Urban Ecological Environment Assessment Of Guilin Based On Remote Sensing Data

The urban ecological environment is the foundation of human survival and sustainable development.Guilin,as a famous international tourist destination,has undergone significant changes in its ecological environment after a long period of development and construction.Therefore,a systematic understanding of the ecological environment changes and current situation in Guilin City is of great significance for its sustainable development.This article takes Guilin City as the research area and selects Landsat remote sensing images from five periods of 2000,2005,2010,2015,and 2020.By inverting the concentration of chlorophyll-a in water quality and constructing a remote sensing ecological index,the ecological environment of Guilin City is evaluated to understand its changes and current situation,providing data reference for the next stage of ecological landscape pattern planning in Guilin City.The main research content and conclusions of this article are as follows:(1)To more accurately extract water body information from remote sensing images,this paper proposes a CS-OTSU adaptive threshold water body extraction method and compares its accuracy with other threshold methods.The results show that CS-OTSU outperforms other adaptive threshold methods in water extraction accuracy in three different environments: urban built-up areas,plain areas,and those with mountain shadows.The overall accuracy is higher than 97%,and the Kappa coefficient is higher than 0.93.(2)The CS-OTSU algorithm was used to extract water body information from Guilin City from 2000 to 2020,and the ratio method was used to invert the concentration of chlorophyll a in the water quality of Guilin City and analyze it.The research results indicate that the overall concentration of chlorophyll a in the water quality of Guilin City is showing an upward trend.Meanwhile,the water area in 2020 increased by 38.71 km2 compared to 2000,Reaching maximum value of 212.56 km2,showing an upward trend.(3)Calculate and analyze the changes in the four indicators of greenness,humidity,dryness,and heat in Guilin city.Between 2000 and 2020,the greenness and humidity indicators showed a trend of first decreasing and then increasing,while the dryness and heat indicators showed fluctuating changes.Overall,all four indicators showed an upward trend.Among them,greenness and humidity indicators have a promoting effect on the ecological environment,while dryness and heat indicators have a negative impact on the ecological environment of Guilin City.(4)Using four ecological indicators for principal component analysis to construct a remote sensing ecological index for evaluating the quality of the terrestrial ecological environment in Guilin City.The overall ecological environment quality in Guilin City is showing an upward trend,increasing from 0.575 in 2000 to 0.656 in 2020,with a growth rate of 14.09%.According to the classification and ecological transformation analysis of the remote sensing ecological index,in 2020,the area of areas with moderate or above ecological level accounted for 94.75% of the total area.The improved areas were mainly distributed in the main urban area of Guilin and some areas with frequent human activities.In addition,the remote sensing ecological indices of Quanzhou County,Yongfu County,Guanyang County,Longsheng County,Ziyuan County,and Gongcheng County are all greater than 0.8,mainly distributed in the edge areas of Guilin City.Land use,rainfall,and temperature are important influencing factors of ecological environment changes in Guilin City.