Consequences of succession on extensively grazed grasslands for central European butterfly communities: Rethinking conservation practices

Because of changes in land use, the quantity of extensively grazed or mown calcareous grasslands and their successional stages have drastically declin ed over the last few decades in Central Europe. Old fallow land has decreas e most. It is often afforested or converted into extensively cultivated gra ssland because extensive cultivation is believed to be favorable for divers ity and rare species conservation. The relative importance of fallow calcar eous grasslands, however, has not been investigated fully and might be much underestimated. To evaluate the relative importance of extensively grazed pastures, early and old fallow land, and young forest, we examined populati ons of diurnal butterflies from 14 sites in the Swiss Jura Mountains. We us ed univariate, multivariate, and qualitative methods to compare the success ional stages. The first 2-3 years of succession had little influence on the butterfly fauna. Therefore, pastures and early fallow land were treated as a single "early stage." Old fallow land had significantly higher species r ichness (+32%) and heterogeneity (+65%) and hosted more Red List species (48%) than the early stage. Young forest was depauperate in butterfly specie s. Further, cluster analysis and correspondence analysis showed a close res emblance of the sites of the early stage to each other and a clear differen ce from the sites of old fallow land. All differences were best explained b y the successional age of the sites. Both early stage and old fallow land s howed a high proportion (>25%) of stage-specific species, but more threaten ed species were specific to old fallow land. We conclude that up to now the importance of old fallow land has been underestimated in conservation effo rts in Central Europe. Contrary to the prevailing opinion, it is at least a s important for butterflies as extensively cultivated grassland. Further co nversion into forest, a common habitat in the region, should be prevented. Because old fallow land has become exceedingly rare, its inclusion in manag ement plans is urgently needed. Otherwise, we may soon lose a valuable but often overlooked part of our biodiversity.