Offshore wind power is a promising clean energy source, but can it be made safe for birds?

by Jennifer Weeks

Wind Power, © Paul Langrock/Zenit/laif

© Paul Langrock / Zenit / laif

Long-tailed duck #41 is a commuter without a briefcase—one of thousands of sea ducks that roost in winter on Nantucket Sound in Massachusetts. These distinctive black-and-white water birds are named for the males' rakish tail feathers, which jut up like exclamation points. Duck 41 has another eye-catching appendage: a satellite transmitter with a spiky antenna on its back. Data points show #41 covered a 50-mile feeding range in late 2007 and early 2008, flying daily out to shoals beyond Nantucket Island to dive for small shellfish and returning to the sound's protected waters at night.  

Longtails depart the sound in spring for their Arctic breeding grounds, but this sparkling 750-square-mile bay is an avian Grand Central Station year-round. Herons, ospreys and egrets stalk baitfish in Cape Cod's salt marshes. Short, stocky piping plovers, a federally threatened species, scurry along outer beaches plucking insects from the sand. Common, least and endangered roseate terns nest on coastal dunes, especially in Monomoy National Wildlife Refuge, a cluster of barrier islands dangling from Cape Cod's elbow. And millions of land birds cross the sound during fall and spring migration seasons, riding coastal winds along the Atlantic Flyway.

That's why leaders at Mass Audubon, New England's biggest conservation group, were alarmed in 2001 when they learned that a developer planned to build the nation's first offshore wind farm on Horseshoe Shoal, a shallow zone in the middle of Nantucket Sound. "We were very skeptical," says Jack Clarke, the group's public policy and government relations director. "We knew that Nantucket Sound was an important place for birds, and there was no permitting process in place for this kind of project."

Much has changed since then. After years of study that included wiring long-tailed ducks with transmitters, Mass Audubon now conditionally supports the Cape Wind project. And as other states seek ways to generate energy from nonpolluting sources, more offshore wind farms are under study along U.S. coastlines.

Many environmental groups, including Defenders of Wildlife, want the United States to expand renewable energy sources like wind, solar and geothermal power. These free and abundant resources generate electricity without producing greenhouse gases that contribute to global climate change, or other pollutants that help create acid rain and smog. All of these pollutants harm wildlife and damage habitat. Climate change also threatens wildlife by changing the timing of migrations, shifting animals' geographic territories, and helping pests and invasive species spread.

But renewables may also have harmful impacts. Wind power, the fastest-growing source, can kill large numbers of bats and birds if turbines are sited poorly. Some fliers collide with spinning turbine blades, while others lose habitat when land is cleared for wind farms. The National Academy of Sciences estimates that wind farms account for less than 1 percent of roughly one billion bird deaths caused each year by collisions with buildings, power lines and communication towers. However, Defenders of Wildlife and other conservation groups are working with federal agencies and the wind industry to develop national siting guidelines that minimize bat and bird deaths and other environmental impacts.

"Being renewable is a necessary but not sufficient condition for being 'green,'" says Defenders' climate change associate Aimee Delach, a member of the federal advisory committee drafting recommendations for the guidelines. "We are trying to get developers to think about wildlife and habitat right at the outset, so that we can enjoy the benefits of wind while minimizing adverse consequences." (See sidebar, page 18, for more on how Defenders is working to limit the wildlife impacts from wind energy.)

These rules are sorely needed, because wind energy is expanding rapidly. Installed U.S. wind power capacity has tripled since 2004 and now totals more than 31,000 megawatts in 37 states—enough to power nearly 9 million homes. Now some developers are looking offshore, where winds blow harder and more steadily than on land.

It costs more to build turbines in ocean waters, but offshore wind also has advantages. Many windy U.S. lands are in rural areas such as the northern Plains, far from population centers. But the Atlantic and Gulf coasts and the Great Lakes have good wind resources near large cities, so electricity can be generated near where it's needed without building long transmission lines.  

Offshore turbines have to be massive to withstand the force of waves and storms, but their size produces economies of scale. For example, Cape Wind plans to use 130 turbines that reach 440 feet above the water when their blades are vertical. Each turbine tower will generate up to 3.6 megawatts—roughly the same output as a solar plant operating today in Arizona that covers 44 acres of desert. More energy per turbine increases profits, which helps wind compete with fossil fuels and nuclear power.

Seventeen state and federal agencies have jurisdiction over various parts of Cape Wind. For Mass Audubon, though, one review mattered most at the outset. Under the National Environmental Policy Act, the Army Corps of Engineers was required to do a broad review of Cape Wind's environmental impacts. Assessing how the project could affect birds was challenging: even though Nantucket Sound was widely recognized as important avian habitat, little hard data existed to show how different species actually used the area.  

To fill the gaps, Mass Audubon highlighted three critical questions for Cape Wind: how songbirds migrated across the sound, where wintering water birds concentrated, and whether terns crossed through the project area as they prepared to migrate. "We told the Corps very strongly that they needed at least three years of study on these three issues," says Taber Allison, the group's vice president for science, policy and climate change. "When they didn't require that much from the developer, we decided we'd have to get the information ourselves." (Ultimately the developer paid for radar studies of songbirds.)

With state and private funding, Mass Audubon scientists crisscrossed Horseshoe Shoals in power boats and small airplanes from 2002 through 2004 tracking terns. These studies took place during the spring breeding season and fall "staging" period, when thousands of terns mass on Cape Cod beaches to rest and build up body fat before migrating south. Even though terns foraged east of Horseshoe Shoal and staged on Monomoy and other beaches to its west, researchers concluded that the shoal was not an important feeding area or travel route. Over three years they saw only 18 terns flying high enough over the project area to come in contact with rotating turbine blades.

The group also did aerial surveys to see how wintering sea ducks used the sound. They counted thousands of eiders, scoters and other water birds, but found that Horseshoe Shoal did not typically attract big "rafts" of floating birds in daytime. Then, to figure out where ducks spent the night, Mass Audubon ornithologists resorted to satellite tracking.

Catching ducks to implant transmitters was easier said than done: Long-tails behave like commuters but fly like fighter pilots, so they easily eluded even fast boats. The solution: shining spotlights on swimming ducks at night, which dazed birds long enough for quick-acting researchers to net them. These studies are still ongoing, but surveys in the winters of 2007-2008 and 2008-2009 logged more than 1,600 location points for instrumented ducks. None of them was in the Cape Wind project area.  

Combining these results with studies commissioned by the developer and reports from offshore wind farms in Europe, Mass Audubon leaders concluded that Cape Wind would not significantly threaten birds or habitat around Nantucket Sound. The Army Corps review, published in 2004, reached the same conclusion. So did a study by the Interior Department's Minerals Management Service (MMS), which licenses offshore energy development.  

Looking forward, MMS has agreed that Cape Wind's permit should require an environmental management system for the wind farm, three years of post-construction wildlife studies, and money to address issues that arise after the turbines are built—all conditions that Mass Audubon recommended. "This project is setting a precedent for U.S. offshore wind power, so we want it to lead the way," says Taber Allison.

Cape Wind is still securing other permits but hopes to start construction this year. Meanwhile, offshore wind proposals are dotting the Atlantic coast. Another developer, Bluewater Wind, has proposed a 450-megawatt wind farm 11 miles off the coast of Delaware. Rhode Island has chosen a third company, Deepwater Wind, to build an offshore wind farm big enough to generate 15 percent of the state's electricity supply (roughly 400 megawatts), and New Jersey is considering several projects that could add up to 1,000 megawatts of capacity. Still other companies are studying sites off Galveston, Texas and in Lake Erie.

Is an offshore wind boom coming? Maybe, says Laurie Jodziewicz of the American Wind Energy Association. "Things may look good at an early stage, but a lot has to come together for a successful project," she cautions.  

Financing is tight, but the Obama administration—which strongly supports developing more clean energy and limiting greenhouse gas emissions—is working to move renewables forward. Last spring the Interior Department published guidelines for offshore renewable energy development, a step that developers welcomed because it creates rules for leasing areas off U.S. coasts. "I expect we're going to see wind turbine projects with significant power generation in the next several years off the Atlantic," said Interior Secretary Ken Salazar.  

This push raises a new issue for wildlife: even if individual projects won't cause harm, what about cumulative impacts? Would some species lose more habitat than others or have to detour farther? (Studies at Danish offshore wind farms have found that waterfowl tend to shift their foraging areas and adjust flight paths to avoid project zones.) Scientists say they can't answer those questions yet.

"The Atlantic coast is huge. There's a lot of information from past bird surveys, but there are big gaps between data sets and some studies are very old," says Andrew Gilbert, an ecologist with the U.S. Geological Survey (USGS). Relatively few Atlantic coast bird surveys have been conducted since 2000, especially on a regional scale, and little data exists from North Carolina's Outer Banks down through Florida.

Gilbert and other USGS scientists are developing a model that will use existing data from Atlantic bird surveys to predict where and how about a dozen key species, including loons, eiders, gannets, petrels and terns, use the ocean. By relating bird observations to information on ocean temperature, plankton concentrations and water depth, they aim to pinpoint other areas that might also be important for birds.  

"We expect that birds will concentrate at fronts and eddies, like other marine species," says Beth Gardner, a researcher with the project. "By combining lots of localized surveys, we can make inferences about how birds use the ocean at a larger scale."

Modeling bird concentrations over broad areas is critical for projecting cumulative impacts from development, according to Gilbert. "We have to understand birds' presence over large scales and time frames," he says. For example, take greater shearwaters—large brown-and-white seabirds that cross the Atlantic twice each year, from breeding grounds off South Africa to New England and eastern Canada, then back again. "Shearwaters make big 20,000-mile migratory loops and are almost constantly moving, so we need more than project-scale studies to understand how development will affect them," Gilbert argues.

If the model flags an area as a possibly important bird zone, regulators will know that potential wind farms there should receive more detailed review. And developers can overlay maps generated by the model with wind resource maps to find coastal zones that look less important for birds (although they would still have to go through stringent environmental reviews.)

Wind power is a polarizing issue for many environmentalists who support shifting to cleaner energy sources but worry about harming ecosystems and wildlife. "You can't be cognizant of climate change impacts in the U.S. and not want to embrace wind energy, but there are other values to consider," says Katharine Parsons, a senior scientist at the Manomet Center for Conservation Sciences in Massachusetts. The center is helping states develop guidelines for energy development along coastlines that will protect sensitive species. "We want to move wildlife concerns to the front of the review process," Parsons says.  

That didn't happen on early wind projects like California's Altamont Pass, which has killed hundreds of raptors since the 1980s. Offshore wind is a chance to do better. "It took a lot of education for us to come to where we are today on Cape Wind," says Mass Audubon's Jack Clarke. "We need to learn from this project."

Massachusetts-based freelance writer Jennifer Weeks specializes in stories about energy, the environment, science and technology.

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