基于能值的生态足迹模型及其在资源型城市的应用

Emergy-based ecological footprint model and its application to a natural resource-dependent economy in Xuzhou City

为衡量和评价区域发展的可持续状况,针对传统生态足迹模型以土地生产力为基础的不足,结合能值理论和方法,运用能值转换率和能值密度对模型进行改进,建立基于能值的生态足迹模型。改进的模型重点在采用区域能值密度,更加全面真实地反映区域生态承载力的大小以及区域发展模式下生态足迹的需求。能值-生态承载力的计算主要考虑区域可更新自然资源和生物生产性土地的可更新部分;能值-生态足迹计算人民生活需求资源消费量和区域经济发展的资源出口量。模型应用的结果为:资源型城市徐州市2006年人均能值-生态承载力1.03hm2,人均能值-生态足迹37.76hm2,分别是其他改进模型计算结果的4.4倍和4.3倍。如果不进行能值转换率的全球能值基准转换,能值-生态承载力将是2.6倍。生物生产性土地的可更新部分在徐州生态承载力中占有很大比重;当地承载了其他地区发展所需要的大量能值-生态足迹(出口资源)。可持续性评价指数为0.97,表明在为其他地区发展做出巨大生态贡献的同时,徐州的可持续发展状况十分堪忧。适度控制资源开采规模,延长产业链,增加出口产品附加值;开发利用可再生能源是资源型城市兼顾社会经济发展和生态环境持续的发展策略。

The traditional ecological footprint models,developed to access the sustainability of regional developments.Their calculations used ＂biologically productive areas with world average productivity＂ as a common measurement unit for ecological footprints and carrying capacity.However,the basis of land productivity was subject to many limitations.In this study we present a new ecological footprint model which is based on the emergy theory.A sustainability evaluation index is also put forward to indicating the extent of the environmental resources use.The new model focused on the ecological carrying capacity and the demand of ecological footprints for sustaining regional development using the emergy transfomity and emergy density concepts in the emergy theory.The emergy analysis measures both the work of nature and that of humans in generating products and services.By multiplying the amount of energy with its solar emergy transformity,we can easily quantify different kinds of products,services and environmental work with a single universal unit in solar emergy emjoules.The objective of this paper is to improve the ecological footprint model by introducing the emergy analysis into the calculation process and test the model in Xuzhou City.The emergy-based ecological carrying capacity（EECC）was estimated based on regional renewable resources and the renewable portion of the biologically productive land.The emergy-based ecological footprints（EEF）were calculated according to the natural resource consumption within the region and the regional resource outputs.Our calculations began with the annual solar emergy of earth geobiosphere in calculating regional emergy density.Then,regional renewable resources,renewable portion of biologically productive land,and most of the consumed resources were converted to corresponding emergy amount through emergy analysis.According to respective formula,total amount of emergy-related divided by regional emergy density can obtain emergy-based ecological carrying capacity and ecological footprints.In this way,the capacity areas and footprints areas both have the same connotation,namely,the regional emergy density.We applied the improved emergy-based model to Xuzhou City and found that the emergy-based ecological carrying capacity was 1.03 hm2 per capita and the emergy-based ecological footprint was 37.76 hm2 per capita in Xuzhou City in 2006,which was 4.4 and 4.3 times higher than those of previous models respectively.The emergy-based ecological carrying capacity would be 2.6 times higher,if the transformities were not modified based on the new global emergy baseline reference standard.Our results indicated that the renewable part of the biologically productive land accounted for a large proportion of the regional ecological capacity and a large portion of the footprints in Xuzhou was contributed to exporting resources to other regions ouside of the city.The sustainability emergy index（SEI）was 0.97 which indicated the sustainable development of Xuzhou was of concern.The developing strategies for the natural resource-dependent economy city should focus on optimizing economic structure,increasing resource use efficiency,and balancing economic development and eco-environment protection.Such as controlling the exploitation scale,extending the industrial chain,increasing the added value of export products and developing and utilizing renewable energy should be taken into account.