Development of butterfly populations in agricultural environments
Changes in agriculture have reduced butterfly populations. In particular, the decrease in grazing, mowing and natural meadows has deteriorated the living conditions of butterflies.
During the monitoring period, there has been significant annual variation in butterfly populations. Weather conditions largely explain this variation. Summers 2013 -2017 were mainly poor for butterflies but summers 2018 and 2019 were warm and very favourable for butterflies. The populations of most species recovered after two poorer years. Summer 2020 was weaker than previous summers for butterflies but summer 2021 was for a change better.
During the monitoring period 1999 - 2020, 18 of the 45 species monitored were decreased and 21 stable or increased. Butterfly populations have been declining slightly in the 21st century as a whole, due to a number of weak butterfly years hitting the 2010s.
Description of the indicator
Changes in butterfly populations indicate the ecological state of the agricultural environment. Butterfly populations react more quickly to changes in their local environment than bird populations and, as a result, indicate any changes in agricultural environments.
Butterfly populations have been monitored in Finland since 1999. They are monitored using the line transect census method. In this method, the census taker walks along a standard route repeatedly at regular intervals, from the beginning of a summer to the end. During each walk, the census taker records all individuals of all species over an area of 5×5×5 m in front of the census taker.
The Finnish Environment Institute is in charge of monitoring butterfly populations in agricultural environments and producing related information.
This is one of the national impact indicators of the 2014–2020 Rural Development Programme for Mainland Finland.
The indicator will next be updated in January 2023.