Will Earth's warming climate silence the flight of the bumblebee?

A warming climate and it's accompanying temperature extremes is wreaking havoc with bumblebee populations, according to a new scientific study.

A paper published in Science today (February 7) says that there has been about a 30 percent drop overall in the likelihood of any given bumblebee population surviving in any particular location in North America and Europe. (North American percentages were considerably higher, on average, than those found in Europe.)

The declines were found to be in areas that had shown increases in temperatures in relatively recent years, especially those places subjected to extreme heat.

"[The study's authors] analyzed a large dataset of bumblebee occurrences across North America and Europe and found that an increasing frequency of unusually hot days is increasing local extinction rates, reducing colonization and site occupancy, and decreasing species richness within a region, independent of land-use change or condition," the paper noted.

"As average temperatures continue to rise, bumblebees may be faced with an untenable increase in frequency of extreme temperatures."

Two of the paper's authors, Peter Soroye and lead researcher Jeremy Kerr, are from the University of Ottawa's biology department. The third, Tim Newbold, is from the department of genetics, evolution, and environment at University College London.

There are more than 250 species of bumblebees in the world, mostly in the Northern Hemisphere, and they are thought to be important agricultural pollinators, especially of tomato and berry crops.

Bumblebees' fuzzy, plump, and colourful appearance, coupled with their reluctance to sting humans, has led to their generally favourable reception by people through the years, including many references in music and literature.

Although increased habitat loss and pesticide use have been blamed for a noticeable decline in bumblebee populations—along with other significant pollinators—since the end of the 20th century, the paper's authors think climate change has played an important role in the losses, although they were unable to specifically pinpoint an exact degree.

"Climate change could increase species’ extinction risk as temperatures and precipitation begin to exceed species’ historically observed tolerances," they wrote in the Science paper, titled "Climate change contributes to widespread declines among bumblebees across continents".

The researchers used 115 years' worth of data—recorded sightings noted from 1900 to 2015—about 66 bumblebee species in North America and Europe to construct a climate model that highlighted population declines when compared to temperature records. The effects, they noted, "were independent of changing land uses".

"The method developed in this study permits spatially explicit predictions of climate change-related population extinction-colonization dynamics within species that explains observed patterns of geographical range loss and expansion across continents.

"Increasing frequencies of temperatures that exceed historically observed tolerances help explain widespread bumblebee species decline."