About the reasons for the rare plant species disappearance in the Upper Volga region Elena Borisova, Nikita Konotop, Julia Vinogradova, Dmitriy Markov and Alexey Sivukhin E3S Web Conf., 169 (2020) 03003 Published online: 19 May 2020 DOI: 10.1051/e3sconf/202016903003