Goats take on a notorious invasive species

[This article originally appeared at Yale Environment 360, a publication of the Yale School of Forestry & Environmental Studies.]

Over the past 30 years, land managers in the eastern U.S. and Canada have spent countless man-hours and millions of dollars trying to tame a pernicious, invasive reed known as Phragmites australis.

Originally from Europe, phragmites (pronounced “frag-MY-tees”) grows in dense, tall stands that choke off native vegetation and litter wetlands with thick mats of decaying biomass.

Toxic herbicides, controlled burns, and even bulldozers have been the go-to solutions to the problem. But recent research out of Duke University suggests another, less aggressive fix: goats.

Using an experimental wetlands site in Maryland, Brian Silliman, an ecologist with the Duke Marine Lab, found that goats were able to reduce phragmites cover by as much as 80 percent in a matter of weeks. The goats lived on a diet of roughly 80 to 90 percent phragmites during the study, and the culling allowed a variety of native plants to gain a foothold, Silliman said.

The idea of using goats for land management has gained momentum in other ecosystems, Silliman said, including in the U.S. South, where goats have helped control invasive kudzu for years. But until recently, Silliman said, “there was a sort of tunnel vision among managers of North American marshes.”

The approach is finding some practical applications — including in New York City, where park administrator Eloise Hirsh deployed a herd of goats at Staten Island’s Freshkills Park, a 2,200-acre landfill reclamation project. In two- to three-week spurts, for a total of roughly 10 weeks, the animals grazed a two-acre section of the marshy park, Hirsh said, after which groundskeepers applied herbicides and then reseeded the area with native marsh grasses.

Two years later, according to Hirsh, phragmites remains under control, and the test area requires minimal maintenance.

“The goats did what we needed them to do,” she said. “They ate everything.”

Of course, not every situation is suited to these hungry herbivores. Goats, for example, will completely avoid some wetland areas — particularly low-elevation marshes with standing water.

And Brian Knox, a supervising forester with Eco-Goats, a vegetation management company in Maryland, noted that goats will not seek out phragmites in an area dominated by other vegetation. In such cases, Knox said, land managers can construct small enclosures to focus the animals on problem areas, moving the fences — and the goats — as the phragmites is consumed.

But that fencing process can be both labor-intensive and expensive, Knox conceded. Depending on the type of land and plant cover, he estimated that using goats to mitigate invasive plants can cost roughly $1,000 to $3,000 per acre.

Often, if a plot of land is small — less than a quarter-acre — it’s more cost effective to simply weed by hand, Knox said.

While Freshkills Park officials did not have a cost comparison available, Hirsh estimated that using the goats was significantly less expensive than bringing in bulldozers. She said she hopes to use the technique park-wide in coming years, largely because relying on goats protects the land from heavy equipment and excessive herbicide use.

“Everyone around here needs to get used to the idea of four-footed greenery management,” Hirsh said.