The recently published European Red List of Bees revealed that 24% of Europe’s bumblebee species are threatened with extinction and 46% have a declining population. While this was only a regional assessment, it is likely that bumblebees in other parts of the world are faring similarly badly. Changes in land use, including agricultural intensification, as well as climate change and introduced pathogens are among the main threats to the world’s bumblebees.
Habitat destruction and degradation as a result of urbanisation and especially agricultural intensification is a major cause of bumblebee decline. Wide-scale conversion of wildflower meadows to monocultures deprives bumblebees of forage and potential nest sites. Agricultural insecticides can spread widely into the surrounding environment. They are often picked up by foraging bumblebees and carried back to their nests, poisoning working colony members as well as the developing brood. Herbicide use can also detrimentally affect bumblebees by killing their preferred forage plants.
Climate change is another growing threat to bumblebee populations, either affecting bumblebees directly or indirectly via their food plants. For example, the Vulnerable Bombus alpinus, a boreal-alpine species favouring higher altitudes, is declining in the southern Alps due to climate change reducing the amount of suitable habitat.