Visit the Honeybee page at N8ture
The Plight of the Bumblebee
By Douglas McInnis
With bees and other pollinators disappearing at an alarming rate, our
fruits and vegetables may be in jeopardy.
EACH FALL, Hawaiian biologists from the National Tropical Botanical
Garden rappel over the edge of some of the world's tallest sea cliffs.
Dangling from ropes 3,000 feet above the Pacific Ocean, they carefully
brush pollen onto a few trumpet-shaped flowers clinging to the cliffs.
The Hawaiian flowers are two rare species of Brighamia, of which only
about 200 plants remain in the wild. Scientists believe the blossoms
were once pollinated by a type of moth that is now extinct. No other
pollinator has taken its place, so without the annual intervention of
death defying human pollinators, the plants face extinction.
If the Hawaiian moth were the only missing pollinator, scientists might
take little notice. But it is not. Habitat destruction, agricultural
chemicals, and other human influences are taking a heavy toll on the
In the United States, the most obvious sign of trouble is the
decimation of the honeybee, the chief pollinator for commercial farms
as well as backyard gardens. During the past three years' beekeepers
nationwide have lost about half of their hives to a lethal combination
of pesticides, two types of parasitic mites, and harsh winter weather.
Wild honeybees have fared even worse; an estimated 90 percent have
Worldwide, losses are also mounting among many lesser known
pollinators, such as monarch butterflies, wasps, flies, beetles, and
vertebrate species-- including hummingbirds, flying foxes, geckos, and
Although some plants-notably grains and cereals-are pollinated by wind,
the vast majority rely on insects or other animals for pollination.
About 90 percent of the world's 250,000 flowering plant species,
including at least 800 species that are cultivated by humans for food,
need pollinators. More than 100 of these food crops including squash,
cranberries, blueberries, and cashews -depend heavily on wild
pollinators, whose value to agriculture has been conservatively
estimated at more than $4 billion per year.
Many other plants, including carrots, can yield fruits or vegetables
without pollinators but need them to produce seeds for future crops.
And some important medicinal plants, including foxglove (from which the
heartstimulating drug digitalis is derived), also depend on animal
pollination. Without animal pollinated fruits and vegetables, our diets
would be high in carbohydrates and low in vitamins, minerals, and
antioxidants. "Believe me, a diet based entirely upon wind pollinated
foods such as rice, barley, oats, sorghum, corn, and millet is pretty
boring," says Stephen Buchmann, a U.S. Agriculture Department researcher and coauthor of The Forgotten Pollinators.
Too often, an endangered species of pollinator is nearly extinct by the time a public
alarm sounds. And until recently, few scientists even noticed the
larger trend."I had no way of knowing that what I saw with flying foxes in Samoa was happening in Ontario with bees," says Brigham Young
University botanist Ian Cox, who has documented losses of flying foxes, a large bat that is an important pollinator of Pacific island rainforests. "We always saw-pollination as a little tidbit of natural history and never realized that it had ecosystem-wide consequences."
To understand why pollinators are so critical, it's important to know
how pollination works. In a nutshell, pollination is the way plants have sex. Some plants don't need a partner; they have all the equipment for both the male and
female roles, and can pollinate themselves. But most plants require a middleman to bring pollen from the male part of one plant to the female part of another.
Animals play this role inadvertently, picking up pollen as they feed on
nectar, and spreading the pollen from plant to plant. The better the
pollinator does the job, the more seeds are produced and the higher the
yield or the better the fruit.
When one pollinator is lost, another may take its place. But the
replacement may not be as effective, because the plant-pollinator
interaction in many cases is like a lock and key. Some pollinators have
long tongues, curved bills, or other body parts that lend themselves to
working with the configurations of a particular plant.
In the United States, rabbit-eye blueberry production thrives when the
southeastern blueberry bee goes to work, but plummets if the common
honeybee tries. "The vaseshaped flower of the rabbit-eye blueberry is a
little bit too deep for the honeybee's tongue," explains James Cane,
associate professor of entomology at Aubum University. "For her to
reach the nectar at the base of the flower, she's got to cram her head
through the opening of the flower. Honeybees aren't happy with that
kind of treatment, and they move on."
Cane says that the better adapted southeastern blueberry bee will in
its lifetime, set $20 worth of fruit. "If you're a grower and you see
these bees flying through your orchard, you can replace each bee with a
Nonetheless, some growers have unwittingly sabotaged the southeastern
blueberry bee and their own prosperity. The desire to produce more
blueberries prompted the growers to enlarge their fields by clearing
and planting adjacent areas. In the process, they destroyed the nesting
sites of the bees best suited to pollinate their crops.
But the most devastating blow to American agriculture is the growing
loss of the honeybee.
Imported from Europe in the 1620s the honeybee thrived here and proved
valuable for pollinating a wide variety of crops. The honeybee's
communal nature makes it easy for beekeepers to manage huge colonies
that can be trucked from farm to farm, although colonies of escaped
honeybees can also be found in the wild.
Unfortunately, the honeybee's crosscountry travels have helped disperse
two mites-a tracheal mite that suffocates the bee by attacking its
respiratory system, and a bloodsucking varroa mite that attaches itself
to the bee's back. Neither mite is native to the United States, which
has banned bee imports since the 1920s to prevent such outbreaks, but
pollination experts think the mites arrived with illegally imported
bees and spread to wild honeybees.
Healthy colonies of domesticated honeybees are critical for a variety
of crops. Modern farms are so huge and densely planted that wild
pollinators can't possibly do the job. Pollinating California's almond
crop, for example, requires about 500,000 hives filled with tiny
But parasites are not the only threat to bees and other pollinators.
Manmade chemicals also play a role. Rachel Carson's bestselling book
Silent Spring is best remembered for linking the nowbanned pesticide
DDT to bird deaths more than three decades ago. But the book also gave
early warning that pesticides threatened to decimate pollinators and
produce "fruitless falls."
DDT has since been banned in the United States and Canada.
Unfortunately, while DDT replacements may be safer for birds, some have
proved far more deadly than DDT for Pollinators. "They're not a magic
bullet aimed at just one organism. They're quite toxic to a broad sweep
of organisms, including bees and butterflies," says Buchmann. One
early case occurred in Canada's New Brunswick province when blueberry
production plunged from 5.5 million pounds in 1969 to 1.5 million
pounds the following year. Canadian researcher Peter Kevan traced the
falling production to the use of Fenitrothion, the pesticide that replaced DDT for controlling spruce bud worms in the province's forests. Fenitrothion killed
blueberry-pollinating bees along with the worms.
The problem isn't so easy to pinpoint when pollinators are killed by
the slow march of development. For instance, migratory pollinators such
as the monarch butterfly must contend with the shrinking number of
stopover points on their annual flights from Mexico to as far north as
Canada, and back again. In Hawaii, pollinators began to die when
imported goats, cattle, deer, and pigs damaged forests.
In the American Midwest, development repeatedly altered the land, first
when vast forests were felled for farms, and again as agriculture gave
way to homes, shopping centers, and factories.
When a pollinator is lost entirely, some plants may have the ability to
evolve so that they can perform both the male and female functions,
scientists theorize. But such transformations take time. "I doubt
enough plants could switch to self-fertilization quickly enough to
solve the pollinator crisis some experts foresee," says Kent Holsinger,
an associate professor of biology at the University of Connecticut.
Self-fertilizing plants may not be as healthy either. Inbreeding among
animals generally produces less vigorous, less fertile offspring, and
the same holds for plants.
Individuals can take steps to help pollinators survive. Backyard
gardeners can attract pollinators by putting up thick wooden boards
drilled with holes of different sizes; the holes are potential nest
sites for bees and wasps. A milk carton packed with paper drinking
straws also provides good homes for pollinators. Larger-scale efforts
to conserve habitat and limit the use of agricultural chemicals are
Scientists warn that if we don't take steps to protect pollinators, we
may face a tasteless future, devoid of some of the fruits and
vegetables we enjoy today. "Pollination is amazing," says Cox. "It's
sort of like the sun rising. We've always taken it for granted. But if
you lose a species of bee, you can't get it back. I think it's safe to
say we're in trouble. What we don't know is how big the trouble is."
Back to Honeybees