Left unmowed, power-line land might suit bees
The land around power lines are generating a lot of buzz among bee advocates. Power line easements, strips of land that utilities use to maintain power lines, cover more than 5 million acres across the United States. Electric companies often mow these areas to prevent vegetation from interfering with the lines. But a new study suggests that leaving easements unmowed and appropriately managed may help bee populations.
Bees are one of the most important transporters of pollen, which helps plants reproduce. Bees pollinate many flowering plants, fruits, vegetables, and crops such as alfalfa, cotton, and flax. Some experts estimate that bees are involved with 15 to 30 percent of the world's food production.
But increased land development and certain agricultural practices, such as pesticide use, have hurt bee habitats. Mites and disease have also decimated bee populations. Areas around power lines could provide a suitable environment for bees if utility companies stop mowing them, ecologists say.
The study compared the number and varieties of bees collected in unmowed power line corridors and in nearby mowed grassy fields at the Patuxent Wildlife Research Center in Maryland. The diversity and abundance of bees were greater in the power line easements than in the grassy fields.
"The power lines themselves are essentially irrelevant," says Kimberly Russell, an ecologist at the American Museum of Natural History in New York and lead author of the study. "The land under power lines is already intensively managed in order to prevent vegetation from interfering with the lines. So why not make even better use of this land and the effort put forth to manage it?"
Electric companies typically use herbicides and periodically mow all the vegetation underneath the power lines. Previous research showed that bee diversity is highest in the floral and nesting resources provided by stable, dense scrub habitats like that found in unmowed easements, abandoned fields, roadsides, railway lines, and similar habitats.
Shrublands are areas dominated by short, multi-stemmed plants. They can be covered in blueberry, huckleberry, and raspberry bushes, along with thistle, goldenrod, and a great variety of other wildflowers. Bees depend on these flowers for food and the habitat for their nests. Increasing the amount of shrubland plants will increase the diversity and abundance of bees.
Managing for shrubland, topping tall vegetation with the use of selective herbicides, requires initial intensive management, Dr. Russell says. With time, though, these habitats will become more stable and low-maintenance. In the end, they may even prove to be more cost- effective.
"Power line easements will remain intensively managed into the foreseeable future and [are] unlikely to be paved over," Russell says. "This stability is important if the land is going to provide a refuge for bee species."
But not everyone thinks it's just about the bees.
"I think the study is worthwhile, but I have a broader view," says David Wagner, associate professor at the University of Connecticut who is conducting similar research.
"The fact that bees thrive in shrublands doesn't mean we should utilize the land just for them," Dr. Wagner says. "I encourage power companies to manage their land to create a mosaic of grassland and shrubland that would enhance [the habitat of] bees, birds, and butterflies, which are merely ambassadors of a bigger umbrella of species."
Russell agrees. "The added advantage of the power line strips is that on either side of the scrubby center you have grassy paths for line workers, which probably add a few species which prefer to nest in grassy areas," she noted. Researchers know that preservation and management of early successional species, plants, and animals that benefit from surfaces that are partially disturbed and require full sun, is a pricey endeavor. That's why they're looking to electric companies to lend a hand.
"Power line companies are the largest land managers east of the Mississippi and have to pour the money in anyway. Why not use studies such as this for wiser management?" Wagner says. "Within the Northeast, power line companies may be managing 20 to 30 percent of early open successional habitats in the next 10 years."
How readily the implications of Russell's study can be transferred to other habitats like the desert Southwest or the Plains states is unclear. But researchers believe that each region should be studied to define proper management of its unused land.
"The message could simply be that the land under power lines could be managed in a way to promote local species," Russell says. "What that means exactly will differ depending on local conditions."
Power lines are generally perceived as negative features. But people might forget to look up at them if they are too busy picking wildflowers and studying bees.