This dissertation draws on multiple methods, including archival research, household survey data, and interviews, to examine the forces, actors, and relations that have transformed the Mekong Delta into the foremost hub of rice production in Vietnam, as well as the ways in which the future of rice production -- and with it Vietnam's broader food security -- is being challenged by both climate change and by the shifting livelihoods of farmers themselves. The first paper traces how the social and environmental landscape of the Mekong Delta was transformed over the course of the 20th century through the construction of water management infrastructures such as dikes, dams, and sluice gates, with the overall aim of increasing rice production. The second paper uses survey data from two areas --- one engaged in rice agriculture and the other shrimp aquaculture --- to examine the divergent dynamics of accumulation and dispossession within these two production systems. The final paper focuses on conflicts which have emerged between shrimp farmers and the state around infrastructure projects designed to ensure national food security and adapt to global climate change. As the state has built up new barriers to protect the rice fields of the Mekong, these efforts have encountered resistance from shrimp farmers themselves, who have engaged in acts of "counter-accumulation," as by subverting government infrastructure and covertly rebuilding the productive forces in shrimp aquaculture.