Tracking annual changes of coastal aquaculture ponds in China during 1986–2021

Abstract

The rapid expansion of coastal aquaculture ponds has made outstanding contributions to global food security and economic development in coastal areas, but this expansion inevitably has a significant impact on coastal ecosystems. Strengthening the spatiotemporal monitoring of aquaculture ponds is crucial for optimizing coastal land use and efficiently managing aquaculture ponds. However, aquaculture pond data on national scale and interannual variability are lacking. Here, we utilized Landsat times series images from 1986 to 2021 to generate annual maps of aquaculture ponds in China's coastal areas and investigated its spatiotemporal characteristics. We find that the overall accuracy of our aquaculture ponds classification was over 90% each year. Aquaculture ponds were concentrated in Bohai Bay, the Jiangsu Coastal Plain, and the Pearl River Delta in China's coastal areas. The time series of aquaculture ponds change could be divided into three stages: rapid growth (1986–2000), stable growth (2001–2016), and a slow decline (2017–2021). The spatial evolution of aquaculture ponds was characterized by (1) continuous seaward expansion, (2) continuous inland and seaward expansion, (3) continuous inland expansion, (4) continuous expansion and then shrinkage, and (5) rapid shrinkage. Moreover, the main aquaculture ponds classification errors were salt pans, reservoirs, abandoned ponds, port facilities, lakes, and pit ponds. Our study demonstrated a new method for applying satellite remote sensing for coastal ecosystem management, and our maps and findings can be used to optimize the development and sustainability of coastal aquaculture ponds.