Global warming is killing off bumblebees, according to a new study published last week by scientists.
Bumblebees – which help pollinate plants, wildflowers and fruit trees as well as important crops like blueberries and tomatoes, providing an invaluable service to agriculture and wildlife – are struggling to adapt to global warming and are dying rather than migrating to cooler climes, the study’s authors reported in the journal Science.
Until now the worldwide decline of the bumblebee had largely been blamed on pesticide use, parasites, disease and loss of areas for habitat.
“As the climate warms, bumblebee species are being crushed as the ‘climate vice’ compresses their geographical ranges,” said lead author Jeremy Kerr, professor of macroecology and conservation at the University of Ottawa. “The result is widespread, rapid declines of pollinators across continents.”
By examining nearly a half million records on 67 bumblebee species in North America and Europe from 1900, researchers were able to track changes in the bumblebees’ range.
They found that bumblebees have lost as many as 300 kilometres of their historical southern range in North America and Europe.
“This is a huge loss and it has happened very quickly,” said Kerr. “We are looking at rates of loss of about nine kilometres per year from those southern areas,” he said.
Meanwhile, bumblebees are “generally failing” to move north and are becoming extinct in some areas.
“They just aren’t colonising new areas and establishing new populations fast enough to track rapid human caused climate change,” Kerr said.
Researchers said the paper shows no indication that bumblebee decline is linked to human land development or to insect-killing chemicals that protect crops.
“Bumblebee range losses began before neonicotinoids were in wide use,” said co-author Alana Pindar, also of the University of Ottawa.
“This cannot be interpreted to mean that neonicotinoids do not and cannot harm bees, just that they do not affect our results,” she said.
Bumblebees are believed to have originated some 35 million years ago. Since they are natives of cooler areas, scientists think they may be not be well-equipped to cope with warming temperatures.
Ways to help the bees survive should include reducing global greenhouse gas emissions, as well as helping establish populations in northern latitudes, a process known as assisted migration.
Until now, “scientists have been fairly relaxed about the effects of climate change, arguing that since pollinators can fly, if confronted by changing and hostile conditions, they would simply move to more suitable conditions, perhaps shifting northwards,” said Norman Carreck, science director of the International Bee Research Association.
“However, this paper reveals that the true picture is more complex and that this does not appear to be happening.”
Given the losses so far, researchers expect the problem will only get worse unless human-caused climate change can be stopped.
The decline in pollination could make food more expensive and some crops harder to grow, researchers said.
“Impacts are large and are already happening, they’re not just something to worry about at some vague, future time,” Kerr said.