Some bee species in North America and Europe might not be dying out at all, a new study from Simon Fraser University claims.
The research used a simulated data model to find how often bumblebees showed up in sites throughout the two continents in the period from 2000 to 2015.
It found that, while there was an approximately five per cent overall reduction in the North American bee population during that time, some bee species stayed stable and some even increased.
The new research is in contrast to years of studies that show consistent population declines across all species of bees due to the effects of climate change, pesticides, and other human activities.
"On average, you have that five per cent decline," said Melissa Guzman, the lead author of the new study. "That doesn't tell you anything about which species are increasing or decreasing."
The paper found that the cuckoo gypsy bumblebee, which is listed on the IUCN Red List as being critically endangered in North America, had its population decline 73 per cent during the research period.
But other species' numbers, like the common eastern bumblebee and the two-spotted bumblebee, saw increases during the same period.
Guzman hopes the study's estimates of various bees' populations can help focus conservation efforts.
"The whole idea is to identify which of the species are actually decreasing," said Guzman. "We can focus our attention to figure out why are those two or three species decreasing and [whether] we can target the sources of that decline."
However, Jeremy Kerr, a professor of biology at the University of Ottawa, says the modelling approach in the research might not reflect the real world.
"I think we should be rather cautious about taking the next step," he said. "And the next step is, do you believe the model or do you believe what you can measure out in nature?"
Kerr says policy should not be based on models alone and wants further observations of vital pollinators like bees before any firm decisions are made.
The SFU study did not estimate bumblebee population numbers directly but looked instead at the spatial distribution of bees throughout the two continents.
"[In the study], we're thinking more about the number of places where you can find [bees] and how that number of places has changed through time," said Guzman.
While the study found a bee population decrease of five per cent in North America, it was a percentage point higher in Europe.
The research was published in the journal Biological Conservation last month, and it measured the statistical changes from a baseline period of 1900-1975.