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So Long and Thanks for all the High Fructose Corn Syrup

The story of the mysterious disappearance of the Western honeybee seems as if it should have sprung from the mind of sci-fi author Douglas Adams, rather than from sunny Florida. The strange nature of this scientific conundrum may explain why it has garnered such bizarre public theories: cell phones, aliens, or genetically modified corn; which is the true killer? Well, as you may not be surprised to discover, the answer is none of the above. In spite of such creative speculation, colony collapse disorder (CCD), as the disappearance of these bees has come to be known, is a serious concern. Not only does it endanger the continued survival of the honeybees but CCD is a grave threat to the food on our plates and to hundreds of other species as well; approximately one third of our diet comes from plants that rely on honeybee pollination.

The Collapse

The Western honeybee, or Apis mellifera, is cultivated throughout America and Europe, and is an essential cog in the behemoth machinery of the agricultural industry. Its charm lies in its promiscuity; unlike many bee species, Apis melifera will pollinate hundreds of different plant species. Two hundred thousand plant species rely on insect pollination, which, in the US agricultural industry, is primarily carried out by the honeybee. Since different crops need pollination at different times, and in different areas, beekeepers transport their bees in boxes via trucks driven thousands of miles across the country. Every year in February 1.25 million honeybees are delivered to California, where they pollinate the almond crop. As the summer progresses they move to the Northeast to pollinate blueberries, or to the South for citrus.
In November 2006, worker bees were reported missing from colonies in Florida. They had abandoned their queen, young, and honey stores. No bodies were discovered in the hive or surrounding environs. It appeared the bees were leaving the hive to die. By June 2007, similar disappearances were reported in 35 states, and the mysterious phenomenon was termed colony collapse disorder. Over the last four years the number of abandoned colonies has been increasing. This winter was the most devastating thus far, with beekeepers losing approximately one third of their hives. While the number of bees in the US has been declining since the 1940’s, due to the introduction of new pesticides and the infiltration of specific pests from Europe, CCD has rapidly accelerated this decline. Also, because of the disappearance of the adult bees from the colonies, instead of death within the hive, CCD is considered distinct from the more general decline.

The Usual Suspects

Despite intense scientific research, no definitive underlying cause of CCD has been identified. Current theory postulates that CCD is caused by a number of factors, all of which erode bee health, including pests, pesticides, stress, and poor nutrition. Bees in the US are far from healthy. They carry a number of viruses and parasites, all of which had afflicted bee colonies before the onset of CCD. One particularly nasty parasite is Varroa destructor, a mite that feeds on bee blood when the bees are most vulnerable, during their pupal stage. An infestation weakens a colony, however it is the diseases it spreads which are the most concerning. Analysis of tissue samples from bee colonies affected by CCD show a high level of viral infection, although research has not yet shown that any single virus causes CCD. Pesticides have also been implicated in CCD, although the role they play is still unclear.

The neonicotinoid class of pesticides has received particular scrutiny in connection with bee deaths, since it is a compound that targets the insect nervous system, and in theory may be acting to confuse the bees, preventing them from finding their way back to the hive. Imidacloprid, a pesticide of this class, was banned in France 10 years ago due to a decline in their bee population. However, the decline has continued, and it seems unlikely that the imidacloprid was the cause. A recent study of US colonies found systemic pesticides, or those absorbed and distributed throughout a plant, in pollen and wax samples taken from 23 states. Due to the high levels and variety of diseases and pesticides afflicting the honeybee population, it is likely that some combinatory effect is responsible for CCD. In addition, bee colonies are under increased stress due to a rise in cross-country transportation to meet agricultural demands, as well as a change in diet from natural pollen to “substitute pollen”, a mixture of protein and high fructose corn syrup.

Cities, the new wildlife sanctuaries?

In spite of appearances, cities might actually be the best bee habitat around. In the countryside, high pesticide use, as well as the lack of plant diversity caused by destruction of wild flowers and monocrop agriculture, decreases bee vitality. Hives maintained in cities have stayed the healthiest during the recent CCD pandemic, and more beekeepers focused on honey production are moving their hives to urban areas. This has raised some concern among the cities’ denizens. Despite being fuzzy with black and yellow stripes (which, in my opinion, makes them adorable), bees have acquired a stigma due in part to their sting, and in part to their conflation with wasps, which enjoy raiding barbecues and picnics. Bees avoid confrontation with humans, and will only attack when their hives or lives are threatened. Instead of fearing bees, people could plant bee-friendly flowers to provide these valuable honeymakers with good sources of pollen, welcoming them into our cities. This might serve to protect the pollinators we depend on while scientists continue the hunt for causes of and treatments for CCD. It’s the least we could do to thank Apis mellifera for supporting the delicious fruits, vegetables and nuts we eat.

Rebecca Reh is a graduate student at Harvard Medical School

Link of Interest

USA Q&A: Colony Collapse Disorder

http://www.ars.usda.gov/News/docs.htm?docid=15572

References

Burke, Garance and Borenstein, Seth. (2010, March 24). Bees in more trouble than ever after bad winter. USA Today via Associated Press. http://www.usatoday.com/tech/science/2010-03-24-disappearing-bees_N.htm

Mirsky, Steve and Benrenbaum, May. (2009, August 14). Bee Afraid, Bee Very Afraid. Science Talk: Scientific American. http://www.scientificamerican.com/podcast/episode.cfm?id=bee-afraid-bee-very-afraid-09-08-14

Tanguy, Marion. (2010, June 23). Can cities save our bees? The Guardian. http://www.guardian.co.uk/commentisfree/2010/jun/23/can-cities-save-bees