Characterization Of Ecosystem Services And Their Trade-off Synergies In The Yellow River Basin

Ecosystems provide human beings with various natural resources and living environments,and are the foundation of human social development.In recent years,the irrational use of natural resources by human beings has led to serious damage to the structure and stability of ecosystems,which has greatly damaged ecosystem services and threatened human well-being.The Yellow River Basin is an important ecological barrier in China,and its ecological protection and high-quality development are of great strategic significance for controlling soil erosion on the Loess Plateau,ensuring grain production in plains such as the Huang-Huai-Hai Dynasty,enriching the biodiversity of wetlands such as Dongping Lake and water conservation in protected areas such as Sanjiangyuan.In this study,land use data from1990,2000,2010,2015 and 2020 were selected to evaluate ecosystem services such as water conservation,carbon storage,soil conservation and habitat quality in the Yellow River Basin through the InVEST model,and then explored the spatial and temporal distribution and evolution characteristics of ecosystem services from the sub-basin and provincial scales,revealed the impact mechanism of land use change on ecosystem services,and explored the trade-off/synergy relationship of ecosystem services.Taking water supply services and carbon sequestration services as examples,this paper conducts a preliminary study on ecosystem service flows in the Yellow River Basin,which provides important theoretical data for ecosystem service assessment and ecological service flow research.It will contribute to the ecological protection and governance of the Yellow River Basin,ensure the long-term peace and stability of the Yellow River,and promote the high-quality development of the entire basin.The main findings are as follows:（1）From 1990 to 2020,the implementation of vegetation restoration projects such as returning farmland to forest（grassland）and shelter forests in the three north and the acceleration of urbanization greatly affected the land use change in the Yellow River Basin.From 1990 to 2020,the cultivated land area continued to decrease,the forest land area continued to increase,and the grassland area first increased and then decreased.In terms of the rate of change,the change rate of construction land was the highest（153%）,followed by unused land（-35.5%）,forest land（18.93%）,arable land（-11.27%）,water area（7.46%）,and grassland（1.64%）.The conversion between different land use types was as follows:cultivated land was mainly converted to grassland（19.76%）and building land（5.28%）;Forest land was mainly converted to grassland（3.09%）and arable land（2.18%）;Grassland was mainly converted into arable land（6.63%）,forest land（3.21%）and unused land（1.63%）.About 57%of unused land was converted into grassland,49.75%of unused land was converted into grassland,4.29%was converted into arable land,and 1.58%was converted into construction land.（2）From 1990 to 2020,the habitat quality of different land use types in the Yellow River Basin is manifested as forest land>grassland>water area>unused land>arable land>construction land.From 1990 to 2020,the quality of arable land habitat continued to decrease,and forest land and unused land first increased and then decreased,while forest land improved year by year.Except for the high quality of Yan’an habitat,the spatial distribution characteristics of"high in the west and low in the east,high in the north and low in the south"were generally displayed in other areas.On the whole,the habitat quality of Qinghai,Shandong and Sichuan Provinces remained good,while the fluctuation of habitat quality in Gansu Province,Shaanxi Province and Inner Mongolia Autonomous Region was obvious.When cultivated land is converted to forest land,grassland and water area,it has a positive effect on the improvement of habitat quality.Overall,the sum of land use HQCI values in each year from 1990 to 2020 was-455,indicating that the habitat quality of the Yellow River Basin was decreasing.（3）From 2000 to 2020,the effect of soil erosion control in the middle reaches of the Yellow River Basin was remarkable.The water conservation in the Yellow River Basin showed a clear trend of decreasing first and then increasing around 2000,which also showed that vegetation restoration and soil erosion control had remarkable effects.Among the different land types,the largest water conservation was grassland>arable land>forest land>unused land>construction land>waters,while the water conservation per unit area of different land use types was as follows:unused land>building land>forest land>grassland>arable land.The main contribution value of water conservation in different provinces is different,for example,the water conservation in Gansu Province is mainly contributed by grassland,while the water conservation in Henan Province is mainly contributed by cultivated land.Around2000,the total soil conservation in the Yellow River Basin showed a trend of first increasing and then decreasing,and the degree of soil erosion slowed down year by year.From a spatial point of view,the total soil conservation in the Yellow River Basin shows the characteristics of"more south and less north,and more east and less west".In general,the total water and soil conservation of Gansu Province,Inner Mongolia Autonomous Region,Ningxia Hui Autonomous Region,Qinghai Province and Sichuan Province is mainly contributed by grassland,and its contribution proportion is>50%,while the contribution of forest land in Shaanxi Province,Shaanxi Province,Henan Province and Shandong Province is the largest,much larger than other land use types.（4）There are obvious regional differences in trade-offs and synergies between different ecological services in the Yellow River Basin.The trade-off between water conservation and soil conservation was mainly distributed in Gansu Province,Inner Mongolia Autonomous Region,Shanxi Province and Shaanxi Province,while the synergistic relationship was mainly distributed in Qinghai Province and Gansu Province.The synergistic relationship between habitat quality and soil conservation（HQ-SC）was much larger than that between other ecosystem services,accounting for 64.2%of the entire Yellow River Basin,mainly distributed in Gansu Province,Inner Mongolia Autonomous Region,Qinghai Province,Shanxi Province and Shaanxi Province.Grassland,woodland and arable land are the main land-use types that affect the trade-off between ecosystem services.The trade-offs between water conservation and soil conservation are more widely distributed in forest land and arable land,while the trade-offs between water conservation and habitat quality,water conservation and carbon storage are mainly contributed by grassland,and the trade-off distribution area is much larger than that of the synergy area.The synergistic relationship between soil conservation and carbon storage was distributed in grassland,forest land and cultivated land,and the synergistic area of cultivated land and forest land was much larger than that of the trade-off area.The synergistic relationship between habitat quality and carbon storage is mainly distributed in forest land,and its synergistic distribution area is much larger than that of the trade-off area.（5）There is an obvious contradiction between supply and demand in water supply services and carbon sequestration services in the Yellow River Basin,that is,the inconsistency between supply areas and beneficiary areas leads to spatial mismatch and imbalance between supply and demand.From the results of water service flow,it can be seen that the middle and upper reaches of the Yellow River Basin have high water supply potential,and the higher water demand mainly occurs in industrial areas and urban areas,distributed in the lower reaches of the Yellow River Basin.Water supply is mainly related to the area of farmland,grassland and water,which has a significant impact on water supply.In terms of total carbon sources,Ordos has the highest carbon emissions(9×107 TC·y^-1),and Linyi and Zhangye far surpass other cities in terms of emissions per unit area.From the perspective of carbon sequestration capacity per unit area,Hanzhong City has the strongest carbon sequestration capacity,followed by Shangluo and Ankang City.From the results of the current ratio of carbon sequestration services,it can be seen that except for Hainan Tibetan Autonomous Prefecture and Guoluo Tibetan Autonomous Prefecture,which are carbon sequestration service demand areas,other areas in the Yellow River Basin are carbon sequestration service supply areas.The self-sufficiency rate of carbon sequestration services in the Yellow River Basin has gradually increased from west to east.Centered on weak carbon sources,the current ratio increases along all sides,and cities and counties with high flow ratios are scattered in the range.