Karlsruhe Institute of Technology: Land use as a threat and opportunity for bumblebees

The global food system benefits greatly from pollination by insects – the European Commission puts this ecosystem service for Europe at several billion euros. Wild pollinators such as bumblebees, whose areas of distribution will change due to climate change, play an important role. “Earlier studies show that more than half of the European bumblebee species are now falling,” says Dr. Reinhard Prestele, from the Institute for Meteorology and Climate Research – Atmospheric Environmental Research (IMK-IFU), the KIT Campus Alpin in Garmisch-Partenkirchen. “However, it is not only the climate that affects the bumblebees, changes in land use can also threaten populations.” The risks of intensive agriculture are known, for example, So far, however, they have not been sufficiently differentiated from climate change in continental considerations. This work is now being carried out by KIT researchers together with partners from the Joint Research Center (JRC) of the European Commission in Ispra (Italy) by simulating the effects of land use changes on the future distribution of European bumblebees.

Models show possible development paths

For their study, the researchers calculated the potential distribution of 47 European bumblebee species for the years 2050 and 2080 in seven scenarios, which are based on different assumptions about future climate and land use changes in Europe. “We compared the projections of a constant climate with dynamic land use to the opposite constellation,” explains Penelope Whitehorn (IMK-IFU). “It became clear that climate changes are most noticeable overall and threaten the existence of many bumblebee species. In some scenarios, however, some rare species are just as badly affected by land use changes as they are by climate change. ”In addition to the loss of habitat, the excessive use of fertilizers and pesticides also plays a role.

Protection through intelligent land management

The simulations also show a glimmer of hope for endangered bumblebee species. Decisive climate protection paired with intelligent land management, for example with larger proportions of organic farming and protected areas of retreat, could probably contribute to the stabilization of some bumblebee species even with moderate climate change. Prestele emphasizes that further research is needed to develop appropriate protection strategies. “For concrete insights into what could help, we need a better illustration of specific ecological processes in our models. For example on the questions of what role small-scale habitats play in agricultural landscapes and how exactly different management methods affect the life cycle of bumblebee colonies. “From long-term simulations of land use changes, not only protective measures for bumblebees could be derived. “Our approach can also be transferred to other important wild pollinators such as wild bees and wasps,” says Prestele.