Dynamic identification and health assessment of wetlands in the middle reaches of the Yangtze River basin under changing environment

Recently, the wetland in the middle reaches of the Yangtze River Basin (MYRB) has been impacted by the human activities and climate change, thereby restricting sustainable development. In order to know the distribution and health of wetlands in the MYRB and provide scientific decision support for environmental protection. This study applied the classification and regression tree (CART) method to extract the wetland areas in the MYRB using remote sensing images and constructed a wetland health index system to quantitatively evaluate the health status of wetlands during 2000-2019 based on the pressure-state-response (PSR) model. The main conclusions are as follows: (1) using the CART method, the classification extraction accuracies of wetlands in 2000, 2006, 2009 and 2015 were higher than 85%, and that of 2019 was 93%; (2) wetland area shrinkage was the main change in the wetland pattern in the MYRB, wherein the landscape diversity index and landscape shape index (LSI) showed decreasing trends during 2000-2009. Then, after 2010, the wetland area has increased, but the wetland area in 2019 was 2045 km(2) less than that in 2000; and (3) the wetland health experienced a downward trend during 2000-2010 before improving from 2010 to 2019. However, many regions in the Dongting Lake Basin (DLB) remained at sub-health and pathological wetland levels. Therefore, it is necessary to pay attention to the health level of the wetland system in the MYRB especially the DLB to achieve future sustainable development.