Rapid expansion of coastal aquaculture ponds in Southeast Asia: Patterns, drivers and impacts.

Aquaculture pond is one of the most important land use types and a main income source in coastal zones in Southeast Asia. However, the fast expansion of aquaculture ponds threatens coastal ecosystems - an issue that Sustainable Development Goals (SDGs)14 seeks to address. Investigating expansion patterns is essential for exploring the drivers and understanding its impacts, and thus the focus of the sustainable management of aquaculture. This study aims to assess the spatio-temporal expansion patterns of aquaculture ponds with multitemporal remote sensing images and geographic information system in the coastal zone of Southeast Asia over a 25-year period (1990-2015), to understanding how globalization and economic policies may have contributed to such changes. The results show that, in 2015, total area of coastal aquaculture ponds was about 23,245 km, and 79% of coastal aquaculture ponds distributed within 15 km from the coastline. And the amount has expanded about 2.6 times in the past 25 years. Vietnam has the largest area of aquaculture in 2015 and the highest annual increasing rate, accounting for 40.28% and 298.5 km/y, followed by Indonesia (31.50% and 156.8 km/y), Thailand (10.79% and 64.8 km/y), Myanmar (8.76% and 61.1 km/y). The expansion pattern of aquaculture ponds in the region altered from outlying to edge-expansion from the year of 2000. The main drivers of rapid expansion lie to the intensified local fisher policies as a result of economic globalization. While development of aquaculture has enhanced family income, it has also led to significant reduction of mangrove and coastal water pollution (eutrophication). With the prevailing antagonism between aquaculture expansion and ecosystem conversion, our research call for the local government's attention to sustainable management of aquaculture. This will be the key to reduce food safety risk and simultaneously prevent inevitable damages to coastal ecosystems, as stipulated by SDGs 2 and 14.