The news has migrated from the front page to back pages, but it’s still news: Honeybees are dying. So many bees have bitten the dust the phenomenon has a name: Colony Collapse Disorder (CCD). And to date, it has been hard to establish a definitive cause.
As with human “cancer clusters” and other diseases related to living environments, it is hard for epidemiologists to state a single cause with any certainty. For example, those seeking to dismiss environmental disease cases might say something like this: “Yes, there used to be a toxic waste site here, but a large percentage of the local population smokes and is overweight, so maybe that’s why a higher than average number of residents have cancer.” Similarly, with the bees, people have thrown out theories that range from mites and other pathogens to cell phone radiation to malnutrition to exhaustion to genetically modified crops. But they have also suggested that a cause might be pesticides, and in particular, neonicotinoids.
As I wrote two weeks ago in my article on strawberries, pesticides are poisonous. They are intended to kill insects that eat crops. Sometimes insects cause only visual damage, making produce more difficult to sell to customers who have grown to expect visually perfect fruit and vegetables. Sometimes they completely destroy the crops: “a plague of locusts” was among the ills brought down on Pharaoh because locusts could totally wipe out staple food crops in a matter of days. But simply because pesticides can be useful does not mean they may not also have negative consequences. The worst of these come from unintended effects.With methyl iodide, these included poisoning farmworkers, drifting into nearby communities, and contributing to climate change. Other unintended negative consequences caused by pesticides include harmful residue on foods we eat, soil and water contamination, and harm to non-target, beneficial insects. These harms can be immediate and direct, but they can also be long-term and chronic.
Part of the issue with neonicotinoids, introduced widely in the 1990s as an alternative to even more toxic pesticides, is this: when applied to a plant, they express throughout the plant tissue, unlike many pesticides that remain at the surface and dissipate more quickly. Because of that, the plants themselves are toxic for extended periods, including when they are flowering, which increases potential exposure for pollinators like honeybees. Bees can be exposed to the pesticide in sap that collects on the plant, as well as through airborne pesticide that is churned up during automated planting when seeds coated in neonicotinoids are shot through air-powered planters, rubbing off and releasing some of the pesticides into the air.
In addition, unlike pesticides that break down quickly in the air, neonicotinoids can remain active and toxic for years in the soil, and there is some possibility that plants may continue to take them up through root systems, meaning that even if they are not applied directly, they could still have an ongoing effect.
While neonicotinoids might not kill bees outright at low levels of exposure, a combination of exposure plus other stressors, and also ongoing, chronic exposure to neonicotinoids, can weaken bees’ immune systems, have developmental effects, and make bees more susceptible to parasites. As with human health problems caused by environmental pollution, exposure does not always lead to death outright, but cumulative and interacting stresses and sub-lethal effects can still decimate entire populations. Within this mix, more and more evidence is pointing to neonicotinoids being a major actor in CCD. And Colony Collapse Disorder is not a minor concern.
Apart from the intrinsic value of bees, and the obvious direct benefits humans get from what they produce – honey, pollen, royal jelly – bees also perform one of the most important services in food production. They are incredibly effective pollinators. Indeed, a recent study by Friends of the Earth, based in England, suggests that bees provide more than $2.86 billion in pollination services annually, which equates to the cost of about 60,000 teachers (I’m not sure why FOE chose teachers as comparator for bees; perhaps because education is sweet). Some places, the study notes, have already been driven to hand pollination to replace the services bees provide, notably some sites in China where intensive industrial agriculture and loss of bee habitat has wiped out entire bee populations.
To avoid this fate in other locales, it is critical to remove stressors and to ensure that there is adequate habitat for honeybees. One way to remove stressors is to stop using pesticides that are particularly harmful to bees – like neonicotinoids. As more and more signs point to the benefits of limiting pesticide use, there’s a growing buzz in the air…
Let’s keep it there!
For more information on this issue, please see an excellent article in Wired that includes hyperlinks to several additional resources. It is available at http://www.wired.com/wiredscience/2012/04/neonicotinoids-colony-collapse/.
As a final point, my last two articles lead me to a question: why do we persistently use toxic products that have the potential to cause long-term environmental and economic harm? In a subsequent column, I will discuss the issue of “regulatory capture,” such as the close links between pesticide-producing multinational corporations and regulatory agencies.
Photo credit: USDA