Partly as an adaptation process to salinity intrusion, intensive saline (commercial/family shrimp farming) and extensive brackish water (polycultures and rice-shrimp farms) aquacultures are nowadays one of the most dynamically growing sectors in Vietnam and increasingly co-occur within formerly rice dominated areas (Joffre & Bosma, 2009). With an annual percentage growth rate of 21% (FAO, 2008), Vietnam became one of the largest fishery export countries in the world (FAOSTAT, 2013), whereby the overwhelming majority of the farmed shrimp (81%) and farmed fish (89%) are produced in the Mekong and Red River deltas (GSO, 2010). However, this type of farming is risky for farmers due to high investment requirements and its high vulnerability to diseases, market price fluctuations, and varying salinity levels. Furthermore, such land use systems are often characterized by a pronounced and sometimes heavy use of agrochemicals. Furthermore, there is a risk of cross contaminations with of agrochemicals in areas were different land use systems are closely adjacent.
Beside vulnerabilities related to land use changes, some farmers maintain rice production but sell their topsoil to extract clay for brick production (see figure 2 below) in order to generate short term income and, thus, risking long term productivity losses of their soils (Guong et al., 2011; Vietnamnews, 2013).