尼泊尔奇旺地区土地利用覆被与地表温度的时空关系

Land use land cover change(LULCC)and land surface temperature(LST)are two important indicators of global environmental change that have significant impacts on both natural and human systems.Urban growth coupled with a rising population is resulting in increased demand for natural resources,causing land use changes into megacities.In the context of climate change,the world is striving to find an effective way to be"carbon neutral".By the end of 2021,136 countries in the world have put forward their"carbon neutral"commitments,among which Nepal has advanced its"carbon neutral"date to 2045,which is a very challenging task.Therefore,it is particularly important to study LULCC and its relationship with LST in Nepal in recent decades,so as to provide scientific and empirical basis for relevant construction departments to make corresponding plans. The main aim of this research was to assess the LULCC and its impact on LST using remote sensing and GIS techniques for 2002,2012 and 2022 in Chitwan District,Nepal,in order to understand LULCC and their influencing factors in the past 20 years,to rationally evaluate environmental changes in this area.Firstly,Landsat images covering the study area were downloaded from USGS Earth Explorer,and normalized difference vegetation index(NDVI),normalized difference water index(NDWI)and normalized difference built-up index(NDBI)were calculated based on the corresponding bands of the images.After image pre-processing,a supervised approach with a maximum likelihood classifier was employed for the classification and generation of LULC maps for the mentioned time periods.Seven land use classes were identified as barren land,built-up area,cropland,forest,grassland,shrub and water bodies. The results showed that almost all the land cover components have changed(gains or losses)in the time period.Change detection analyses showed that built-up areas increased,especially in the last 10 years.The built-up area increased from 152 km2 to 412.48 km2 in the total study area between 2002 and 2022.The rate of urbanization was dramatic between 2012 and 2022.Cropland area decreased by 11.24%,grassland area decreased by 4.14%,and shrub area increased from 2.15%to 6.08%from 2002 to 2022.In terms of the forest area,it increased from 1393.51 km2 to 1492.31 km2(2002-2012),later in 2022,the area decreased 67.54 km2.It was observed that there has been a rapid change from cropland to built-up areas.The LST also dramatically changed over the time period.The highest LST in the study area was observed in 2022(40.96◦C)and it increased by 5.3◦C from that of 2002(35.66◦C).Therefore,it is crucial to enhance the urban planning,including adopting green city technology,to mitigate the rising LST. Nepal,as one of the least developed agricultural countries in the world,has been seriously affected by urbanization in recent years.The area of vegetation in Chitwan(including cultivated land,grassland,shrub and forest)has been reduced to varying degrees,and the LST has also increased significantly,which needs to attract the attention of some concerned authorities.This study provides scientific support and empirical evidence for the concerned authorities to promptly act upon the issue and formulate plans accordingly.