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Can Wild Bees Take Sting From Honeybee Decline?

John Roach
for National Geographic News
October 20, 2004
 
Decades of disease and overuse of pesticides have put the squeeze on populations of the domesticated honeybee. As a result, farmers are increasingly left with fields of flowering crops that fail to bear fruit.

Since some 15 to 30 percent of the food we humans eat directly or indirectly depend on the pollination services of bees, scientists say the problem threatens to take some excitement—and potentially abundance—from our diets.



Claire Kremen, a conservation biologist at Princeton University in New Jersey, thinks native wild bees can take some of the sting from the honeybee decline. These wild bees buzzed North America for thousands of years before the domesticated European variety arrived.

"We need to ensure we can keep on having [honeybees] around, but at the same time we can reduce the risk of relying on honeybees for crop pollination by protecting wild bees and ensuring their pollination services can be maximized," she said.

Scott Hoffman Black is executive director of the Xerces Society, a Portland, Oregon-based invertebrate-conservation organization. He says North American farmers rely so heavily on domesticated honeybees today that they often forget that pollinated food crops existed before the domesticated honeybee was introduced.

"Prior to the advent of large-scale monoculture agriculture [the practice of growing only one kind of plant in a given plot] in the fifties and the use of lots of chemical pesticides, native bees and feral honeybees pollinated everything. It wasn't an issue. People didn't cart bees all over the country," he said.

Kremen and Black's organization are collaborating to spread the word about the role wild bees play in crop pollination.

While they acknowledge that farmers cannot and will not revert to pre-1950s practices for the sake of wild bees, they advocate steps to conserve and use native wild bee populations as an insurance policy for when a honeybee shortage would otherwise leave fields sapped of their full potential.

Wild Bee Needs

Scientists estimate there are about 4,000 different species of wild bees that are native to North America. They nest in thick grass, soil, and wood; are rarely kept in hives; and generally do not make surplus honey or form large colonies.

While the mites that have proven so devastating to domesticated honeybee populations cause little effect to the wild bees, pesticide use and habitat loss are taking their toll, according to Black.

"Like any animal, native bees need a place to live," he said. "They need nest sites and floral resources, and if they don't have them, they won't be there."

According to Black, people can take small steps to augment wild bee populations, such as making nesting areas available. Given that about 70 percent of wild bees nest directly in the ground, not in hives, this is simpler than it seems, he added.

Wild bees also need natural habitat to forage, which can include small woodlots, areas along a stream, or even a hedgerow between fields of crops. As an added bonus, Kremen said, wild bees help keep wild areas healthy.

"They help us maintain the natural landscape, which provides spiritual beauty, recreational quality, and other ecosystem services we depend on," she said.

Viable Populations?

Kremen has been documenting the extent wild bees play in crop pollination in California and has found that on farms in narrow valleys surrounded by wild vegetation the native bees can do most of the work.

But this is the exception, not the rule. The bulk of California farms are sprawling monoculture fields in the central valley that are completely devoid of natural bee habitat, meaning that wild bees will never be able to provide all of a farmer's pollination needs.

"In most of the central valley—no way. The bee populations are not healthy enough," she said. "There's a dramatic decline in bee diversity and bee abundance when you go from the narrow valleys to the wide central valley."

Robust wild bee populations do not thrive in the central valley's monoculture fields. But Kremen said small improvements could allow some native bees to flourish, as long as larger source areas are also restored and protected. These small steps could include reintroduced native vegetation to areas around tractor sheds and irrigation ditches.

"If you can get 10, 20, 30 percent of your needs met by wild bees, that would help a lot," she said.

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