THE BEE HITTING THE BIG TIME

Tree bumblebees first reached the UK two decades ago and have since become one of our most prevalent species. How are these enterprising insects managing to thrive?

- Carolyn Cowan

Bumblebees are being hit hard. Agricultural intensification, the loss of flower-rich meadows, shock heatwaves and surprise frosts are driving global populations into decline.

But curiously, not all species are affected. One, in particular, is the tree bumblebee, which has recently taken up residence in the UK. Scientists are now getting to the bottom of how this bumblebee has not only claimed new ground – but is thriving.

“The tree bumblebee is one of these amazing species that, in the face of other bumblebee declines, is expanding massively in range,” says Ryan Brock, from the University of East Anglia, who is studying the UK population.

Tree bumblebees were first recorded in the UK in 2001, when a lone individual was found on a bramble flower on the outskirts of the New Forest. Native to continental Europe and Asia, their abundance had steadily increased through the 20th century in nearby countries such as Belgium and Germany. To experts, the bee’s appearance in the UK was intriguing, but foreseeable.

However, what no one could have predicted is the astonishing success of tree bumblebees once they reached the UK. Spreading at an average rate of roughly 11,500km2 per year, they rapidly colonised England and Wales. They had buzzed north to Scotland by 2013 and winged over to Ireland by 2017. Now, tree bumblebees are one of the UK’s commonest and most widespread species.