Smoking gun for bee collapse? Popular Pesticides
Commonly used pesticides may be a primary driver of the collapsing bee populations, finds two new studies in Science. The studies, one focused on honeybees and the other on bumblebees, found that even small doses of these pesticides, which target insect's central nervous system, impact bee behavior and, ultimately, their survival. The studies may have far-reaching repercussions for the regulation of agricultural chemicals, known as neonicotinoid insecticides, that have been in use since the 1990s.
Scientists first started recording alarming declines in bees in North America in 2006, including some bee producers losing up to 90 percent of their colonies. Similar declines occurred throughout Europe, and have also been recorded in Taiwan. Known as Colony Collapse Disorder, bee hives are found missing nearly all of their adult bees. While colony collapses have been recorded since the 19th Century, the current crisis has proven much worst than past ones.
A number of theories for the collapse have been posited, including disease, parasitic mites, habitat loss, and, of course, pesticides. Some researchers have suggested a combination of these factors. While pesticides has been an important target of studies for years, researchers have had proving that pesticides, which aren't immediately lethal, might still be harming bee colonies—until now.
Case study number one: missing queens
Researchers investigating Colony Collapse Disorder have often focused on honeybees, but bumblebees have also suffered.
"Some bumblebee species have declined hugely. For example in North America, several bumblebee species which used to be common have more or less disappeared from the entire continent. In the U.K., three species have gone extinct," explains Dave Goulson of the University of Stirling, U.K., co-author of a study that looked at the long-term impact of neonicotinoid insecticides on bumblebees.
The U.K, team exposed buff-tailed bumblebees (Bombus terrestris) to small doses, similar to what is expected in the wild, of a commonly used neonicotinoid pesticide called imidacloprid, and placed the bees in an enclosed natural setting where they could forage free. After six weeks, the team weighed the nests and compared them with control colonies that had not been exposed. Pesticide-exposed colonies were on average 8-12 percent smaller than the colonies that had not been exposed, which implies that exposed bees were not gathering as much food.
Honeybee Image via Shutterstock