Biodiversity: European Grassland Butterfly Indicator in decline

Published on 28/08/2015

The European Grassland Butterfly Indicator Report, to which twenty-two European countries (EU and non-EU) contributed by providing their butterfly counts has just been accepted by the European Environment Agency (EEA).

In Luxembourg, the national monitoring scheme for common butterfly species, was implemented by researchers from LIST's Environmental Research and Innovation (ERIN) department.

Due to their high numbers of species and their wide range of ecological requirements, butterflies, like birds and vascular plants, are good expressions of the level of biodiversity (that is, the variety of life forms) in our landscapes. Their generally low dispersal capacity, their short life cycle and a high sensitivity and responsiveness to climate conditions also make butterflies good bioindicators of environmental change. In addition, butterflies are emblematic, well known and easy to identify in the field.

The European Grassland Butterfly Indicator represents one of the EU biodiversity indicators of the European Environment Agency (EEA). Data for seventeen grassland butterfly species have been used to assess abundance trends between 1990 and 2013. Of those seventeen species, "ten have declined in the EU, three have remained stable and three increased. For one species the trend is uncertain". At the European scale, grassland butterfly abundance has declined by 30% since 1990 (Fig. 1). Nevertheless, the downward curve shows a slowdown in abundance decline in the last 5-10 years.

 

 

Figure 1. The Pan-European Butterfly Indicator for Grassland species 1990-2013.

 

The two main reasons for this decline are the "agricultural intensification where the land is relatively flat and easy to cultivate; and abandonment in mountains and wet areas, mainly in Eastern and Southern Europe".

"Agricultural intensification leads to uniform, almost sterile grasslands for biodiversity. Fertilisation reduces plant diversity (both host-plants and nectar sources) and the cessation of haymaking in favour of more profitable silage regimes is particularly detrimental. Grassland butterflies thus mainly survive in traditionally farmed low input systems (High Nature Value Farmland; HNV) as well as nature reserves, and marginal land such as road verges and amenity areas."

Given the abundance trends described above, the following recommendations are given:

  • Extend protection of the remaining semi natural grasslands, and improve restoration and recovery programs of grasslands that have become degraded;
  • "Member States can choose to identify, designate and protect "Environmentally Sensitive Grasslands" under the Common Agriculture Policy 2013 reforms [...] to help prevent further losses of HNV grasslands and support restoration." This includes greater financial support for HNV farming.

"Butterflies offer the possibility to be used as a structural headline indicator, not only for grasslands, but also for other habitats and help evaluate agriculture policy and track other pressures such as climate change."

The full report is available here.

The Common Butterfly Scheme in Luxembourg

In 2010, the Public Research Centre Gabriel Lippmann, today integrated into the Luxembourg Institute of Science and Technology (LIST), implemented a national monitoring scheme for common butterfly species, with the financial support of the Ministry of Sustainable Development and Infrastructures. The sampling strategy for this monitoring is based on an internationally standardised method, where repeated butterfly counts are undertaken along +/- 2.5 km transects representing Luxembourgish landscapes.

 

Figure 2. Luxembourgish abundance trends of two common grassland species. Reference value of year 2010 is set to 100.

Fig. 2 illustrates that declines in butterfly populations also have occurred in Luxembourg. However, butterflies typically have high inter-annual variations, and therefore population trends need to be analysed over a longer period. With further analyses we will also be able to distinguish population trends given different land uses (e.g., grassland, crop, urban area), regions (e.g., Oesling, Gutland, Minette) or even environmental policies (e.g., nature reserves, European directives, agroenvironnemental measures, etc.).

In 2015, 30 transects across the country will be monitored for the 6th year. It is not too late to take part: there is now unequivocal scientific evidence that biodiversity loss affects the functioning of ecosystems and thus certain benefits that these provide to humanity. Hence, additional data is essential to track environmental changes that might contribute to such biodiversity loss. This is especially important during these times of rapid global changes (such as in climate, land use, Common Agricultural Policy...)!

 

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 Xavier MESTDAGH M.Sc.
Xavier MESTDAGH M.Sc.
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 Ivonne TREBS
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