An Emergy Research On Zhoushan Archipelago Ecosystem Services Based On The InVEST Model

China has a vast ocean area,with energy,biology,minerals and other vital resources for human survival and development.With the increasing shortage of resources,the potential and advantages of the ocean development are gradually revealed.The position of the ocean in the strategy of realizing the high quality development of China’s economy is becoming more and more prominent.Under the background of advocating developing blue economy,as an important fulcrum of the development of marine economy,the sustainable supply of island ecosystem services is the basis for the development and utilization of islands and the realization of high-quality development of marine ecological economy.However,due to the inherent vulnerability of island ecosystem,natural disasters and improper human development are easy to cause island ecosystem imbalance.The island ecosystem with relatively single ecological structure is difficult to recover after disturbance,and may even face the risk of collapsing.Therefore,how to plan and utilize the limited resources,coordinate the contradiction between the limited resources and the economic development,and realize the rational development and utilization of island resources has become one of the urgent problems to be solved in the development of blue economy in China.In this study,Zhoushan Archipelago is taken as the research area.Based on the InVEST model,the ecosystem of Zhoushan Archipelago is comprehensively and quantitatively analyzed,and the results of four important ecosystem services in 2015 and 2017,namely,water yield,soil conservation,water purification and carbon storage,are obtained.The mechanism and current situation of ecosystem services of Zhoushan Archipelago are comprehensively analyzed by using the emergy analysis method,to clarify the types and quantity differences of ecosystem services provided by different land use types.The development scenarios of Zhoushan Archipelago are simulated and analyzed to assess quantitatively the impact of different urban expansion and island remediation measures on the ecosystem services of Zhoushan Archipelago.This study means to provide scientific and effective decision-making basis for island land use planning and ecosystem service management,as well as to provide relevant reference for the research of similar regions.The main conclusions are as follows:(1)Time scale: influenced by climate and land use,the water yield and carbon storage services generated by Zhoushan Archipelago ecosystem in 2017 were less than those in 2015.In general,the intensity of soil erosion in the islands was micro erosion,and the soil conservation service in 2017 slightly increased compared with that in 2015.As the output of nitrogen and phosphorus went up,the amount of water purification in the islands ecosystem increased in 2017.(2)On the scale of Archipelago: the spatial distribution trends of four ecosystem services in Zhoushan Archipelago are different.Water yield services were affected by the uneven distribution of precipitation,decreasing from southwest to northeast.The spatial characteristics of soil conservation services decreased from both sides of the upstream river with high altitude to the area with low altitude and gentle slope.The areas with high nitrogen output were mainly distributed in the cropland around the coast and rivers,while the coastal construction areas had high phosphorus output.The carbon storage services decreased from high altitude area to low altitude coastal area.(3)On the scale of single island: the water yield services in rainy years showed the trend of high in southwest islands and low in northeast islands.When the annual precipitation was less,the spatial distribution of water yield services was affected by land use.The comprehensive development island with large population and area had a high level of ecosystem services.The ecosystem service level of over developed comprehensive islands such as Daishan island and Xiushan island was average.The service level of industrial islands was poor.The same was true for a few remote islands with poor natural endowment and strong ecological vulnerability.(4)Land use mode: different land use modes provide different ecosystem services.Construction land and bare land had the greatest water yield capacity.The fixation ability of forest and shrub to soil sediment was the strongest.Cropland and construction land were the main sources of nitrogen and phosphorus nutrients.Forest,shrub and other natural ecosystems had the highest carbon storage services.Comprehensively,the ecosystem services emergy of different land use from large to small were: forest,shrub,grassland,cropland,construction land,bareland,wetland,water.(5)Scenario analysis: in the scenario of forest expansion and sea reclamation,the ecosystem service level of the large comprehensive utilization island was higher than before,while that of the small remote island declined.Under the ecological remediation scenario,the ecosystem services of most cropland in Zhoushan Archipelago decreased after being replaced with forest.Only the two sides of rivers with serious soil erosion and the marginal zone between the cropland and urban land had an improvement trend after replacement.