Abstract: This dissertation examines the interaction between environment and society on a mid-sized oceanic island that has experienced repeated cycles of settlement over a 1,600-year period. It seeks to understand how environmental degradation is caused by economic and social activity and how it in turn influences and shapes them. It looks at the central role played by variation in the availability of water and the control of water resources in the history of Molokai, and by extension, the other Hawaiian Islands. Chapter One looks at the impacts of the arrival of the Polynesians in Hawaii, with detailed comparisons with the overall history of Polynesian colonization of the island Pacific. Chapter Two lists the consequences of the arrival of Euro-Americans and others following 1778, and situates Hawaii's experience in the broad context of politics and trade in the Pacific. Chapter Three examines the first half-century after Contact and establishes a baseline for looking at ecosystem change in Molokai, principally through a detailed survey of plant species and distribution. Chapter Four looks at the historical roots of the land tenure reform enacted in the 1850s and charts the subsequent distribution of land in the market economy by charting property sales by size, location, economic use, and the social and economic status of buyers, sellers, lessors and lessees. Chapters Five and Six examine efforts to bring native Hawaiian people to Molokai for medical or economic remediation or 'rehabilitation,' and efforts to bring economic growth, in the form of plantation agriculture, to the island. The principal finding of this study is the intricate role that environmental variation plays in shaping human social and economic structures over time, particularly how human-caused environmental degradation rebounds in powerful ways on those structures. It finds surprising and suggestive parallels between two, widely-separated experiences of colonization, involving very different societies---leading to hypotheses about the roles of water and ecological marginality in history. Additionally, it rewrites the history of the economic marginalization of the Hawaiian people following the land reform process by carefully charting the property market in Molokai.