This monograph contains the results of studies of forest ecosystem of the mountain area, which were carried out on the territory of one of the largest nature reserves in Crimea - Yalta Mountain Forest Nature Reserve, as well as other test areas. Section I. gives landscape and ecological characteristics of the study area, which is accompanied by a series of maps of the propagation of rare species of plants and animals, and plant communities; phytopathological situation, landscape organization, etc. The methodology and results of the studies are reflected in section II. The state environmental policy and legal framework of biological diversity were analyzed, the structure and content of the environmental monitoring of forest ecosystems in the mountainous Crimea was shown (Section III, IV). Sections V and VI identify the main threats to the conservation of biological diversity in forest ecosystems of the mountain area and clear up the problem of regional management of mountain forest areas.