| Increased urbanization is altering natural and semi-natural ecosystems,causing the loss of vegetation,biodiversity,open spaces,and changing both hydrologic and biogeochemical cycles.Urban green-space,has a significant impact on improving urban ecological environment and living conditions for citizens.Over the last few years,people has gradually realized the importance of ecosystem services that urban forest can provide,such as energy conservation,carbon storage,reducing stormwater runoff,improving air quality,and enhancing human health and well-being.One of hotspot is to estimate the value of ecosystem services,and it should be recognized that urban trees will not be valued for the same ecosystem services in all towns and cities,as each urban center presents its own topographical,climatic,cultural and industrial context.Therefore,when assessing urban forestry ecosystem services for the sake of maximizing its value,it is necessary to take the local social factors into consideration.Based on the study of economic and social development factors and the relationship between factors and value of ecosystem services,the value of urban forestry ecosystem services of Beijing is estimated in this paper.The result just as follows:(1)This study extracted two main factors by using the Principle Component Analysis for the selected social factors(per capita GDP of Beijing,disposable income of urban residents,population density,the level of urbanization,sex ratio,the number of 60 years old and above,the propotion of undergraduate students),the first component was social and economic factors(contribution rate with 66.39%);The second one was the population factor(contribution rate with 25.41%).In addition,by using multicollinearity combined analysis,three main social factors,like per capita GDP,the sex ratio and the number of people above 60 years of age were extracted.(2)The evaluation system of urban forestry ecosystem services in Beijing from the perspective of human being's concern was formed by using the Delphi and AHP.The system was divided into three levels,a total of 13 indicators,to be specific,human comfort including temperature,humidity,light and wind speed four indicators;ecological health of forest contains providing volatile organic compounds,negative ions and killing bacteria;environmental cleanliness comprising fixing carbon and releasing oxygen,reducing noise,purifying water,absorbing harmful gases and dust lag.In this system,the proportion of human comfort was the largest(0.62),which was corresponded to people's needs because of the urban heat island effect.(3)The changment of ecosystem services' value from 2000 to 2014.The value of ecosystem service was accounted about 13.92 billion yuan,about 4 times than 4.8155 billion yuan under without any consideration of social factors.When considering the social factors,the value increased from 0.20 to 29.76 billion yuan.The development of society elaborated value's trend: increasing urbanization will inevitably lead to the damage of ecological function of urban green space.The difference and changement of urba forest's type or amount of influence affect the ecosystem functions,in the constract,changement in ecosystem services would support or restrict the further development of urban functions.Overall,the relationship between them showed as a "behavior-feedback".(4)The value of urban green space ecosystem service were analyzed among counties of Beijing.The value of Chaoyang District was max,85.10×104 yuan,the value of Xicheng District was smallest,only 6.26×104 yuan.Sequence just as followed below Chaoyang> Haidian>Daxing>Fangshan>Shunyi>Changping>Fengtai>Tongzhou>Shijingshan>Huairou>Yanqing>Miyun>Mentougou>Pinggu>Dongcheng>Xicheng.The value is corresponded with the size of the green area.(5)The total value of Beijing's urban green space ecosystem services in 2014 was 29.76 billion yuan when taking social and economic factors into consideration,which was less than 48.155 billion yuan when not taking the social factors into account.The coefficient of ecosystem services under social factors was less than 1,indicating that under current social development,the value of ecosystem services in its natural state was not completely understood.The fact that value of ecosystem services in different society is fully acknowledged helps people recognize their own local conditions and propose a corresponding policy and plan.In addition,based on the index of value of ecosystem services of urban green space system established in this study,the final value is 10.46 billion yuan in 2014.(6)Environment-ecology relationship.Based on the Kuznets study,sex ratio and 60 years or above had no significant effect;the fitting degree of curves about per capita GDP and per capita carbon emissions,the regional environmental noise,SO2 concentrations of nitrogen oxide emissions,sulfur dioxide emissions and respirable particulate matter concentration respectively were relatively high(correlation coefficient greater than 0.7),and the Kuznets curves about per capita carbon emissions,regional environmental noise and SO2 concentration and per capita GDP showed that with the development of the three pollutions' levels,the curves had a turning point,i.e.'pollution zero point',at 103.821 yuan,102.513 yuan,77223.4 yuan respectively,indicating that when GDP per capita reached a degree,per capita carbon emissions,the regional environment noise and SO2 concentration would achieve 'zero pollution values'.The fit degree of cubic equations about nitrogen oxide emissions,emissions of sulfur dioxide and respirable particulate matter concentration of were also high,but did not exhibit environmental Kuznets curve like inverted "U" shaped,and had no pollution turning point.Two other factors like sex and social development over 60 years of age had no significant correlation with all environmental indicators. |
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