Who Killed All Those Honeybees? We Did
It
was mid-July, and
Sam
Comfort was teetering at the top of a 20-foot ladder,
desperately trying to extract a cluster of furious honeybees
from a squirrel house in rural Dutchess County, New York. Four
stingers had already landed on his face, leaving welts along the
fringe of his thick brown beard. That morning, the owner of the
squirrel house had read an article in the local paper about
Comfort’s interest in collecting feral honeybees, so he called
and invited him over. Commercial bee colonies, faced with
massive mortality rates, are not faring so well these days, and
unmanaged hives like this one could be their salvation. Comfort
hurried over, eager to capture the hive’s queen and bring her
home for monitoring and, if she fares well, breeding.
The nation’s great bee die-off has provoked a furious debate:
What has caused a third of all commercial honeybee colonies to
perish each year since 2006? Although widespread bee deaths have
occurred before, the current sharp decline is different. This
time some bees have simply vanished, abandoning their hives. The
phenomenon, known as
colony collapse disorder (CCD), has been attributed in part
to the same viral and bacterial infections, pesticide
poisonings, and mite infestations that devastated bees in the
past.
Whatever the proximate cause, it increasingly appears that
the bees are succumbing to a long-ignored underlying
condition—inbreeding. Decades of agricultural and breeding
practices meant to maximize pollinating efficiency have limited
honeybees’ genetic diversity at a time when they need it the
most. Addressing CCD may therefore require more than a simple
fix. “We need to have a diverse set of genetic raw material so
we can find bees resistant to disease,” says
Steve Sheppard, an entomologist at Washington State
University. “Genetic diversity is an important part of the
solution.”
The problem is hardly trivial. A third of the total human diet
depends on plants pollinated by insects, predominantly honeybees. In
North America honeybees pollinate more than 90 crops with an annual
value totaling almost $15 billion. Indeed, that importance lies at the
root of what went wrong. In trying to make bees more productive,
apiarists have torn the insects from their natural habitats and the
routines they mastered over millions of years. As a result, today’s
honeybees are sickly, enslaved, and mechanized. “We’ve looked at bees as
robots that would keep on trucking no matter what,” says
Heather Mattila of Wellesley College, who studies honeybee behavior
and genetics. “They can’t be pushed and pushed.”
In the beginning, honeybees and their partners, the flowers, drove an
explosion of natural diversity. While most bees preferred a specific
type of plant, honeybees were equal-opportunity pollinators—“pollen
pigs,” beekeepers called them. The most socially complex of the bees,
they thrived in colonies led by the egg-laying queen, who ensured the
genetic fitness of her progeny by breeding with multiple male drones
from other colonies.
All that began to change in the early 20th century, when farms and
orchards started enlisting honeybees to pollinate their crops. Bees that
were adapted to harvesting pollen from a variety of plants suddenly
spent a month or more at a time surrounded by nothing but almond or
apple trees. Farmers eager to increase their crop yields turned to
commercial beekeepers, who offered up massive wooden hives stocked with
queen bees genetically selected to produce colonies of good pollinators.
These breeding practices slashed the genetic variety that helps any
species survive infections, chemicals, and other unforeseen threats.
And lately those threats have been profound. During the 1980s,
tracheal mites and then varroa mites arrived in North America,
decimating honeybee populations. One entomologist studying the mite
invasion was
Michael Burgett of Oregon State University, who spent much of his
career searching for pesticides that would kill the mites but not the
bees. In 1995 he published the results of a 10-year bee survey. The
average annual honeybee loss, attributed to both mites and chemicals,
was about 23 percent.
The stresses endured by honeybees became clear to Sam Comfort earlier
in this decade when he was working for a Montana pollination outfit
called Arlee Apiaries. Every February at the start of pollinating
season, Comfort and fellow contract workers used forklifts to move
12-foot-tall towers of wooden hives onto flatbed trucks. “Five hundred
hives to a truck, all of them covered by a giant net,” he says. With the
loads jammed in tight, drivers set out for the almond groves of
California, where the bees’ whirlwind pollination tour began. Every
month brought a new destination: apple orchards in Washington, cherry
groves in Montana. During each assignment, the bees fed on row after row
of the same crop. After pollinating throughout the spring and producing
honey in the summer, Arlee Apiary bees were sent to a sandy lot near San
Francisco, where they spent the winter living on corn syrup—a scene that
Comfort describes as “fear and loathing in a city of 5,000 hives.” One
worker would pop off the hive lids and set them aside, a second would
use a gasoline nozzle to pump corn syrup from a 300-gallon tank into the
hives, and a third followed to put the lids back on. When warm weather
arrived in Montana, the drivers would truck their worn-out bees home,
only to begin the whole process again.
One of the most devastating pressures on the bees, according to
Mattila’s research, is the limit on what they can eat. “Vitamins,
minerals, fats, proteins—all the same things we need to survive come
from pollen,” she explains. In the wild, honeybees get different
nutrients from different types of plants, but industrial agriculture
limits bees to monoculture crops. “Once nutritionally stressed,
honeybees burn through their body’s reserves; then they shut down brood
rearing,” Mattila adds. “It’s all tied together.”
The bees not only receive an insufficient diet but must compete
strenuously for it. “Hundreds of colonies go into an almond orchard at a
time,” Mattila says, “so food can get spread pretty thin.” With so many
bees around, some will also get lost and go home to the wrong hive.
After all, she notes, “bees are used to nesting in trees, not in one of
a thousand boxes that all look the same.” The upshot is that a
malnourished, disoriented bee carrying mites could end up infecting a
whole new colony. “It’s like having the flu and going on a crowded
subway. Bees spread disease the same way.”
Jammed in tight, The bees set out for the almond groves of
california to begin their whirlwind pollination tour.
Inbreeding then provides the devastating final insult to the bee
colonies. The looming genetic crisis made its first blip on the
entomological radar more than a decade ago, after Sheppard began
comparing the mitochondrial DNA of commercial and feral queens. The
differences were stunning. About 30 percent of bees in the 700 feral
colonies he studied showed traces of genetic code from northern European
ancestors, compared with just 2 percent in commercial stock. “It was a
genetic bottleneck,” he says. And the problem persists. A
study published by Sheppard in July revealed that breeders use only
500 select mothers annually to produce almost a million queen bees,
which then get shipped out to lead commercial hives. Making matters
worse, the severe loss of wild honeybees due to mite infestation
virtually eliminates any chance that feral drones will mate with
commercial queens and liven up the gene pool.
Mattila explores the grim effects of loss of genetic variety in the
glass-walled bee colonies she keeps in her lab, where video cameras
capture it all—bees building honeycombs, producing honey, rearing
offspring, doing waggle dances. One of her studies compared colonies
having 15 different drone fathers (similar to the natural state) with
those having only one. The more diverse colonies stored more honey,
spent more time foraging, and experienced faster growth; the
single-father colonies could not even amass enough supplies to survive a
winter. “They’re not aggressive. They don’t communicate, their approach
to food is lackluster, and they don’t put on weight,” Mattila says.
In response to the sharp decline in commercial bee populations,
scientists and beekeepers like Comfort are working to wind back the
clock. “It’s all about diversity,” he says. After years in industrial
beekeeping, he had an epiphany in 2007 while sitting on an elk path in
Montana thinking about the situation: dead bees, missing bees, mites
thriving on chemical strips meant to kill them. He decided to pack it in
and head back East. He drove to Dutchess County in the truck he now
lives in, with an empty honeycomb dangling from the mirror and a
Montana license plate that read BEESWAX.
Today Comfort shuttles around in his truck, fetching hives out of
local squirrel houses, conducting a one-man breeding project. His goal
is not to furnish the large-scale migratory beekeepers with more robust
stock but rather to create an infrastructure of small-scale beekeepers.
After he collects a new colony, he monitors it for a while, watching to
see if it survives the winter, resists pathogens, and produces a good
amount of honey. The ones faring well are the keepers. He uses the
progeny from those hives to establish new queens, then sells those
queens to local beekeepers, mostly hobbyists who “just want to let the
bees do their thing.”
Fortunately, Comfort is not alone. Michael Burgett is doing similar
work in his lab space at Oregon State. Firemen and other locals call him
up when they come across feral hives, and Burgett snaps them up. He
hangs on to queens from hives that survive the stress of winter and
mates them with bees from other healthy colonies. At North Carolina
State University, entomologist
Debbie Delaney is lending a hand as well, seeking out feral colonies
that have survived the spread of the varroa mite in the hope that she
will find genes that confer resistance.
Slowly, beekeepers like Comfort and Burgett are trying to ease bees
away from their troubled state, allowing them to drift back toward a
healthier, more natural way of life. “Bees have been doing this for 80
million years,” Comfort says. “All we have to do is get out of their
way.”
From the
October 2009 issue, published online October 19, 2009 To
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