Have Bees Become Canaries In the Coal Mine? Why Massive Bee Dieoffs May Be a Warning About Our Own Health
What scientists are beginning to understand about the cause of colony collapse could be a message for all of us.
February 12, 2012 |
It's often said that we have bees to thank for one out of every three bites we take of food. In addition to producing honey, honeybees literally criss-cross the United States, pollinating almonds, oranges, melons, blueberries, pumpkins, apples, and more. And while carrots are a biennial root crop that are harvested long before they flower, all carrots are planted from seed, and honeybees pollinate the carrot flowers that produce the seeds. Other species of bees, both social and solitary bees, pollinate other crops. And the populations of all these species of bees are in decline.
The decline of bees has been in the headlines for several years, and theories to explain their deaths abound. But perhaps there is not just one single cause. University of California San Diego professor of biology James Nieh studies foraging, communication and health of bees. "I would say it's a combination of four factors; pesticides, disease, parasites, and human mismanagement," says Nieh. Bees might be weakened by having a very low level of exposure to insecticides or fungicides, making them more susceptible if they are attacked by viruses or parasites. "It's kind of like taking a patient who is not doing so well -- very weak, poor diet, exposing them to pathogens, and then throwing more things at them. It's not surprising that honeybees are not very healthy."
One class of pesticides, neonicotinoids in particular has received a lot of attention for harming bees. In late 2010, the EPA came under fire from beekeepers and pesticide watchdog organizations. This happened when Colorado beekeeper Tom Theobald spoke out about how the EPA allowed clothianidin to be used without any proof it was safe and despite the fact that the EPA's own scientists believed it "has the potential for toxic risk to honey bees, as well as other pollinators."
At that time Theobald had reported losing up to 40 percent of his bees, and now, things are looking even worse. "As a business, I think it's over," he says. "I think my business is no longer viable. I'll continue to keep bees as best I can and may be able to pull off a halfway decent crop for another year or two but the trendline is down and over the edge of a cliff and that's typical of what's going on nationally."
A recently published study sheds a little more light on the impact of clothianidin. The study, which focuses on pesticide exposure in bees, looks at two pesticides that are used by treating seeds prior to planting. Each corn seed contains enough pesticide to kill 80,000 honeybees. Once the plant develops, all parts of the plant -- including the pollen collected by bees -- contain lower doses of the pesticide. One of the main revelations of the study is that bees get a hefty dose of these pesticides, clothianidin and thiamethoxam, during spring planting as the seeds are coated in talc to keep them from sticking together and then much of the talc enters the environment either with the seed or behind the planter through its exhaust fan.
The study found the pesticides on the soil of fields -- even unplanted fields -- and on nearby weeds, as well as in dead honeybees and in pollen collected by honeybees. Clothianidin is used on both corn and canola in the U.S., and while corn does not rely on honeybees for pollination (it is wind pollinated), the study found that "maize pollen comprised over 50 percent of the pollen collected by bees, by volume, in 10 of 20 samples."
Tucked in the middle of the study is a bombshell: "The levels of clothianidin in bee-collected pollen [from treated maize] that we found are approximately 10-fold higher than reported from experiments conducted in canola grown from clothianidin-treated seed."