Itasca State Park using new, four-legged weed control

Goat with crowd
Managers of Itasca State Park are using a herd of goats to control invasive weeds near the Mississippi River. The goats tend to draw a crowd, so park officials use the opportunity to spread the word about the dangers of invasive plants.
MPR Photo/Tom Robertson

Non-native weeds have been a problem in Minnesota for decades. They spread in ditches, forests and farmland, choking out native species. State and local governments spend millions trying to control the aggressive plants.

Itasca State Park officials say goats are not only environmentally friendly, they're also drawing attention to the invasive weeds problem.

Becky Marty
Becky Marty, resource manager at Itasca State Park, says goats are more environmentally friendly than herbicides, especially so close to the fragile Mississippi River.
MPR Photo/Tom Robertson

Goats aren't usually part of the landscape at Itasca State Park. At the park's west entrance, a herd of 19 goats graze on a small plot of land not far from the Mississippi River. The good-natured animals draw a crowd of park visitors.

While children play with the goats inside a mesh enclosure, park officials use the opportunity to educate parents and other visitors on the damage invasive plants can do.

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The goats munch on a couple of plants that are on Itasca State Park's most wanted list of exotic species. One is a nasty purple flowered plant called spotted knapweed. The other is a plant with bright yellow flowers called common tansy.

Both are aggressive weeds that arrived from Europe decades ago. They have few natural enemies, and they both release a toxin that's distasteful to deer and other animals. But Itasca Park resource manager Becky Marty says the goats don't seem to mind them.

Spotted knapweed
Spotted knapweed is an aggressive non-native species that tends to push out native plants. The stem contains a toxin that makes it undesireable as a food source for most animals. Goats don't seem to mind, though.
MPR Photo/Tom Robertson

"The goats really like both of them," said Marty. "The goats will come in, they graze off all the buds and leaves and the flowers of each of these plants almost immediately, the first thing they do when they get into an enclosure. So they're really starting to slow down the production that we can get off of these plants."

The three-year goat experiment costs about $1,000 a year. It's funded by neighboring Clearwater County's invasive weeds task force. Clearwater officials are interested to see if the project would work on a larger scale in the ditches along county roads.

The goats come to the park twice each summer to munch on a six-acre site. The visits are timed so the goats eat the plants' flowers before they have a chance to spread their seeds. Meanwhile, work crews spread native grass seeds on the site. The goats' small hooves help grind those seeds into the ground.

Marty says using herbicides on the site would probably be much cheaper, but she thinks herbicides are too risky on land so close to the Mississippi River.

"I think we will see more invasives get here, but I also think our knowledge is getting better."

"Many of the herbicides go straight down through the soil to the water table," said Marty. "And being this close to the Mississippi River -- we're less than 100 feet away in much of this area -- we can't afford to have anything going to the water where we might potentially damage any of the aquatic systems, or have any chemicals going downstream."

Using goats to control invasive weeds is more of a novelty in Minnesota. State and county governments spend thousands of dollars each year on the effort. They're more likely to use herbicides, burning, pulling or aggressive mowing to control exotic plants.

Invasive plants cost the U.S. economy billions of dollars. In Minnesota, it's a constant battle for farmers who need to keep up with the latest herbicides to protect their crops.

In the state's forestland, an invasive called buckthorn can take over a forest understory after a timber harvest, making it difficult for trees to regenerate.

Luke Skinner, invasive species unit supervisor for the DNR, says if left unchecked, the impacts of invasive plants would be enormous.

Common tansy is becoming more common in northern Minnesota, where it's found along roadsides, abandoned farmyards and along the North Shore. Common tansy is distaseful and even toxic to some grazing animals.
MPR Photo/Tom Robertson

"It can not only reduce the diversity of the native plants, it can change how the system operates, like more nutrients going into the soil or less," Skinner said. "It reduces habitat for wildlife. And on an agricultural site, as you can imagine, terrestrial plants can really impact agriculture -- such as making a certain species outcompete the forage that you need for animals such as cows, and cattle and sheep and things like that."

This year, lawmakers nearly doubled the Department of Natural Resources budget for managing invasives. The DNR and the University of Minnesota are experimenting with using non-native insects to control certain invasive plants. In northern Minnesota, weevils native to Europe have been introduced to attack large patches of spotted knapweed.

Skinner says methods of dealing with invasive plants are getting better. But he says the problem will never go away.

"I think we will see more invasives get here, but I also think our knowledge is getting better on how to manage these at the same time," he said. "I think the awareness of invasive species is much greater than it was 10, 15, 20 years ago. And so just that knowledge of that, and people see things that are strange or new, allows us to react more quickly to new infestations or maybe keep things out when they get here."

Skinner says projects like using a herd of goats at Itasca State Park might not be the most efficient answer to controlling invasive species. But the goats are such a crowd pleaser, they create a good opportunity to educate the public about the importance of keeping exotic plants in check.