Butterflies play an important role in ecosystems and provide a range of ecosystem services, including pollination. Butterflies are sensitive to environmental change and are a good indicator of the health of the environment. Currently their numbers are declining. Monitoring data from 18 EU Member States show that between 1991 and 2020 populations of 15 grassland butterfly species decreased strongly, by 29.5%.  To ensure their recovery, Member States need to significantly increase the implementation of existing policies and put in place new conservation and restoration measures.

Figure 1. Grassland butterfly index in the EU, 1991-2020
Grassland butterfly index in the EU, 1991-2020

The status of grassland butterflies has been the subject of long-term monitoring in Europe, most of it done voluntarily, and is a good example of the power of citizen science.

Butterflies play an important role in the functioning of ecosystems and provide a range of services. They pollinate crops and wild plants and serve as a food source for other animals throughout all stages of their life cycle. Butterflies react rapidly to changes in their habitats , hence they are a valuable indicator of environment health and can help measure progress towards biodiversity targets.

While butterfly populations are characterised by year-to-year fluctuations, long-term trends can be revealed by standardised monitoring schemes over longer periods. Data from 18 EU countries show that between 1991 and 2020 the numbers of 15 typical grassland butterfly species declined strongly by 29.5%.  Although this indicator uses 1991 as a baseline, substantial decreases in species abundance, richness and diversity had occurred before this date .

The main drivers of the decline in grassland butterfly numbers are agricultural intensification and changes in land use , including habitat loss fragmentation and degradation . Abandonment of grasslands and the loss of species-rich semi-natural grasslands have been particularly detrimental for specialist species. Agricultural intensification entails high inputs of agrochemicals, including pesticides, which can dramatically reduce insect populations, including butterflies . Climate change often negatively affects specialist species and favours widespread generalist species .

It is difficult to forecast how soon butterfly populations can recover, as they are influenced by a combination of socio-economic and environmental factors and policy measures.  Measures set out in the Habitats Directive, including the establishment of Natura 2000 sites, have helped some populations. However, the declines continue to occur both inside and outside of protected areas . The proposal for an EU regulation on nature restoration paves the way for a broad range of ecosystems to be restored, with an increasing trend in grassland butterfly index  by 2030 as one of the indicators of restoration of agricultural ecosystems and of restoration of pollinator populations. This will require Member States to put appropriate restoration measures in place across different ecosystems.

In addition, it is crucial that more effective and ambitious measures to halt biodiversity loss are included in other policies, such as the EU common agricultural policy (CAP) and that CAP strategic plans support the implementation of the current and upcoming EU biodiversity and nature legislation.