Changes Of Ecosystem Services In Yulin City And Its Ecological Security

The ecological civilization is the sum total of material and spiritual achievements obtained by the objective law of harmonious development of human beings, nature and society,meanwhile, it is a social morphology which takes the harmonious coexistence, benign circulation, comprehensive development, continuous prosperity between human and nature, man and society as basic principle. With the advancement of reform and opening up, the population growth and the development of social economy generates the mounting pressure of human activities on the environment, and the increasingly prominent contradiction between human and land. Although the world has achieved no small amount of success on the ecological security strategy, but it did not fundamentally change the tendency of environment reverse evolution. The environmental disasters and ecological disaster caused by the environmental degradation and ecological destruction didn’t get slow, and the global ecological problems related to human itself safety of global warming, sea level rise, the emergence of the hole in the ozone layer and expanded rapidly, and the sharp decline in biodiversity has ring alarm bells to human again and again. The development of ecological civilization has been written into the constitution at the18th CPC National Congress, and it makes the strategic position of ecological civilization more clear.Yulin, which has a special geographic location, is located in a transitional zone from the forest to grasslands, agriculture to animal husbandry, and its ecological environment is extremely sensitive and vulnerable. The ecological civilization construction and the sustainable development of social economy of Yulin is restricted by all kinds of ecological environment problems, such as soil erosion, desertification, salinization, drought, wind erosion, biodiversity reduction and wetland degradation. Therefore, this article takes the ecological benefit and ecological security as the research subject of Yulin’s ecological civilization construction. Specifically, this article use the time variation in21st century’s first decade time as the main line, and combines related knowledge of statistics, ecology, sustainable development theory, ecological economy theory, the ecological security early warning theory and cybernetics, and analysis techniques of geographic information system (GIS), remote sensing (RS) interpretation and mathematical, etc.Using GIS and AHP method to evaluate the level of ecosystem services of yulin on the the basis of the analysis of its evolution characteristics of pattern. In addition, through the design of ecological security evaluation index system, Yulin’s ecological security has been evaluated by using the PSR model and gray theory methods, and on this basis to carry out the study of ecological security early warning of Yulin. The main results are as follows:1. In terms of ecosystem service function of Yulin:(1)The evolution characteristics and evaluation results of ecosystem service function in Yulin has been clear by analyzing the pattern evolutionary process and spatial variation characteristics of the five aspects of ecosystem service function of the soil conservation, water conservation, windbreak and sand-fixation, carbon fixation and products supply, so the change trend from2000to2010of ecosystem services function of Yulin has identified. And using GIS and AHP evaluation method to divide the class of ecosystem service function in Yulin into five level, they are low, relatively low, medium, relatively high and high.The whole ecosystem services of Yulin is given priority to low and relatively low level, and rarely to high level. From2000to2010, the whole ecosystem service function of yulin has the characteristics of relatively concentrated and regional differences, the overall service function is weak, and showed a worsening trend.(2)Ecological asset value contribution of Yulin was cleared. The biggest contribution rate of ecosystem is water, its contribution rate is as high as36.8%; The second is the most widely covers of grassland ecosystem, the contribution rate is29.01%; The contribution rate of the most powerful ecological service function is20.23%, the rest of the types of ecological services value contribution rate is small:13.42%of farmland,0.79%of desert and0.79%of wetland.(3)The composition of ecological assets of Yulin was discussesed. Ecological assets is mainly manifested in two aspects of soil formation and protection and waste disposal, secondly for biodiversity conservation, water conservation, climate regulation, as well as gas regulation. The ecological assets of biological production, raw materials and entertainment of culture, which represent a small proportion, were1.6%,1.6%and1.6%respectively.2. In terms of ecological evaluation and early warning of Yulin:(1)Using the traditional method of ecological security evaluation, with the natural ecological environment and the characteristics of economic and social development of coal resource-based cities-Yulin as the starting point, building ecological security evaluation index system based on PSR model, through the composite index method of ecological security to evaluate the ecological security of Yulin in2001-2011. the results showed that the index of ecological security, pressure, state and response presents a downward trend in these11years. Meanwhile, the ecological security index, which remained mostly between0.4～0.6, was in a state of less security and general safety, and its ecological security problem is more serious, ecological risk is much higher.(2)Different from the traditional evaluation methods, taking Yulin as a grey system to analyz. Combining with dynamic trend analysis method based on the grey relation theory, evaluated the general urban ecological security of Yulin in2001-2011. This ecological security evaluation method of combining grey relation and dynamic trend can compare differences in different periods of urban ecological security, and make up for the deficiency of the static evaluation method. This evaluation results were consistent with the PSR model from the angle of variation trend, but from the point of ecological security evaluation value, the results were smaller than the PSR model level, which explained that there was a gap between Yulin and the standard state of ecological security city. What’s worse, the gap is becoming more and more big with the continuous development of coal industry. So Yulin was in the relatively dangerous state.(3)By applying the multivariate linear regression forecast model and GM (1,1) forecasting model of grey theory which corresponds to the above-mentioned use of evaluation methods, the next ten years early warning of ecological security status was analyzed. The results showed that, no matter regression prediction or gray prediction, the value of ecological security represent a decline trends, what’s more, it is close to the bottom of the ecological security warning threshold in2020. In fact, If Yulin, as a youth resource-based city, will alert as soon as possible, adhere to the road of the development of green mining, adhere to the diversified economic development, it can be developed to ensure the supply of mineral products and promote the development of urban economy, simultaneously, protect the ecological environment and benefit the livelihood of the people’s ecological safe city.