Climate change threatens bumblebees. In the period 2000 to 2014 the survival of a bumblebee in Europe or North America was due to the climatic conditions by average 30 percent less likely than in the period 1901 to 1974. This is reported by a group led by Peter Soroye from the University of Ottawa in the scientific journal “Science”.
“Bumblebees are the best pollinators we have in wild landscapes and the most effective pollinators for plants like tomatoes, pumpkins and berries,” Soroye said in a statement from his university. If there were fewer bumblebees, not only would the biodiversity decrease, but possibly also the food supply for humans.
The researcher warns that many species of bumblebee may disappear forever within a few decades if the decline continues at the current pace.
Settlement by bumblebees in Europe decreased by 17 percent
Soroye and colleagues used about 550. 000 Records of the occurrence of 66 species of bumblebees (bombus) from the year 1900 to 2015 to create a computer model. They designed a distribution map of the species for the period 1901 to 1974, in which the habitats of the Insects linked to temperature and rainfall data.
So they calculated the tolerance limits of individual bumblebee species with regard to climatic conditions . They compared these basic data with the climate and Hummel distribution data for the period 2000 to 2014.
“With our new measurement method for climate change, we were able to predict changes for individual species as well as for entire bumblebee communities with surprisingly high accuracy,” says Soroye. Using their calculations, the researchers found that bumblebees in a region are less concerned with an increase in the average temperature than with the frequency of extreme weather events . Therefore, the probability for the settlement of any region in North America during the mentioned period is by 46 percent, in Europe by 17 percent decreased.
The decline in bumblebee populations is not solely due to climate change, the scientists write. “Other changes caused by humans, such as the intensification of agriculture, the use of pesticides and pathogens, can also affect the colonization and the risk of eradication of bumblebees.” However, the researchers are convinced that their model offers clues for protective measures in certain regions.
“Alarming, widespread loss of biodiversity”
In a comment in “Science” Jon Bridle and Alexandra van Rensburg from the English University of Bristol: “The new study provides further evidence of alarming, widespread biodiversity losses and global rates of change that are now exceeding the critical limits of ecosystem resilience.”
The study shows that bumblebees could also colonize new regions as a result of climate change. However, this could by no means compensate for the loss of many areas due to excessive temperatures.
The biogeographer Axel Hochkirch from the University of Trier considers the researchers’ data to be reliable. The chairman of the Committee for the Protection of Invertebrates of the World Conservation Association (IUCN) emphasizes the importance of animals as pollinators: “Since bumblebees have a social lifestyle and are active even at low temperatures, they are considered extremely efficient pollinators and are also used in agriculture for fruit and vegetables and used as pollinators in garden centers. Among the wild bees, they are the species group with the highest pollination efficiency. ”
As the reason for the different degrees of decline in bumblebees in North America and Europe Hochkirch suspects the respective land use. “Intensive agriculture in very large regions of the USA – for example in the so-called” corn belt “- could play a role here. In Europe, small replacement habitats can often be found in the vicinity of agricultural land. ” Stefan Parsch (dpa)
