In ecology, advancements in technology, theories, and modeling have broadened our abilities to explore and synthesize the patterns, amplitudes, and scales at which species populations, community structures, and species distributions are affected by the environment (climate, habitat). Yet, such understandings remain difficult to similarly synthesize when species are affected by human activities. While the connection between ecosystems and humans has become obvious in the Anthropocene, these connections have yet to become a part of ecological theory. As studies around the globe are increasingly attempting to assess human influence, revised ecological models and theories are needed to advance our understanding of and find solutions for species under pressure. For my PhD dissertation, I worked to enhance our knowledge and predictions on patterns of human-nature relationships by synthesizing and advancing theories and methods in ecology.For my first chapter, I conducted a systematic review of 12,854 species distribution modeling (SDM) articles to assess the current state of methods in modeling human influence (human presence, activities or pressures) on species distributions. I found that over the past 20 years, only 1,429 articles used human predictors in SDMs, representing only 11% of all literature on this popular methodology. The articles collectively studied 58,000 species and used 2,307 unique human predictors. In contrast to environmental predictors, I found no “rule of thumb” for human predictor selection in SDMs. Nearly half the articles projecting to future climates held human predictors constant over time, risking false optimism about the effects of human activities compared to climate change. I highlight considerable gaps in human predictor use for understanding current and future species distributions in the Anthropocene, opening opportunities for new inquiries. SDMs help define protected areas, assess connectivity, and highlight areas for community engagement to prevent human-wildlife conflict, among other purposes. Improving human predictor use in SDMs is paramount for accurately informing and advancing ecology, policy, conservation, and management. I formulate 15 questions for SDM methods, ecological theory, and applications, aiming to push forward a new paradigm for SDMs.In my second chapter, I challenge traditional ecological perspectives to enhance the realism of ecological niche theory in the Anthropocene. Ecological niche theory is a central concept in ecology that traditionally focuses on natural systems. In reality, however, natural systems interact with human systems to form coupled human and natural systems (CHANS). Thus, a critical theoretical link between humans and the ecological niche remains underdeveloped. As human systems interact with species and their surrounding environment, species’ niches are inevitably being affected, so a way to operationalize those effects is sorely needed. To advance theoretical ecology for global sustainability, I reviewed ecological niche theory as it has evolved over the past two centuries. I explored the foundational ideas of seven ecological niche theories—from the metaphorical niche to modern coexistence theory. I present new, more accessible ways of interpreting each theoretical concept’s assumptions, and propose how humans (as individuals, populations, activities, influence, or pressures) can be integrated into various components of each ecological niche theory. I use empirical evidence from CHANS and other empirical research to support my proposed integrations. In total, I fit humans into 18 niche components (roles, interaction types, mechanisms, or factors) that hold to each theory’s assumptions. As the ecological niche is a complex, highly debated, and ever-evolving topic, I do not claim that any specific niche concept is the best fit for human integration. Instead, I show how each theory has its own set of strengths that help elucidate a multitude of complex CHANS relationships and sustainability paradigms. Cumulatively, my ideas create a new direction for ecology worth further exploration: a coupled human and natural niche.In my third chapter, I bring these ideas on the coupled human and natural niche together to form coupled human and natural niche theory (CHANNT). Like its homonym, “chant”, I show that coupling multiple niche theories with CHANS can create a “chorus” of ideas to advance knowledge and theory on humans’ place in the ecological niche to build a sustainable world. I show that based on my previous synthesis, existing niche theories as well as any new, developing niche theories can be adapted for human integration. I describe what “human” implies when humans are integrated into the niche, and show which types of assumptions across niche theories are important for making human integration feasible. I then offer guidelines for selecting among niche theories in future theoretical or empirical research.I close my dissertation with a short synthesis of these chapters. Together, my work forms a steppingstone for building a bridge between theory and practice in an ever-changing world.
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