Bumblebee populations are dying at an alarming rate and nobody knows why.

Fingers have been pointed at pesticides called neonicotinoids, as well as bee habitat loss from human development.

But an extensive new study suggests climate change is also killing off the bees. The study shows that rising temperatures are pushing the pollinators out of the south, but they can't seem to move north to cooler areas.

"We think part of the problem is they've evolved in cold weather. They're adapted to cold weather, and there are things about their ecological climates that are not keeping up with climate change," said Sheila Cola, one of the authors of the

study and an assistant professor in the Faculty of Environmental Studies at York University.

Buff-tailed bumblebee composite flower

Researchers suggest that humans may be able to help save bumblebees by physically moving them further north. (Jeremy T. Kerr)

"It seems that bumblebees are not moving north, with climate change, but they're also going extinct at the southern portions of their range. So really their ranges are contracting," said Cola.

According to Cola, one of the reasons they aren't moving north is there might not be large enough fields of flowers for them. Bumblebees need large flowery fields from early spring until the fall to support the kind of populations they need. 

Bumblebees also need rodent burrows for nesting, and Cola says that perhaps the rodents aren't keeping up with climate change either.

"It looks like it's a very hard time to be a bumblebee right now," said Cola.

"There's issues with pesticides and habitat loss, but this is showing us that climate change is also something that we need to be aware of, and when we do our conservation planning going forward we need to keep an eye on where their ranges are shifting over time."