Assessment on the vulnerability of different ecosystems to extreme rainfalls in the middle and lower reaches of Yangtze River

The vulnerability of major ecosystems to extreme rainfalls was investigated across the middle and lower reaches of the Yangtze River, China, during 1961–2000, by using an improved process-based model (Carbon Exchange between Vegetation, Soil, and Atmosphere, CEVSA). The simulated Net Primary Productivity (NPP) was selected as the indicator to identify impacts of extreme rainfalls on ecosystem functioning. The changing characteristics of the NPP in the five extreme rainfall years are employed to represent the sensitivity and adaptive capacity of ecosystems to extreme rainfalls events. The vulnerability of major ecosystems to extreme rainfalls was then examined by comparing with the averaged status during 1961–1990. Our results suggest that the relatively lower and higher vulnerable agro-ecosystems were mainly distributed in the central and northwest of the study area. The proportions of high and very high vulnerable agro-ecosystems to rainfall were about 19 and 5 % of the total area. For the forest ecosystem, the lower vulnerability mainly occurred in the south, while the higher vulnerability happened in the north of the study area which had taken about 15 % of the high vulnerable level and about 2 % of the very high vulnerable level. The extreme rainfalls enhanced the vulnerability both of agro-ecosystems and forest ecosystems. The vulnerability of agro-ecosystems to droughts was higher than that of forest ecosystems, while the vulnerability of forest ecosystems to floods was higher than that of agro-ecosystems. Our study demonstrates that both human-dominated (e.g., agro-ecosystem) and natural ecosystems are vulnerable to extreme climatic events. Future warming climate might further worsen the ecosystem sustainability in this area if no mitigation and adaptation measures are adopted.