Pollution Footprint: A Type of Ecological Footprint Based on Ecosystem Services
污染足迹：一种基于生态系统服务的生态足迹

After nearly twenty years of development, ecological footprint has become one of the most widely methods for sustainable development assessment. The ecological footprint is, however, unable to evaluate the impacts of human activities on natural ecosystems in an all-round way. There are a multitude of deficiencies in conventional ecological footprint theories. For example, neither does the conventional ecological footprint involve the utilization of other ecosystem services except primary product provision, nor it accounts for other pollutants except CO2 released by human activities. In addition, there have some inherent contradictions involved in both the calculation methods and the selection of variables involved in the energy footprint. Through comprehensive analysis of such deficiencies, the authors indicated that the failure of the conventional ecological footprint in providing a comprehensive measurement on human impacts lies in that the assumption of the exclusive land function has prevented the non-bioproductive commodities and services from being considered. To overcome the limitations in conventional ecological footprint theories, the authors suggested that the multi-functionality of land should be acknowledged. Furthermore, a concept of ecosystem services-based ecological footprint was proposed. The ecosystem services-based ecological footprint is defined as the aggregated area of land and water in a variety of ecological categories that is claimed by a certain group of population to provide all types of ecosystem services they consume. The authors also elaborated the model construction and calculation methods of ecosystem services-based ecological footprint, in particular pollution footprint. The pollution footprint, an ecological footprint based on pollution absorption, is a typical ecosystem services-based ecological footprint. It is noted that the pollution footprint is not a simple replacement of energy footprint in the conventional ecological footprint; it is able to account for most pollutants incurred by human activities and to be further clarified in terms of different classes or types of pollutants. Difficulties in pollution footprint calculation include 1) pollutant transfer mechanisms and 2) the determination of the quantity of pollutants for each type of land cover and the capability of these land covers to accommodate pollution. The difficulty in application rests on the determination of the relationship among footprints of different classes or types of pollutants.