基于GEE平台的1991—2020年环洱海地带土地利用时空变化分析

洱海作为我国重点保护湖泊“新三湖”之一，近30年间环洱海地带经济发展与人地矛盾的问题日益突出. 研究环洱海地区长时间序列的土地利用变化规律，分析人类活动的影响程度对保护治理洱海具有重要意义. 基于谷歌地球引擎(GEE)云平台，以1991—2020年7期Landsat TM/OLI影像为基础数据，融合光谱、归一化差异指数和增强型植被指数等特征，采用随机森林方法对环洱海10 km范围进行了土地利用分类，结合土地利用变化图谱、人类活动指数模型定量分析了城镇化背景下环洱海地带土地利用类型的演变趋势及人类活动强度. 结果表明:1991—2020年林地、草地面积整体呈减少趋势，主要转出方向为耕地；建设用地面积持续增长，主要转入来源为耕地；水域面积变化较小，湿地呈先增加后减少趋势，上述变化趋势与环洱海地区城镇化快速推进有关；人类活动强度总体逐年上升，以低影响区为主且保持相对稳定.高影响区和中高影响区主要集中于环湖南侧和环湖西侧，中低影响区呈零星块状分布且一直呈减少趋势. 

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.