They’re fuzzy, they’re furry, they’re funny and they eat everything. But are goats the best option to manage Wisconsin’s invasive species? Agronomy Ph.D. student Stefania Cartoni Casamitjana is trying to find out.
Casamitjana is a member of the Renz Weed Science lab and she is working on a multi-year study to determine the best invasive species management practices. The study includes two test sites — one in Prairie du Sac and another at the American Family Insurance national headquarters on Madison’s east side.
Wisconsin’s woodlands have a problem with invasive species, and there is little guidance for landowners on how to manage these invaders. So when a plant starts growing and reproducing in a new environment, there is often nothing to stop its growth, Casamitjana said.
“They are causing economic harm to farmers who can’t use their land and environmental harm because they are excluding other species that use the territory,” Casamitjana said.
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These threats are especially important to farmers and landowners. A lot of farmers have oak savanna on their property, which contains grasses and an overstory of trees under normal conditions. When invasive shrubs enter the environment, they create another layer between the grasses and the overstory, Casamitjana said. These shrubs become too dense, and landowners can’t profit off the land by allowing cattle to graze there or by harvesting the wood.
“So we’re trying to find a balance between giving farmers or landowners the opportunity to use their land for profit but also in a way that allows us to restore the ecosystem a little bit,” Casamitjana said.
In these wooded test sites, Casamitjana is testing the use of herbicides, physical removal by a forestry mower and goat grazing to determine the best ways to manage invasive species. Finding the best way to control invasive plants can be tricky, but it’s necessary since invasive species are always being introduced, Casamitjana said.
A previous study on hardwood forests in southern Indiana showed goats can be effective in reducing invasive shrubs, though the study recommended land managers continue to use herbicides and physically remove invasive species after the goats leave the site.
Using goats to manage invasive species is something new to American Family Insurance facilities program manager Casey Olson. Olson is part of the team that manages 280 acres of land on American Family Insurance’s Madison property. Casamitjana uses a 13-acre wooded area on the property as a test site.
One of American Family Insurance’s core values is land management and sustainability, Casamitjana said. These values coincide with their goal of having 25% of native landscape in their properties nationwide by 2030. Managing invasive species on wood lots is part of this goal and that is where Casamitjana’s study comes in.
Prior to the partnership with the Renz lab, Olson only used more traditional methods of invasive species management, such as herbicides and hand removal of plants.
“[The goats] definitely made changes and definitely for the better,” Olson said. “They have taken out a lot of invasive species that we don’t want.”
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Using goats to manage invasive species isn’t a new technique, but Casamitjana said it’s definitely gaining popularity. In 2020, the City of Madison used goats in their parks as an alternative to herbicides, and goats are also used in Dane County parks.
Casamitjana knows the public finds using goats as an invasive species management technique to be appealing but that doesn’t mean they’re always the best option. The main goal of this study is to look at the possible treatment methods and find the best option for each situation. The best option may include multiple methods, and the study is designed to test different combinations of treatments as well.
“They’re cute and they’re popular and it’s fun to watch,” Casamitjana said. “But is it actually the best or the most economical?”
Goats are definitely not the quickest option. The area goats clear in a week is smaller than what a forestry mower can clear in a day, Olson said. Additionally, goats require constant care.
During the five week study, Casamitjana said she had to drive to the site every day to ensure the goats were healthy and had enough water. This constant care can make goats a hard sell for land managers who sometimes only enter an area a few times a year. In those cases Casamitjana said a forestry mower would be a better option.
While forestry mowers are faster, herbicides are more selective. It’s easier to use herbicides to spot treat the specific invasive plants while leaving the native plants alone.
“Goats eat everything,” Casamitjana said. “They just don’t discriminate. They eat everything that grows from one foot to five or six [feet tall] so that includes any species that are endangered.”
Casamitjana is still collecting and analyzing the data, but she said goats could be a good option for really steep terrains where it’s hard to move machinery around. Goats could also be good option for organic farmers who can’t use herbicides. Conveniently, some farmers own goats already, so this treatment would be a feasible option for them.
At the end of the day, it’s very possible goats are not the best option for invasive species management, Casamitjana said. They could be too labor intensive, too expensive or simply not as effective as other management methods. Only time and data will tell.
There is another summer of treatments before Casamitjana’s study will be completed. In addition to finishing the forestry mower, herbicide and goat grazing treatments, Casamitjana also plans on planting grass seed in the treatment areas to observe how well it grows in each test plot. This part of the experiment mimics what farmers who want to graze cattle in the previously invaded land would need to do in order to graze cattle.
“What drew me to this project is that it’s so complex. We’re measuring so many different things. It’s just exciting to see how the vegetation will change … how each of these treatments will work,” Casamitjana said, “It’s just so many different things that we’ll be sharing, and we will have so much data that we’ll be able to release and hopefully people will use [it].”
