Goats are increasingly being used in efforts to manage invasive common buckthorn in Midwestern woodlands. New research demonstrates when and how they are best used.
In a new study published in Restoration Ecology, a University of Minnesota research team examined the effectiveness of goat browsing (targeted grazing using goats) as part of a broader restoration strategy, and the potential for collateral damage of goats on native vegetation.
Funding for this project was provided by the University of Minnesota's Minnesota Invasive Terrestrial Plants and Pests Center, supported by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources.
The researchers performed field experiments in which buckthorn-dominated areas were or were not treated with goat browsing across eight sites. All vegetation (including buckthorn, other invasive species and native species) was sampled before, immediately after and at least one year (and up to three years) after browsing ended.
The study found:
- Targeted grazing is one more potential tool for woodland restoration. Situations when it may be most useful include limited availability of human labor, prevalence of stakeholders that are strongly opposed to herbicide use and steep or rugged terrain.
- Conversely, use of goats may be ill-suited where there are key native species at high risk of negative impacts, such as threatened or endangered plants, high-priority shrubs or juvenile trees, or other sensitive organisms.
A primary concern of land managers regarding targeted grazing is potential negative impacts on native plants. While such impacts can be substantial in the short-term, the study found that over longer time frames, targeted browsing by goats can increase native plant diversity. However, this potential benefit is tempered by a finding that immediate decreases in buckthorn cover were short-lived, suggesting that land managers will need refined strategies for employing goat browsing to reduce buckthorn on the landscape.
"Is the enemy (goats) of native plants' enemy (buckthorn) their friend?," said Dan Larkin, co-author of the study and a professor in the University of Minnesota College of Food, Agricultural and Natural Resource Sciences, and an Extension specialist. "That's the question we sought to answer. Goats cause visually impressive damage to buckthorn and native plants alike when they browse. But then both more or less bounce back within a year. Goat browsing can be a useful element of the Swiss Army knife of woodland restoration, but they need to be used in the right way at the right time as part of a broader, multi-pronged strategy."
Sara Nelson, a natural resources specialist at Dakota County Parks, added that the findings from this study have influenced how she considers the use of goats for ecosystem restoration in her role as a land manager with Dakota County Parks in Minnesota. Nelson earned her M.S. from the University of Minnesota on this research and is now applying lessons learned in her professional capacity with Dakota County Parks.
"Rather than thinking of prescribed goat browsing as a binary yes/no action to restore a site by itself, I think of it as one potential piece of a restoration puzzle that in our region often also includes activities like canopy thinning, seeding and re-establishing regular prescribed fire," said Nelson. "I manage several sites where the use of regular goat browsing is opening up space in the understory for appropriate understory plants to get a toe-hold. Our team's research helped me have appropriate expectations for what goat browsing is likely to be able to contribute to the restoration of a particular site."
Tiffany Wolf, the project's principal investigator and an associate professor in the University of Minnesota College of Veterinary Medicine, noted that, "This project has been a great collaboration and case study in ecosystem health research - thinking not just about the immediate invasive species problem we are trying to solve, but the larger community within that ecosystem and the unintended consequences that might occur with our interventions."
About the College of Food, Agricultural and Natural Resource Sciences
The University of Minnesota's College of Food, Agricultural and Natural Resource Sciences strives to inspire minds, nourish people, and sustainably enhance the natural environment. CFANS has a legacy of innovation, bringing discoveries to life through science and educating the next generation of leaders. Every day, students, faculty, and researchers use science to address the grand challenges of the world today and in the future. CFANS offers an unparalleled expanse of experiential learning opportunities for students and the community, with 12 academic departments, 10 research and outreach centers across the state, the Minnesota Landscape Arboretum, the Bell Museum, and dozens of interdisciplinary centers. Learn more at cfans.umn.edu.
About the Minnesota Invasive Terrestrial Plants and Pests Center
The Minnesota Invasive Terrestrial Plants and Pests Center was founded by the Minnesota Legislature to research the prevention, detection and control of terrestrial invasive species. MITPPC researchers use transformative science to prevent and minimize the threats posed by land-based invasive plants, pathogens, and pests. Founded in 2015, MITPPC is the only research center of its kind in the country, and the center's work to protect the state's native prairies, forests, wetlands, and agricultural resources benefits all of Minnesota and beyond. MITPPC receives program support from the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources. Learn more at mitppc.umn.edu.
