Climate change is expected to reduce the growth and stature of big bluestem, a dominant prairie grass, by up to 60% in the next 75 years. According to scientists from Kansas State University, Missouri Botanical Gardens and Southern Illinois University who collaborated on a study published in the peer-reviewed journal Global Change Biology.
“Our results predict that climate change could greatly impact the tallgrass prairie as we currently know it, reducing forage for cattle in the drier parts of grasslands, places like Kansas,” says Loretta Johnson, professor of biology at Kansas State.
Big bluestem is a common grass in prairies across the central Midwest including Kansas, Nebraska, Oklahoma, Missouri and Iowa. It is readily found in the Kansas Flint Hills, a region of tallgrass prairie covering 9,936 square miles. The region’s economy is dependent on agriculture and cattle ranching.
Big bluestem—Andropogon gerardii—can grow to 4' to 6' tall, but the researchers found that could be reduced by up to 60%. As a result, the form of big bluestem in the Midwest could shift to the Great Lakes region and come to resemble the form in eastern Colorado.
The research team, in addition to Johnson, included Mary Knapp, associate agronomist and state climatologist; and Jacob Alsdurf, master’s student in biology. They found most of the change was due to alterations in rainfall expected across the area, not because of increase temperatures.
The authors are concerned the reduction in the size of big bluestem foretells a fundamental shift in the nature of the Midwestern grassland ecosystem.
“Because big bluestem is currently a dominant grass species of the Great Plains and makes up to 70% of the plant biomass in places, how the ecosystem works could be affected by predicted changes in growth of this species,” Johnson says.
“It was said in the past that the tallgrass prairies were so tall that a person riding a horse could literally get lost,” says Adam Smith, assistant scientist in global change at the Missouri Botanical Garden. “Big bluestem is an iconic species in this system owing in part to its stature. If smaller forms come to dominate, it could cause a fundamental shift in the habitat and ecosystem services prairies provide, such as forage for cattle.”
Big bluestem grass can live several decades, so prairie restoration projects need to consider the form of plants that would thrive at a site decades into the future, researchers say.
The analysis also highlights effects of climate change on common species that are not expected to be as vulnerable to climate change. Worldwide, one in five plants is already on the brink of extinction and climate change is only expected to add pressure on species struggling to survive. This study indicates common species also might be vulnerable, the researchers say.
