Leaving an uncut grass refuge promotes butterfly abundance in extensively managed lowland hay meadows in Switzerland

Abstract

The main goal of this study was to experimentally test whether maintaining a fraction of a meadow uncut would create a refuge that can efficiently conserve butterflies in extensively managed meadows registered as biodiversity promoting areas, the most common type of agri-environment scheme in Switzerland. Leaving part of the meadow uncut was expected to benefit butterflies by providing shelter and food resources once the rest of the meadow has been mown. The measure was experimentally applied since 2010 in 12 sites of the Swiss lowlands (Plateau). There were two experimental meadows per site, with one mowing regime applied at random within the pair. One meadow was managed according to the standard regulations for meadows in biodiversity promoting areas, meaning that the meadow was entirely mown at least once a year, but not before 15 June (control meadows). The second meadow was only partially mown, and a grass refuge of 10-20% of its area was left uncut during mowing operations (refuge meadows). In 2013 we conducted Pollard walk surveys to assess the efficiency of the refuge scheme. Results indicate that after mowing the uncut refuges were occupied by butterflies, with much higher abundances than in control meadows. Keeping an unmown grass refuge within hay meadows would be a simple and easy measure to promote butterfly populations within current agri-environment schemes.