Utilizing the cloud-based satellite platform to explore the dynamics of coastal aquaculture ponds from 1986 to 2020 in Shandong Province, China.

Coastal pond aqua farming is critical in aquaculture and significantly contributes to the seafood supply. Meanwhile, the development of aquaculture ponds also threatens vulnerable wetland resources and coastal ecosystems. Accurate statistics regarding the distribution and variability of coastal pond aquaculture are crucial for balancing the sustainable development of coastal aquaculture and preserving the coastal environment and ecosystems. Satellite imagery offers a valuable tool for detecting spatial-temporal information related to these coastal ponds. Furthermore, integrating multiple remote sensing images to acquire comprehensive spatial information about the coastal ponds remains challenging. This study utilized a decision-tree classifier applied to Landsat data to detect the spatial distribution of coastal ponds in Shandong Province from 1986 to 2020, with data analyzed at five-year intervals, primarily based on the Google Earth Engine cloud platform. A pond map in 2020, extracted from Sentinel-2 imagery, was used as a reference map and combined with the results from Landsat data to explore the landscape changes of coastal ponds. The results indicated that Shandong Province's coastal pond area underwent significant expansion before 1990, followed by slower growth from 1990 to 2010 and eventual shrinkage after 2010. Specifically, the pond area expanded from 428.38 km in 1986 to a peak of 2149.51 km in 2010 before contracting to 2012.39 km in 2020. The region near Bohai Bay emerged as the epicenter of Shandong's coastal aquaculture, encompassing 62 % of the total pond area in 2020. The government policies previously promoted the expansion of coastal pond farming but shifted to curbing the uncontrolled development of aquaculture ponds.