Vegetation dynamics induced by climate change and human activities: Implications for coastal wetland restoration

Coastal wetlands are valuable ecosystems that have been gravely threatened by climate change and human activities. Understanding vegetation dynamics and relevant driving mechanisms is important for the management and restoration of coastal wetlands. Here, based on Landsat data and field surveys, the spatiotemporal variations in normalized difference vegetation index (NDVI) were analyzed for the Beidagang Wetland Nature Reserve in northern China to understand the vegetation response to climate change during periods with different human impacts (i.e., low-disturbance, high-disturbance, and recovery stages). The results showed that the average growing-season NDVI (NDVI_gs) over the area exhibited a significant decreasing trend from 1984 to 2023 at -0.0025 a^-1 (p < 0.001), even during the recovery stage (2014-2023); however, NDVI_gs across the area revealed varying trends due to the interactive impacts of climate change and human activities. Specifically, NDVI_gs showed significant increasing trends in less human disturbed areas due to rising temperature (T); whereas, this increasing trend was greatly weakened in human disturbed areas. During the recovery stage, the legacy impact of human activities, particularly the excavation of aquaculture ponds in the high-disturbance stage, persistently prohibited vegetation recovery; moreover, the increase in open water area due to ecological water replenishment also contributing to the declining NDVI_gs. By comparison, appropriate restoration measures (e.g., constructing embankments and connecting drainage ditches) aided vegetation recovery during the same stage. This study demonstrates the interactive impacts of climate change and human activities on coastal wetland vegetation dynamics, which provides an important perspective for improving restoration efforts in coastal wetlands.