An Assessment Of Ecosystem Health For Jiayuguan City Based On Emergy Analysis

With the advancement of urbanization process,the demand and consumption scale of resources in cities are expanding rapidly,which leads to many problems of urban ecological environment.Jiayuguan City is a typical resource-based industrial city in Northwest China.Although its economy has developed rapidly in recent years,it is situated in an environment-sensitive area.At the same time,the industry is dominated by the”two high and one surplus,industry,which has great pressure on the environment and is facing severe ecological and environmental problems.Therefore,it is of practical significance to study its ecosystem health.Based on the theory of emergy value,this paper constructs an ecosystem health assessment system based on the actual situation of Jiayuguan City,and uses the pressure-state-response evaluation model to evaluate the health status of the ecosystem and find out the main problems of the Jiayuguan ecosystem.The results show that:(1)From 2004 to 2017,the total emergy usage,renewable resources emergy and non-renewable resources emergy of Jiayuguan ecosystem show an upward trend.The increase of renewable resources is mainly caused by the increase of agricultural and animal husbandry production,and the increase of non-renewable resources emergy is mainly due to the accelerated exploitation of mineral resources.The input and output emergy of Jiayuguan City are on the rise in general,but the growth rate of input emergy is less than that of output emergy.The energy value of waste is rising,but the growth rate is less than that of total energy value.(2)From 2004 to 2017,the Emergy Return Rate of Jiayuguan City showed a wavy upward trend,and finally remained stable,contrary to the trend of GDP growth.Emergy density and net emergy output rate showed an overall upward trend.The emergy ratio,emergy self-sufficiency rate and emergy exchange law of non-renewable resources are relatively stable.Among them,the ratio of non-renewable resources and emergy self-sufficiency rate remain above 60%,while the emergy exchange rate remains below 0.2.Per capita energy value and power energy ratio are rising.The increasing pressure of population carrying capacity and ecological load rate on the environment and the declining index of urban sustainable development reflect the urgent need to change the current development model of Jiayuguan City.(3)The health level of ecosystems in Jiayuguan City is generally on the rise.From 2004 to 2013,it was in the fourth stage of ecosystem health,and the ecosystem was unhealthy.Since 2014,the Jiayuguan City Ecosystem has entered the third grade.Although the health level is still low,it has returned to a sustainable stage.(4)The mam problems of urban ecosystem in Jiayuguan City are:unreasonable industrial structure,resource-based industries,low level of output products,unreasonable energy structure and high environmental pressure.