Spatio-temporal variation in the value of ecosystem services and its response to land use intensity in an urbanized watershed

Ecosystem services have been described as the direct and indirect benefits people obtain from ecological systems.Maintenance and conservation of functioning ecosystem services is the basis for achieving sustainable development.This anthropocentric view has led to increased efforts to identify,quantify,and place a monetary value on ecosystem services.In recent years,with the gradual deepening of this field of study as well as the development of 3S technology,more research has begun to focus on spatial ecosystem patterns and factors influencing the value of ecosystem services while achieving a series of impressive results.However,most previous studies lack quantitative analysis which includes the study of how accumulation rules,association patterns of the value of ecosystem services vary spatially,and few studies focus on the how the intensity of land use effects the value of ecological services.Studying the spatial variation of the value of ecosystem services and factors affecting the value helps us to gain an in-depth understanding of the characteristics of regional ecosystems and reveal the mechanisms driving changes in the value of the ecosystem services they provide. Exploring the spatio-temporal variations in the value of ecosystem services is critical to a thorough understanding of typical urbanized watersheds.The Jiuxiang River watershed in the city of Nanjing is used here as a case study to estimate the spatial distribution and dynamics of ecosystem services,based on QuickBird imagery collected in 2003 and 2009,a spatial autocorrelation model and geographic information system technology.A study of the impacts of how urbanization changes land use patterns and the effect on the value of ecosystem services was conducted.Results show a decline in the value of ecosystem services from 0.230 to 0.224 billion yuan from 2003 to 2009,respectively,in the study watershed,which indicated the value of the watershed′s ecosystem services decreased 2.59% because of land use change caused by urbanization.Also,a trend toward spatial clustering of ecosystem service values was enhanced;the areas of high value ecosystem service were mainly concentrated in the upstream portions of the watershed and the low value areas were mainly concentrated in Xianlin University City in the downstream areas;the change of spatial distribution of ecosystem service value was significant in the Jiuxiang River watershed.The low value area has experienced rapid expansion around Xianlin University City in the downstream portion of the watershed,and the high value area increased only in local areas of the Jiuxiang River headwaters and upstream areas.The spatial autocorrelation of watershed ecosystem service value showed significant scale effects;the value of ecosystem services gradually increased as the scale increased.The spatial distribution and the corresponding change in the value of ecosystem services were mainly caused by land development and use patterns;the higher levels of land use in the watershed had a significantly negative effect on value of ecological services,which shows the ecological service value decreased as the intensity of land use increased.Therefore,we should consider appropriate land use options to adapt future land use patterns in light of impacts to ecological services,based on past and present land use changes.Most importantly,land use planners should strive to protect water bodies,wetlands,vegetation,and environmentally sensitive areas.Also,the density of construction land should be restrained,and appropriate engineering and mitigation measures should be initiated to repair degraded areas,including urban afforestation,pollution control,and so on.