More small bees and fewer bumblebees. This is one of the unexpected effects of climate change on wildlife, according to a study published Wednesday April 20, 2022, which warns of the effects « en cascade » on pollination and throughout the ecosystem.
In the United States, scientists trapped and studied more than 20,000 insects of the bee family over an eight-year period in the Rocky Mountains (west), to study how the different families reacted to changing climatic conditions.
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Smaller bees, which nest in the ground
According to the authors of the study published in the journal Proceedings of the Royal Society Bthe mid-mountain zone from which the samples are taken is “particularly vulnerable to climate change”generally milder spring temperatures and earlier snowmelt.
They found that the abundance of specialized nest comb-digging and large bees decreased with increasing temperatures, while that of smaller, ground-nesting bees increased.
“Our research suggests that climate-induced changes in temperature, snow accumulation and summer precipitation could radically reshape bee communities”say the authors.
Bumblebees more vulnerable
The results suggest a reduction particularly in the families of bumblebees, leafcutter bees and mason bees, the former being according to the researchers “more threatened by global warming than other bees in our system”.
These results are consistent with other studies showing that bumblebees, dominant pollinators in many ecosystems, have lower heat tolerance and move to cooler regions at higher elevations when temperatures warm.
The results seem to suggest that the body size of bumblebees and also their behavior at nest could make them more vulnerable to a warming climate.
A strong impact on pollination
Overall, the authors believe that these changes “could have cascading effects on pollination and ecosystem functioning”.
For example, the loss of larger bees, which tend to fly further to forage, could lead to a reduction in long-distance pollination. The authors point out, however, that these results may not apply to ecosystems where climate change would imply more abundant precipitation.
Insects are the main pollinators in the world: 75% of the 115 main crops depend on animal pollination, including cocoa, coffee, almonds or cherries, according to the UN.
In a landmark report published in 2019, scientists concluded that almost half of all insect species in the world are in decline, and that a third could be extinct by the end of the century.
One in six bee species has become regionally extinct somewhere in the world. The main factors of extinction would be the loss of habitat and the use of pesticides.