A modified model of ecological footprint accounting and its application to cropland in Jiangsu, China

Based on the theory of emergy analysis, a modified model of ecological footprint accounting, termed emergetic ecological footprint (EMEF) in contrast to the conventional ecological footprint (EF) model, is formulated and applied to a case study of Jiangsu cropland China. Comparisons between the EF and the EMEF with respect to grain, cotton, and food oil were outlined. Per capita EF and EMEF of cropland were also presented to depict the resources consumption level by comparing the biocapacity (BC) or emergetic biocapacity (EMBC, a new BC calculation by emergy analysis) of the same area. In the meanwhile, the ecological sustainability index (ESI), a new concept initiated by the authors, was established in the modified model to indicate and compare the sustainability of cropland use at different levels and between different regions. The results from conventional EF showed that per capita EF of the cropland has exceeded its per capita BC in Jiangsu since 1986. In contrast, based on the EMBC, the per capita EMEF exceeded the per capita EMBC 5 years earlier. The ESIs of Jiangsu cropland use were between 0.7 and 0.4 by the conventional method, while the numbers were between 0.7 and 0.3 by the modified one. The fact that the results of the two methods were similar showed that the modified model was reasonable and feasible, although some principles of the EF and EMEF were quite different. Also, according to the realities of Jiangsu' cropland use, the results from the modified model were more acceptable.