Rapid development of thermokarst lakes and driving factors along a highway in Northeast China (2000–2020)

In the northern Da Xing'anling Mountains of Northeast China, thermokarst lakes have undergone significant changes. These changes are particularly evident along the Highway X302, which stretches from Yakeshi in the south to Yituli'he in the north, across zones of discontinuous to patchy Xing'an permafrost (XAP). Thermokarst lakes are highly sensitive to both climate warming and human activities. However, changes in their areal extent and number over the past two decades remain unclear. To identify the drivers of thermokarst lake changes in the XAP region, this study analyzes the relationship among lake dynamics, climate change, and human activities. Rich data on lake changes were extracted using the modified normalized difference water index (MNDWI) from the Google Earth Engine (GEE) and verified against the Joint Research Centre (JRC) global surface water datasets. The results show a net increase in both the number and areal extent of thermokarst lakes along the Highway X302 from 2000 to 2020. Larger lakes (greater than 0.01 km 2 ) expanded in surface area. Meanwhile, smaller lakes (less than 0.01 km 2 ) increased in number. A bell-shaped trend was observed, with an initial increase in lake area followed by a decline around 2013. Before 2013, climate factors such as precipitation, air temperature, and potential evapotranspiration (PET) strongly influenced lake changes. After 2013, annual precipitation became the dominant driver of lake expansion. Human activities also contributed to changes in permafrost thermal regimes, further influencing lake dynamics. These findings provide valuable insights into the management of thermokarst lakes and wetlands in the region, and offer a reference for mitigating frost-related hazards along the Highway X302.