Watermelon fans can stop biting their nails, at least around the Delaware Valley region. Even if the beleaguered honeybees disappear, native bees should be able to buzz in and take care of most of the crop by themselves, says a new study.

It's a compelling example of biodiversity as insurance, says Rachael Winfree of Princeton University.

U.S. farmers who need pollinators for their crops use European honeybees (Apis mellifera). Those bees have had their troubles lately, with parasitic mites and colony-collapse disorder, among other ills (SN: 7/28/07, p. 56). But the United States has hundreds of species of native bees that drop in on farms.

Within the past 5 years, two studies have analyzed the role of native bees as pollinators on watermelon farms. The studies found that the natives assisted but that their numbers were rarely large enough to pollinate entire crops, reports Claire Kremen of the University of California, Berkeley and her colleagues. Where wild lands were scarce within a bee's flight from the field, native bees were scarce too.

Kremen's studies took place in and near the intensely managed agricultural lands of California's Central Valley. In the new study, Winfree, Kremen, and their colleagues turned to the Delaware Valley of New Jersey and eastern Pennsylvania, where more scraps of natural vegetation survive amid the farmland.

The researchers tallied bees visiting watermelon plants on 23 farms. Computer simulations based on those observations predict that native bees alone could handle the job at 21 of the farms, the researchers report in the November Ecology Letters.

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