The Lower Mekong region (LMR) is experiencing rapid social-ecological changes due to infrastructure development and climate change. The construction of dams along the Mekong River and its tributaries has triggered significant biophysical alterations, including changes in water flow, nutrient cycling, and sediment exchange. These changes have profound implications for the 86 percent of the Lower Mekong Basin (LMB) population who rely on the river for their livelihoods, primarily in agriculture and fisheries. Besides, the region faces an increasing frequency of extreme climate events, particularly droughts and floods. These combined pressures have heightened the vulnerability of resource-dependent communities, further exacerbated by unjust resource governance that often marginalizes them. This dissertation explores the multifaceted challenges faced by resource-dependent communities in the LMR, with a particular focus on their responses to the uncertainties driven by dams, climate change, and resource shifts. The study hypothesizes that most noticeable changes are occurring at the household level, influenced by their perceptions of climate risk and their capacity to access and utilize vital livelihood resources. These shifts exert pressures on land and watershed ecosystems, raising concerns over the sustainability of critical ecosystem services. Adopting a mixed-method approach, this research unfolds across three chapters: Chapter 1 assesses the impacts of dams on various livelihood resources in downstream farming communities at different distances from affected rivers, using unbalanced panel data analysis. The findings reveal a decrease in natural and financial resource accessibility, alongside a positive effect on physical resource accessibility post-dam construction. Communities closer to dams (<10 km) experience more pronounced negative effects on natural resources, while financial resource access improves for those within 20 km. Physical resources show spatial improvements, primarily within 10 km. Although no temporal effects are observed for social resources, spatial effects indicate reduced accessibility near dams. However, communities nearby irrigation dam experience increased social resource access post-dam construction. These findings highlight the spatial and temporal variations in resource impacts, emphasizing key areas for improving Environmental Impact Assessments (EIAs) and adaptation strategies to better support downstream ecosystems and communities. Chapter 2 delves into drought risk perceptions among households in irrigated and flood-pulse communities, exploring the factors explaining variations in risk perception at both household and community levels. Utilizing a mixed-effects model alongside qualitative information from interviews and observations, this chapter reveals the significance of psychological and socio-economic factors, including households' knowledge of drought, perceived ability, affiliation with various organizations, and wealth condition, shaping risk perception. These findings suggest the development of context-tailored risk communication and management strategies, enhancing the adaptive capacity of vulnerable communities. Chapter 3 examines the role of perceived peer effect and formal networks in shaping farmers' adaptive behaviors using influence network modeling. The findings suggest the need for leveraging both formal and informal networks, increasing knowledge about drought and improving economic conditions to build farmers’ capacity to navigate climate-related challenges and adopt practices that ensure the sustainability of resource-dependent farming communities in Cambodia and beyond.
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