Research On Assessment Of Ecosystem Services In The Three Gorges Reservoir Area

The unique geographical conditions and socio-economic characteristics of the Three Gorges Reservoir Area(TGRA)make the prominent contradiction between the population,resources and ecological environment.Its ecological and environmental processes is very typical and representative in reflecting the coordinated symbiosis between economic development and natural ecological environment in basin scale.In the context of ecological civilization construction and the development strategy of Yangtze River Economic Belt,promoting assessment of ecosystem services(ESs)in basin scale will provide important implications in term of optimizing basin eco-environmental management and constructing a sustainable pattern of natural-social sustainable development.In this paper,based on characteristics and content of basin ecosystem services,a theoretical framework of ecosystem services assessment and grid evaluation technology in basin scale was proposed,and then was applied in the TGRA.The main research contents and findings are as follows:(1)In view of the connotation and characteristics of basin-scale ESs and the perspective of human demand for ESs,the classification system of basin-scale ESs is proposed from three aspects of water resources,water environment and water ecology.combined with watersheds.Combined with the basin water environment model and the ES model,a scientific and effective quantitative evaluation framework was constructed for basin-scale ESs.(2)Taking the spatial heterogeneity of the basin ecosystem into account,the high-precision Digital Elevation Model(DEM)was used to construct the grid unit of the study area.Together with MPI computing technology,the block parallel computing technology based on30 m refined grids is proposed,for accurately identifying the spatial variations of the evaluation elements and their responses to the natural conditions of the basin ecosystem.(3)Based on the spatial difference of natural conditions and the imbalance of social and economic development in the TGRA,water resources supply,basin water environmental capacity,soil retention and water conservation are selected as the main indicators to evaluate ESs and their value in the TGRA.The results showed that the total water consumption in the TGRA was 6.37 billion m~3 in 2015.The regions with higher water consumption are concentrated in the main urban area of Chongqing and its surrounding areas as well as Wanzhou District,where social and economic development degree is relatively higher.Basin water environmental capacity of the TGRA is still surplus,which can support the TGRA's development demand to a certain extent,but there are also some areas where the water environmental capacity is negative,and the basin water environmental capacity of total nitrogen(TN)and total phosphorus(TP)exceeds the standard seriously.Soil retention service in the TGRA is 10.25 billion tons,and its distribution is higher in the east and lower in the west.Water conservation service in the TGRA is 43.14 billion m~3,and its spatial distribution shows a pattern of higher in the middle and lower on both sides.(4)The total ecosystem services value in the TGRA was 509.773 billion yuan in 2015,which was mainly based on the indirect economic value by 63.1%.The direct ES value in the TGRA was 66.89 billion yuan in 2015,and the value of each ES from high to low is water conservation>water supply>soil retention>basin water environmental capacity.Water resources supply service is the dominant ES in regions with higher social and economic development degree,while the key ecological functional areas are mostly dominated by soil retention and water conservation service.(5)Water resources supply service has a strong correlation with urbanization rate,population density and economic density.Population growth and river basin economic development have a high degree of demand and dependence on water resources.The effect of urbanization rate on water environmental capacity is more significant than population density and economic density.Soil retention and water conservation are affected by many factors,such as topographic conditions,climatic conditions,land use/land cover and socio-economic conditions.Among them,topographic conditions,land use/land cover and socio-economic factors have greater impact on soil retention,while climatic conditions,land use/land cover and socio-economic factors have greater impact on water conservation.(6)There are some correlations between the four ESs in the TGRA.There is a weak synergy between water supply and basin water environment capacity,and a weak trade-off relationship with soil retention or water conservation.There is a synergistic relationship between basin water environmental capacity,soil retention and water conservation.The TGRA should adhere to the strategic orientation of ecological priority and green development,make full use of its resources advantages,implement discrepant developing strategy,to guide the socio-economic development and industrial structure optimization with the carrying capacity of basin resources and environment,correctly handle the relationship between economic development and ecological protection,to realize the sustainable development of both socio-economy and ecological environment.