The maximum values of NDVI increased in the plant communities by 30% on Vaigach Island and by 15% on Kolguev Island over the past two and a half decades. "Greening" of the territory is a response of vegetation to climate warming over the last 40 years. The increase in green phytomass closely correlates with the rise in average summer temperatures, elongation of the growing season (at the beginning and in the end), and the amount of accumulated heat. Changes in air temperature and the feedback from vegetation were weaker on Kolguev than on Vaigach.