One of the goals of the EU Nature Restoration Regulation, which came into force in 2024, is to halt species loss and preserve important ecosystem services provided by agricultural landscapes. Scientists at the Helmholtz Centre for Environmental Research (UFZ), in collaboration with the Senckenberg German Entomological Institute (SDEI), have now calculated the Grassland Butterfly Index for Germany – an indicator of the state of biodiversity proposed in the EU regulation. The results, published in the journal Nature Conservation, show a negative trend, especially in recent years. For their calculations, the researchers were able to draw on 4 million observation data collected at the UFZ over the last 20 years as part of the ‘Butterfly Monitoring Germany’ programme.
Agricultural landscapes are among the most degraded habitats worldwide. Their restoration is one of the key measures for halting global biodiversity loss and preserving important ecosystem services. ‘The Nature Restoration Regulation (NRR), which came into force in 2024, is an essential instrument for achieving the restoration targets set for the European Union,’ says Prof. Josef Settele, agroecologist at the UFZ. The objectives also include increasing biodiversity in agricultural ecosystems (Article 11 of the NRR), taking into account climate change, the needs of rural areas and sustainable agricultural production. To implement the overall objectives, EU Member States are required to develop national restoration plans and implement concrete measures in terrestrial, freshwater, coastal and marine habitats.
The extent to which the specific measures are effective and the ecosystems develop positively will be determined using indicators. For agricultural landscapes, these are (a) the grassland butterfly index, (b) the stock of organic carbon in cropland mineral soils, and (c) the share of agricultural land with high diversity landscape features. For at least two of these three indicators, the EU regulation calls for an upward trend towards a satisfactory level by 2030. Since natural conditions vary across EU countries and there is a wide range of different land management practices, Josef Settele argues that all EU countries should start by recording all three indicators so that none of them is prematurely dropped.
With the ‘Grassland Butterfly Index’, a research team led by the UFZ has now calculated one of the three indicators for Germany for the first time and published the results in the journal Nature Conservation. The data for this analysis comes from Butterfly Monitoring Germany (Tagfalter-Monitoring Deutschland - TMD), a long-term programme coordinated by the UFZ and the Society for Butterfly Conservation (GfS). Every week during the summer, volunteers count butterflies at fixed locations using a standardised European method. ‘Since the TMD was launched in 2005, this has resulted in around four million data records being collected, which provide information on the development of butterfly populations in Germany,’ explains one of the co-authors of the publication, biologist Elisabeth Kühn, who coordinates the German Butterfly Monitoring programme at the UFZ.
What does the index show for Germany?
The ‘Grassland Butterfly Index’ tracks the development of populations of 15 butterfly species from 2006 to 2023 that are considered typical inhabitants of various grassland biotopes. ‘Four species have increased, five species show a declining trend. For six species, the trend is uncertain, which is probably due to insufficient data and large differences between the locations where they were found,’ says the study's lead author, bioinformatician Alexander Harpke. In the first decade of the period analysed (2006 to 2016), the index for Germany as a whole shows a slightly positive trend – which does not rule out the possibility that this may vary greatly for individual species.
However, if we look only at recent years (2016 to 2023), the index shows a significant decline overall. This mainly affects specialised species such as the Small Blue (Cupido minimus) or the Dingy Skipper (Erynnis tages); generalists such as the Small Copper (Lycaena phlaeas) or the Meadow Brown (Maniola jurtina) are hardly affected.
These results show that the trend for grassland butterflies in Germany during the comparison period corresponds to the trend at European level, which was last determined by Butterfly Conservation Europe in 2025 for all 27 member states.
Butterflies as indicators
Butterflies are known to be sensitive to changes in their environment. Land use plays a decisive role in this. "The loss and fragmentation of habitats have a proven negative effect on the long-term survival of butterfly populations. Intensive mowing, nitrogen inputs and pesticides contribute to a deterioration in habitat quality or increased mortality. Species that depend on specific habitats, such as nutrient-poor grasslands, also suffer from a lack of use, e.g. through grazing or mowing," explains Prof. Thomas Schmitt from the Senckenberg German Entomological Institute (SDEI) in Müncheberg, who is also co-author of the study. In addition to land use, climate change is increasingly contributing to changes in butterfly fauna. Higher temperatures favour the spread of heat-loving or tolerant species, while species adapted to cooler conditions are in decline.
These dependencies of butterflies on land use and climate change make them excellent indicators of the state of our ecosystems. In addition, they are easy to record – especially by qualified volunteers. Together, these two factors have provided an invaluable database for butterfly monitoring in Germany, which scientists are now evaluating to calculate trends and indicators for reporting under European environmental legislation. ‘The significance and representativeness of the indicator could be further increased if government programmes such as Habitats Directive monitoring or nationwide insect monitoring were integrated into the analysis,’ says UFZ biologist and co-author of the publication Dr Martin Musche. The same would apply if data from neighbouring countries were included.
The work on this publication was funded by the UFZ and the GfS, as well as by the National Monitoring Centre for Biodiversity and the Federal Agency for Nature Conservation (BfN) as part of the FAMos project, with funds from the Federal Ministry for the Environment, Climate Protection, Nature Conservation and Nuclear Safety (BMUKN).
Publication:
Harpke A, Kühn E, Schmitt T, Settele J, Musche M (2025) The Grassland Butterfly Index for Germany. Nature Conservation 59: 315–334. https://doi.org/10.3897/natureconservation.59.162812
Further Information:
Online until 3 October: Participation process for the EU Nature Restoration Regulation (German only): https://beteiligung.bundesumweltministerium.de/de/wiederherstellung-der-natur
How biodiversity can be measured (German only): https://www.sciencemediacenter.de/angebote/24033#section_4_subsection_3
UFZ press release: Butterflies in descent https://www.ufz.de/index.php?en=36336&webc_pm=19/2023
Grassland Butterflies, an identification guide (in German): https://www.ufz.de/tagfalter-monitoring/
Contact
Elisabeth Kühn
UFZ Department of Conservation Biology & Social-Ecological Systems
elisabeth.kuehn@ufz.de
Alexander Harpke
UFZ Department of Conservation Biology & Social-Ecological Systems
alexander.harpke@ufz.de
Dr Martin Musche
UFZ Department of Conservation Biology & Social-Ecological Systems
martin.musche@ufz.de
Prof Dr Josef Settele
Head of the UFZ Department of Conservation Biology & Social-Ecological Systems / German Advisory Council on the Environment
josef.settele@ufz.de
