photo by Gary Braasch
Researchers on the farm are trying to
boost dwindling native bee populations by
providing habitat for them to live in. Traditionally, agriculture has relied on honeybees imported from Europe because they
live in hives, can be easily transported,
pollinate in large numbers, and produce
honey. Unlike honeybees, all but 45 of the
4,000 native bee species in North America
are solitary, nesting in tiny holes in timber or the ground. Some native bees are
generalists—they’ll eat nectar and pollen
from a variety of plants—while specialists
rely on a specific plant or group of closely
related plants. On the Butler Farm and six
other sites, scientists are attracting a variety of native bees by planting 1.5 miles
of hedgerows made up of 25 species of
plants that bloom in the spring, summer,
and fall. In addition to preventing soil erosion and shading streams, the hedgerows
provide abundant pollen and nectar for
crop-pollinating bees. Interspersed in the
hedgerows are blocks of wood with holes
and bare patches of earth for nesting.
Increasing the numbers of native bees
isn’t an instant solution to our honeybee
woes, but it will help solve some of t he
problems. “We know that it’s probably not
going to be the case that almonds in gigantic fields are going to be pollinated by
native bees,” says Neal Williams, a biologist at Bryn Mawr College. “But knowing
where native bees can provide pollination
might allow us to take pressure off the
need for as many honeybees.”
Researchers around the world are trying to
determine whether their regions’ native bees
can pollinate blueberries, squash, and dozens of other crops. So far, results have been
encouraging. For example, the bees increase
the quality of cherry tomato and coffee crops.
And when it comes to pollinating sunflowers,
native bees actually make honeybees up to
five times more efficient. Researchers believe
the native bees’ presence makes honeybees
skittish, causing them to move from male to
female sunflowers, pollinating more seeds.
Yet many native bee populations have
suffered declines, in large part due to
habitat loss and destructive agricultural
practices. The insects are most productive
and abundant on farms with natural areas,
such as forest fragments, less than a halfmile from the edges of fields. The varied
landscape provides nesting habitat and
diverse floral resources.
Claire Kremen, an ecologist at the University of California, Berkeley, has found
that farms in New Jersey have diverse and
abundant wild bee populations. Farmers
there tend to plant multiple crops, and there
are patches of natural habitat nearby. The
same isn’t true in California, where the land
was transformed to grow acre after acre of
one type of crop. In these areas, large crops
like almonds are pollinated by commercial
honeybees that are trucked in. “The problem with monoculture cropping is that for
a few weeks there’s a massive bloom, but
the rest of the time there’s nothing for bees
to eat,” says Kremen. “Coupled with habitat
loss, it’s not very good for native bees.”
Kremen is working with the conservation group Xerces Society and Audubon
California on the Butler Farm project. “We
want to see, if we restore habitat for these
bees, can we bring the bee communities
back to healthy condition in areas that were
degraded?” she says. The groups surveyed
the areas before planting hedgerows and
will monitor them over the next three years
as plants mature and bees colonize the nest
sites. Ultimately, they hope to calculate the
dollar value of the increased crop pollination
that comes from restoring bee habitats.
It’s too early to determine whether native bee populations will rebound. But
researchers and farmers are optimistic
about what they’ve seen so far. “In some
of the newly planted areas, there are a lot
of bees flying around,” says Katharina Ullmann, California Pollinator Conservation
Coordinator of the Xerces Society. “It’s really buzzing, in terms of the numbers and
kinds of bees.” ✤
“Knowing where native bees can provide
pollination might allow us to take
pressure off the need for honeybees.”
Metallic Green
Sweat Bee
The Buzz on
Native Bees
•
Three-fourths of the world’s
flowering plant species rely on
pollinators.
•
Native bees provide about
$3 billion in pollination services
in the US each year.
•
There are 4,000 species
of native bees in North
America, hundreds of which
contribute significantly to the
pollination of cherries, squash,
watermelon, tomatoes, and
other crops.
•
About 70 percent of native bees nest in the ground;
usually a solitary female digs
her own nest tunnel where she
places a mixture of pollen and
nectar and lays an egg.
•
Native bees come in a
variety of colors, from metallic green with white stripes to
black, and range in size from
less than ¼ to 1 inch long.
•
Only about 45 native bee
species in the US are social
bumble bees, which live in
colonies of up to several hundred; the rest are solitary and
nest individually.
•
Many native bee species
are more efficient pollinators, on a bee-per-bee basis,
than honeybees: 250 female
orchard mason bees can
effectively pollinate one acre
of apples—a task that would
require 15,000 to 20,000
honeybees.
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