大兴安岭是我国高纬度多年冻土最发育的地区，现已呈现出较明显的退化趋势。季节融化深度增大，多年冻土地温升高，厚度减薄，融区范围扩大。造成冻土退化的主要原因是气候变暖，以及强烈的人为扰动，包括原始地表严重破坏，地表迳流和排泄条件的改变，以及采暖建筑物的影响等。气候变暖造成大兴安岭冻土的区域性退化，但对局部地方（如林业局、城镇所在地）而言，人为扰动是冻土退化的重要原因。

The Mt. Dahinggan Ling is the high-latitude large permafrost distribution area in China. The permafrost in the region shows an apparent tendency of degeneration. In Amur area, the permafrost also presents an obvious degeneration trend during 1978-1991. (1)The seasonally thawing depth has deepened more than 30cm. The ground temperature at the depth of 20cm has gone up 0. 8℃. (2)The mean annual ground temperature has increased 2. 1-0. 7℃. The thickness of permafrost has reduced 17-52m.(3)The area of talik is expanding. In the I and Ⅱ level terraces and the sunny slope terrains, the high temperature makes the thin permafrost get into ablation gradually and finally leads to talik. The permafrost boundary in Amur North Gully declined about 80m towards the bottom of Gully.The reasons for the change of permafrost are summed up as follows:(l)Climate warming.The mean annual air temperature of the last 30 years has increased about l.6℃. It is a major contributor to regional degeneration of permafrost in the Mt. Dahinggan Ling region. Climate warming can also lead to a rise in the amount of snowfall in winter and a ground surface temperature increase. The increase of the thickness of snowcover would also contribute to the degeneration of permafrost. (2)Influence of the increasingly intense human activity. The increasingly intense human activity has led to severe damages to the vegetation and increase of permafrost ground temperature. It is a major contributor to the local dengeneration of permafrost.