Where Have All the Bumble Bees Gone?
The population of bumble bees has declined disastrously, according to a just-published study in the Proceedings of the National Academy of Science. The dramatic drop in population is especially being seen in domesticated bees who are useful in agriculture.
Bumble bees have long tongues, high-frequency buzzing (which helps release pollen from flowers), and a large body, all of which makes them excellent pollinators.(USA Today via the Tucson Citizen) They pollinate many native wildflowers and crops such as cranberries, blueberries, raspberries, squash, melons, and hothouse tomatoes. (University of Minnesota) In the US, bumble bees pollinate some 15% of all crops grown in the nation, for a total of about $3 billion.
University of Illinois entomology professor Sydney Cameron, who led the research, analyzed historical records going back to the late 1800s and repeated surveys of about 400 sites in the US to study the geographic distribution and genetic diversity of eight species of bumble bees. The researchers put together a database of more than 73,000 museum records, and compared these with a current sampling based on intensive national surveys of more than 16,000 specimens.
As noted in Science Daily, the researchers found that ‘the relative abundances of four of the eight species analyzed have declined by as much as 96 percent,’ while the geographic ranges of the species shrunk by 23 to 87 percent. Even more telling was that some of these changes have occurred in the last two decades. That is, in the past 20 years, four species of bumble bees have all but shrunk in their populations to the point of being non-existent.
Declining populations of bumble bees lead to lower genetic diversity than in bumble bee species with healthy populations. And, populations with lower genetic diversity are more likely to be infected with a deadly intracellular parasite that has affected some species in Europe, nosema bombi—this fungus has been suggested as a reason for the declining bee populations.
In an article about her study in the January 6th News-Gazette, Cameron noted that ‘people should be aware of the decline as a loss to nature and to the agricultural industry. Why these significant changes in this country’s bumblebee population have occurred is open to speculation. Some factors that Cameron note are climate change (which appears to account for the declines in some bumble bee species in Europe); habitat loss; and the above-mentioned parasite, nosema bombi.
(The decline in the bumble bee population is a separate issue from honeybee colony collapse disorder.)
Cameron encourages people to ‘plant native species that can provide habitat for the big bees’ (here is a list of some native plants in California).
So forget about those jokes about killer bees—- it’s really that something is killing the bumble bees.
Photo by steve p2008.