Spatial and temporal change in ecological assets in the Yangtze River Delta of China 1995-2007

This paper analyses the characteristics of, and drivers for, spatial and temporal change in the ecological assets in the Yangtze River Delta from 1995 to 2007. The ecological assets are simulated by using remote sensing quantitative retrieval and economic evaluation methods. The remote sensing data sets include NOAA/AVHRR-NDVI at a spatial, resolution of 1 km in 1995 (February 1995--January 1996), MODIS/NDVI in 2000 (February 2000--January 2001) and 2007 at a resolution of 250m, land use interpreted by using Landsat TM images in 1995, 2000 and 2007 at the scale of 1:100000, and land cover in 1980S and 2005 at the scale of 1:250000. The ecological adjustment coefficient is estimated on the basis of the net primary productivity and vegetation coverage in the region, which are simulated by a modified Carnegie Ames Stanford Approach (CASA) terrestrial carbon model and the Pixel Binary Model, respectively. The results show that the overall amount of ecological assets in the Yangtze River Delta declined by 5.1%, changing from 89.1 billion yuan in 1995 to 84.6 billion yuan in 2007. The ecological assets in the region consist of forest, rivers/lakes and cropland, accounting for 48.0%, 26.7% and 20.5%, respectively. The total amount of ecological assets for each major city in the region presents a decreasing trend, and there is a spatial heterogeneity. The reduction of ecological assets in the cities of Shanghai, Suzhou, Jiaxing, Huzhou, Shaoxing and Ningbo was substantial, at 798, 486, 441, 427 and 403 million yuan, respectively. However the decreased amount and rate of the ecological assets in other cities such as Nanjing, Zhenjiang, Hangzhou and Taizhou were small, at 57, 47, 122 and 155 million yuan, respectively. The spatial distribution of ecological assets in the Yangtze River Delta exhibits a declining pattern from the south to the north, increasing slightly in the south and north but decreasing severely in the central area from 1995 to 2007. Such a pattern of change in ecological assets implies that it may reduce the ecological safety in some affected areas, but this will not be an ecological constraint for sustainable development in the Yangtze River Deltaic region as a whole. Land-use change is found to be the dominant factor resulting in the reduction of ecological assets and their dissimilarities in spatial distribution. Change in ecological assets is also mediated by urban expansion, land reformation and reclamation. However the national ecological re