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From NPR News, this is ALL THINGS CONSIDERED. I'm Melissa Block.

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And I'm Audie Cornish. This year's wildfire season was among the worst in America's history. Drought and heat are two obvious factors, but another is cheatgrass. Cheatgrass is about as Western as cowboy boots and sagebrush, but in fact, it's an invasive species. It grows in yellowish clumps about knee-high to a horse and likes arid land, and cheatgrass burns. In fact, according to a new study, it burns more easily than anyone realized. Here's NPR's Christopher Joyce.

CHRISTOPHER JOYCE, BYLINE: Jennifer Balch used to start fires in the southern Amazon to understand how they burn. Now, she's turned her attention to the American West, where big wildfires are on the rise. Instead of lighting fires, though, she studies satellite photos of the Great Basin that bowl of arid land stretching from California to Utah and Wyoming. It's cheatgrass central, and it burns a lot, but no one realized just how much until Balch started measuring those fires.

JENNIFER BALCH: So what we found was that cheatgrass actually doubles the likelihood of fire that it burns twice as much as any other vegetation type, native vegetation type in the Great Basin.

JOYCE: These cheatgrass fires are increasing partly because the climate is warmer and also because more people are living in cheatgrass country. More than half the fires Balch documented were started by people, and cheatgrass spreads because it's hardier than many native plants, especially in dry regions. Once it's moved in, cheatgrass becomes a fire hazard. The plant sets down roots early in spring and grows fast, filling in areas between native juniper or pinyon trees or sagebrush. When it dies in the summer, it becomes fuel.

BALCH: So it creates literally a continuous carpet of fuels, and so it's able to not only outcompete its neighbors, but it literally is able to burn them out.

JOYCE: Balch, who's now at Penn State University, discovered that of the 50 biggest fires in the Great Basin over the past decade, 39 of them involved cheatgrass.

BALCH: They're more easily ignited. They spread faster. They tend to cover larger areas, and they occur more frequently.

JOYCE: Oh, it's all bad.

BALCH: Yeah, all bad and a huge management challenge.

JOYCE: A challenge for people like Matt Brooks, an ecologist with the U.S. Geological Survey who's spent years in the Great Basin. His opinion of cheatgrass:

MATT BROOKS: In a word, I would probably say bad.

JOYCE: Brooks says Balch's research, which appears in the journal Global Change Biology, confirms what he's seen.

BROOKS: It's a disturbing thing to see because you end up losing the habitat for a wide range of species. And once it occurs, there's very little that restoration science can do to restore the previous conditions.

JOYCE: There are some things that can be done: planting green borders of less flammable vegetation around cheatgrass as a fire break, for example. And there's a fungus that kills cheatgrass. It's called the black fingers of death, but introducing it could be biologically risky to other plants. Jeanne Chambers of the U.S. Forest Service is another combatant in this war on cheatgrass. She says in Nevada, they're seeing fires burning as late as November and as early as January.

JEANNE CHAMBERS: And that really has never happened in the past. When we have dry conditions and we have cheatgrass in the understory, we have fuels that can allow those fires to burn almost any time of the year.

JOYCE: And Chambers says a warming climate and an atmosphere with ever more carbon dioxide in it, essentially plant food, are just what cheatgrass likes. Christopher Joyce, NPR News.

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