Abstract
Under the combined effects of climate change and human activities, permafrost is undergoing accelerated degradation, significantly affecting the boreal ecological, hydrological processes, climate systems, and engineering infrastructure. Northeast China, on the southern margin of permafrost regions on the East Asian continent, has experienced the formation, expansion, and interconnection of taliks (thawed or unfrozen parts in permafrost zones) due to human activities (e.g., mining and urbanization) and natural disturbances (e.g., wildfires), resulting in abrupt and accelerated permafrost degradation. This study leverages extensive remote sensing data and ground observations to explore the impacts of engineering activities on the permafrost environment in the Hola Basin in the northern Da Xing'anling Mountains in Northeast China. The results showed that engineering activities substantially altered the surface landscapes of the permafrost region. From 1969 to 2025, engineering disturbed areas expanded at a rate of 0.31 km2/yr, resulting in the loss of 14.27 km2 of natural surface landscapes, equivalent to 6.42% of the total basin area. Engineering activities also intensified vegetation degradation within and around the disturbed areas. The annual maximum normalized difference vegetation index (NDVImax) in engineering disturbed areas decreased significantly at a rate of −0.010 yr−1 (p < 0.001), and the primary spatial extent of their influence on surrounding vegetation was approximately 360 m, with a bootstrap 95% confidence interval of 296–426 m. Land surface temperatures (LST) were generally higher in engineering disturbed areas than in natural surface areas, with a mean difference of 2.12 ± 2.78 °C and pronounced seasonal variability. Borehole ground temperature observations further indicated that intense engineering disturbance increased the maximum thaw depth or active layer thickness (ALT) and substantially altered ground freeze-thaw processes. In areas of intense engineering disturbance, the ground thawing duration is prolonged, the total duration of ground freezing in the active layer is shortened, and taliks developed locally. These changes can further accelerate permafrost degradation, increase freeze-thaw hazards, and adversely affect the geological environment and engineering safety. These findings provide important empirical and a scientific basis for further elucidating the interactions among climate change, engineering activities, the active layer, and permafrost, while also supporting the sustainable management of northern forests ecosystems and the planning and maintenance of engineering infrastructure in cold regions.