One-Third of U.S. Honeybee Colonies Died Last Winter

One-Third of U.S. Honeybee Colonies Died Last Winter, Threatening Food Supply








Image: Jennifer C./Flickr

Nearly one in three commercial honeybee colonies in the United States
died or disappeared last winter, an unsustainable decline that
threatens the nation’s food supply.

Multiple factors — pesticides, fungicides, parasites, viruses and malnutrition — are believed to cause the losses, which were officially announced today by a consortium of academic researchers, beekeepers and Department of Agriculture scientists.

“We’re getting closer and closer to the point where we don’t have
enough bees in this country to meet pollination demands,” said
entomologist Dennis vanEngelstorp of the University of Maryland, who led
the survey documenting the declines.



Beekeepers lost 31 percent of their colonies in late 2012 and early
2013, roughly double what’s considered acceptable attrition through
natural causes. The losses are in keeping with rates documented since
2006, when beekeeper concerns prompted the first nationwide survey of
honeybee health. Hopes raised by drop in rates of loss to 22 percent in
2011-2012 were wiped out by the new numbers.

Honeybee colony losses over the last seven years. Image: Engelstorp et al.

The honeybee shortage nearly came to a head in March in California, when there were barely enough bees to pollinate the almond crop.

Had the weather not been ideal, the almonds would have gone
unpollinated — a taste, as it were, of a future in which honeybee
problems are not solved.

“If we want to grow fruits and nuts and berries, this is important,” said vanEngelstorp. “One in every three bites [of food consumed in the U.S.] is directly or indirectly pollinated by bees.”

Scientists have raced to explain the losses, which fall into
different categories. Some result from what’s called colony collapse
disorder, a malady first reported in 2006 in which honeybees abandon
their hives and vanish. Colony collapse disorder, or CCD, subsequently
became a public shorthand for describing bee calamities.

Most losses reported in the latest survey, however, don’t actually
fit the CCD profile. And though CCD is largely undocumented in western
Europe, honeybee losses there have also been dramatic. In fact, CCD
seems to be declining, even as total losses mount. The honeybees are
simply dying.

“Even if CCD went away, we’d still have tremendous losses,” said
entomologist Diana Cox-Foster at Pennsylvania State University. “CCD
losses are like the straw that breaks the camel’s back. The system has
many other issues.”

Studying these issues isn’t easy. In real-world agricultural
settings, it’s hard to run the rigorous, every-last-variable-controlled
experiments on which definitive conclusions are founded. These
experiments can be run in labs and small-scale test fields, but whether
those accurately reflect real-world complexity is debated.

Amidst the uncertainties, scientific attention has settled on a group of culprits,
the most high-profile of which is a class of pesticides known as
neonicotinoids. These were developed in the 1990s, rushed to market with
minimal studies of potential harms, and subsequently became the world’s
most-used pesticides.

In the last several years, it’s become evident that neonicotinoids
are extremely toxic to honeybees and, even in small, sub-lethal doses,
make bees more vulnerable to disease. The European Union recently limited neonicotinoid use, and the U.S. Environmental Protection Agency is reviewing their use.

Pesticide companies have fought the restrictions, arguing that
neonicotinoids are unfairly blamed. Most non-industry scientists say the
question isn’t whether neonicotinoids are a problem, but where they fit
into a constellation of problems.

“Different studies indicate that this class of pesticide is rather
harmful to the bees,” said honeybee pathologist Cédric Alaux of the
French National Institute for Agricultural Research, who said the E.U.’s
restrictions are sensible. “However, we should not be too naive and
think that it will solve the bee problem.”

Just as important as neonicotinoids, and perhaps more so, are Varroa destructor
mites. First detected in the United States in 1987, the mites weaken
bees by sucking their hemolyph, the insect analogue of blood, and also
transmit viruses and other parasites. A recent USDA report called Varroa “the single most detrimental pest of honey bees.”

The report also noted that neonicotinoid exposure alters immune system function in Varroa-infected bees and makes bees more vulnerable to infection by Nosema ceranae,
another parasite implicated in honeybee losses. It’s possible that
neonicotinoids used on crops don’t usually kill bees outright, but
weaken them enough for other stresses to become lethal.

Agricultural entomologist Christian Krupke of Purdue University
likened the effects to “living in an area with extreme levels of smog,
causing your body and immune system to become overtaxed so that a common
cold progresses to pneumonia.”

Krupke noted that although neonicotinoids are the most common
poisonous chemicals in honeybee environments, they’re far from the only
chemicals. Cox-Foster and vanEngelstorp stressed that point, referencing
research that found 121 different pesticides in honeybee hives. On average, each hive contained traces of 6 pesticides, and sometimes several dozen.

Research on pesticide interactions is in its infancy, but combinations may be extremely harmful
to bees, amplifying what the chemicals would do alone. “I worry that
the neonicotinoid attention is distracting from the other pesticides
that have clear effects, and might even have stronger effects. Things
like fungicides are completely unregulated for bees,” said
vanEngelstorp. “I think we need to keep the pesticide investigation
broader.”

'We’re getting closer and closer to the point where we don’t have enough bees.'Another,
less-appreciated aspect of honeybee life also gained attention in the
winter survey and new USDA report: what they eat. Though commercial bees
are trucked on pollination circuits around the United States, most
beekeepers have home bases in the upper Midwest, an area that’s
undergone significant changes in recent years.
Rising food prices led farmers to plant crops in fields previously
considered marginal or set aside as grasslands. Honeybees forage in
those grasslands, and can’t get the nutrition they need from flowering
crops alone.

Add the record-setting drought of summer 2012, and bees were
hard-pressed for nourishment. Malnourishment could in turn make bees
more vulnerable to pests and infections, or exacerbate the effects of
pesticides.

“The drought, the possible combination of factors that went with it,
was clearly a big problem for a lot of beekeepers,” vanEngelstorp said.
“In some cases, it was a combination of Varroa and these malnourished, pesticide-exposed bees.”

Commercial bees pollinate dozens of crops,
and though colonies can be replaced, continuing losses could soon
render beekeeping economically unviable. Researchers are trying to breed
more resilient bees, but the combination of chemicals, nutrition and
disease will likely prove insurmountable by genetic improvements alone,
said Cox-Foster.

She said native pollinator habitat needs to be left intact or
re-established; a field that goes unplanted, or a roadside left unmowed,
can be thought of as insurance against commercial honeybee loss. Dennis vanEngelstorp recommended that, as a rule of thumb, 10 percent of land mass should be managed as pollinator havens.

Pesticides can also be used more carefully. Rather than being applied broadly, across entire fields and locales, they can be precisely targeted to outbreaks. Other unnecessary uses can be averted.

“Many entomologists and pest management professionals have been
saying for years that there is no pest management justification for
using these insecticides on virtually every crop grown in North
America,” said Krupke. “Yet, the opposite trend is occurring.”

The honeybee catastrophe could also signal problems in other
pollinator species, such as bumblebees and butterflies, that are not
often studied.

“Thinking of honeybees as our canary in the coal mine, a monitor for
environmental conditions, is very appropriate,” Cox-Foster said. “With
honeybee colonies, you have the ability to open them up and see what’s
going on. There are many other species needed for pollination, but with
most of those, we don’t have the ability to see what’s happening.”


source:-
http://www.wired.com/wiredscience/2013/05/winter-honeybee-losses/