| Land is the result of human activities in the past and present.It has such natural characteristics as irreplaceability,limited area and economic characteristics as scarcity of supply and diversity of use.With the development of economy and the advancement of urbanization,the structure of land use has changed a lot.The use of land resources is faced with many ecological problems,such as the continuous decrease of grassland and forest land,the shrinking of wetlands,and the destruction of biodiversity.Ecosystem service value is the benefit that human beings get from the ecosystem.Land is the carrier of ecosystem operation,and the change of land use structure has direct impact on the stability of the ecosystem.Therefore,the evaluation of regional ecological demand degree based on the ecosystem service value,and optimizing the land use structure accordingly can provide a basis for improving the economical and intensive level of land use and realizing the coordinated development of society,economy and ecology.This study takes Changsha City and nine districts(counties and cities)under its jurisdiction as the research area,calculates the ecosystem service value in each region,and analyzes the changes of land use structure and ecosystem service value change in each region from 1997 to2017.This study combines the services provided by the land ecosystem with human needs,that is,from the perspective of the supply and consumption of ecosystem services value using the multi-index comprehensive evaluation method to evaluate the ecological demand in each region of Changsha City.On this basis,multi-objective linear programming model is used to optimize the land use structure in Changsha.The research conclusions are as follows:(1)From 1997 to 2017,the proportion of arable land and garden land in Changsha decreased continuously,and the proportion of construction land increased year by year.The total value of ecosystem services decreased from 52445.45 million yuan in 1997 to 49403.89million yuan in 2017,which decreased by 3041.56 million yuan in 20years,with a change rate of-5.81%.From the perspective of land types,the ecosystem service value of forest decreased the most,with a decrease of 1230.08 million yuan,followed by water area,urban village,industrial and mining land,garden land and arable land.From a regional perspective,the ecosystem service value in Wangcheng District decreased the most,reaching 2165.09 million yuan,followed by Changsha County,Liuyang City,Ningxiang County,Kaifu District and Furong District.The rapid expansion of construction land occupies a large number of grasslands,gardens and wetlands with high ecological value,which is an important reason for the decrease of the total value of ecosystem services in Changsha.(2)In 2017,the comprehensive evaluation value of ecological demand in nine districts(counties and cities)under the jurisdiction of Changsha City was ranked from large to small,namely,the degree of ecological demand was ranked from high to low as as follows:Furong District>Tianxin District>Kaifu District>Yuelu District>Yuhua District>WangchengDistrict>ChangshaCounty>Ningxiang City>Liuyang City.The minimum value and maximum value of the comprehensive evaluation of ecological demand(W_j)in each region of Changsha are 0.3647 and 1.4123,and the range span is large.The comprehensive evaluation value(W_j)of ecological demand in Changsha City is 0.9327,and there is much room to improve the ecological demand in Changsha.(3)The optimized land use structure and ecological demand situation of Changsha in 2020 have been improved compared with that in2017.The area of garden and forest land has been increased,and the scale of construction land has been effectively controlled,which is conducive to adjusting the layout of garden land,establishing characteristic agriculture,protecting the forest land in ecologically fragile areas and optimizing the ecological environment.After the optimization of land use structure,the ecosystem service value of Changsha City is 50354.92million yuan,an increase of 951.03 million yuan over 2017.According to dimensionless and weighted calculation of the index values before and after optimization,the comprehensive evaluation value of the ecological demand(W_j)of Changsha City in 2020 is 0.3947,which is less than1.6012 in 2017,and the degree of ecological demand has decreased.In general,the land use structure optimization and adjustment plan in 2020makes full and reasonable use of land resources,improves ecological benefits,and better realizes the coordinated development of society,economy and ecology in Changsha. |
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