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This article is part of ±¬ÁϹ«Éç's Fossil Fuel Boom series, which explores how oil and gas extraction in the United States is affecting wildlife, habitat, and people. Read more stories .

Sara Barwinski lives next to a small wetland in Greeley, Colorado. Not so long ago the prairie oasis was home to noisy flocks of red-winged blackbirds, a pair of nesting hawks, and owls that hooted almost every night. "We had a front-row seat," remembers Barwinski, who moved with her husband, a Lutheran minister, to Colorado from St. Louis a few years ago to be near their grandchildren. After an oil and gas company drilled six wells in the neighborhood last year, less than 1,000 feet from Barwinski's front door, the hawks abandoned their nest and the wetland became eerily quiet. The energy industry plans to sink 600 more wells in Greeley, a town of about 95,000 some 50 miles north-northeast of Denver, in the coming year.

"We love Colorado, and would like to stay," says Barwinski. "But the oil and gas industry needs to make better decisions about where it puts its wells. I think we can find a peaceable balance—but that's not where the state is at the present time."

Colorado is no stranger to energy booms. Miners began pulling coal from its mountains more than a century ago. But today new technologies and growing demand are fueling extraction of a different resource.

Natural gas and oil wells now puncture the state's farmland and ranchland, forests and high deserts. Roads and pipelines snake through some of its remotest parts, including habitat for sensitive bird species such as the greater sage-grouse and Gunnison sage-grouse. And energy development is moving closer and closer to populated areas. Natural gas produces less carbon dioxide than coal when burned, so in that sense it is a "cleaner" fuel. But its extraction carries costs. Environmentalists and other activists are calling for a more measured approach to natural gas development, one that addresses growing alarm about wildlife and human health.

Development in Colorado has advanced rapidly in the past three years as industry has tapped the Niobrara Formation, an oil-and-gas-rich layer of chalk and shale that underlies much of the greater Denver region. Weld County, where Barwinski lives, now has some 18,000 active wells, more than any other county in the country.

To get at the deposits, the companies use hydraulic fracturing, or "fracking"—a process that cracks underground rock formations using high-pressure injections of water, sand, and chemicals. Fracking in Colorado and elsewhere has raised concerns about pollution of domestic water supplies. People who live near well pads also worry about the effects of natural gas releases on air quality.

While the connection between air and water pollution and human health are nearly always difficult to prove, well-pad neighbors have numerous anecdotes about respiratory problems and persistent headaches. After development began in their neighborhood, Barwinski's husband suffered a severe and still-unexplained allergic reaction. "We're seeing a proliferation of drilling just a stone's throw from people's homes and businesses," says Sam Schabacker, the Mountain West Region director of the nonprofit .

The wells are steadily moving into these more densely populated areas, driving down property values, damaging roads—and making families sick." There have been some moves to rein in the effects of development. A statewide network of groups called is calling for local bans or suspensions of fracking. They're having some success. The cities of Longmont and Fort Collins have both approved bans in recent months. Colorado's oil and gas commission voted in early 2013 to require a 500-foot buffer zone around drilling operations, and state legislators have proposed a raft of bills designed to better protect property owners. The state has also proposed rules to regulate the leakage of methane from fracked wells.

But these moves have spurred a backlash. The oil and gas commission, supported by Colorado Governor John Hickenlooper, joined an industry lawsuit that seeks to lift Longmont's fracking ban. Hickenlooper that hydraulic fracturing fluid, the mixture of water, sand, and chemicals used in the fracturing process, was so safe that he'd taken a swig of it himself.

In the midst of this emotional debate, some see room for compromise. executive director Brian Rutledge recently worked with the state of Wyoming, energy companies, and other stakeholders on a plan that severely limits energy development—solar and wind as well as oil and gas—in designated "core areas" of greater sage-grouse habitat. With the plan in place, the precipitous decline in sage-grouse numbers in Wyoming has slowed. In cooperation with the U.S. Fish and Wildlife Service, the core-areas strategy is now being expanded for use with other species and habitats.

Rutledge has been discussing a similar plan with Colorado officials, arguing that effective sage-grouse protections at the state level can help avoid the less flexible and further-reaching protections of a federal Endangered Species Act listing. But the state has been slow to act. "It's very clearly the same issue here as it is everywhere else," says Rutledge. "The birds can't handle the level of disturbance and fragmentation that comes with uncontrolled gas drilling." Rutledge points out that an effective plan is as good for the industry as it is for wildlife, providing some regulatory certainty in a chaotic landscape. "We can do this and have gas, too," he says.

In Greeley, Sara Barwinski sees daily evidence of the need for compromise—for the sake of both wildlife and human health.