A review of spatiotemporal evolution and driving mechanisms of small wetlands based on remote sensing

Small wetlands are widely distributed landscape elements that support biodiversity, improve water quality, retain floodwater, regulate local climate, and connect ecological networks, yet their small area and dispersed occurrence make them especially sensitive to hydrological fluctuations and human disturbance. With the rapid development of remote sensing, cloud computing, and intelligent interpretation, their distribution and dynamics can now be observed more accurately and more frequently than before. This review synthesizes research on the information acquisition, spatiotemporal evolution, driving mechanisms, ecological consequences, protection, and restoration of small wetlands. It first compares the principal data sources and monitoring approaches, including aerial photography, medium- and high-resolution satellite imagery, hyperspectral and synthetic aperture radar data, field surveys, citizen-science observations, CubeSat imagery, Google Earth Engine, and machine-learning or deep-learning workflows. High-resolution and multi-source observations improve boundary delineation and the detection of seasonal or short-term changes, whereas differences in spatial and temporal resolution, cloud contamination, processing costs, and insufficient field validation continue to limit consistent long-term monitoring. Landscape metrics, land-use transfer matrices, and centroid-migration analysis remain the main methods for identifying changes in wetland area, number, fragmentation, connectivity, and spatial redistribution, but they need to be combined with higher-frequency observations and process-based indicators to capture internal heterogeneity and functional change. The evolution of small wetlands results from the coupled effects of natural and anthropogenic drivers. Climate-related water-heat balance, precipitation seasonality, evapotranspiration, relative elevation, slope, and local hydrological conditions establish the environmental background, while agricultural expansion, urban and infrastructure development, drainage, groundwater extraction, and water-resource regulation often accelerate habitat loss and hydrological disconnection. These drivers interact through feedbacks, thresholds, time lags, and spatial overlap; consequently, climate stress may amplify water demand, topography may concentrate both wetland occurrence and human disturbance, and changes in temperature and precipitation may jointly alter water availability and vegetation processes. Degradation can therefore propagate beyond individual patches, reducing habitat connectivity and biodiversity, weakening nutrient removal and flood retention, changing carbon storage, and destabilizing regional wetland networks. Existing policies and restoration practices show that small wetlands require fine-scale, site-specific interventions, including hydrological reconnection, fine-scale topographic reconstruction, substrate and vegetation optimization, targeted habitat creation, smart monitoring, adaptive management, and community co-governance. Future research should develop unified identification and assessment standards, integrate remote sensing with field and sensor observations, construct wetland-watershed coupling models, quantify dynamic ecological thresholds under climate change, and establish long-term governance and financing mechanisms. These advances will improve monitoring accuracy, clarify cross-scale mechanisms, and support the sustainable protection and functional maintenance of small wetlands.