Wetland ecosystem health assessment through integrating remote sensing and inventory data with an assessment model for the Hangzhou Bay, China.

Due to rapid urbanization, industrialization and population growth, wetland area in China has shrunk rapidly and many wetland ecosystems have been reported to degrade during recent decades. Wetland health assessment could raise the public awareness of the wetland condition and guide policy makers to make reasonable and sustainable policies or strategies to protect and restore wetland ecosystems. This study assessed the health levels of wetland ecosystem at the Hangzhou Bay, China using the pressure-state-response (PSR) model through synthesizing remote sensing and statistical data. Ten ecological and social-economic indicators were selected to build the wetland health assessment system. Weights of these indicators and PSR model components as well as the normalized wetland health score were assigned and calculated based on the analytic hierarchy process (AHP) method. We analyzed the spatio-temporal changes in wetland ecosystem health status during the past 20years (1990-2010) from the perspectives of ecosystem pressure, state and response. The results showed that the overall wetland health score was in a fair health level, but displayed large spatial variability in 2010. The wetland health score declined from good health level to fair health level from 1990 to 2000, then restored slightly from 2000 to 2010. Overall, wetland health levels showed a decline from 1990 to 2010 for most administrative units. The temporal change patterns in wetland ecosystem health varied significantly among administrative units. Our results could help to clarify the administrative responsibilities and obligations and provide scientific guides not only for wetland protection but also for restoration and city development planning at the Hangzhou Bay area.