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The prairie is burning in part of Eastern Kansas. It's an annual ritual. Ranchers depend on these fires. The fires bring new grass, fatter cattle and eventually bigger stakes. But there's a curious twist to this tradition. Environmentalists have come to celebrate it, even though it sends polluted air into nearby communities. NPR's Dan Charles reports.
DAN CHARLES, BYLINE: When I drove up to Bill Sproul's cattle ranch outside Sedan, Kansas, he was sitting on a chair in his front yard, looking out over miles of rolling hills.
BILL SPROUL: So this the prairie.
CHARLES: Sproul runs cattle on 17,000 acres of this land during the summer. Right now it's an ocean of brown dried grass left over from last year. This land has never been plowed. Nobody ever planted the dozens of grasses and legumes and wildflowers that make up this prairie. They're just here, God's gift to bison and now to ranchers and their cattle.
SPROUL: We get quite a bit of rain. In fact, we get so much rain that we can grow big,tall grass.
CHARLES: Once upon a time, the tall grass prairie stretched from Illinois to Nebraska, from Minnesota to Texas. But now almost everywhere it's gone. It really only survives here, in what's called the Flint Hills of Kansas, because you can't drive a plow through this soil.
SPROUL: Most people cuss rocks, but that's what saved the Flint Hills. If it wasn't for these rocks, we'd be standing in corn and soybeans out here right now.
CHARLES: And because the grass survived, the Flint Hills have turned into a central link in the chain of American beef production. This grass becomes steak on your plate. Every spring about a million young steers come here to graze and put on some weight before they go on to feedlots. The cattle come from as far away as Florida and Pennsylvania.
SPROUL: They all show up in a two-week period and there will just be hundreds and almost thousands of these semis of these cattle trucks coming every day.
CHARLES: But before they arrive, ranchers like Bill Sproul do something that seems strange, even frightening the first time you see it. They burn the prairie, millions of acres of it.
SPROUL: Fire is always part of the equation out there.
CHARLES: That equation involves business, but also the preservation of an ecosystem. First the business part. It's really pretty simple.
SPROUL: The thing about burning this grass is you get this new growth back and it comes back almost instantly, and it just grows at a phenomenal rate. And that is the highest, most nutritious part of that plant, is that new growth.
CHARLES: Cattle love it. They put on weight faster. According to studies, they put on an extra quarter-pound of meat each day, compared to grazing on prairie that wasn't burned. And meat is money. So ranchers here always loved fire. There was a time, though, when other people, including academic experts, tried to get the ranchers to stop.
The fires seemed barbaric, also dangerous. But then scientists took a closer look and changed their tune. To see what they saw, I drove to another part of the Flint Hills, to Konza Prairie. This is an 8,000-acre laboratory owned by the Nature Conservancy and managed by Kansas State University.
As I arrive, they're getting ready to burn one section of it. Conditions are perfect, a light, steady wind from the south.
UNIDENTIFIED MAN: I bet half the county's burning today.
UNIDENTIFIED MAN #2: I bet you're right.
CHARLES: We're out on a ridge, ready to drop some fire, as people say here. There's a hint of tension in the air. Nobody knows for sure how a fire will behave once it starts. That's part of the thrill for the volunteers who are helping out, like Anna Zahner, a graduate student.
ANNA ZAHNER: They had to limit the signup list because too many people want to sign up.
CHARLES: Brings out the inner pyro or what is it?
ZAHNER: Definitely, definitely. My brothers are all jealous, I think, because I've set a bigger fire than they have.
CHARLES: They start with a line of fire along the road. The fire can't go back across the road so it moves in the other direction, into the wind, creating a wide charred strip. John Blair, an ecologist from Kansas State who's in charge of scientific research here, explains what they're doing.
JOHN BLAIR: So this is a backfire, low intensity backfire. And what that'll do is it'll create a strip of no-fuel, a buffer strip.
CHARLES: The volunteers create burned, charred strips like this all around the area they want to burn. These strips are supposed to keep the fire contained. And a little bit later I see why those strips need to be wide. The volunteers light a new fire at the bottom of the hill. This one is driven by the wind and it turns into a scary monster. It races up a hill faster than a person could ever run, orange flames as tall as trees erupting from a cloud of thick smoke.
JOHN BRIGGS: Oh, look at that one. Whoa.
CHARLES: John Briggs, director of the Konza Prairie Biological Station, is here watching, too.
BRIGGS: I mean, you can imagine, if you were a settler and saw something like this coming, just how scary it must have been. I mean, look at those flames.
CHARLES: And this is an important point. Settlers who came here did see fires coming. In fact, as long as the prairie's been here, it's been burning because if there's no fire, there's no prairie. John Briggs shows me the evidence for this, another section of this research station.
BRIGGS: This is why we need to burn the tall grass prairie because if you don't, this is the kind of situation you get.
CHARLES: The researchers stopped burning this section of Konza Prairie in 1991. At that time there were just four cedar trees here.
BRIGGS: And last year we counted 1,200 cedar trees in this area.
CHARLES: In fact, wherever people stop allowing fire in this kind of prairie, trees grow. And then grasses die out, ground-nesting birds move away. Brigg's colleague, John Blair, says it's amazing how fast an ecosystem that's thrived for thousands of years can just disappear.
BLAIR: You can see that in as little as a couple of decades, without fire, you convert these grasses to woodlands.
CHARLES: Blair says it raises an interesting question. How do you conserve the prairie?
BLAIR: It's not an ecosystem that you can simply fence off and keep humans away from.
CHARLES: Native Americans set prairie fires to attract bison who loved the fresh grass. These days the prairie depends on ranchers. They bring the grazing cattle, and they now set the fires. Which leaves just one big complication: A lot more people now live in the prairie, or nearby, and smoke is n0t good for people.
TOM GROSS: You can definitely see it and also people can feel it.
CHARLES: Tom Gross is responsible for monitoring air quality for the Kansas Department of Health and Environment. According to Gross, the day I was at Konza Prairie, there were so many fires in the Flint Hills that ozone levels in Wichita exceeded federal limits. On other days this spring, smoke from the fires in Kansas blew so far north, it violated air pollution limits in Omaha and Lincoln, Nebraska.
Gross and his colleagues have come up with an online tool that uses the latest weather forecasts to show ranchers where their smoke will go if they burn, say, tomorrow.
GROSS: And whether or not you're going to avoid populated areas like the big cities.
CHARLES: It's not really clear how many ranchers are really using this tool to decide when to burn. State officials are hoping that if they do, the prairie can still burn and cities can still have clean air. Dan Charles, NPR News.