In a recent Safeguard study, published in Proceedings of the Royal Society B: Biological Sciences, researchers investigate how local habitat quality as well as agri-environmental schemes (AES) and configuration of the surrounding landscape can contribute to the preservation of pollinator diversity.
Habitat loss, low habitat quality and limited habitat connectivity are among the main drivers of pollinating insects in recent decades. In Central Europe, semi-natural habitats like calcareous grasslands are major remaining refuges for wild pollinators in human-dominated agricultural landscapes. Crop fields alone are unlikely to fulfil the actual needs of pollinators, whereas calcareous grasslands are valuable habitats because of their ability to provide a variety of floral resources and nesting sites. However, due to the unprofitability of extensive farming and the continued agricultural intensification, calcareous grasslands have become increasingly fragmented and isolated.
To address this issue, Safeguard researchers sampled wild bee, butterfly, and hoverfly species in 40 calcareous grasslands in Germany to assess the effects of calcareous grassland area and quality, habitat connectivity, agricultural landscape configuration, and agri-environmental schemes (AES) on species richness and abundance.
Results show that larger calcareous grasslands support more bee and butterfly species, especially endangered ones. Pollinator richness also increases with more flower resources and organic fields, nesting sites, smaller fields, and better connections between grasslands, with varying effects on the three studied species. However, in contrast to expectations, AES flowering fields did not benefit pollinator communities in grasslands.
In conclusion, improving local habitat quality in combination with targeted landscape management effectively promotes pollinator richness in highly fragmented protected grassland. The authors of the study recommend more efforts to be put into expanding the area and connectivity of high-value habitats in order to mitigate extinction debts in fragmented habitats and ensure the long-term preservation of pollinator richness in human-modified landscapes.
Read the full article here.
Figure 1. (A,B) Locations of the 40 study sites (calcareous grasslands) in two study regions: Lower (red) and Upper Franconia (yellow). Map source: Corine Landcover 2018 © GeoBasis-DE / BKG (2023). (C) Calcareous grassland in Upper Franconia. (D) Visualization of variable transect walks for bees, hoverflies and butterflies on calcareous grassland in Upper Franconia.