Ecosystem Service Function Value Research After The Operation Of The Three Gorges Reservoir In The Dongting Lake Wetland

In order to reveal the variation trends of the different ecosystem service functions and values in Dongting lake wetland before and after the impoundment of the Three Gorges Reservoir, to promote the wetland ecosystem service function and work out the strategic decisions on the protection and exploitation of the wetland resources, taking the Dongting lake wetland as the research object, basing on the field investigation and determination, and using relevant data and theory and method on the ecology and resource economics, the author carries on the preliminary analysis and research on the changes of the ecosystem service functions in Dongting lake wetland, estimates and compares ecological system mainly service function values of the Dongting lake wetland before and after the impoundment of the Three Gorges Reservoir.In recent years, especially after the impoundment of the Three Gorges Reservoir, the landscape form and structure have changed in the Dongting lake wetland. The impoundment operation of the Three Gorges Reservoir, changing the water and sediment process in the Yangtze River and the Dongting lake, has caused the changes of lake area, volume and flooded days of the lake beach etc. in the Dongting lake, therefore the wetland ecosystem service functions generate some responses such as the lake area reducing, the wetland shrinking and landscape fragmentation. The driving factors, leading to the service function change in the Dongting lake wetland, include climate changes, lake basin settlement and sediment deposition, water conservancy project operation, reclaiming farmland from lakes and restoring it to them, and other social economic factors, etc.In the research, some estimate methods are used, including market value method, carbon tax and afforestation cost method, shadow engineering method, the travel cost method, etc. After the impoundment of the Three Gorges Reservoir since2003, the changes of the ecosystem service functions in the Dongting lake wetland are gradual, and need to continue with time and become clear-cut little by little, so using the2008s data to estimate service function value, and the comparative analysis will be achieved with the result using the data in1996, the corresponding period before water storage.The research shows that:(1)The total service function values of the wetland ecosystem, increase by small extent from156.69×108yuan in1996to177.11×108yuan in2008, but flood-adjusting, leisure travel, traffic transportation value change significantly, which reflect that the wetland ecosystem service function without obvious improvement, but parts of the service functions are weaken or enhanced with the changes of natural, social and economic conditions.(2) The service function value form of the wetland ecosystem changes greatly. If putting the main service function value of the wetland ecological system in order in1996, four of them are ranked in the front, including flood-adjusting, water-supplying, atmosphere-adjusting and education and scientific research. Their proportions reach82.70%of the total value and the flood-adjusting value, the highest of them, is about53.18%, which indicates that the Dongting lake is a typical throughput lake. In2008, the proportions of the main service function value, including leisure travel, traffic shipping, atmosphere-adjusting and water-supplying value, reach82.17%of the total value, and the leisure travel value, ranking the first place, is about52.04%, so that wetland ecotourism and transportation are driven vigorously by the social economy development.(3) Among the wetland ecosystem service function values, the core values related direct to water less significantly, from110.85×108yuan in1996reduced to27.47X108yuan in2008by75.22%, it shows that the service function values of the water’s carrying reduced with the decrease of the water volume in Dongting lake.Overall, in the Dongting lake wetland, the proportion of direct value on material products production and supply increases slightly, from18.07%in1996to23.42%in2008, but it is still a small portion of the total value of the service function. On the contrary, in the regulation and maintenance of ecological environment and on the culture and society aspect, the indirect value has always maintained in about80%of the total value. This suggests that the wetland doesn’t only play significant in direct economic benefit but also plays a bigger role in the ecological and social benefit, so people must change the traditional ideas that the wetland ecosystem value lies only in material products production and supply, and should regard the wetland ecological system as a dynamic and vulnerable composite system, which connecting with a variety of benefits, and take measures to maintain and control the wetland ecosystem service functions.