Published January 29, 2026 | Version 1.0
Report Open

EU Grassland Butterfly Index 1991-2024 Technical report

Authors/Creators

  • 1. De Vlinderstichting / Dutch Butterfly Conservation
  • 2. Butterfly Conservation Europe
  • 3. ROR icon UK Centre for Ecology & Hydrology
  • 4. EDMO icon Centre for Ecology and Conservation, University of Exeter
  • 5. ROR icon Butterfly Conservation
  • 6. UK Butterfly Monitoring Scheme
  • 7. Bulgarian Butterfly Monitoring Scheme, National Museum of Natural History, Sofia, Bulgaria.
  • 8. Dutch Butterfly conservation - De Vlinderstichting
  • 9. SOCEME - Society for the Conservation and Study of Butterflies in Spain, Spanish Butterfly Monitoring Scheme,
  • 10. De Vlinderstichting/Dutch Butterfly Conservation
  • 11. ROR icon Lund University
  • 12. Swedish Butterfly Monitoring Scheme
  • 13. Latvian Butterfly Monitoring Scheme
  • 14. Institute of Life Sciences and Technology
  • 15. ROR icon Universität Innsbruck
  • 16. Viel-Falter Monitoring, Austria
  • 17. Danish Butterfly Monitoring Scheme (Danmarks Dagsommerfugle)
  • 18. ROR icon University of Turin
  • 19. Italian Butterfly Monitoring Scheme
  • 20. CSIC-National Museum of Natural Sciences, Madrid, Spain.
  • 21. SOCEME - Society for the Conservation and Study of Butterflies in Spain, Spanish Butterfly Monitoring Scheme, Spain
  • 22. Andorran Butterfly Monitoring Scheme
  • 23. Andorra Research + Innovation, Andorra
  • 24. ROR icon University of Florence
  • 25. Swiss Butterfly Monitoring Scheme, Switzerland
  • 26. French Butterfly Monitoring Scheme (STERF)
  • 27. Office pour les insectes et leur environnement (Opie), France
  • 28. Wallonia Butterfly Monitoring Scheme
  • 29. Natagriwal asbl, Gembloux, Belgium
  • 30. ZERYNTHIA Spanish Butterfly Monitoring Scheme
  • 31. ROR icon Czech Academy of Sciences, Biology Centre
  • 32. Hazi Foundation
  • 33. Basque Country Butterfly Monitoring Scheme
  • 34. Muséum National d'Histoire Naturelle
  • 35. Slovenian Butterfly Monitoring Scheme, Society for the Conservation and Study of Lepidoptera in Slovenia, Slovenia.
  • 36. Norwegian Butterfly Monitoring Scheme
  • 37. Norwegian Institute for Nature Research (NINA)
  • 38. Austrian Butterfly Conservation – ABC, Austria.
  • 39. ROR icon University of Vienna
  • 40. German Butterfly Monitoring Scheme, (Tagfalter-Monitoring Deutschland - TMD)
  • 41. ROR icon Helmholtz Centre for Environmental Research
  • 42. ROR icon Finnish Environment Institute
  • 43. Finnish Butterfly Monitoring Scheme
  • 44. ROR icon Aarhus University
  • 45. National Biodiversity Data Centre
  • 46. Irish Butterfly Monitoring Scheme
  • 47. University of Ioannina
  • 48. Greek Butterfly Monitoring Scheme (apollo-grBMS)
  • 49. Austrian Butterfly Conservation – ABC, Austria
  • 50. Büro Lang, Zell im Wiesental, Germany
  • 51. Research Institute for Nature and Forest
  • 52. Research Institute for Nature and Forest (INBO)
  • 53. Jersey Butterfly Monitoring Scheme (UKBMS)
  • 54. ROR icon Universitat de Barcelona
  • 55. Urban Butterfly Monitoring Scheme (uBMS)
  • 56. ROR icon Luxembourg Institute of Science and Technology
  • 57. Luxembourg Butterfly Monitoring Scheme
  • 58. Tagis - Centro de Conservação das Borboletas de Portugal
  • 59. Hazi Foundation, Granja Modelo, Arkaute, Spain
  • 60. Centro de Investigación en Biodiversidad y Cambio Global (CIBC-UAM)
  • 61. ROR icon Universidad Autónoma de Madrid
  • 62. Red de Seguimiento de Mariposas Diurnas de Sierra Nevada
  • 63. Cyprus Butterfly Monitoring Scheme
  • 64. ROR icon Near East University
  • 65. Andorra Recerca + Innovació
  • 66. Czech Butterfly Monitoring Scheme, Czech Butterfly Conservation Society, Czech Republic
  • 67. Babes-Boyai University
  • 68. Romania Butterfly Monitoring Scheme
  • 69. Hintermann & Weber AG
  • 70. Biodiversity Monitoring Switzerland (BDM),
  • 71. ROR icon Croatian Natural History Museum
  • 72. Croatia Butterfly Monitoring Scheme
  • 73. Consiglio per la ricerca in agricoltura e l'analisi dell'economia agraria
  • 74. Helmholtz Centre for Environmental Research - UFZ
  • 75. German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany
  • 76. Polish Butterfly Monitoring Scheme, Association for Butterfly Conservation, Poland
  • 77. ROR icon University of Białystok
  • 78. Polish Butterfly Monitoring Scheme
  • 79. Catalan Butterfly Monitoring Scheme, Natural Sciences Museum of Granollers, Spain
  • 80. Lithuanian Butterfly Monitoring Scheme, Ukmerge, Lithuania
  • 81. Hungarian Butterfly Monitoring Scheme, Hungarian Lepidoptera Monitoring Network, Jozsef Szalkay Hungarian Lepidopterists' Society, Hungary
  • 82. Centre of Estonian Rural Research and Knowledge
  • 83. ROR icon University of Tartu
  • 84. Estonian Butterfly Monitoring Scheme
  • 85. Open University of Cyprus
  • 86. Catalan Butterfly Monitoring Scheme
  • 87. Natural Sciences Museum of Granollers, Spain
  • 88. Lithuanian Butterfly Monitoring, Lithuanian Entomological Society, Lithuania
  • 89. ROR icon Temple University

Description

Executive Summary

  1. Butterflies have been systematically monitored in Europe for several decades using standard protocols that are now adopted in over 30 countries. Butterflies are ideal biological indicators: they are well-documented, measurable, sensitive to environmental change, occur in a wide range of habitat types, represent many other insects, and are popular with the public because of their beauty. 
  2. Records from over 16,150 standardized butterfly transects are gathered by National BMS and integrated into a central database as part of the European Butterfly Monitoring Scheme (eBMS) run by Butterfly Conservation Europe (BCE) and the UK Centre for Ecology and Hydrology (UKCEH). The database provides trends on individual species, which can be combined to give trends for different habitats.
  3. In this report, trends for 17 species have been used to generate an updated Grassland Butterfly Index (GBI) for 1991-2024, using data from all 27 EU countries. The GBI is mentioned explicitly in the EU Nature Restoration Regulation (NRR) in Article 11 on the Restoration of Agricultural Ecosystems as one of the three indicators that Member States can elect to monitor. Member States choosing the GBI as one of their two mandatory indicators shall achieve an increasing trend at the national level until the satisfactory levels as set in accordance with Article 14(5) are reached.
  4. The EU Grassland Butterfly Index shows a decline of 47% since 1991. In North-western Europe, the decline is primarily attributed to habitat loss resulting from the intensification of agricultural grasslands, nitrogen deposition and pesticide drift in nature reserves. In Northern Europe (Scandinavia, Finland and the Baltic states), Eastern and Southern Europe and the Alps, the abandonment of grasslands is also a strong driver as shrubs and secondary forest encroachment result in net habitat loss for grassland butterflies. The decline observed over the last 34 years likely reveals only part of the historical decline in grassland butterflies, as many populations were extirpated from the landscape before 1990.
  5. The GBI is the indicator on the EU Dashboard Target 5 for evaluating progress with improving agroecosystems for biodiversity. It is also part of the EU Sustainable Development Indicator set for evaluating the implementation of the Global and EU Biodiversity Strategy.
  6. This report provides an essential message from scientists to policymakers - that butterflies are still declining at an alarming rate across the EU and that urgent action is required to protect and restore habitats to reverse this trend, not only for butterflies but also for other wild insect pollinators and their ecosystem services. The completion and appropriate management of the Natura 2000 network across Europe are crucial for helping grassland butterflies. Restoration and creation of landscapes with mosaics of habitats, both within and outside Natura 2000 areas, are essential to protect grassland butterflies in the EU.
  7. We are grateful to the many thousands of volunteer butterfly recorders who contribute their records to this important database, to the many BMS schemes, coordinators and funders who support the work, and to the EU for funding the eBMS through the EMBRACE project.

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Additional details

Related works

Has version
Report: 10.5281/zenodo.17174718 (DOI)

Funding

European Union
Expanding Monitoring of Butterflies for Restoration and Conservation across Europe 2021-2026 Contract no. 090201/2024/929792/SER/ENV.D2