A new series of studies is demonstrating what most experts have assumed for some time: that at least one of the causes of the devastating collapse of bee colonies is being caused by pesticides and other chemicals.
In two studies published in the journal Science last week, British and French researchers took bumblebees and honey bees and subjected them to a class of insecticides – the neonicotinoids. These poisons were first introduced in the 1990s and are now among the most commonly used crop pesticides in the world.
In one of the studies, a team from the University of Stirling in Scotland exposed developing colonies of bumblebees to low levels of neonicotinoids – not enough to kill them – and then placed the colonies in an enclosed field where the bees could fly around collecting pollen under natural conditions.
Compared to colonies that were not exposed to the insecticide, the treated colonies grew steadily weaker.
In the other study, a team from the French National Institute for Agricultural Research tagged free-ranging honeybees with tiny radio-frequency identification microchips glued to each bee’s back and tracked them as they came and went from hives. The researchers gave some of the bees a low dose of the pesticide and saw that they were up to three times as likely to die while away from their nests as other bees. They concluded that the pesticide interferes with their navigation abilities so they can’t find their way back home.
”In North America, several bumblebee species which used to be common have more or less disappeared from the entire continent,” said David Goulson, who led the British study. Three species in Britain have become extinct, and bees are suffering in South America, Asia and the Middle East.
Quite apart from their intrinsic worth, bees are invaluable to the human food supply. A United Nations report last year estimated that insects and other animals who pollinate flowering plants do work that’s worth more than $203 billion a year to the world economy.
But no amount of dollars will bring back the bees if something is not done to stop the ongoing spraying of crops with poisons that kill them.