http://e360.yale.edu/feature/declini...iculture/2645/

Declining Bee Populations Pose
A Threat to Global Agriculture


The danger that the decline of bees and other pollinators represents to the world’s food supply was highlighted this week when the European Commission decided to ban a class of pesticides suspected of playing a role in so-called “colony collapse disorder.”

by elizabeth grossman
elizabeth_grossman_author.jpg
ABOUT THE AUTHOR
Elizabeth Grossman is the author of Chasing Molecules: Poisonous Products, Human Health,and other books. Her work has appeared in Scientific American, Salon, The Washington Post, The Nation, Mother Jones, Grist, and other publications. In earlier articles for Yale e360, she explored the potentially harmful health effects of flame retardants, and reported on recent studies suggesting a possible link between prenatal exposure to pesticides and the mental abilities of children.

ABSTRACT:

No one investigating the issue is suggesting that neonicotinoids are the sole cause of current bee declines. Tucker, other beekeepers, and entomologists say that the cause of colony collapse disorder is likely a combination of factors that includes the widespread use of pesticides and fungicides, as well as the spread of viral pathogens and parasitic mites in beehives. While mites and diseases have long been known to cause significant declines in domesticated bee populations, no single pathogen or parasite, say entomologists, appears to sufficiently explain the current rate of hive collapse.

A recent study that found unprecedented levels of agricultural pesticides — some at toxic levels — in honeybee colonies is prompting entomologists to look more closely at the role of neonicotinoids in current bee declines. Some studies have indicated that neonicotinoids can lead to a sharp decline in queen bees in colonies and can also interfere with the ability of bees to navigate back to their hives. James Frazier, a professor of entomology at Pennsylvania State University, said more research needs to be conducted into whether neonicotinoids, particularly in combination with other pesticides, may suppress the immune system of bees at “sub-lethal” levels, enabling diseases to take hold.

“This is uncharted territory,” said Purdue University associate professor of entomology Christian Krupke. “We’ve never done pest management like this before.”

In the U.S., neonicotinoids are currently used on about 95% of corn and canola crops; the majority of cotton, sorghum, and sugar beets; and about half of all soybeans. They’re also used on the vast majority of fruit and vegetable crops, including apples, cherries, peaches, oranges, berries, leafy greens, tomatoes, and potatoes. Neonicotinoids are also applied to cereal grains, rice, nuts, and wine grapes.

Charles Benbrook, research professor at Washington State University’s Center for Sustaining Agriculture and Natural Resources, has estimated that neonicotinoids are used on approximately 75 percent of the acres devoted to these crops in the U.S. They are also widely used on landscaping plants and urban trees and in numerous home garden pest-control products — all in places frequented by bees, domesticated and wild.

“There is no place to go hide,”
says New York beekeeper Jim Doan, a director of the American Beekeeping Federation.“The outlook is not good.”

When governments around the world registered and approved these insecticides for use in the 1990s, many questions about the environmental impacts of neonicotinoids were left unanswered. Neonicotinoids were welcomed as a safer alternative to previous generations of pesticides, ‘These compounds are a nightmare scenario for pollinators,’ says one beekeeper. particularly organochlorines (such as DDT) and organophosphates, which have known adverse environmental and human health effects. Neonicotinoids attack insects by harming their nervous systems and are considered of low toxicity to mammals. They are also typically used as systemic pesticides — meaning that they stay with the plant as it grows — and are applied as seed treatments, to roots, or into tree trunks, rather than applied with as a spray. This greatly reduces the potential for human exposure compared to other pesticides.

But because the insecticide stays with the plant as it grows, it raises questions about the potential for bees to be exposed through nectar, pollen, or leaf surface moisture, where a growing number of studies are finding evidence of neonicotinoids. Neonicotinoids are known to be toxic to bees, earthworms, and other terrestrial and aquatic invertebrates, as was noted in documents submitted to the EPA when they were registered.

“The motivation for producing neonicotinoids was reduced human toxicity, but the environmental and ecosystem impacts were not considered in enough detail to predict what’s going on,” says Frazier of Penn State.

“These compounds are a nightmare scenario for pollinators,” says Steve Ellis, a Minnesota-based beekeepeer whose bees primarily pollinate California almonds. “There is no way to prevent exposure to these chemicals. The only question is the exposure level, whether that is a problem or not. The pesticide industry claims not. The beekeeping industry says yes.”

Both Doan and Ellis have experienced dramatic losses of bees in recent years, including complete hive failures. Both say their bees and hives have tested positive for neonicotinoids. Yet in both cases the agricultural authorities and pesticide manufacturers who participated in testing the damaged hives said the insecticides’ presence was not conclusively linked to the bees’ deaths. Doan and Ellis are now part of the lawsuit filed against the EPA.