Analysis of spatio-temporal change of land use around Erhai Lake from 1991 to 2020 based on GEE platform

Erhai Lake is one of the key protected lakes in China. In the past 30 years, the contradiction between economic development and human and land has become increasingly prominent. It is of great significance to study the law of land use change around Erhai Lake in a long time series and analyze the influence degree of human activities. Based on the google earth engine (GEE) cloud platform, and based on the Landsat TM/OLI image data of 7 periods from 1991 to 2020, the random forest method was adopted to classify the land use within 10 km around Erhai Lake by combining the characteristics of spectrum, normalized difference index and enhanced vegetation index. The land use change map and human activity index model were combined to quantitatively analyze the evolution trend of land use types and human activity intensity around Erhai Lake under the background of urbanization. The results show that from 1991 to 2020, the area of forest land and grassland showed a decreasing trend, and the main direction was farmland. The area of construction land continued to increase, and the main source was farmland. The change of water area was small, and the wetland showed a trend of increasing first and then decreasing. The intensity of human activities increased year by year, mainly in the low-impact areas and remained relatively stable. The high-impact areas and medium-high impact areas were mainly concentrated in the south and west of the surrounding lake. The medium-low impact areas presented a sporadic and block-like distribution and a decreasing trend.