Brussels, 20 Mar 2006
Butterfly populations are in sharp decline throughout Europe. The authors of a new study, published in the Journal of Insect Conservation, believe the reason for this loss to be a parallel loss of biodiversity.
Not only do the researchers mourn the loss of butterfly populations, they also believe that butterfly populations are excellent indicators of the general health of European natural spaces. 'The sensitivity to environmental changes and the availability of data across Europe suggest that they [butterflies] are very good candidates to build biodiversity indicators and, along with other major groups such as birds, suitable to monitor progress towards the EU target of halting biodiversity loss by 2010,' reads the article.
The study tracked 576 butterfly populations across 45 European countries, with the lead researchers based in Wageningen in the Netherlands, Dorset in the UK and Paris, France. They found worrying rates of decline: 71 of those 576 species are now classified as 'threatened', although rates of decline are not stable throughout Europe. Butterfly populations have fallen by between 75 and 100 per cent in Belgium, and by zero to 25 per cent in Ireland in the last 25 years.
The researchers identified three main causes for the decline in butterfly numbers: habitat loss, as many butterflies inhabit arable-type farmland, and these areas are disappearing. Loss of wetlands, especially in eastern Europe, which are drained for farming, and climate change, which is driving butterflies north, to cooler areas which have even less habitat.
The overall decline in butterflies varies according to habitat. The overall decline is 11 per cent over 25 years, but taking specific habitats, wetland species are 15 per cent down, forest species 14 per cent down and grassland species by 19 per cent. Butterflies living in general habitats experienced the smallest, at only one per cent. The steep declines in butterfly populations that live in specialist habitats can thus be seen to reflect the declines in those habitats.
'We were surprised how clear-cut this is,' British researcher Martin Warren told the New Scientist. However, there was some good news from the study. Agri-environment schemes have already succeeded in slowing and in some cases reversing the declines certain species. 'Policies such as the EU Habitats and Species Directive may also help to slow declining trends but many countries have been slow to implement this directive,' reads the report.
The researchers hope that the depth of their work can improve further thanks to a generally high interest in butterflies throughout Europe. 'The infrastructure needed to obtain butterfly data at a European level is [...] already well developed and, given sufficient resources, could produce an even more scientifically robust method of monitoring change in the future,' reads the report.