Monitoring Spatiotemporal Dynamics, Drivers, and Ecosystem Service Values of Small and Micro Wetlands in Anhui, China (1990–2020) Based on Multi-Temporal Landsat Data

Comprehending the spatiotemporal dynamics, spatial heterogeneity, and pattern-process relationships of small and micro wetlands (SMWs) holds paramount significance for their conservation, restoration, and sustainable management. We integrated Landsat imagery, land-use, topographic, climatic, socioeconomic, and statistical data for 1990–2020 in Anhui Province. Random forest classification, kernel density estimation, standard deviation ellipses, centroid migration, landscape metrics, land-use transition analysis, ecosystem service value (ESV) assessment, and Geodetector were used to characterize SMW change. Total SMW area increased from 53,843.67 ha in 1990 to 71,637.39 ha in 2020, while patch number increased from 104,011 to 125,971; patches smaller than 3 hm2 remained dominant. High-density areas were concentrated in the Jianghuai Plain, Yangtze River plain, Chaohu Lake region, and agricultural drainage networks, with a persistent northeast–southwest distribution orientation. Land-use transitions were dominated by exchanges among cropland, water bodies, and SMWs. At constant 2020 grain prices, total ESV increased from approximately CNY 3.668 billion in 1990 to CNY 6.840 billion in 2020, with hydrological regulation remaining among the largest service components. Geodetector results showed temporally varying single-factor spatial associations, while interaction patterns suggested potential joint spatial associations among natural and anthropogenic factors. These results support spatially targeted SMW conservation and management in Anhui Province.