Compound extreme inundation risk of coastal wetlands caused by climate change and anthropogenic activities in the Yellow River Delta, China

The coastal wetlands of the Yellow River Delta (YRD) in China are crucial for their valuable resources, environmental significance, and economic contributions. However, these wetlands are also vulnerable to the dual threats of climate change and human disturbances. Despite substantial attention to the historical shifts in YRD's coastal wetlands, uncertainties remain regarding their future trajectory in the face of compounded risks from climate change and anthropogenic activities. Based on a range of remote sensing data sources, this study undertakes a comprehensive investigation into the evolution of YRD's coastal wetlands between 2000 and 2020. Subsequently, the potential fate of coastal wetlands is thoroughly analyzed through the Land Use/Cover Change (LUCC) simulation using System Dynamic-Future Land Use Simulation (SD-FLUS) model and the extreme water levels projection integrated future sea-level rise, storm surge, and astronomical high tide in 2030, 2050, and 2100 under scenarios of SSP1-2.6, SSP2-4.5, and SSP5-8.5. Results reveal that YRD's coastal wetlands underwent a marked reduction, shrinking by 1688.72 km2 from 2000 to 2020. This decline was mostly attributed to the substantial expansion in the areas of artificial wetlands (increasing by 823.78 km2), construction land (increasing by 767.71 km2), and shallow water (increasing by 274.58 km2). Looking ahead to 2030–2100, the fate of coastal wetlands appears to diverge based on different scenarios. Under the SSP1-2.6 scenario, the area of coastal wetland is projected to experience considerable growth. In contrast, the SSP5-8.5 scenario anticipates a notable decrease in coastal wetlands. Relative to the inundated area suffered from the current extreme water levels, the study projects a decrease of 6.8%–10.6% in submerged coastal wetlands by 2030 and 9.4%–18.2% by 2050 across all scenarios. In 2100, these percentages are projected to decrease by 0.4% (SSP2-4.5) and 27.1% (SSP5-8.5), but increase by 35.7% (SSP1-2.6). Results suggest that coastal wetlands in the YRD will face a serious compound risk from climate change and intensified human activities in the future, with climate change being the more important factor. More efficient and forward-looking measures must be implemented to prioritize the conservation and management of coastal wetland ecosystems to address the challenges, especially those posed by climate change.