Background & Aims

Biodiversity loss is one of the biggest issues of our generation. In conservation ecology biodiversity loss is the number one priority. As temperatures rise due to climate change the likelihood of extreme weather events such as droughts, floods and storms are increasing conservation efforts has to include predictions of how habitats can change as a result of extreme weather events.

Conservation projects are focused on one specific species, usually one that is especially important or threatened. Habitat suitability evaluation is the first step of conservation efforts for a species. In this study the focus has been on the large blue (Phengaris arion). The impacts of extreme weather events on species distribution and habitat choice can give implication on how conservation efforts can be allocated to ensure that species survive extreme weather, and will therefore become more important for conservation research as the climate is changing.

In the summer of 2018, an extreme drought caused a crash in the population of P. arion on Gotland, and in 2019 only 9 individuals were found. Since then the population has increased and 2021 population was almost back to pre-drought size. The underlaying factors for this extraordinary recovery are so far unknown but can be of great importance to mitigate effects of future extreme droughts. By considering both habitat requirements for a normal year and factors for surviving an extreme year a long term conservation of P. arion will be possible. By analyzing habitat factors where individuals of P. arion survived the extreme year of 2018 on Gotland and recovery patterns, factors for P. arion surviving an extreme drought will be identified.


In this study, habitat requirement assessments of P. arion was done on both individual and population scale. By comparing habitat preferences from previous years and evaluating the habitat requirements of individuals, key factors to survival of populations on Gotland was assessed. By doing this, the aim was to determine: (1) effects of the drought on the distribution of P. arion, (2) habitat choice for adult P. arion on Gotland during the recovery from the extreme drought in 2018, (3) small scale habitat preferences for P. arion on Gotland.