Missing Buzz

Bees and other vital pollinators are in danger as they lose friendly habitat. Scientists are studying the problem in a man-made refuge at the Patuxent Wildlife Research Center.

November 04, 2007|By Frank D. Roylance | Frank D. Roylance,Sun Reporter

Forty years ago, wildlife managers and utility engineers struck a deal to keep power flowing to the growing Washington region without destroying the wooded bottomlands of the Patuxent Wildlife Research Center.

The Potomac Electric Power Co. would clear-cut a right-of-way for electric lines across an upland portion of the reserve, but manage the 250-foot-wide utility corridor as a unique "scrub-shrub" habitat friendly to migratory birds.

Four decades later, the plan is working - in critical ways neither side predicted. The swath of low-growing blueberry, huckleberry and honeysuckle, holly, alder and buttonbush provides more than a pit stop for migratory birds.

"It's also turning out to be prime habitat for pollinators," said Holliday Obrecht, senior refuge biologist at the National Wildlife Service's Patuxent Research Refuge.

These are the bees, flies, butterflies, wasps, moths, beetles, hummingbirds and bats that co-evolved with key plants to carry pollen from flower to flower. From this arrangement the animals provided fertilization in exchange for protein (pollen) and carbohydrates (nectar).

Across North America, at least some of these vital species are in trouble, according to a recent National Academy of Sciences report. They're victims of habitat loss and fragmentation, parasites and disease, as well as competition from invasive species - including European honeybees.

The U.S. Department of Agriculture says a third of the nation's diet depends on insect pollinators. Billions of honeybees, in millions of commercial colonies trucked around the country with the seasons, do much of the work on food crops.

But wild, native pollinators play a role, too. And they're vital to perhaps three-quarters of all the world's flowering plants, among them wildflowers and tomatoes, holly and laurel bushes, dogwood and chestnut trees.

With scientists unsure about how well the native pollinators are faring, Patuxent researchers are tackling the issue on two fronts. In the lab, they're learning more about the poorly documented lives of America's 4,000 species of native bees. Some 500 of those still have no names and have never been formally described or counted.

On the wildlife refuge, they're working with PEPCO to figure out how landowners can manage their property to benefit pollinators - the subject of some debate.

Everyone agrees that power companies must keep their lines clear of trees. But after 40 years of experience at Patuxent, scientists argue it's no more costly to cut and kill the unwanted trees and plants every few years - providing a friendly habitat for pollinators amid the remaining low scrub - than it is to mow the utility corridor regularly and keep it in grassy meadow.

PEPCO is not persuaded. Its staff forester, Dave Paduda, said it's 2 1/2 times as expensive to cull selectively for shrubby pollinator habitat as to mow a meadow. The scrub shrubs at Patuxent are "impenetrable," he said, making hard work for the crews and heavy equipment needed to maintain and repair the lines and towers.

So, outside the refuge, PEPCO mows, cuts and uses approved herbicides on its right-of-way as needed, every four years.

"We can work with adjacent property owners to modify our work a little, but overall, we're going to manage it the way we think is best for the company," Paduda said.

But that may not be best for pollinators. Under the PEPCO lines at Patuxent, "almost all of the shrubs and small trees are really good flowering species, high-quality and attractive to bees," said Sam Droege, a U.S. Geological Survey bee biologist. Droege spoke recently as he led rain-soaked biologists and environmentalists from the Pollinator Partnership through the PEPCO scrublands.

"When pollinators are healthy in any ecosystem, everything else is also likely healthy. And the reverse is also true," added Paul J. Growald, chairman of the Coevolution Institute, which arranged the tour.

Out in the rain, Droege and Obrecht pointed out shadbush, which blooms when the shad run and attracts early spring bees. Next, American holly, an "excellent bee plant," they said. Huckleberries are mid-spring bloomers attractive to bumblebees, while honeysuckle's trumpet flowers evolved for hummingbird visits.

After it was clear-cut in 1961, Obrecht said, the PEPCO corridor was left fallow for nine years while natural plant succession repopulated the landscape. Then land managers moved in.

Every three or four years, under the refuge's direction, PEPCO crews walk the 3 1/2 -mile corridor, cutting or poisoning unwanted species, including young hardwood trees that would grow to interfere with the 250-kilovolt lines overhead.

"Kill a tree, save a bee," Droege quipped.

The remaining shrubs and bushes produce the succession of blooms needed to feed bugs and birds throughout the growing season. Narrow paths mowed through the scrub provide wildflowers, while the corridor itself hosts nesting sites for pollinators.

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