Bumblebee territories crushed, many species in decline

Eric Hopton for redOrbit.com – Your Universe Online

Bumblebees, nature’s essential pollinators, are being relentlessly squeezed into smaller territories under assault from global warming and pollution. The number of bee colonies and even the number of species are declining rapidly.

“We’re hitting these animals with everything. There’s no way you can nail a bee with neonicotinoids, invasive pathogens, and climate change and come out with a happy bee,” said ecologist Jeremy Kerr of the University of Ottawa in Canada in a report for the journal Science. The loss of bee species could be disastrous for ecosystems and for people. Plants depend on “loyal” pollinators and wild bees help pollinate many crops.

Knocking down nature’s scaffold

“We play with these things at our peril,” says Kerr. “The human enterprise is the top floor in a really big scaffold. What we’re doing is reaching out and knocking out the supports.”

The decline is rapid in both North America and Europe, and a new study points the finger directly at climate change. Bumblebees are losing large amounts of the southern portion of their ranges. But unlike other species, they are not expanding north as the climate warms. Bee ranges are compressing by as much as 200 miles, and some populations are in terminal decline.

The study accessed vast collections of curated specimens in museums and compiled data from around 423,000 observations of 67 bumblebee species, dating back to 1901.

One third of North American species are in decline. In some cases they have reduced by more than 90 per cent. Many previously common species, like the Rusty-patched Bumblebee, are now rarely seen, says co-author, York University environmental studies Professor Sheila Colla.

Fewer bees for our children

“One of the scariest parts of the work that I’ve done is just realizing how quickly the situation is changing. The bumblebees that are in decline were doing fine 50 years ago. We’re talking about large changes in community composition of essential pollinators over just a few decades.” The adults of today were seeing species as children that are no longer there. Their own children won’t see them at all.

The study compared changes in individual bee species’ northward movements in recent decades, against baseline bumblebee activity from 1901 to 1974, when the climate was cooler. The researchers were surprised to find bumblebees were not moving north in recent, warmer decades. At the same time, many populations disappeared from the southernmost and hottest parts of their ranges as they moved to higher, cooler elevations.

“Global warming has trapped bumblebee species in a kind of climate vise. The result is dramatic losses of bumblebee species from the hottest areas across two continents,” said Kerr. “For species that evolved under cool conditions, like bumblebees, global warming might be the kind of threat that causes many of them to disappear for good…We may need to help these species establish new colonies to the north and at continental scales.”

The researchers found no significant correlation between other factors, like land use and pesticide application, as well as range losses, although we know these are damaging bee populations generally. “Bumblebee disappearances from warm, southern areas are just as likely when there is no pesticide use and little agriculture,” said Kerr. “But we know that increasingly frequent weather extremes, like heat waves, can hit bumblebee species hard, and climate change poses threats that are already being felt.”


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