types of biological production. The overall philosophy is to classify ecosystems according to their capability of producing living organisms of various kinds (and economic potential) under various combinations of circumstances. While it may be argued that all ecosystems should not be evaluated as production units, the fact that it is a knowledge of ecosystems and ecological theory which predicates the evaluation process sets an important precedent. In addition, Hills' methodology began to examine the interaction between natural and inherent land use 94 capabilities and public welfare and institutional demands for land use controls. This examination of natural and human ecosystem development provides a foundation for more meaningful ecosystem classification. Other Canadian attempts at land classification are also notable. Dansereau (1978) and Brady, et. al., (1979) have begun to classify eco- systems according to their cultural-natural mix as well as placing such methodologies within an ecological framework. Although both classifica- tion schemes are directed more toward urban ecosystems, the approach used can be very helpful in understanding environmental problems caused by the subjugation of natural systems by human activities and also the ecological cost of such activities normally viewed in social, political, and economic terms. Both approaches are recommended to provide back- ground material in developing an ecosystem classification process. The first pragmatic approach to ecosystem classification (as well as planning and management) has been proposed by Van der Maarel (1978). Since ecosystems provide a number of functions to human systems (and damage to those ecosystems results in a loss of function), ecosystems should be classified, renewed, and managed according to the interactions between human and natural environments. Functions include production of food and materials, regulation of waste products, scientific informa- tion, carrying capacity, etc., and overuse or overexploitation of such functions may cause total system breakdown. Van der Maarel recommends a classification using a set of indices which can be used to describe the state of the system and to establish baseline points for system re- newal and management. The overall classification is based on degree of naturalness with indices (value descriptors) of scarcity, diversity, and structural diversification. Together, these indices can describe the 95 state of the ecosystem to provide information for projections of what the system might do in case of an environmental impact from proposed plans or management activities. The use of indices can be of value in guiding the information- gathering process because such natural functions are determinants of productivity, structure, and species composition of ecosystems. This is helpful in the determination of what information should be gathered in an ecological inventory. Basically, an inventory is taken to find out what is there and how much. This gives planners, resource develop- ers, and managers not only an idea of the richness of the ecosystem from a biophysical standpoint, it also indicates the degree to which the system may respond to human activities and influences. Ecological Inventories and Descriptors The compiling of extensive and exhaustive lists, which has been done in past environmental impact assessments, is largely a waste of time and money, as are comprehensive ”state of the system" surveys and detailed descriptive studies (Holling, 1978). The major benefit of in- cluding lists of species present or descriptions of physical conditions is to notify planners of potential constraints presented by an ecosystem. Obvious constraints to planning the use of ecosystems - rare or endan- gered species, areas of geological instability, unique ecological condi- tions, natural hazards, and so on - should be listed. It is recommended that, if a listing is necessary and required, the activity be done as cheaply and simply as possible using survey checklists such as those de— veloped by the U.S. Environmental Protection Agency which indicate as- sessment parameters specific to particular resource or environmental 96 problem areas (for example, water quality management (EPA, 1972)). Other, more extensive inventory systems may also be helpful, such as The Natural Resource Inventory Checklist developed for the National Science Foundation by the Montana Agricultural Experiment Station (1979). Such approaches can be modified to suit particular circum- stances and planning constraints and need not be followed religiously. 0f greater importance than listing ecosystem components is the organization of those components according to their causal relation- ships: their structure and function, how they interact, and how they influence the processes which are essential to humans. In order to plan for ecosystem renewal and/or maintenance, these relationships must be intensively and extensively studied and then manipulated - but only after they are understood through simulation techniques. The measure- ment of ecological relationships is essential to establish a meaningful information system which can be useful to the land use planner. Follow- ing is a list of ecosystem components and conditions which should be measured, and a recommended method by which they can be measured: (1) Productivity and biomass supported (bioenergetics) are mea- sures of community dynamics and are quantified by establish- ing the ratios: (a) P/K where P is gross production (amount of organic mat- ter photosynthesized by the producers of the ecosystem) and K is community respiration (biomass lost through respiration or metabolism). (See Chapter Two.) (b) P/B where P is gross production and B is standing crop biomass (the dry weight of living organisms). P can also be expressed as GBP or gross biomass productivity, (2) 97 thus yielding the fraction GBP/B. Likewise, NBP or net biomass productivity (measuring loss of biomass through respiration) gives a more meaningful interpretation of K in equation (a). (c) B/E where B is biomass supported and E is unit energy flow (available energy for production within a defined area; Odum, 1969; pp. 262—270). (d) Another measure of importance in bioenergetics is that of turnover time (the time needed for the ecosystem to produce an amount of biomass equal to that of the stand- ing crop. It is the inverse of the equation in (b): T = B/GBP. Young and simple ecosystems (early succes- sional states) tend to have shorter turnover times than ecosystems further along on the continuum toward climax (Brower and Zar, 1977; p. I49). Trophic relationships of species (or who connects with whom via energy and nutrient pathways) can be quantified by (a) predator-prey studies which list “species eaten" and ”species eaten by" to produce an index of a particular orga- nism's position within the food web (Tyler, l975; p. 102), and (b) by the construction of a model food web with arrows showing major energy transfer pathways and diversity indices which give an indication of relative ecosystem stability (Brower and Zar, 1977; pp. 135, 136-142). Figure 14 is an example of food web models constructed by an ecologist after field observation. Note that the simple model on the left is more susceptible to disruption than the 98 relatively more complex model on the right. Such models are good indicators of ecosystems which must be carefully managed. EVERGLADE KITE GREAT HORNED OWL APPLE SNAIL / MEADOW VOLE FROG MOTH CORN SPROUT SWAMP VEGETATION OTHER VEGETATION FIGURE 14. Two EXAMPLES OF MODEL Fooo WEBS USED TO INTER- (3) PRET TROPHIC RELATIONSHIPS. Scarcity, diversity (richness, number, and abundance of spe- cies), and variability of organisms, landscapes, soils, etc., within a community or habitat can be measured according to a relative proportion of occurrence within a given geographical area (Odum, op. cit.; Van der Maarel, 1978; pp. 421-423, 435). Of the many measurements of species diversity, Brower and Zar (op. cit., pp. 136-140) recommend Simpson's Index (Simpson, 1949) and information-theoretic indices for use in ecological data collection. Simpson's Index considers number of species (5), total number of individuals (N), and the proportion of 99 the total that occurs in each species (n1 = relative abun- dance): Ds = l - where the species were randomly sampled. Information-theoretic indices can calculate diversity of ran- dom samples according to abundance, habitat heterogeneity, diversity of biomass, and relative abundance or relative bio- mass. Nonrandom samples can also be used to predict species abundance: Random: H' (N log N - 2 n; log n1)/N (log base e, 10) Nonrandom: H (log N! - 2 log ni!)/N (log base e, 10) Structural differentiation and successional stages of commu- nities can be measured through stratification or life-form analyses based on indices of relative maturity of dominant species (usually vascular plants). Whittaker (l975; pp. 174- 179) lists measurements of (a) productivity, (b) biomass, (c) biomass per annual net productivity (biomass accumulation ratio), and (d) growth in stock of inorganic nutrients as indicators of successional stage. Detailed observations are sometimes necessary to note changes in populations, increases in diversity, and shifts in dominances attributed to ecologi- cal succession. Whittaker (op. cit.; p. 104) also utilizes vertical and hori- zontal gradients to demonstrate structural differentiation in (5) 100 ecosystems. Profile diagrams (measuring stratification) show different plant growth forms and indicate animal species at different levels (according to niche). Measurement of stems per hectare, moisture gradients, and soil types which create moSaics of species correlations (those that tend to occur to- gether) are examples of horizontal gradients. Other workers, particularly Van der Maarel (op. cit.) have recommended mea- suring gradients of climate, hydrology, geomorphology, soil texture, soil chemistry, and animal or human influence to es— tablish structural (or niche) differentiation. Spatial and temporal relationships of populations and commu- nities are difficult to measure unless extensive observations are taken and compared with research results. However, gain- ing this information will provide insight into species' habi- tat requirements and the relative richness and health of habi- tats in question. This can be of value in scheduling manage- ment activities for the least amount of disturbance to natu- ral processes. Measurements include: (a) species movement - diurnal and seasonal, migration pat- terns, dispersion of population - can be measured by dis- tribution of nests or burrows, bird banding, browse lines, radio telemetry, etc. (Avery, 1975; p. 223; Watt, 1968; pp. 252-352); (b) population age and health can be determined by live-trap- ping and the analysis of habitat utilization; evaluation of population change over time can be based on the number of individuals gained or lost relative to the original 101 population in an area or on changes in the predator-prey balance (Pianka, 1978; pp. 99-118; Odum, 1959; PP. 150- 177; Watt, op. cit.; PP. 21-36, 189-224); (c) habitat utilization is a measure of habitat quality, or the ability of a habitat to provide food and shelter for any particular species - in essence, an indication of carrying capacity (Pianka, op. cit.; pp. 238-251); habi- tat analysis procedures presented by Avery (op. cit.; pp. 220-235), Giles (1969), and Brower and Zar (op. cit.; pp. 27-33) will give a representation of available habi- tat resources and how they are being utilized by species present; it will also be useful in determining inter- specific relationships in time and space (e.g., competi- tion, niche utilization, etc.). (6) Degree of naturalness has been discussed above and in Chapter Four. Classifying ecosystems according to their relative naturalness requires generally subjective measurements on the part of the observer. In addition, Van der Maarel (1975, pp. 265-266) lists a cross-matrix of measurement categories which can assist in determining degree of naturalness. These include: (a) rate of influence of man on biotic components of an eco- system (land use classification forming six categories: natural, near-natural, semi-natural, agricultural, near- cultural, and cultural); (b) origin of ecosystem (four categories: natural, semi- natural, agricultural, and cultural); and 102 (c) present state of development or successional state (three categories: pioneer, development, and nature). The preceding list was developed with an ecological orientation. It is recommended that such parameters be measured by a team of quali- fied ecologists who are aware of the constraints and implications of the proposed planning activities on natural components and functions. The measurements listed are by no means the only ones available for use by data collectors. There are several recommended texts on ecological measurement and sampling techniques, including Ecology and Field Biology (Smith, 1980; Appendix B, C) and Field and Laboratory Methods for Gen- eral Ecology (Brower and Zar, 1977). The information collected can be used to establish a description and weighting of those biophysical sup- porting functions (listed below) which are essential to human ecosystems and may be affected by the planned activities (McHarg, 1969; p. 57): 1) natural water purification; 2) air pollution dispersal; 3) climatic improvement and regulation; ) water storage; 5) flood, drought, and erosion control; 6 topsoil accumulation; and ( ( ( (4 ( ( ) (7) plant and animal inventory increase. Because the proposed classification contains a mix of natural and human (cultural) ecosystem components and functions, it is necessary to provide inputs of ecosystem descriptors from the human as well as eco- logical standpoint. A description of the degree of naturalness would be the logical first step to which would be added an assessment of en- vironmental quality and ecosystem richness. This method not only 103 provides a description of land types, uses, and capabilities, it also allows the input of natural and human values and needs. Such values can be interpreted as philosophical, as well as economical (e.g., agri- culture, forestry, or land values) and ecological (e.g., plant associ- ations, wetlands, floodplains, or endangered species). The latter two values are obvious and well documented: there are definite benefits in maintaining system integrity by protecting ecological components and processes, and there are benefits in maintaining productive cultural entities such as farms, factories, and communities. Value descriptions should also include determinations of past and present damages and dysfunctions along with some projection of what it may cost to replace the damaged areas. If natural functions (such as the cooling effect of a forest canopy) are destroyed, they must be re- placed by expensive and energy—wasting tools (in this case, air condi- tioners). Listing philosophical values such as aesthetics (a beautiful and scenic view), tradition (protection of historical artifacts), exis- tentialism (protecting a species for its own sake), symbolic (preserv- ing a wilderness as an example of "nature in balance"), and enhancing the ”perfect" community of ”Man and Nature.“ Including values in the information-gathering process of describing lands and land uses helps establish perspectives for present and future interaction with and man- agement of natural ecosystems. Application of Environmental Information Applying the information gathered for the solution of environmental problems and planning goals represents the analysis and assessment phase of an ecologically based planning methodology. This analysis and 104 assessment phase requires a thorough and sometimes exhaustive organiza- tion of information to be meaningful in each decision-making situation. It is also in this phase of planning that ecological theory is applied co-equally with ideas and requirements of economics, politics, technol- ogy, and social institutions to plan truly balanced natural/cultural ecosystems. Not only is the integration of the various disciplines necessary from a decision-making standpoint, it is also necessary from the point of view of individual citizens - those who are most directly affected by any planning situation. Therefore, a plan must be accept- able as well as meaningful. It is helpful from a conceptual and practical standpoint to iden- tify certain phases of a plan where information should be applied. These areas, listed below, have been identified by McHarg, through his ”ecological determinism" methodology used in Design With Nature (1969); by Holling's adaptive environmental assessment and management approach (1978); and by Andrews (1978), who has developed the following applica- tion framework consisting of three parts: 1. Identification of Constraints Constraints confronting the planning and use of ecosystems can be both natural and institutional as shown in Figure 15. Such constraints present limiting factors which must be accounted for in feasibility studies, site planning, or in the development and application of land use controls. Natural constraints are based on natural laws and proc- esses which, if ignored, may result in death or costly destruction, as in the cases of developments in geologically unstable or flood-prone areas, the irreversible extinction of flora or fauna, or the expensive 105 .Aoom .a «mmmfi .wzwmnz< some mmHanozv manomo mmmxh opz_ nmmm 4