Ecological-Botanical Garden of the University of Bayreuth is a hotspot for wild bees in Central Europe

Bees are the most important pollinators worldwide and are not only indispensable for the preservation of wild plant species, but also for the pollination of a large part of our crops. Bees are thus considered an ecologically and economically very important group with indispensable ecosystem functions. Worldwide, however, fewer and fewer bee species have been recorded since the 1990s. Against this background, the high number of species of 214 wild bee species found in the Ecological Botanical Garden (ÖBG) is very pleasing.

In his Master's thesis, Daniel Schanz mapped the wild bees of a 13.5 hectare section of the ÖBG's open space in almost 40 inspections from March to September 2022. This was the second study of the wild bee fauna in the ÖBG after its first survey in 2000. In addition, he recorded the flower-visiting behaviour of native and non-native plant species. The work was supervised by Prof. Dr. Elisabeth Obermaier (ÖBG, University of Bayreuth) and Prof. Dr. Stefan Dötterl (University of Salzburg), who carried out the survey in 2000. Compared to the survey 22 years ago, the 85 newly added bee species are often more heat-loving and significantly less widespread northwards than bee species with a record in both surveys.

"The high number of species in the ÖBG is mainly justified by the high habitat diversity in a small area and with many different flowering plants and nesting areas," says Daniel Schanz. "These include the willow culture with flower-rich ground vegetation, many rarely mown meadow areas, the useful plant garden and the Calluna heath, as well as a sandy slope for ground-nesting species. In addition, dead wood provides further opportunities for species that rely on such structures to establish their nesting sites." In the ÖBG, spontaneously emerging wild herbs are also tolerated in many places, and their importance for the bee fauna can be considered very high.

Overall, the studies prove that the ÖBG with its many native plant species and diverse nesting opportunities is a hotspot for bees in Central Europe.

"Against the background of an increasing intensification of the cultivated landscape with fewer and fewer habitats for wild bees, near-natural gardens are becoming more and more important, also for endangered bee species," emphasises Prof. Dr. Elisabeth Obermaier. "Furthermore, the study shows that the bee fauna has changed significantly within 22 years." Among the newly added species, quite a few are particularly heat-loving, such as the Halictus subauratus, which has already become more common than the Halictus tumulorum. Prof. Dr. Stefan Dötterl therefore states: "The bee fauna in the ÖBG is clearly responding to climate warming".