Based on the computation of the coefficients of interspecific conjugacy of Brave, the modern structure of vegetation is established, represented by eight pleiades: forests with Abies sachalinensis; spruce forests with Picea ajanensis; thickets of Sasa senanensis(Franch. et Sav.) Rehder (Shikotan Island), ilm-maple forests with Acer ukurunduenseTrautv. & C. A. Mey and Acer mayriiSchwer. (Kunashir Island), maple-oak forests with Acer mayriiSchwer. and Quercus crispulaBlume (fr. Iturup); Juniperus sargentii(A. Henry) Takeda ex Nakai (Shikotan Island) thickets and communities with Pinus pumila(Pall.) Regel (O. Iturup, Kunashir); alder-birch phytocenoses, reed-grass and coastal meadows, ruderal vegetation. The species diversity of plants is ensured by local species of East Asian origin. An amphipacific group is represented along the coastline, demonstrating the affinity of local species with the North American flora. The proportion of weeds increases on sites with violations. The indigenous phytocenoses are fir and spruce forests, as well as thickets of Pinus pumilaand Juniperus sargentiiin the mountains and on the rocks. Under the influence of unfavorable factors, indigenous groups are replaced by birch forests with Betula ermaniiand secondary meadows, including ruderal-grass-grain cenoses; in places of felling and fires – bamboo forests with Sasa senanensis. According to preliminary estimates, the share of disturbed lands in Shikotan accounts for 40 % of the territory, of which 30 % is due to anthropogenic impact, and 10 % is due to natural factors. In Kunashir, these numbers are 16 and 17 %, respectively, in Iturup – 23 and 16 %. It is shown that despite the secondary nature of the Sasa senanensisthickets, these communities play a key role in preventing further degradation of natural complexes, soil erosion and the development of exogenous geological processes.