War of wills: Clemson’s goats battle invasive plants
CLEMSON — Armed with teeth, horns and cloven hooves, a herd of heroes has raced to Clemson University’s rescue, bravely confronting marauding invaders who have held a creek hostage for decades.
Dozens of hungry goats — immune to poison ivy and oak and impervious to the sharpest of thorns — have clomped heedlessly into dense tangles of invasive plants choking the banks and adjacent areas of Hunnicutt Creek.
Where we see kudzu, goats see dinner.
“It’s like candy to them,” Clemson Extension water resources specialist Cal Sawyer said. “I recently saw one of the big ones balancing on its hind legs just to get to the tail end of a kudzu vine and yank it down a little bit to get a better grip.”
Goats 1, kudzu 0. Game on.
Clemson researchers Sawyer, Donald Hagan and Jeremy Pike have teamed with campus landscape director Tommy Fallaw and a slew of student and civic volunteers to evaluate the effectiveness of using goats to lessen the spread of invasive plants. These non-native species include the aforementioned kudzu, along with Chinese privet, silverthorn, English ivy, nandina, liriope, Japanese stiltgrass and Japanese honeysuckle.
The project began Aug. 30, 2014, when a herd of 40 goats — on loan from Ron Searcy of Wells Farm in North Carolina — was released into a prescribed area adjacent to a portion of Hunnicutt Creek for 56 days. For the voracious ruminants, this was the equivalent of a free trip to a buffet. Within the confines of an electric fence, males and females of various sizes and breeds went about their business of chewing and swallowing.
“Goats benefit from a diverse diet,” Sawyer said. “Otherwise, they would be browsing single species of grasses in a field. Here, they get to browse on multiple species. And though invasive plants are a nuisance to us, they can be a healthy and highly nutritious food for goats.”
The results of the initial trial have been favorable. Within the browsing areas, almost every invasive plant species showed a significant reduction in cover, including three that were eliminated entirely. Even better, the goats were physically able to plunge into thorny thickets, maneuver within snarls of vines, and rub against poison ivy and oak with little risk of injury. They also clung to the sides of steep banks almost as nimbly as their mountain goat cousins.
“The goats are able to go into areas where it wouldn’t be safe for our staff,” Fallaw said. “They eat the plants and keep on going where if I put our personnel in there, I’d probably lose a lot of them for several weeks from exposure to the poison oak and ivy.”
Though the goats do much of the work all on their own, they are only one part of a multi-pronged approach.
- The goats are sent in first to devour the leaves and stems of the plants, clearing out most of the dense foliage and making the area more accessible to humans.
- Student and civic volunteers — including members of service clubs and athletic teams — then enter the cleared area and chop down most of what remains.
- Clemson University Facilities staffers finish the job by strategically applying herbicide on the stumps and other remnants.
“The goats reduce the cover, making it possible for people to get into those dense thickets and follow it up,” said Hagan, a forest ecologist and assistant professor in the forestry and environmental conservation department at Clemson. “That’s a real positive. The advantage to cutting it and pulling it out is that you get an immediate and dramatic change. If all you did was go in and spray herbicide, you’d be left with an ugly tangle of dying plants.”
The amount of under-story and mid-story vegetation removed from relatively small areas proved to be stunning in scope.
“It’s one thing to look at the biomass when it’s standing and how intimidating it is,” said Pike, an associate scientist in forestry and environmental conservation. “But when the volunteers started to pull it out, there was about a half-acre of material stacked six feet high. Even after the goats were finished with their part, what was left to be removed was no small undertaking.”
Because they ate so much, the goats produced copious amounts of fecal matter in the form of pellets, many of which were filled with seeds. This caused the investigators to wonder if the goats might end up spreading the very plants they were commissioned to destroy.
“We had Japanese stiltgrass with thousands upon thousands of fertile seed heads,” Hagan said. “And we watched the goats just munch them up. So we had a couple of students collect some of the pellets and then incubate the seeds in one of our greenhouses to see if anything came up. Luckily, nothing did. It appears that the gut of the goats is harsh enough to kill the seeds.”
Other potential problems the investigators considered were water pollution and sediment buildup in the creek caused by the presence of the animals.
“When you release a bunch of animals on steep slopes, there will be a lot of pooping and soil disturbance,” Sawyer said. “But our laboratory analysis showed that though there was a temporary spike in bacteria and sediment levels while the goats were there, things returned quickly to normal once the goats were gone. Things like this are always going to be a question of risk management. Which risk do you want to take? Excessive herbicides? Injury to human personnel? To me, these risks outweigh the temporary risk to water quality caused by the animals.”
An unexpected discovery caught the researchers by surprise. In addition to clearing the vegetation, the goats uncovered piles of ugly trash that the dense thickets had hidden for decades. But even this became a positive.
“They exposed a lot of trash that had been blown in, thrown in, or floated in for years and years,” Sawyer said. “The vegetation was so thick and so high nobody could see all the garbage. So picking it up became another part of the clearing process. We certainly filled a lot of black trash bags.”
The project, titled “Evaluating Control Strategies for Effective Invasive Species Management – Prescribed Grazing with Goats,” could not have been completed without the involvement of Clemson University’s Creative Inquiry students and volunteers from service clubs, athletic teams and service-learning classes. Clemson University Facilities funded most of the project. Additional costs were covered by internal and external sources.
“Our students have been hands-on and have helped us considerably,” Pike said. “The amount of work that has been done is unbelievable — about 300 volunteer hours. Almost five acres were cleared last year. And the best part was that the goats were really embraced by the university and perceived as a green alternative. They were certainly more appealing than 10 guys with backpack sprayers.”
As part of the ongoing watershed project, a second herd — 69 of them, this time — is currently stuffing itself with invasive plants at an upstream site on Clemson’s campus to help prevent further spread downstream. This year’s goal? Seven acres.
Chew on that for awhile.