Assessment On Comprehensive Benefits Of Soil And Water Conservation At Small Watersheds In The Rocky Desertification Region, Guangxi

Guangxi is a typical karst landform development area, rocky desertification problem has siginificantly restricted its socio-econimic development. In order to assess the comprehensive benefits of soil and water conservation (SWC) in the rocky desertification regions, a set of benefit evaluation indexes were selected through principal component and correlation analyses, on the basis of field survey and historical data from 8 small watersheds (Xilin County:Longying, Bayang, Putuo, Weimang; Longlin County:Longwoba, Changme, Zheteng, Dagan) in the typical Karst region of Guangxi. A SWC comprehensive benifits assessment model was developed using the Analytic Hierarchy Process (AHP) and the values of the ecological, economic and social benefits of SWC activities were evaluated by adopting ecological economics methods, such as, opportunity cost method, market value method, shadow engineering method and equivalent alternative method, et al. The results of this study provid scientific references for the optimization of SWC measures and for the development of ecological and environmental protection policy in rocky desertification regions. The main results are as follows:(1) An evaluation indicator system of SWC with 17 evaluation indexes was established through principal component and correlation analyses, and these indexes were separated into 3 groups, i.e., ecological, economic and social efficiency indexes. The eco-efficiency indexes include control area of roky desertification, river runoff depth, soil erosion modulus, sediment yield modulus, soil bulk density, soil fertility, storing sediment, vegetation coverage, biodiversity index, and plants carbon fixation. Economic efficiency indexes were increases in food production, forestry and fruit production, per capita net income, and output-input ratio. Social efficiency indexes comprised of reduction of numbers of flood disasters, improvement of land productivity, increasing in land utilization rate.(2) A SWC comprehensive benefits assessment model was developed and used to assess the SWC benefits of typical small watersheds. Each small watershed comprehensive benefit scores from high to low are Putuo(0.682), Longying(0.548), Changme(0.522), Weimang(0.490), Zheteng(0.488), Bayang(0.463), Longwoba(0.462), and Dagan(0.410). The evaluation results were basically consistent with the actual situation of these small watersheds, which indicated that the AHP was applicable to evaluate the comprehensive benefits of SWC in this area.(3) The values of SWC comprehensive benefits for each of the small watersheds were quantitatively evaluated by using several ecological economic methods. The values of SWC for the small watersheds from high to low are Putuo, Longying, Changme, Zheteng, Longwoba, Weimang, Dagan, and Bayang, the corresponding values are 67 034 700,47 414 000,39 930 800,34 036 200,25 825 200,21790 600,17 435 900, and 13 936 500 RMB.(4) The value of SWC benefits of each small watershed increased with the investment in SWC. However, non-linear regression analysis showed that the values of SWC benefits for all the small watersheds could reach relatively stable values and did not increase significantly when the investments reached certain amounts.Based on the results, it is suggested that, in small watersheds (e.g., Putuo, Longying and Changme) which have relative high ecological, economic and social benefits, the investments for watershed goverance can be converted into watershed maintenance funds, for the purpose of sustainable development of these watersheds. In small watersheds (e.g., Weimang, Longwoba, Zheteng, and Dagan) which have relative high ecological and economic benefits, but relatively low social benefits, the watershed goverance investments and land use structures shouled be adjusted and optimized in order to improve land productivity and land use capability. In Bayang watershed, which has moderate economic and social benefits and low ecological and comprehensive benefits, the investment for vegetation measures (e.g., planting water conservation forest, economic forest, etc.) should be increased to not only improve ecological environments, but also promote economic development.