Evaluation of the combined threat from sea-level rise and sedimentation reduction to the coastal wetlands in the Yangtze Estuary, China

In recent decades, the prospect of climate change, in particular sea level rise (SLR) and its impacts on low-lying coastal areas has generated worldwide attention. The coastal wetlands located in the Yangtze Estuary, with their low elevation and decreasing sediment loading, are susceptible to both SLR and anthropogenic activities. Taking the Chongming Dongtan wetlands as a study area, two scenarios of SLR were evaluated: the present trend (1980-2010) of SLR 2.6mm/yr (PSLR) and the IPCC A₁F₁ scenario of 5.9mm/yr (HSLR). In addition, two scenarios of sedimentation rate were adopted for the Yangtze Estuary: the current sedimentation rate (CSR) and a reduced sedimentation rate of half of the present rate (1/2CSR). The combined effects of SLR and sedimentation reduction were evaluated by projection of the combinations of these phenomena for 2025, 2050 and 2100, using a Sea Level Affecting Marshes Model (SLAMM). The results showed that the combined effects of sea-level rise, reduced sedimentation and land subsidence could result in a considerable decrease in or even complete loss of the coastal wetland habitat in the Chongming Dongtan nature reserve, particularly under the medium-term (2050) and long-term (2100) scenarios. Without proper mitigation measures, the potential decrease in and loss of habitats and ecosystem services is inevitable. Such mitigation measures should be considered in the future for securing the coastal wetland ecosystems, which include the management of sedimentation, the rehabilitation and re-creation of wetland habitat and the control and limitation of reclamation.