(USA TODAY/AP) -- Goats are helping the USA go green.
Cities, residents and even airports are bringing in herds to clear overgrown parcels of land as an alternative to using chemicals.
The animals grabbed national headlines this past week as the Historic Congressional Cemetery in Washington brought them in to help trim down a 1.5-acre, overgrown area the cemetery owns. Chicago's O'Hare International Airport turned to goats recently, along with sheep and llamas, to feast on plants on 120 acres in the northeastern corner of the airport.
These aren't the only places where goats have been used across the country in the past month. Haverford College in Pennsylvania is using them to eliminate invasive plants. And in Sandy Hook, N.J., they're helping remove about 40 years' worth of poison ivy from roughly 6 acres of property at the Mortar Battery, a historic site.
The use of goats has been around worldwide for centuries, but they're now "catching on" in the eastern part of the country as a sustainable method to clear land, and more companies deploying the animals are popping up across the nation, says Brian Knox, president of Sustainable Resource Management, which focuses on the protection and management of natural resources.
"We're seeing them more and more as a relatively inexpensive way to clear these areas," says Knox, who is also the supervising forester for the Maryland-based company Eco-Goats, a company that brings in a herd to help clean up areas.
USA TODAY reported in November that goats were used to help clear brush out West to prevent wildfires. The San Francisco International Airport recently brought in goats to eliminate brush, as it does every year through a company called Goats R Us. And in Boulder, goats help get rid of chicory, a type of invasive weed.
"Goats will eat a majority of the real problems that people run into," Knox says, noting that they prefer wooded vegetation as opposed to grassy plants.
Knox says he has seen more people turning to goats for their own private homes, particularly those on waterfront properties, to prevent chemicals from entering the water.
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At the Congressional Cemetery, where 58 goats have grazed since last week, the goats have aided in clearing the swamp, says Lauren Maloy, the cemetery's program director. She says the goats "really just don't stop eating," and take only the occasional break to sleep. Onlookers can watch the goats but must stay behind a fence.
"They've been great for the community, and it's heartening to see people coming in," Maloy says. "It's important to us to be a leader in the green movement."
Haverford College is "strictly organic," says Martha Van Artsdalen, plant curator for the school's arboretum. So goats served as a good replacement for "men and machines," she says.
Goats graze along a stream bank on the campus' perimeter, chomping away at thickets and poison ivy.
Don't worry: Poison ivy doesn't harm the goats, Van Artsdalen says.
"They really did clear out a lot of rough terrain," she says. "It's not perfect - you don't tell the goats, 'Hey, you missed a spot.' But you have to let them eat what they want to, and this was the perfect place."
At the Chicago airport, llamas and burros help scare away coyotes.
"The wild burros chase them and stomp them to death," says Pinky Janota, who donated some of the animals from her shelter and helps manage them on site.
Goats were among the first domesticated animals, Knox says. He describes the more recent trend as "a rediscovery of what people have been doing around the world for thousands of years."
Contributing: The Associated Press