Instead of herbicides, use goats

Where herbicides and mowers have failed, goats might succeed. In a new study, scientists have found that these humble herbivores can devour 12-foot-high invasive plants, allowing native species to regain a foothold in wetlands.

The plant in question is the common reed (Phragmites australis), which arrived in North America from Europe in the 1700s and “has invaded with unrelenting success,” the authors write in PeerJ. This tall grass blocks sunlight from reaching native plants and has taken over many marshes in the eastern United States. Managers have tried to quash the reeds with herbicides, mowing, and burning, but to no avail.

The researchers took a cue from European farmers, who use grazing livestock such as cows and goats to control unwanted plants. They set up four wire enclosures in a Maryland marsh that had been infested with the common reed. The team let two goats loose in each enclosure for a few weeks, allowed the reeds to grow back, and then repeated the process two more times.

The goats happily chowed down on the reeds, and the area covered by the plants shrank from 94 to 21 percent. The reeds’ height also dropped from 3.9 to 1.4 meters, and the density fell by about half. Meanwhile, the number of plant species increased: the researchers counted 22 native species in the grazed enclosures and only 12 in ungrazed enclosures.

The team also gave pieces of the reeds to 20 horses and cows. All of the animals ate the samples within 30 seconds, suggesting that other livestock besides goats could effectively do the job as well.

Grazing could have downsides too, the authors warn. The livestock could change other marsh properties, such as soil density and mineralization. And the strategy will probably work only in wetlands so overrun by the reeds that the goats have few other food options. Otherwise, these grazers might decide that native plants are tastier — and eat them instead. Roberta Kwok | 2 October 2014

Source: Silliman, B.R. et al. 2014. Livestock as a potential biological control agent for an invasive wetland plant. PeerJ doi: 10.7717/peerj.567.

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