生态足迹的模型修正与方法改进

生态足迹是测定人类活动的资源消费需求,判明自然资产是否被过度利用的有效工具。介绍了生态足迹的基本概念和模型,简单分析基本模型存在的主要缺陷和争论,重点解析了近年来生态足迹模型在参数调整、项目计算、账户扩展等方面的演变和修正。介绍生态足迹研究的传统方法:综合法和组分法,评述了生命周期评价,基于投入产出分析,三维模型,净初级生产力,能值理论,时序分析等的方法改进。对未来的研究方向提出自己的看法,期望对我国的生态足迹研究有一定的启示作用。

Ecological footprint model modification and method improvement

The Ecological Footprint (EF) method, originally developed by Wackernagel and Rees in the mid 1990s, is a useful approach to determine human sustainability. EF can measure human demand on bioproductive land area that is required to support resource demands of a given population or specific activities, and identify whether natural assets have been overly exploited. The aim of this paper is to elaborate and analyze the progress of EF modeling and methods in recent research. First, we explain the basic EF model and the concepts of ecological footprint, biological capacity, ecological remainder and ecological deficit. Second, we comment on major defects and controversies of the basic model. One example of this is the assumption that biologically productive land use types are a mutually exclusive, partial index of the ecological accounting, which overlooks the complexity of land quality or ecological function and ignores the influence of socioeconomic factors on the productivity of land. More importantly, we discuss evolution and modification of the EF model in recent years, which includes three aspects: parameter adjustment (equivalence factor and yield factor), item calculation (energy land, cropland, fishing ground, and built-up land), and accounting extension (carbon footprint, water footprint, pollution footprint, and ore resource footprint). Third, after introducing the two main conventional EF methods (the compound and component-based approaches), we comment on EF methodology improvement based on life cycle assessment (LCA), input-output analysis, three-dimensional modeling, net primary productivity, emergy theory, time series analysis, and others. Key issues from the method review are as follows. (1) The LCA method can be applied to the EF of a final product. LCA-EF has the advantage of detail, as individual product types and even brands can be analyzed, with the general disadvantage of lacking complete upstream coverage of the production chain. (2) The main advantage of input-output based EF analysis lies in its unambiguous and consistent accounting of all upstream life-cycle impacts and good availability of expenditure data that permit fine spatial, temporal and socioeconomic breakdown of consumption footprints. (3) The 3D EF model can help distinguish between the use of natural capital flows and the depletion of natural capital stocks, while maintaining the structure and advantages of the classical EF formulation. (4) Basing bioproductivity calculations on Net Primary Production (NPP) is a promising approach that provides an explicit link between human consumption and ecosystem services. EF-NPP relates land overuse to land productivity, whereas the overshoot measured by the EF alone results in essence from a translation of carbon dioxide emissions into virtual land. (5) The EF approach based on energy provides a method by which it is not necessary to consider equivalence factors that are controversial in the accounting of conventional EF. However, the transformity for products or processes is difficult and uncertain because of the complexity of ecosystems, which affects the reliability of conclusions at high levels of detail. (6) Time-series footprint studies can show the benefits and pitfalls of previous practices and illuminate the effects of economic/demographic growth on EFs via historical analysis. Finally, future research directions are presented, with an aim to inform EF research in China.