Study On Ecological Environment Quality Restoration And Its Influencing Factors In "5.12" Severest Disaster Area

The ecological environment is the material basis for human survival and development,and the quality of the ecological environment reflects the suitability of the ecological environment for human survival and social and economic development.It’s an important evaluation indicator of whether a region can achieve sustainable development.Human activities and large-scale natural disasters will have a huge impact on the quality of the regional ecological environment.On May 12,2008,a magnitude 8.0 earthquake occurred in Wenchuan County,and the earthquake severely damaged an area of more than 100,000 square kilometers.Among them,there were 10 counties(cities,districts)in the worst-hit area,41 in the most severely-hit area,and 186 counties(cities)in general disaster areas.The earthquake not only caused a large number of casualties and major economic losses,but also caused a series of serious ecological and environmental problems such as vegetation destruction,soil erosion,and damage to biodiversity,which severely threatened the safety of the regional ecosystem.The 10 counties(cities,districts)where the worst-hit areas are located are important ecological barriers in the upper reaches of the Yangtze River,and they undertake a variety of important ecological functions such as water conservation,soil and water conservation,and biodiversity maintenance.Therefore,the analysis of the damage and restoration degree of the ecological environment quality in the extremely severely disaster-stricken areas is of great significance for grasping the dynamic changes of the ecological environment quality in the extremely severely-affected areas and promoting the restoration of the ecological environment.This article takes 10 counties,cities and districts in the severely stricken area of the "5.12" earthquake as the study area: Qingchuan County,Pingwu County,Mao County,Beichuan County,An County(now Anzhou District),Mianzhu City,Wenchuan County,Shifang City,Dujiangyan City,Pengzhou City.Based on MODIS data products,we select 5indicators,including Land Surface Temperature(LST),Gross Primary Productivity(GPP),Leaf Area Index(LAI),Fractional Vegetation Cover(FVC)and ground humidity(Wet),then we use principal component analysis method to scientifically determine the index weights,to comprehensively evaluate the study area before the earthquake(2007),earthquake time(2008),after the earthquake(2019)),analyze the damage of the "5.12" earthquake to the ecological environment of the study area,and evaluate the restoration level of the ecological environment of the study area after the earthquake.And in-depth analysis of the factors affecting the restoration of the ecological environment in the study area in a qualitative and quantitative manner,in order to scientifically grasp the dynamics of the ecological environment in the study area.The changes provide theoretical research ideas and data support for the smooth implementation of the "combined protection and not development strategy" of the ecological protection barrier in the upper reaches of the Yangtze River.The main research conclusions of this paper are as follows:(1)The earthquake caused great damage to the ecological environment quality of the study area,and its ecological environment quality is slowly recovering after the disaster.Before and during the disaster period,the ecological environment quality in the study area was destroyed as high as 78.46%.The ecological environment quality in most areas was slightly damaged,and the proportion was 65.04%.During the disaster-post-disaster period,the proportion of the improvement part of the ecological environment quality in the study area was 54.26%,and the main type of improvement was slight improvement,and the proportion was 44.50%;From the comparison between the pre-disaster and post-disaster,the eco-environmental quality of the study area is mainly restored to medium type,and the proportion of well restored type and poorly restored type is relatively small.The proportion of moderately recovered type was 48.34%,and the proportions of well-recovered type and poorly recovered type were 27.46% and 24.2%,respectively.(2)The quality of the ecological environment in the study area has not been restored to the pre-earthquake level,but the restoration status of each county is different.The average values of the eco-environmental quality index for the three years in the study area were 0.66,0.57,and 0.59,which experienced a process of first decline and then rise,but the end of the study was lower than the beginning of the study.And from the perspective of the ecological environment quality level,the proportion of medium and good grades at the end of the study is smaller than that at the beginning of the study.In 2007,the proportion of medium and good grades in the study area was 72.28%.In 2019,the proportion of medium and good ecological environment in the study area was 69.86%,which was not as good as the initial stage of the study,even less than the initial stage of the research.Pingwu County and Qingchuan County are well-restored areas,Anzhou District,Maoxian,Mianzhu City,and Beichuan County are moderately restored areas,and Pengzhou City,Dujiangyan City,Shifang City,and Wenchuan County are poorly restored areas.(3)The ecological restoration of the study area is affected by policy planning and natural and socio-economic factors,but policy planning is the main factor,and the explanatory power of natural and socio-economic factors is relatively small.The main guarantee of ecological restoration in the study area is the special planning of ecological restoration and the planning of main functional areas.The order of the explanatory power of each influencing factor to the ecological restoration of the whole study area is altitude > terrain relief > slope > aspect >precipitation > temperature > evapotranspiration.For different restoration types,the order of the explanatory power of each influencing factor to the well restored area is altitude >precipitation > distance from town > distance from highway > evapotranspiration > terrain relief > slope > population density > aspect > temperature > GDP > land use degree,the order of the explanatory power of the influencing factors to the moderate recovery area is as follows:altitude > terrain relief > population density > precipitation > distance from town > GDP >land use degree > slope > temperature > evapotranspiration > aspect > distance from road,and the order of the explanatory power of the influencing factors to the poor recovery area is as follows: altitude > temperature > distance from town > distance from road The results showed that the order of population density > precipitation > land use > evapotranspiration >terrain relief > GDP > population density > slope > aspect.(4)Starting from the overall study area and the level of different restoration areas,different ecological restoration strategies should be adopted.From the overall perspective of the study area,the ecological restoration work of the administrative regions in the severely affected areas should enhance the ecological management and protection capabilities of the nature reserves,and enhance the coordination between departments and improve the efficiency of ecological restoration,and improve the awareness of ecological safety and implement strict Ecological protection policy.From the perspective of different restoration areas,Pingwu County and Qingchuan County in the well-restored areas should clearly restore the medium and poor concentrated distribution areas,and adopt a combination of natural and artificial restoration methods according to the topographic characteristics.Restoration of Anzhou District and Mianzhu City,which are key development zones in the medium-sized area,should strictly control the permitted construction area of the city,and artificially restore vegetation.The Mao County and Beichuan County in the restricted development zone should mainly be restored naturally,supplemented by appropriate manual intervention.In the key development zones in the poorly restored area,Dujiangyan City,Pengzhou City,and Shifang City should focus on artificial cultivation of green vegetation,and strictly control the ecological damage caused by urbanization.Wenchuan County in the restricted development zone should focus on natural restoration,and limit the ecological disturbance caused by human activities.