There has been an ongoing debate over whether a controversial type of pesticide has harmful effects on bees and other pollinators. Lab-based investigations seemed to conclude that honeybees are heavily impacted by the pesticides, whereas field studies claimed that bee colonies were not. A new study seems to have filled the gap between these discrepancies, and has found that while the chemicals are indeed harmful to individual honeybees, the colonies compensate for this by increasing the number of worker bees produced.
Two years ago, a Europe-wide ban on the use of neonicotinoids was put in place as the pesticide was linked to the deaths of bees and the collapse of colonies that have been affecting farmers around the globe. Despite opposition to the blanket ban, with conflicting data both for and against it, because of the huge economic service provided by bees, the ban was enacted to give some time for more research to be conducted. That ban is now coming to an end, and already the U.K. is phasing it out.
This new study seems to have found that rather than the previous data being contradictory, it was simply two sides of the same coin. By tagging 6,847 individual honeybees from 17 colonies living over a gradient of neonicotinoid use on test fields, the researchers were able to track which bees came and went from the hive. “We could find evidence of troubles at the individual scale in the field but these troubles were compensated for by the colonies,” Dr. Mickael Henry, who led the study published in Royal Society journal Proceedings B, told BBC News. “The population inside the hive was able to compensate for the increased loss of worker honeybees by increasing brood production.”
A buff tailed bumblebee on apple blossom during the study on the effect of neonicotinoids on bumblebees published in Nature. Dara Stanley
While this might be good news for the honeybees, they’re not the only pollinating insect that might be feeling the effects of heavy neonicotinoid use. Concentrating on bees alone, there are nearly 2,000 separate species in Europe, of which the European honeybee is just one. In fact, with many other species of bee being solitary, the honeybee might be better suited to adapt to the impact of the pesticides simply due to its sociality which buffers them from the death of individual bees.
But as ever, things are never simple. Another study, published in Nature, has documented how exposure of bumblebee colonies to neonicotinoids affects the bees’ ability to pollinate apple trees. They found that colonies that had been in contact with the pesticide spent more time foraging and less time visiting flowers and collecting pollen. This resulted in a 36 percent drop in the number of seeds found in the apple trees they were meant to be pollinating, with the number of seeds closely related to the fruit's quality.
So, while honeybee colonies might be able to survive increased exposure to neonicotinoids, the overall impact to other economically important pollinators, and other species of bee, is not so straight forward. But in an absence of an effective, safe alternative, scientists and policymakers need to weigh up the costs and benefits of using these pesticides when deciding usage regulations.