Assessment On The Land Eco-Risk Of Tuojiang River Basin Based On Its Ecological Service Value

Ecosystems provide resources for human survival and development,and ecosystem services are conditions for human survival and development.The service function of ecosystems is directly affected by changes in land use.The Tuojiang River Basin is a relatively fragile area in the central Sichuan Basin.In recent years,the rapid development of social economy,accelerated urbanization,and frequent changes in land use structure have affected the ability of ecosystems to provide services,leading to deterioration of ecological environment and increased ecological risks.The research on land ecological risk assessment based on ecological service value is of great significance to the sustainable development of the ecological environment in the Tuojiang River Basin.In order to reveal the spatial and temporal differentiation of land ecological risk in the Tuojiang River Basin based on the value of ecological services,this paper took the Tuojiang River Basin as the research object,using software such as ArcGIS,GeoDa,GS+and Conefor Sensinode,based on the four remote sensing data of landuse in 2000,2005,2010 and 2015,analyzed of land use change,calculated the ecological service value,improved the calculation method of ecological risk,thus building the land ecological risk evaluation system based on ecosystem service value change.Then,the ecological risk community and administrative unit of the basin were superimposed,and the spatial autocorrelation analysis method and geostatistical analysis method were used to explore the temporal and spatial variation of land ecological risk in the Tuojiang River Basin of the rapid urbanization area,and the countermeasures for reducing the land ecological risk in the Tuojiang River Basin were proposed.The main conclusions are as follows:(1)The land use structure had changed significantly in the Tuojiang River Basin from 2000 to 2015:the proportions of cultivated land,forest land,grassland,water area,construction land and unused land in 2000 were:79.65%,15.28%,1.43%,1.53%,2.09%,0.01%.Respectively in 2015,the proportion of arable land,forest land,grassland,water area,construction land and unused land had became:79.07%,13.48%, 1.48%,1.62%,4.11%and 0.23%.The cultivated land had been the dominant land in the Tuojiang River Basin during the research period,but the area had generally decreased,reducing by 150.20km~2;the forest land had decreased,but the construction land area had been increasing,and the water area and grassland area had increased less.During the study period,the dynamic change of land use was high,and the change speed of construction land and forest land area was fast.The increase of construction land was corresponding to the decrease of forest land and cultivated land area,indicating that the increase of construction land was at the cost of the reduction of forest land and cultivated land area.The changes in water use,grassland,and unused land area were not significant.The change in land use area was mainly driven by economic development and industrial structure,and was affected by human activities such as returning farmland to forests and rural tourism development.(2)During the study,the total value of ecological services in the Tuojiang River Basin increased firstly and then decreased.The total value of ecological services in the Tuojiang River Basin in 2000,2005,2010 and 2015 were 263.648×10~8 yuan,392.926×10~8 yuan,389.549×10~8yuan and 387.791×10~8 yuan respectively.From 2000 to2015,the net value of ecological services increased by 124.143×10~8 yuan,an increase of 47.086%.The contribution of land use types to the total value of ecological services was quite different.Forest land and cultivated land contributed the most to the total value of ecological services;the contribution of waters decreased during the study period,which was related to the reduction of water area;the contribution of construction land to the value of ecological services is negative.The ecological service value of the northern and western regions of Tuojiang River Basin was high,and the value of ecological services in the eastern part of the basin was low.The results based on the county were similar to those based on the grid scale.The main factors affecting the contribution of localities to the total value of ecological services were the ecological service value coefficient of each category and the area of each type.(3)The spatial distribution pattern of ecological risk in the Tuojiang River Basin changed significantly from 2005 to 2015.The ecological risk in the north was higher than that in the south.The high ecological risk was mainly distributed in Longquanyi,Pengzhou,Guanghan,Shifang,Mianzhu,etc.in the northern part of Tuojiang River Basin;low ecological service value was concentrated in Shizhong District,Longchang,Luxian and so on in the south of the basin.The overall level of ecological risk was mainly from the lower ecological risk in the initial stage of the study period to the middle ecological risk in the middle stage.The changes in ecological risk area of Tuojiang River Basin were mainly the increase of the area of medium and high ecological risk areas and the decrease of the area of lower ecological risk areas.The medium ecological risk had increased by 5531.27km~2,and the high ecological risk area had increased by 775.46km~2,and the magnitude were 67.25%and 40.89%;the lower ecological risk area decreased by 6219.38km~2.The ecological risk of the Tuojiang River Basin had a tendency to increase with the increase of slope and elevation.The vegetation with large slope and high altitude was sparse and ecologically fragile.In addition,due to the development of economic technology,human activities were disturbing the ecological environment,and the land landscape changed frequently and the ecological risks increased.The ecological risk level transfer was mainly based on high-to-low-level ecological risk transfer,and the total area from high-level to low-level ecological risk was 3838.12 km~2.It showed that the ecological risk situation of the Tuojiang River Basin was severe.(4)According to the land use change,the distribution of ecological service value and the spatial and temporal differentiation of ecological risk in Tuojiang River Basin,the whole area of the Tuojiang River Basin was divided into the ecological risk need to be key controlled area,the ecological risk need to be strictly controlled area and the ecological risk need to be general controlled area.In the actual situation of the region,the district measures were proposed to reduce the ecological risk,and then conducted regional integration on the basis of this to jointly manage ecological problems and share governance,thus improving land use efficiency,improving land use pattern,reducing ecological risks,promoting ecological sustainable development of Tuojiang River Basin.