Distribution of Butterflies (Lepidoptera: Papilionoidea) in Estonia: Results of a Systematic Mapping Project Reveal Long-Term Trends

The distribution of butterflies was mapped throughout entire Estonia in 2016 and 2017. Butterflies were surveyed during three phenologically targeted visits at more than 1200 pre-selected sites. In total, over 180 000 individuals belonging to 97 species were recorded. We compare the resulting distribution maps with historical records, and discuss changes in the species' distribution. We conclude that, within the time frame of century, the changes in the Estonian butterfly fauna were moderate. For about 75% of species, there was no conclusive evidence of a change in distribution or abundance. In case of the remaining 25%, there were more butterfly species with an increasing rather than a decreasing trend in abundance and/or distribution. Some but not all of those changes could be associated with ongoing climate change. The decline of several dry-meadow specialists can be regarded as the most urgent conservation concern.