The Impact Of Urbanization On Ecosystem Services

With the development of social economy,the level of urbanization in China has increased significantly,and the speed of urbanization is accelerating.Along with the development of the city,farmland,garden plot,and forest land were converted to residential land,industrial and mining land,traffic land,affecting the normal operation of the ecological system fundamentally and destroy the ecosystem service function.The impact of urbanization on ecosystem services is closely related to human's production and life,and has become a hot issue in regional research.Therefore,under the background of the urbanization,the quantitative assessment of temporal and spatial changes of urban ecosystem service and the impact of urbanization on urban ecosystem service,and simulate urban expansion based on the urban expansion model of cellular automation,analyzing the trends of the ecosystem services changes under different expansion scenarios,which has important reference meaning for the regional ecological environment protection and sustainable development of economy and society.We choose Nanjing as the research area in this study.The population of Nanjing has exceeded 8 million and more than 6 million occupy the urban area,the contradiction between urbanization and ecosystem services is more prominent,and has important research significance.The main contents of this study include:1)calculate the ecosystem services of each year by using historical land use data and analyze the impact of urbanization on ecosystem services;2)set up urban dynamic change model based on cellular automation model and simulate the process of urban expansion under different expansion scenarios;3)analyze the impact of urban development on ecosystem services under different scenarios quantitatively,select the most suitable development model and take the urban development speed as precondition,provide a reference for the urban planning,land use and ecological protection.The main conclusions of this study are as follows:(1)We calculated 4 categories of 6 kinds of ecosystem services in 2000,2008,and 2013 in Nanj ing,four kinds of ecosystem services including the food supply,carbon fixation,soil water storage,and habitat in this study area decreased with time,which was most serious in urban built-up area.Although the air conditioning and entertainment services have a certain upward trend,the increase of urban area is significantly smaller than the surrounding areas.Spatially,there was significant correlation between urban construction areas and low ecosystem services value areas.(2)With rapid urbanization of Nanjing from 2000 to 2013,the urbanization index shows obviously gradient change from urban to rural.We use decoupling analysis estimate the degress of de-linking and re-linking urbanization index from 6 ecosystem services.The urbanization index and ecosystem services have relative decoupling in majority.The development of urban brings loss of ecosystem services,but the growth rate of urbanization index is higher than the ratio of ecosystem services decrease.It shows highly spatial cluster features in ecosystem services and urbanization index,while most ecosystem services have negative correlation with urbanization index.(3)We simulated urban expansion from 2014 to 2023 in two scenarios,before 2018,Nanjing is in the fast developing stage of urbanization and the number of urban construction land increased rapidly.Urban development tends to be stable after 2018 and the increasing of urban construction land is become stable which is obvious in Cluster expansion scenario.Spatially,Cluster expansion scenario expand around the main city,the growth of urban areas in Jiangning and Pukou are also lager.In addition to the rapid growth of urban land in main city in Scattered expansion scenario,large scale urban expansion was also occurred in Jiangning,Pukou,Liuhe,Lishui,and Gaochun,which forms multicore urban growth model.(4)After comparing ecosystem service simulations of urban expanding under scattered expansion scenario and cluster expansion scenario in study area,we found that the increase or decrease with time of six kinds of ecosystem service was consistent with 2000-2013.Only air pollution removal and recreation services were increased with time,while others were decreased.The loss of ecosystem services caused by urban land expansion is greater when simulated under scattered expansion scenario.Thus,using cluster expansion scenario to guide urban expansion can reduce the ecological pressure of urban development in a short time.