Mangrove forests and aquaculture in the Mekong river delta

The mangrove area in Viet Nam is dramatically decreasing in the last decades. Since 1995, mangrove forests in south Viet Nam are allotted and contracted to households for protection, management and logging. Under this policy, households are allowed to convert 20–40% of the allotted forests into other uses, mainly shrimp farming. Most households develop mixed shrimp-mangrove farming systems, in which shrimp ponds are mixed with mangrove forest. With the poor enforcement of the forest assignment policy, however, the mangrove forest is over-extracted as farmers are converting more than the allowed level for larger water surface areas for shrimp farming and higher returns. In this study, we examine the impacts of mangrove coverage of mixed mangrove-shrimp ponds using the production and profit functions. Our analyses show that mangrove density has no impacts on shrimp farming. However, mangrove coverage affects productivity and profit of shrimp farming. The optimal mangrove coverage for shrimp farming is found to be approximately 60%. This implies that maintaining the level of mangrove coverage of 60% does not only to comply with the policy, but also bring about the highest level of output and profit for shrimp farmers.