Honeybees are aggressively muscling other pollinators out of Britain's flowers, according to a two-year Cambridge study that provides the first detailed evidence of how extensively managed hives interfere with wild insects' access to food.
Researchers at Anglia Ruskin University tracked pollinator activity at five sites around Cambridge over 93 hours of observation, watching encounters between honeybees, bumblebees, solitary bees, hoverflies and other insects competing for bramble and ivy flowers, published in Ecological Entomology. Doubling the density of honeybees was associated with a 14% drop in bumblebee numbers on bramble, and with fewer solitary bees and hoverflies on ivy. In at least a fifth of the contests honeybees won, they physically pushed aside or chased off their rivals rather than simply arriving first.
"The aim of our study was not to discourage beekeeping, but to better understand how competition happens between wild and managed pollinator species," said lead author Victoria Buckle, a PhD student at Anglia Ruskin University. "We found that most interactions when competing for food were instigated by honeybees and they had a greater number of 'wins,' resulting in a loss of forage for other pollinators." The number of registered UK beekeepers has climbed from 19,000 in 2010 to 47,000 last year.
One native species held its own: the non-native ivy bee, first recorded in Britain in 2001, was the only pollinator observed actively challenging honeybees for territory rather than avoiding them. Researchers warned that rising temperatures could tip the balance further in honeybees' favour, since warmer conditions make honeybees more active while making heat-sensitive bumblebees and hoverflies less so.