Analysis Of Land Use Change And Ecological Effects In The Lower Reaches Of The Yellow River Based On Google Earth Engine

As the most visual landscape marker on the earth’s surface,land use/cover change（LUCC）objectively records the surface landscape’s spatial and temporal change processes,and it is an essential tool for rational control of natural resources and monitoring of them environmental changes.LUCC has become a hot issue in the field of global change-related research.LUCC is not only closely related to human production activities but also profoundly affects the sustainable development of the ecological environment.An in-depth analysis of LUCC and its ecological effects is of great significance in optimizing the spatial pattern of land and ensuring environmental security.In recent years,the land use/land cover（LULC）of the lower reaches of the Yellow River has changed considerably under the combined effect of various factors such as population growth and urban expansion.This has led to intensifying the conflict between human activities and the ecological environment.This phenomenon seriously threatens the sustainable development of the lower Yellow River region.Scientific analysis of LUCC and their ecological effects in the lower reaches of the Yellow River is of great significance for the comprehensive optimization of regional land resource allocation and sustainable socio-economic development.This thesis takes the lower reaches of the Yellow River as the study area,based on the Google Earth Engine（GEE）cloud platform,using Landsat remote sensing imagery as the data source,and integrating and analyzing Support Vector Machine（SVM）,Random Forest（RF）and Gradient Boosting Decision Tree（GBDT）through a voting method.Then the article obtains the LULC information of the study area for three periods from 2000 to 2020 based on the knowledge of this method and quantitatively evaluates the ecological environmental quality of the study area by using the Remote Sensing Ecological Index（RSEI）.Finally,combining the LULC data and the ecological quality evaluation data,we analyze the inner connection between LUCC and ecological environmental quality and reveal the ecological effect of LUCC.The main conclusions are as follows:（1）This thesis obtains the LULC and ecological environmental quality in the lower reaches of the Yellow River by coding with the data resources and computing power of the GEE cloud platform.The emergence of the GEE platform effectively solves the low processing efficiency of large-scale long-time series remote sensing data,improves the work and scientific research efficiency.（2）The accuracy of the integrated classification results of the voting method is higher than any of the three classification methods,with an overall accuracy of more than 86%and a Kappa coefficient of more than 0.85.Different LULC types also have a higher producer accuracy and the user’s accuracy.These data indicate that the classification algorithm used in this thesis has reliable accuracy in classification results.By analyzing the spatial and temporal characteristics of LUCC,the thesis finds that the main LULC types in the study area are farmland and construction land,in which the area of farmland accounts for more than 50%.The area of construction land always accounts for more than 20%.The area of farmland,forest land,and grassland decreases,and the area of construction land gradually increases,increasing about2953.06 km~2.The most critical transfer methods are farmland to construction land and grassland to construction land in terms of land use transfer.（3）The average values of RSEI in the lower reaches of the Yellow River from 2000 to 2020are 0.58,0.63,and 0.60,respectively,indicating that the ecological environmental quality in the study area rises first and then decreases overall trend is in improvement.The ecological environmental quality grades in the lower reaches of the Yellow River are mainly good and average,and the general ecological grade changes are better and unchanged,indicating that the ecological environmental quality in the study area is durable and enhancing.（4）LUCC and ecological environmental quality have a strong correlation.Ecological environmental quality and land use patterns have a high degree of consistency.By analyzing the RSEI of different LULC types,we found that the mean values of RSEI of farmland,forest land,and grassland are higher than those of construction land.The relationship between LUCC and ecological environmental quality was analyzed by correlation and regression analysis.It was found that the proportion of area with improved ecological quality and the increase in the area of farmland and grassland had a significant positive correlation（R>0,P<0.01）,indicating that the rise in the area of farmland,forest land,and grassland had a positive effect on the improvement of ecological quality.Hence,the proper planning of regional land use patterns is essential for improving the quality of the regional ecological environment.