To reverse the decline in plant and animal biodiversity, it is urgent to restore species-rich grasslands. Identifying successful restoration strategies is therefore highly relevant, especially with regard to the national implementation of the EU nature restoration regulation. In this context, butterflies can be used as sensitive indicators that allow for a holistic assessment of restoration success and take the landscape context into account.
Our study aimed to determine under what conditions species-rich butterfly communities can be restored. For this purpose, we conducted a large-scale study and surveyed 121 restored meadows and pastures, 33 positive (old, species-rich) and 33 negative (old, degraded) reference sites in northern, central, and southern Germany. To provide a more refined assessment of restoration success, we defined target butterfly species that are associated with high-quality grasslands and have a lower dispersal ability. A central aspect of our study was the comparison of four common restoration methods, such as sowing cultivar or regional seed mixtures, transferring seeds harvested directly from suitable donor sites, and adjusting management without actively introducing plant species.
Our results show that the establishment of a high plant diversity is closely linked to the recovery of butterfly assemblages. Future restoration efforts should aim to develop species-rich habitats exclusively through high-quality restoration methods and maintain them through site-specific and insect-friendly management. Of all methods, the sowing of cultivar seed mixtures was the least successful, with this failure being even more pronounced for target species.
We found that successful grassland restoration promotes butterflies in various landscapes. However, further efforts are needed to enable target species with low dispersal ability to establish themselves; for example, the proportion of species-rich grassland areas in the surrounding area and landscape heterogeneity should be increased. Finally, although the restoration of species-rich meadows and pastures is usually successful, the conservation of existing, species-rich grasslands must be given the highest priority.
The Applied Ecologist 