Using a modified ecological footprint model to analyze agro-economic ecosystem before and after Grain for Green Policy of a typical watershed on the loess plateau in China

摘要

Based on the theory of emergy analysis and introduced the concept of emery density, a modified ecological footprint model was established to evaluate the environmental status of sustainability. The main process was to transform all kinds of energy flows into the corresponding biological productive units and then combine with emergy density to calculate ecological footprint and ecological carrying capacity. A modified model and a traditional model of ecological footprint were used to analyze the changes before and after Grain for Green Policy in zhifanggou watershed. By using the modified model, the carrying capacity per capital was 0.256hm2/cap and 0.201hm2/cap separately before and after grain for green policy, while the ecological footprint per capital was 0.183 hm2/cap and 0.118hm2/cap separately. All results showed ecological surplus. And the sustainability index was 0.528 and belonged to slight sustainability condition before this policy, but this index was 0.630 after this policy while it belonged to middle sustainability condition. The results of ecological footprint per capital were 0.733hm2/cap and 0.650hm2/cap separately. By using the traditional model, the ecological carrying capacities were 1.559hm2/cap and 1.781hm2/cap separately before and after this policy, which showed ecological surplus. The results all showed that the modified model was more realistic and reasonable.