Ca Mau Peninsula, which lies at the extreme southern tip of the Mekong Delta in Vietnam, has experienced rapid environmental and socio-economic change, particularly since the 1990s when the doi moi (renovation) policy introduced an agenda of agriculture-led growth. The peninsula lies entirely within the zone of saline intrusion, which previously extended up to 50 km inland during the dry season, thus limiting traditional rice production to only one rainy-season crop. To promote the intensification of rice production, a plan was devised to build a series of coastal embankments and tidal sluices to control salinity intrusion. The protected area lying within Bac Lieu Province, which covers approximately 160,000 ha, is the focus for this discussion.Data collected on environmental and socio-economic conditions within the protected area during the study period reflect a complex spatial and temporal pattern of impacts. However, the pattern can be seen as a transition between a freshwater environment supporting rice production and a brackish environment supporting shrimp production. The impacts of these changes in environmental management strategies are discussed. A strategy favouring rice production depends on the operation of sluices in such a way that a freshwater environment is maintained. Intensification of the rice production system involves relatively low risk for farmers, but results in relatively low income. On the other hand, shrimp production requires that a brackish environment be maintained and is seen to offer the potential for increased wealth, but at high levels of risk and indebtedness. Currently available evidence of impact cannot easily be extrapolated to assess long-term sustainability.