Emergy assessment and sustainability of ecological–economic system using GIS in China

Abstract

Emergy analysis, combined with geographical information system (GIS), provides an excellent framework for understanding and interpreting issues related to resources, environment, popularity and development. In the work, emergy analysis was combined with GIS to evaluate the sustainability countrywide. This study involves 91 indices of ecological and economic system about resources and environment, output, input, waste, import and export, including emergy currency ratio (ECR, unit: sej/￥), environment load ratio (ELR, unit: dimensionless), waste load ratio (WLR, unit: dimensionless), emergy yield ratio (EYR, unit: dimensionless), emergy output ratio (ENR, unit: dimensionless), environment load capacity (ELC, unit: person), emergy sustainability indices (ESI, unit: dimensionless) and sustainability time (ST, unit: year). The main objective was to explore sustainability of nationwide ecological and economic system by integrating GIS with emergy evaluation. Among 91 indices, the index of top soil erosion was captured by combining thematic maps with remote sensing images (modis, 250m) and digital elevation model (DEM) based on the universal soil loss equation (USLE). A precipitation thematic map was interpreted from meteorological data and remote sensing images, using Kriging interpolation and spatial analysis in ArcGIS. Consequently, the whole precipitation data could be integrated from the precipitation thematic map. Two indices of wind and solar radiation energy that could not be found in the yearbooks were extracted from thematic maps and statistical data, using Kriging interpolation method in ArcGIS. The other indices were acquired from statistical yearbooks. A combined application of emergy assessment with GIS technology presents a complementary view of territorial sustainability in 30 provinces except for Tibet, Hong Kong, Macao and Taiwan in 2000, 2005 and 2009. Based on spatial analysis in geographic information system (GIS), province-level administrative vector diagram and emergy indices in 2000, 2005 and 2009 are used to establish the sustainability index maps. The results were summed up as follows. First, the number of population exceeded the environmental carrying capacity greatly, and regional economic growth has depended more on the resources, environment, and territorial sustainability has become more fragile. Secondly, in a global view, the remaining time of the traditional development becomes shorter. In 2009 the average ST was 27years; the maximum 129.4years in Shanxi; the minimum less than 2years in Shanghai, Zhejiang, Tianjin, Jiangsu and Guangdong. Thirdly, the remaining years of regional sustainability (ST) have been shorten, and there were still severe environmental pressures on the countrywide ecological–economic system due to high living and productive consumption level and low productivity efficiency. The ST decreased from 84years in 2000 to 27years in 2009. It is necessary and extremely important to explore an authentic approach of sustainable development. Obviously, there has been a spatial heterogeneity of territorial sustainability, with a general decrease from the eastern to the western China according to the regional development level and local resources. A new development model was suggested to problems of ecological compensation, industrial structure optimization, population control and sustainable consumption and production.