2:16pm

Tue March 25, 2014
The Salt

In Ranchers Vs. Weeds, Climate Change Gives Weeds An Edge

Originally published on Tue March 25, 2014 5:28 pm

Most climate models paint a bleak picture of the Great Plains a century from now as a hot region besieged by heavy rainstorms and flooding.

And new studies suggest that climate change may bring farmers another headache: more invasive plants.

Ask most Midwestern and Rocky Mountain ranchers about the weeds they pull their hair out over and be prepared for a long list. There's cheat grass in Nebraska, red brome in Utah and yellow star thistle in California.

And they can't count on cattle to gobble them up. Depending on the plant, most cattle either don't want to eat it or could get sick if they do.

"You kinda have to teach them about a new plant," says Ellen Nelson, a rancher in north-central Colorado who has a weed problem. "I've gotten some of them to eat some, but in general, that's a hard one."

As climate change takes hold, it's likely to only get worse, not just for Nelson, but for ranchers across the country. In 2005, U.S. Department of Agriculture research ecologist Dana Blumenthal set out to find out just how it will get worse. Specifically, he wanted to know what effect climate change will have on a noxious weed called Dalmatian toadflax that's encroached on grasslands in 32 U.S. states.

For about eight years Blumenthal and his team simulated one possible future climate in the Wyoming grassland. They used a heating apparatus to keep test plots warmer than normal, and pumped carbon dioxide into the air surrounding the toadflax.

The warming and CO2 weren't set at doomsday levels, but rather conservative levels Blumenthal says the Plains could see within a century. Under those conditions, Dalmatian toadflax flourished, growing in size 13-fold and producing more seeds.

"The simplest reason that invasive species are likely to do well under future conditions is that they are pretty much by definition good at dealing with change," Blumenthal said.

That's why Dalmatian toadflax could be emblematic of an even larger problem. Invasive species are invasive because they can adapt quickly.

Similar field studies across the country have shown other nasty weeds do well in warmer, more CO2-heavy conditions. Blumenthal's results were published in the journal New Phytologist late last year. He says there is a trend toward global climate change increasing invasion, but scientists need more data to make solid predictions.

"There are going to be cases of invasive species, some of which we care a lot about, becoming much more problematic, and there are going to be cases of invasive species retreating from where they now exist," Blumenthal said. "We don't know enough to say how common this is going to be yet."

Dalmatian toadflax is just one piece of a much larger ecological puzzle.

Back at Ellen Nelson's ranch, she's formulating this year's plan of attack against the toadflax. She's welcoming a new class of steers. Their first lesson will be to learn to love the taste of toadflax.

"Maybe we're going to learn how to live with some of these weeds," she says. "That might be heretical to say."

But it's a heresy that many of her fellow ranchers will have to get used to keep producing beef for American tables.

Luke Runyon reports from Colorado for KUNC and Harvest Public Media, a public radio reporting collaboration that focuses on agriculture and food production issues. A version of this story originally appeared on Harvest Public Media's site.

Copyright 2014 KUNC-FM. To see more, visit http://kunc.org.

Transcript

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ROBERT SIEGEL, HOST:

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Invasive weeds are a big headache for cattle ranchers. Left to grow, they become food for the herd, and it's not exactly what ranchers want their cattle to eat. So the ranchers spend thousands of dollars to get rid of those weeds. Research now suggests that climate change may make the problem even worse. In a warmer climate, the weeds will thrive. Luke Runyon reports from member station KUNC in Colorado.

LUKE RUNYON, BYLINE: Ellen Nelson has a weed problem.

ELLEN NELSON: How about if we go this way?

RUNYON: In the summer, one hillside of her small ranch near Bellvue in North Central Colorado turns bright yellow. The culprit? A tall, rubbery weed with golden flowers called Dalmatian toadflax.

NELSON: See there's these little rosettes.

RUNYON: The plant is a pain. It crowds out native grasses that her cattle actually like to eat.

NELSON: And it's such a tough, waxy plant that by the time it really gets going, you just can't get the herbicide in it.

RUNYON: The expensive herbicide is a relatively new weapon for Nelson. It's already cost her thousands of dollars. She's tried pulling the plant by hand and releasing weevils that burrow into its stalks. Lately, Nelson's put her faith in her livestock, her steers, trying to convince them toadflax doesn't taste so bad.

NELSON: You kind of have to teach them about a new plant. I've gotten some of them to eat some, but in general, that's a hard one.

RUNYON: Nelson admits, so far, the toadflax is winning. And as climate change takes hold, it's likely to only get worse, not just for Nelson but for ranchers across the country.

DANA BLUMENTHAL: Right. There's Dalmatian toadflax.

RUNYON: U.S. Department of Agriculture researcher Dana Blumenthal studies how climate change will affect large swathes of grassland. For about eight years, Blumenthal and his team simulated a possible future climate - warmer and more concentrated with carbon dioxide - in the Wyoming grassland. Under those conditions, Dalmatian toadflax flourished.

BLUMENTHAL: The simplest reason that invasive species are likely to do well under future conditions is that they are pretty much, by definition, good at dealing with change.

RUNYON: Invasive plants are invasive because they can adapt quickly and more rapidly than the tastes of the grazing cattle that end up on your plate. To help ranchers adapt, Blumenthal says scientists need more data to make solid predictions.

BLUMENTHAL: There are going to be cases of invasive species, some of which we care a lot about, becoming much more problematic. And there are going to be cases of invasive species retreating from areas where they now exist.

RUNYON: What will America's grasslands look like a century from now? The answer to that question affects ranchers across the country who will face expensive headaches when weeds out-compete native grasses. Blumenthal says Dalmatian toadflax is just one piece of a much larger ecological puzzle.

BLUMENTHAL: We don't know enough to say how common this is going to be yet.

STEVE RYDER: We are just treading water at the moment.

RUNYON: Steve Ryder is with the State of Colorado's Noxious Weed Management Program. He says like managers in most states, his focus is on keeping new weeds out. Some have already gained a foothold.

RYDER: If climate change is going to accelerate that, then we need to decide whether we're going to accelerate the response.

NELSON: Come on. Go.

RUNYON: Back at Ellen Nelson's ranch outside Bellvue, she's formulating this year's plan of attack against Dalmatian toadflax. She's welcoming a new class of steers. The first lesson? Learn to love the taste of toadflax.

NELSON: Maybe we're going to learn how to live with some of these weeds, I don't know. That might be heretical to say.

RUNYON: But it's a heresy that many of her fellow ranchers will have to get used to to keep producing beef for American tables. For NPR News, I'm Luke Runyon in Greeley, Colorado.

SIEGEL: And that story came to us from Harvest Public Media, a reporting collaboration that focuses on agriculture and food. Transcript provided by NPR, Copyright NPR.