Climate change and human activity are reshaping coastal systems, yet global impacts on water clarity remain poorly quantified. Here we leverage remote sensing big data to develop a global model of coastal suspended particulate matter across continental coastal waters, and show that global coastal suspended particulate matter concentrations have declined by 0.28 mg L−1 annually since 2000, driven by natural processes and human intervention. Furthermore, the spatial extent of areas exceeding the 2000 global mean threshold has shifted landward at an average rate of 0.014 km year−1. Long-term sea level rise and diminished sediment delivery—driven by urbanization and expanding impervious surfaces—were the dominant drivers of this global clarification trend. In contrast, moderate increases in wave height and salinity enhanced resuspension, while larger shifts promoted suspended particulate matter settling. These findings provide a basis for tracking suspended particulate matter trends and guiding sustainable coastal management under urban and climatic pressures. Global coastal waters have experienced a long-term decline in suspended particulate matter, as a result of rising sea surface height, urbanization reducing land-to-sea transport, and nonlinear salinity and wave effects, according to an analysis of remote sensing data.
Yan et al. (Thu,) studied this question.