Midwestern Scientists Join Global Effort to Study Extreme Drought in Grasslands

By Kate Grumke

Both the length and intensity of drought can work together to have cumulative, negative effects on grasslands, according to a new global study published in Science.

An international group of scientists ran the same drought study across six continents, including sites in Kansas, Minnesota, Oklahoma and Texas. They imposed extreme drought conditions for four years in a row to find out what these conditions do to a diverse array of grasslands and shrublands.

“With changing climate, particularly atmospheric warming, we're expecting to see more extreme events such as droughts, but those events are likely to be longer in duration,” said Colorado State University Professor Melinda Smith, who co-led the study and worked on multiple sites, including one near Manhattan, Kansas.

Smith and her team brought together a network of scientists from around the world to study drought, using a research coordination grant from the National Science Foundation. The International Drought Experiment, as it’s known, was born from that work and involved sites around the world.

It’s important to understand how more extreme drought events will affect ecosystems like prairies, said Cristy Portales-Reyes, an assistant professor of biology at St. Louis University in Missouri who studied sites in Minnesota.

“Grasslands are one of the most widespread ecosystems in our region,” Portales-Reyes said. “About 40% of North America used to be a grassland, and they're very important culturally and also for conservation purposes.”

Research has found evidence that longer, more intense droughts are already becoming more common and scientists expect climate change to increase that trend even more.

But the impacts of multi-year, extreme droughts have been understudied, said Timothy Ohlert, another co-lead of the study and a postdoctoral associate at the University of Colorado Boulder.

“Up until this point, there had been a lot of people doing their own individual studies, focused on their own sites, maybe their own regions,” Ohlert said. “So this was the first kind of coordinated effort to kind of time things all in one bin so that we can do this research together.”

At each site, scientists put up shelters with clear gutters to block a specific percentage of rainfall without blocking the sun. The amount of blocked rain depended on long-term historical records from the locations, to impose a 1 in 100 year drought that was unique to the site itself.

“You have to keep that infrastructure up for four consecutive years,” Ohlert said. “And so there's a lot of maintenance, there's a lot of wrenches and drills that go into this work.”

That was especially hard in the Flint Hills of Kansas, where researcher Seton Bachle conducted his work. Bachle now works for LI-COR, an environmental biotech company in Lincoln, Nebraska.