The Science
of Grazing
An interview with our 2025 UNCG Early Career Research Excellence Award winner
UNCG Associate Professor of Biology Sally Koerner says balancing the economic benefits of commercial land use with conservation doesn’t have to be a zero-sum game. In fact, some conservation measures can actually reduce costs for ranchers and loggers.
The big idea
“Grasslands are particularly well-suited to be working landscapes that also contribute to conservation. A lot of my research asks whether we can make changes in how those landscapes are managed to maintain their productivity while also protecting biodiversity. Supporting people and conserving nature do not have to be competing goals.”
Internationally recognized for her research on grassland ecosystems and how humans affect biodiversity, Dr. Koerner founded and leads the Grazing Exclosure Consortium, a global network of more than 90 researchers studying over 250 grazing experiments around the world. By bringing together studies that include animals as different as cattle, elephants, kangaroos, and small mammals, the consortium is testing whether the ecological effects of grazing follow general rules across continents and ecosystems.
“For a long time, ecologists thought grazing worked differently in the Northern and Southern Hemispheres, or that the animal — cattle, wildlife, etc. — would determine the effect. But when we put all of these experiments together, what mattered most was whether the herbivore ate the dominant plant species. If it did, grazing opened up light and space for less common species and plant diversity increased. That was surprising because it suggested there is a general ecological rule operating across very different grasslands and very different herbivores.”
Essentially, when a grazing animal gobbles up the dominant plant taking up most of the room, the result is greater biodiversity, which is necessary for a healthy planet long term.
“Right now, a little rare species might not seem especially important. But environmental conditions change, and that species may possess exactly the traits a grassland needs in the future. Maintaining biodiversity gives ecosystems more options for responding to drought, warming, and other changes in the future.”
Carbon Dioxide, Grasslands & Grazing
Koerner and her collaborators are also investigating how rising carbon dioxide, grazing, fire, and climate interact to contribute to woody plant encroachment — the replacement of open grasslands by shrubs and trees.
“Many of the world’s warm grasslands are dominated by C4 grasses, which are particularly successful under relatively low atmospheric carbon dioxide. As carbon dioxide rises, that advantage can weaken. If woody shrubs start replacing your grass, you’re not going to be a successful cattle rancher anymore.”
Koerner serves as principal investigator on funded research projects totaling $9.8 million. The U.S. Department of Agriculture is a major funder of her research on the effects of cattle grazing on grasslands, while the National Science Foundation supports work in Kruger National Park, South Africa. She has published 65 peer-reviewed papers — including six in Nature, Science, and Proceedings of the National Academy of Sciences — with over 3,900 citations. She has also produced four nationally archived data sets and been quoted as an expert in The New York Times. As a researcher, she is known as “the grazing person.”
“The next step is turning these broad ecological patterns into tools people can actually use. If we can predict how grazing will impact plant diversity and how grazing interacts with drought, fire, and woody plant encroachment, we can help land managers make decisions that support both productive working lands and conservation. I think we can identify rules that allow us to make much better, place-specific decisions.”
“Dream job”
“I wanted to be a vet that worked with cheetahs and lions. And I loved African savannas.”
Koerner’s path to becoming “the grazing person” began in elementary school, where she was interested in science, animals, nature, and being outside. As an undergraduate, she did a study abroad program in Kenya to see cheetahs and zebras in the wild. It just so happened to be an ecological and conservation study. The next year she studied abroad again in South Africa in an ecology program.
“I realized that if I wanted to save cheetahs, it was too late. That’s when I decided I want to study why grasslands have the biodiversity they have and how fire and grazing and everything else interact to maintain it.”
Now, her work focuses on keeping grasslands healthy while supporting the needs of humans, animals, and the planet.
“How can we work within lands we use to help support a healthy planet, clean water, and clean air? There are so many people on this planet — we need a lot of earth working towards supporting our populations. But we can do that in a way that provides food and also provides biodiversity to maintain a healthy planet.”
Koerner’s past has also made her a passionate educator.
“I had these amazing experiences abroad that showed me different paths that you could take with science. That’s why I am so passionate about mentoring undergraduate research at UNCG. I love it here. It is my dream job.”
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