Evaluation of ecological security in the Wujiang river basin using remote sensing and GIS technologies

To understand the situation and existing environmental protection problems, and to promote coordinated development of the Wujiang river basin economy and ecological construction, the environmental ecological safety of the Wujiang river basin is evaluated in this paper. Applying the RS and GIS techniques, on basis of analyzing the changes of watershed land use and the space-time changes of landscape pattern,an assessment system for ecological security is builded by natural environment,economy and landscape ecology.And with this assessment system,integrating entropy method with attribute identification model,the ecological security of 41 regions of the watershed are assessed. The evaluation results are divided into five categories: good, moderately-good, medium, moderately-bad and bad. The results indicate that: in 2000 the Wujiang river basin had 745.8 km2 (1.13%) of bad, 15,212.2 km2 (23.05%) of moderately-bad, 40,670.7 km2 (61.63%) of medium, and 9,361.4 km2(14.19%) of moderately-good conditions. It is noted that there are some differences between the results for 2000 and those for 2010. In 2010, the Wujiang river basin had 4,330.5 km2(6.58%) of bad, 12,254.1 km2(18.57%) of moderately-bad, 42,804.0 km2(64.86%) of medium and 6,591.4 km2(9.99%) of moderately-good conditions. No good conditions occurred in the Wujiang river basin in 2000 and 2010. However, compared with 2000, the moderately-bad area increased in 2010, and the moderately-good area decreased, indicating that ecological environment is facing a negative trend. The ecological security situation in the upper and the middle catchment is poorer than that in the lower catchment of the Wujiang river basin. In the lower catchment, the problem of hydropower resources over-exploitation is very serious, while in the middle catchment, mining of mineral resources and high population density in big cities play significant roles in ecological security. In the upper catchment, the main problems which affect ecological security include the fragility of the ecological environment, the serious contradiction between people and land, and the problems of soil and water loss and rocky desertification. In summary, the ecological security in the karst area is very fragile, and unreasonable development and utilization of natural resources and the environment leads to deterioration of the ecological environment. In order to ensure sustainable development of the natural and social economy in the Wujiang river basin, it is suggested that the protection of ecosystem, ecological reconstruction, and the systematic research on ecological restoration be strengthened.