Bumblebees are having a hard time dealing with climate change, say researchers who express fear they could go extinct as suitable habitats for the insects shrink.

Global warming is steadily reducing the areas where the bees — important pollinators of our food supplies — are found in both North America and in Europe, the scientists say.

Writing in the journal Science, researchers, including Leif Richardson of the University of Vermont, report their examination of more than 420,000 current and historical records of a number of bumblebee species has confirmed steep declines in their numbers at continental scales.

The loss of habitats will have an impact on more than just the bees, Richardson says.

"Bumblebees pollinate many plants that provide food for humans and wildlife," he explains. "If we don't stop the decline in the abundance of bumblebees, we may well face higher food prices, diminished varieties, and other troubles."

While many species such as butterflies are adapting to climate change by enlarging or shifting their habitats as temperatures change, that's not the case with bumblebees, the research team notes.

Northern populations are staying in place, while those in southern habitats find those habitats retreating north away from the equator.

That was unexpected, Richardson says.

"The bees are losing range on their southern margin and failing to pick up territory at the northern margin — so their habitat range is shrinking," he says.

Two other known major threats to healthy bumblebee populations — pesticides and changes in land use — aren't the culprit in the current case, the scientists say.

The "range compression" of suitable bumblebee habitats is tracking exactly with warming global temperatures, they report.

In the 110 years recorded in the data the researchers examined, bumblebees have lost around 185 miles from the southern edge of their habitat ranges in both North America and Europe.

"The scale and pace of these losses are unprecedented," says study leader and biologist Jeremy Kerr from the University of Ottawa.

One reason bumblebees are having trouble adapting to warmer temperatures could be explained by their evolutionary origins, says Alana Pindar, an ecologist at the Nature Conservancy of Canada.

"Bumblebees originated perhaps some 35 million years ago in cool to temperate environments," she explains. "Most other species that have often shown positive responses to climate change, like butterflies, evolved in the tropics."

The loss of habitat is a great concern, she says, because bumblebees pollinate more fruits, vegetables and flowers than the European honeybee does.