Researchers find that bumblebees’ body size could make them more vulnerable in a warming world

Researchers find that bumblebees’ body size could make them more vulnerable in a warming world

According to new research, the climate crisis may result in more small-bodied bees but fewer bumblebees, with potentially “cascading” implications on plant pollination and ecosystems.

Over the course of eight years, scientists in the United States trapped and studied more than 20,000 bees in a region of the Rocky Mountains to see how different varieties of bees reacted to changing climatic conditions.

The authors of the study claimed that while environmental conditions varied from year to year, the sub-alpine region from which they gathered samples was “especially sensitive to climate change,” with generally warmer spring temperatures and faster snow melt.

Honey on a farm near Elkton in rural western Oregon. The use of neonicotinoids, hailed by industry as a key to bumper crop yields, has exploded since the 1990s.

They found that larger-bodied bees and comb-building cavity nesters declined in abundance as temperatures increased, while smaller, soil-nesting bees increased.

“Our research suggests that climate-induced changes in temperature, snowpack and summer precipitation may drastically reshape bee communities,” the authors said.

Researchers said the findings suggested a reduction of bigger bees, including in the families of bumblebee, leafcutters and mason bees, with higher temperatures.

Declines were particularly marked for bumblebees, which the researchers said suggested “this group is more threatened under climate warming than other bees in our system”. That tallies with other studies showing that bumblebees, the dominant pollinators in many ecosystems, have a lower heat tolerance than other bees and move to cooler regions at higher altitudes as temperatures warm.

Researchers said their findings suggested both bumblebees’ body size and nest behaviour could also make them more vulnerable in a warming world.

More broadly, the authors said climate-driven changes to pollinator communities “could have cascading effects on pollination and ecosystem functioning”. For example, they said losing bigger bees, which tend to fly further for food, may mean a reduction in longer-distance pollination.

The study was specifically focused on mountainous areas, but the researchers said other research across the US showed declines in larger bees in response to environmental changes.

Insects are the world’s top pollinators: 75% of 115 top global food crops depend on animal pollination, including cocoa, coffee, almonds and cherries, according to the UN.

In a landmark 2019 report, scientists concluded that nearly half of all insect species worldwide are in decline and a third could disappear altogether by century’s end. One in six species of bees have gone regionally extinct somewhere in the world.

The main drivers of extinction are thought to be habitat loss and pesticide use.

This article was first published by The Guardian on 21 April 2022. Lead Image: Researchers believe the number of bumblebees, leafcutters and mason bees will fall as temperatures rise. Photograph: Imagebroker/Alamy.

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