Natives emerge from the shadows

  • Gary Nabhan

    Paul Larmer
 

Note: This article is a sidebar to this issue's feature story.

TUBAC, Ariz. - Gary Nabhan squats down in the field of crooked-neck squash, reaches inside a large orange blossom and exclaims, "I got one."

"Don't worry; this guy can't sting," Nabhan says, holding a tiny bee between his fingers.

That's because it's not a honey bee. Though records of beekeeping stretch back at least to ancient Babylon and the Greek civilization, the honey bee has been in the Americas for only 375 years. It's an import, like European starlings and Russian thistle.

The bee Nabhan holds is a squash bee in the family Xenoglossa, a solitary bee that doesn't produce honey, but has pollinated wild and cultivated squash plants in the Southwest for as long as native peoples in the region can remember. With the recent crash in the numbers of honey bees in the United States and predictions of a pollination crisis, Nabhan and a number of other biologists are curious whether the more than 4,000 species of native bees in the country can pick up the slack.

In this field at Tubac Farms, an hour and a half south of Tucson, the natives seem to be doing just fine: Native squash bees visit blossoms earlier in the day than honey bees, make more frequent visits and fly farther between squash patches. By the time honey bees arrived at the fields, most receptive female squash flowers have already been pollinated by the squash bees, say researchers funded by the Arizona-Sonora Desert Museum, of which Nabhan is the science director.

The role of wild species in crop pollination has been little studied. The U.S. Department of Agriculture focuses on the contributions of honey bees to agriculture, yet, as Nabhan and biologist Steve Buchmann point out in their recent book, The Forgotten Pollinators, even the agency believes that wild species pollinate one-fifth of the nation's crops.

Nabhan and Buchmann point to a study done by a federal bee biologist in the 1970s which suggested that of some 1,330 cultivated crop species grown in the world, about 73 percent are pollinated at least partially by a variety of bees, 19 percent use flies to move pollen, 6.5 percent use bats, 5 percent use wasps, 5 percent use beetles, 4 percent use birds and 4 percent use butterflies and moths. In the United States, squash, cranberries and blueberries are all pollinated primarily by wild insects.

"Eliminating these pollen-moving creatures would take the food right out of our mouths," write Buchmann and Nabhan.

The two authors, based in Tucson, believe protecting wildlands around agricultural fields and limiting the use of dangerous pesticides are essential to keeping populations of wild pollinators healthy for crop pollination. But their concerns go beyond agriculture.

Many wild pollinators have evolved closely with particular wild plants. For example, the bearclaw poppy, which lives in only a few enclaves in southern Utah and Nevada, is pollinated by an equally rare bee that feeds almost exclusively on just two species of widely distributed poppies. Though such tight dependencies are rare, they show that protecting wild plants is fruitless if you don't protect the wild species that pollinate them, says Vince Tepedino, a bee biologist who works at the USDA bee lab in Logan, Utah.

In conjunction with the publishing of their book, Nabhan and Buchmann have begun a campaign to promote awareness of the complex relationships between agriculture, native pollinators and the need to protect native habitat. They also hope to convince federal agencies to boost research efforts.

One question that intrigues Buchmann, but might well alarm beekeepers, is what effect honey bees have on native pollinators and plants.

"We have no data to show that honey bees have caused extinctions, but we know they are at least causing other pollinators to get less food," he says.

Though natives such as squash bees may beat them to breakfast in the morning, honey bees are extremely efficient at removing pollen and nectar from flowers, says Buchmann. One colony of bees can forage over an area of 80,000 "100,000 acres and gather 20-50 pounds of pollen a year.

"They are a foraging superorganism," says Buchmann, who has traveled the world studying both honey bees and native bees over the last 20 years.

Honey bees are also inefficient pollinators of many plant species, says Buchmann. They wet the pollen with their saliva and regurgitated nectar and at frequent intervals push it into their "saddlebags." But wet pollen doesn't fertilize the flower, he says. Most native bees collect and carry pollen dry.

Honey bees also don't know how to "buzz" pollinate. Some flowers, such as those on a tomato, blueberry or chili plant, have tiny holes in them that release pollen only when a bee buzzes so hard it becomes a living tuning fork, says Buchmann, who discovered the phenomenon, called sonication. Bumblebees and other natives can do this, but honey bees can't.

In the long-term, says Buchmann, honey bees can never be a 1-to-1 replacement for native pollinators.

For more information about the Forgotten Pollinators Campaign, contact the Arizona-Sonora Desert Museum, 2021 N. Kinney Road, Tucson, AZ 85743, (520/883-3007), http://www.oldwestnet.com/asdm/fp