Аннотация:ABSTRACT: Permafrost represents a stable environment that has allowed the prolonged survival of ancient microbial lineage at subzero temperature. Significant numbers, of viable ancient microorganisms and their metabolic end products are known to be present within the permafrost. They are the only organisms known to have retained viability over geological time periods and upon thawing renew their physiological activity. Therefore the permafrost can be characterized as a unique physical-chemical complex which can maintain life incomparably longer than any other known habitat. Permafrost thawing due to anthropogenic or natural processes exposes ancient life to modern ecosystems. The paper discussed the geoecological role of such processes.