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Environmental information systems
Butterflies play an important role in ecosystems and provide a range of ecosystem services, including pollination. Butterflies are sensitive to environmental change and a good indicator of the health of the environment. Currently their numbers are declining. Between 1991 and 2023 the index of 17 grassland butterfly species in the European Union decreased very strongly, by 50%. To ensure the recovery of butterflies, 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, 1991-2023
The status of grassland butterflies has been the subject of long-term monitoring in Europe. Most of it is 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 ecosystem 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 the health of the environment and can help measure progress towards EU 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. According to data from 27 EU Member States, the index of 17 typical grassland species showed a very strong decline of 50% between 1991 and 2023. This declining trend is mainly driven by the rarer specialist species, whose numbers have been decreasing consistently since 2003.
The European Red List of Butterflies 2025 report lists four of those specialist species as having a Near Threatened status in the EU: Erynnis tages, Lysandra bellargus, Phengaris arion and Phengaris nausithous. Moreover, 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 , such as 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.
Butterfly loss is part of a wider dramatic decline in wild pollinators and other insects, which has broader implications for ecosystems and their services. The recovery of butterflies depends on 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 recover. However, declines continue to occur both inside and outside of protected areas.
Reversing the decline of pollinators is an objective of the EU Biodiversity Strategy for 2030 and the EU Pollinators Initiative. The EU regulation on nature restoration (NRR) paves the way for a broad range of ecosystems to be restored. The grassland butterfly index is included among three indicators in agricultural ecosystems out of which Member States have to select at least two, with the obligation to put measures in place which aim to achieve an increasing trend in the chosen indicators by 2030 and thereafter until satisfactory levels are achieved.
The NRR also requires Member States to reverse the decline of pollinators by 2030 and maintain positive trends thereafter until satisfactory levels are achieved. The Member States will have to put appropriate restoration measures in place across different ecosystems in order to achieve these objectives.
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 its strategic plans support the implementation of the current and upcoming EU biodiversity and nature legislation.