| Human activities always change the Earth's natural environment. Land use is the most direct manifestation of such activities. The direct result is the change of land cover. These changes have a major impact on the ecological environment and endanger the ecological security. Acquainting the mechanisms and evaluation methodology of ecological security, researching the development status and problems of the ecological security and counter measures will play an important role in the sustainable development of the city.The land use maps of 2002, 2006 and 2008 of Hefei by visual interpreting the images, with RS and GIS spatial information technology and multi-period satellite remote sensing image, such as TM and ETM+. Land use Changes in Hefei were analyzed on the basis of the 2002, 2006 and 2008 land use maps. The main ecological effects caused by the changes in land use structure were researched. Combined with the "pressure - state - response" conceptual model and socio-economic indicators to establish the evaluation system of ecological security of land use. The ecological security of Hefei from~2002 to 2008 was evaluated. The reasons of the changes in land use of ecological security were studied. Based on the outcome measure the solution of is proposed to improving the land use ecological security of Hefei were put forward. The main conclusions are as follows:The features of land use in Hefei from~2002 to 2008: forest land and construction land increased, of which the construction land increased the most, the construction land increased 6006.05 hm~2 during 6 years. Farmland, water area, grassland and unused land decreased. And the area of farmland and water area reduced more, reduced by 4564.02 hm~2 and 1072.84 hm~2 during 6 years.Changes in land use caused a series of ecological effects: the values of ecosystem service and environmental quality were reduced. From 2002 to 2006, the value of ecosystem service was brought down from 593.1716 million Yuan to 573.137 million Yuan, and the value of ecosystem service is 52395.19 million Yuan. Decreased 11.67%. From 2002 to 2006, the value of environmental quality was brought down from 0.3530 in 2002 to 0.3381 in 2006, and that was 0.3254 in 2008.The change of land use undermined the pattern of ecological security, leading to the reduction of the level of ecological security. In this study, the author uses the gray correlation analysis method to evaluate the ecological safety in study area. And the evaluation results show that: In 2002, Hefei's ecological safety is the critical level; And in 2006 and 2008,the level of ecological safety are extremely unsafe, meanwhile, the situation in 2006 is better than that in 2008.From~2002 to 2008,Hefei's level of overall ecological security is of declining trend.Changes of ecological security in the study area are mainly caused by farmland, construction land and water area. Of which, conversion of farmland for the construction land is the main reason for changes of ecological security in this region. Natural disasters, non-agricultural population, economy, transportation, policy and regulation are all main factors to cause changes of ecological security in Hefei.The measures to promote the level of ecological security in Hefei. We should focus on protecting land that is of high ecological position; we should control strictly the situation of land expansion of villages, mining in basic farmland protection areas; we should plan the land for urban land rationally, and improve the efficiency of land use and prevent blind expansion. |
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