Scientists discover what’s killing the bees and it’s worse than you thought
As
we’ve written before, the mysterious mass die-off of honey bees that
pollinate $30 billion worth of crops in the US has so decimated
America’s apis mellifera population that one bad winter could leave fields fallow.
Now, a new study has pinpointed some of the probable causes of bee
deaths and the rather scary results show that averting beemageddon will
be much more difficult than previously thought.
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Scientists
had struggled to find the trigger for so-called Colony Collapse
Disorder (CCD) that has wiped out an estimated 10 million beehives,
worth $2 billion, over the past six years. Suspects have included
pesticides, disease-bearing parasites and poor nutrition. But in a
first-of-its-kind study published today in the journal PLOS ONE,
scientists at the University of Maryland and the US Department of
Agriculture have identified a witch’s brew of pesticides and fungicides
contaminating pollen that bees collect to feed their hives. The findings
break new ground on why large numbers of bees are dying though they do
not identify the specific cause of CCD, where an entire beehive dies at
once.
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When
researchers collected pollen from hives on the east coast pollinating
cranberry, watermelon and other crops and fed it to healthy bees, those
bees showed a significant decline in their ability to resist infection
by a parasite called Nosema ceranae. The parasite has been
implicated in Colony Collapse Disorder though scientists took pains to
point out that their findings do not directly link the pesticides to
CCD. The pollen was contaminated on average with nine different
pesticides and fungicides though scientists discovered 21 agricultural
chemicals in one sample. Scientists identified eight ag chemicals
associated with increased risk of infection by the parasite.
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Most
disturbing, bees that ate pollen contaminated with fungicides were
three times as likely to be infected by the parasite. Widely used,
fungicides had been thought to be harmless for bees as they’re designed
to kill fungus, not insects, on crops like apples.
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“There’s
growing evidence that fungicides may be affecting the bees on their own
and I think what it highlights is a need to reassess how we label these
agricultural chemicals,” Dennis vanEngelsdorp, the study’s lead author,
told Quartz.
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Labels
on pesticides warn farmers not to spray when pollinating bees are in
the vicinity but such precautions have not applied to fungicides.
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Bee
populations are so low in the US that it now takes 60% of the country’s
surviving colonies just to pollinate one California crop, almonds. And
that’s not just a west coast problem—California supplies 80% of the
world’s almonds, a market worth $4 billion.
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In recent years, a class of chemicals called neonicotinoids has been linked to bee deaths and in April regulators banned the use of the pesticide for two years
in Europe where bee populations have also plummeted. But vanEngelsdorp,
an assistant research scientist at the University of Maryland, says the
new study shows that the interaction of multiple pesticides is
affecting bee health.
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“The
pesticide issue in itself is much more complex than we have led to be
believe,” he says. “It’s a lot more complicated than just one product,
which means of course the solution does not lie in just banning one
class of product.”
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The
study found another complication in efforts to save the bees: US honey
bees, which are descendants of European bees, do not bring home pollen
from native North American crops but collect bee chow from nearby weeds
and wildflowers. That pollen, however, was also contaminated with
pesticides even though those plants were not the target of spraying.
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