More butterflies in the forest

Cutting back trees in the traditional way has a positive effect on bio-diversity / Getting wood for energy sustainably

Münster (upm), Mi, 20 Feb 2013

The Hardtwald forest in Alsace, showing an area in its second year after coppicing was carried out.

photo: Cornelia Müller

Woodland butterflies are among the most endangered butterflies in Europe. Their habitat is sparse forests of the kind that were once plentiful in Central Europe. Landscape ecologists from Münster University have now for the first time studied how a traditional form of woodland usage, whereby selected trees are heavily cut back over decades, affects communities of various species of woodland butterflies. The conclusion they have come to is that if this method were more widespread there would be significantly more butterflies in the forests of Europe. The results are being published in the March issue of the journal "Biological Conservation".

In the past people used forests for example as grazing pasture, or they cut back the trees for firewood. "As recently as the 17th and 18th centuries, coppices with a variety of deciduous trees at all stages of growth were the most frequently encountered type of forest in large areas of Central Europe," explains Dr. Thomas Fartmann from the Institute of Landscape Ecology at the University of Münster and lead author of the study. One characteristic method of woodland management is the use of coppicing whereby, in a 30 to 40-year cycle, selected trees are cut back to their stump, from which new shoots then grow. Based on studies in the Hardtwald forest in Alsace in north-eastern France, where the traditional coppicing is still carried out, the researchers have now demonstrated that the number of different species of butterfly – including endangered species – is increasing as a result of this form of thinning-out, with different species preferring different stages of woodland growth.

"The bio-diversity in the forest can be increased by using a suitable form of woodland management," says Fartmann. For researchers, butterflies in coppices also serve as indicators of the occurrence of other species of insects with similar habitat requirements. Coppices with a rich diversity of species are, however, the exception. In Germany the area they cover accounts for less than one percent. Today in Central Europe there is predominantly high forest woodland, i.e. woodland consisting of tall trees standing close together whose crowns allow hardly any sunlight through to the ground. These tall, straight trunks are suitable for obtaining high-quality timber. But, says Thomas Fartmann, "in order to get wood for energy, an increased use of coppicing on the historical model and the recultivation of coppices is a worthwhile alternative – also economically – especially in view of the debate about producing renewable raw materials."

Grasses and herbs can establish themselves naturally in sundrenched coppices. Clearings – where cutting-back took place only a few years ago – are particularly full of butterflies. Here there is a layer of herbs and shrubs with many of the melliferous plants so important for butterflies – as well as plants providing food for the caterpillars. Only a few species occur in high-growing woodland areas. The researchers have recorded a total of 36 species of butterfly in the area they studied, including 13 endangered species.

Original publication (online first):

Fartmann T., Müller C. und Poniatowski D. (2013): Effects of coppicing on butterfly communities of woodlands. Biological Conservation 159, 396-404; DOI: 10.1016/j.biocon.2012.11.024

Original publication (online first)

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