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Recently, ominous headlines have described a mysterious ailment,
colony collapse disorder(CCD)，that is wiping out the honeybees that pollinate
many crops. Without honeybees, the story goes, fields will be sterile,
economies will collapse, and food will be scarce.
But what few accounts acknowledge is that what’s at risk is not
itself a natural state of affairs. For one thing, in the United States,
where CCD was first reported and has had its greatest impacts, honeybees
are not a native species. Pollination in modem agriculture isn’t alchemy,
it’s industry. The total number of hives involved in the U.S. pollination
industry has been somewhere between 2.5 million and 3 million in recent
years. Meanwhile, American farmers began using large quantities of
organophosphate insecticides, planted large-scale crop monocultures, and
adopted “clean farming” practices that scrubbed native vegetation from
field margins and roadsides. These practices killed many native bees
outright—they’re as vulnerable to insecticides as any agricultural pest—and
made the agricultural landscape inhospitable to those that remained.
Concern about these practices and their effects on pollinators isn’t new—in
her 1962 ecological alarm cry Silent Spring, Rachel Carson warned of a
‘Fruitless Fall’ that could result from the disappearance of insect
pollinators.
If that ‘Fruitless Fall, has not—yet—occurred, it may be largely
thanks to the honeybee, which farmers turned to as the ability of wild
pollinators to service crops declined. The honeybee has been
semi-domesticated since the time of the ancient Egyptians, but it wasn’t
just familiarity that determined this choice: the bees’ biology is in many
ways suited to the kind of agricultural system that was emerging. For
example, honeybee hives can be closed up and moved out of the way when
pesticides are applied to a field. The bees are generalist pollinators, so
they can be used to pollinate many different crops. And although they are
not the most efficient pollinator of every crop, honeybees have strength in
numbers, with 20,000 to 100,000 bees living in a single hive. “Without a
doubt, if there was one bee you wanted for agriculture, it would be the
honeybee, “says Jim Cane, of the U.S. Department of Agriculture. The
honeybee, in other words, has become a crucial cog in the modem system of
industrial agriculture. That system delivers more food, and more kinds of
it, to more places, more cheaply than ever before. But that system is also
vulnerable, because making a farm field into the photosynthetic equivalent
of a factory floor, and pollination into a series of continent-long
assembly lines, also leaches out some of the resilience characteristic of
natural ecosystems.
Breno Freitas, an agronomist, pointed out that in nature such a high
degree of specialization usually is a very dangerous game: it works well
while all the rest is in equilibrium, but runs quickly to extinction at the
least disbalance. In effect, by developing an agricultural system that is
heavily reliant on a single pollinator species, we humans have become
riskily overspecialized. And when the human-honeybee relationship is
disrupted, as it has been by colony collapse disorder, the vulnerability of
that agricultural system begins to become clear.
In fact, a few wild bees are already being successfully managed for
crop pollination. “The problem is trying to provide native bees in adequate
numbers on a reliable basis in a fairly short number of years in order to
service the crop，” Jim Cane says. “You’re talking
millions of flowers per acre in a two-to three-week time frame, or less,
for a lot of crops.” On the other hand, native bees can be much more
efficient pollinators of certain crops than honeybees, so you don’t need as
many to do the job. For example, about 750 blue orchard bees (Osmia
lignaria) can pollinate a hectare of apples or almonds, a task that would
require roughly 50,000 to 150,000 honeybees. There are bee tinkerers
engaged in similar work in many comers of the world. In Brazil, Breno
Freitas has found that Centris tarsata, the native pollinator of wild
cashew, can survive in commercial cashew orchards if growers provide a
source of floral oils, such as by interplanting their cashew trees with
Caribbean cherry.
In certain places, native bees may already be doing more than they’re
getting credit for. Ecologist Rachael Winfree recently led a team that
looked at pollination of four summer crops (tomato, watermelon, peppers,
and muskmelon) at 29 farms in the region of New Jersey and Pennsylvania.
Winfiree’s team identified 54 species of wild bees that visited these
crops, and found that wild bees were the most important pollinators in the
system: even though managed honeybees were present on many of the farms,
wild bees were responsible for 62 percent of flower visits in the study. In
another study focusing specifically on watermelon, Winfree and her
colleagues calculated that native bees alone could provide sufficient
pollination at 90 percent of the 23 farms studied. By contrast, honeybees
alone could provide sufficient pollination at only 78 percent of farms.
“The region I work in is not typical of the way most food is produced，” Winfree
admits. In the Delaware Valley, most farms and farm fields are relatively
small, each fanner typically grows a variety of crops, and farms are
interspersed with suburbs and other types of land use which means there are
opportunities for homeowners to get involved in bee conservation, too. The
landscape is a bee-friendly patchwork that provides a variety of nesting
habitat and floral resources distributed among different kinds of crops,
weedy field margins, fallow fields, suburban neighborhoods, and semi
natural habitat like old woodlots, all at a relatively small scale. In other
words, ’’pollinator-friendly” farming practices would not only aid
pollination of agricultural crops, but also serve as a key element in the
over all conservation strategy for wild pollinators, and often aid other
wild species as well.
Of course, not all farmers will be able to implement all of these
practices. And researchers are suggesting a shift to a kind of polyglot
agricultural system. For some small-scale farms, native bees may indeed be
all that’s needed. For larger operations, a suite of managed bees—with
honeybees filling the generalist role and other, native bees pollinating
specific crops—could be augmented by free pollination services from resurgent
wild pollinators. In other words, they’re saying, we still have an
opportunity to replace a risky monoculture with something diverse,
resilient, and robust.
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