This research examines the transitions in rural livelihoods across the ecological gradient of Eastern Indonesia, from upland forests to coastal areas. Over the last 80 years, rural communities have shifted from isolated, subsistence-based systems—relying on swidden agriculture, hunting, and forest product gathering—toward increasingly diversified and market-oriented livelihoods. Through qualitative and quantitative fieldwork, historical reconstruction, and site-specific interviews, the study uncovers how environmental changes, infrastructure development, and shifting socio-economic contexts have shaped livelihood adaptation. In mountain areas, traditional farming persists alongside new strategies like livestock raising and wage labor, while coastal communities increasingly engage in sea foraging, coconut gathering, weaving, and fishing-related trade. The research distinguishes between “progressive diversification”—driven by improved access to markets, education, and infrastructure—and “distress diversification,” a response to environmental degradation or economic vulnerability. For example, low-risk, low-entry-barrier activities such as sea foraging during full moon periods continue to serve as fallback strategies for households with limited options. The study underscores the critical role of ecological and resource diversity, particularly in coastal zones, in supporting livelihood stability. By documenting these transitions, the research offers insights into how rural households build resilience amid socio-ecological changes. The findings are intended to inform context-specific rural development strategies that recognize the geographic, environmental, and cultural diversity within Eastern Indonesia’s mountain-to-sea continuum.