Study On The Sustainability Of Cropland Use In Jiangsu Based On The Modified Ecological Footprint Model

Based on the theory of emergy analysis, a new modified model of ecological footprint is provided, which puts forward a new way to calculate cropland ecological capacity, and establishes a new concept of ecological sustainable index (ESI) to evaluate the sustainability of cropland use. This new modified ecological footprint model is applied to the studies of the current situation, temporal evolution, and spatial change of cropland use in Jiangsu Province, China. Some specified measurements and conclusion are as follows:1. Comparisons are made between the modified model and conventional model for the studies of current situation and temporal evolution of Jiangsu's cropland use. The results from two models show that the cropland use in Jiangsu is unsustainable since 1980's, with differences that thus unsustainability took place in 1981 by modified model, 5 years earlier than that by conventional model. The ESI of Jiangsu's cropland use, with the deadline of 0.5 for sustainability and unsustainability, has decreased from 0.7, indicating a situation of sustainable cropland use, to 0.3, a unsustainable situation, from 1961 to 2004 by modified model, comparing with that of from 0.7 to 0.4 in the same period by conventional model. The results from the modified model are closer to the realities of Jiangsu.2. The author considers the solar radiation, precipitation, fertility of soil, the efficiency of land use and eara of cropland as natures of ecological capacity of cropland. Spatial pattern of cropland's ecological capacity in Jiangsu is that the ecological capacity in northern region is more than that in the middle and southern regions. Cities of Yancheng, Huaian and Suqian in northern Jiangsu have highest cropland ecological capacity, in the meanwhile, cities in southern Jiangsu such as Nanjing, Wusi and Suchou have lowest ecological capacity. Ecological deficits of cropland in all cities in Jiangsu Province appeared in 2004 because their ecological footprints of cropland are greater than their ecological capacities. However, the situations of cropland use in Wusi and Suzhou cities are better than that in cities of Yancheng, Nantong and Taizhou, etc.3. This paper designs and establishes a spatio-temporal regression model to simulate and predict the spatio-temporal variability of cropland use sustainability in Jiangsu by the method of cross moving. The results indicate that there are some decreasing for most cities' ESI of cropland use, even the cropland ESI of Taizhou city goes down to the next class.4. The order of 7 factors affecting sustainability of cropland use in Jiangsu is obtained by the methods of correlation analysis and gray modeling, which is from the stronger to the weaker as follows: area of grain planting, area of cropland, area of cotton planting, population, area of food oil crop planting, productivity of animals, fertilizer application. There are five problems in the sustainability of cropland use in Jiangsu: (1) area of cropland is decreasing due to the rapid increasing area for the country's industrial construction and citizens' house building; (2) per capita cropland area go down quickly because of large population increasing; (3) more energy of cropland is exhausted owing to more crops of higher energy demand like rape replacing that of lower energy demand like wheat; (4) negative affects of applying more chemical fertilizer and less organic materials are appearing; (5) the quality of cropland is decreasing because of its bing polluted. 9 counter measurements are pointed out to deal with these problems.