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JULIA ROSEN: I flew to Colorado, not to go to the beautiful, majestic Rocky Mountains but to drive the other direction, four hours into the shortgrass prairie of southeast Colorado.
AARON SCOTT, HOST:
That's reporter Julia Rosen. She wrote a story about grasslands for The Atlantic.
ROSEN: I just drove way down these quiet rural roads and then further down these bumpy dirt roads and pulled off.
SCOTT: She was visiting the Southern Plains Land Trust. It's an organization whose mission is to protect and preserve shortgrass prairies. And the executive director, Nicole Rosmarino, had given Julia GPS coordinates for one of their more isolated preserves.
ROSEN: And I got out of the car, and I walked out into this grassland, and pretty soon the car was tiny and basically obscured. And I was just in the middle of this sea of grass.
SCOTT: There were grasshoppers and wildflowers, prairie dogs and pronghorns. And she realized, walking out there, just how extraordinary grasslands are.
ROSEN: One of the reasons I think it's easy to overlook grasslands is that they now are typically pretty small. Like, you might see a field, and there's nothing particularly imposing or terrifying about a field. You would never get lost in it. But in this landscape, where it was literally grass for miles and miles in every direction, it was like, wow, this is a forbidding landscape for a little human.
SCOTT: But also an essential landscape for little humans and a lot of other animals.
ROSEN: There's all sorts of life that evolved to live on them. I mean, grazing animals like bison and antelope and - you know, these animals only exist because grasslands exist on Earth. And then, of course, you have pollinators and all sorts of other, you know, smaller animals that are equally important. And then, from our point of view, they have these really rich soils that absorb water and filter water, and then they store a ton of carbon. By some estimates, they store a third of all the terrestrial carbon on Earth. And so, you know, we always are talking about forests being these great reservoirs of carbon, but really, grasslands are equally important.
SCOTT: And these grasslands, well, they're disappearing at an alarming rate.
ROSEN: They are being destroyed faster than we are losing forests.
ROSEN: In the U.S., we've lost about half of our grasslands in this country. And then among certain types of grasslands - so the tallgrass prairie, which is what grew in sort of the wetter parts of the Midwest - there's less than 1% of that left. There's less than 1% of the Texas prairies left. And there's less than 1% of the Palouse prairie out here in the Pacific Northwest left. So some of those ecosystems are basically gone. There's basically nothing but tiny little slivers of it left.
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SCOTT: Today on the show, why we should care about grasslands and the role they have to play in the fight against climate change. I'm Aaron Scott, and you're listening to SHORT WAVE, the daily science podcast from NPR.
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SCOTT: So, Julia, the opening of your article blew me away - I mean, this idea that grass and grasslands aren't really that old in the timeline of the earth. Would you read the beginning for us?
ROSEN: (Reading) Once upon a time, not a blade of grass could be found on this planet we call home. There were no verdant meadows, no golden prairies, no sunbaked savannas and certainly no lawns. Only in the past 80 million years, long after the appearance of mosses, trees and flowers, did the first shoots of grass emerge. We know this in part because a dinosaur ate some, and its fossilized poop forever memorialized the plant's arrival. Grass then was still an odd little weed vying for a spot on the forest floor. It took ages for grasses to grow in numbers that might constitute a grassland. And grasslands only started to occupy serious real estate in the past 10 million years - basically yesterday. They now cover roughly one-third of Earth's land area.
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SCOTT: So, Julia, tell us about how these relatively new grasslands fit into the complex puzzle that is planet Earth now?
ROSEN: Well, I mean, the amazing thing about the rise of grass is they went from not existing to covering 40% of the planet, and, in many cases, they beat back forests. That's kind of amazing because you just think of puny little grass leaves - like, how can that compete against a giant tree? And we now understand that grasslands evolved closely together with fire, which kept trees at bay, and with grazing animals that evolved specifically to live in those landscapes. And grass doesn't mind being burned or being eaten. It can rejuvenate. But woody plants tend to not like it very much, and so those would keep the shrubs and the trees at bay and allow the grass to take over.
And now, yeah, they're a huge component of Earth's ecosystems and Earth's biodiversity and the climate system. I mean, they even - there are scientists who think that that expansion of grasslands over the last 20, 30 million years helped cool the planet because grasslands are lighter in color than forests, and so they would reflect more sunlight. And then also, they absorb all this carbon in their soils, taking it out of the atmosphere. And so they could have actually helped drive global cooling, which is - over the last 20 million years, the Earth got cooler and cooler and cooler until we grew these ice sheets and ended up, you know, in the ice age that we're still technically in.
SCOTT: I mean, it feels really counterintuitive because in a forest, you see these grand trees, you see the carbon. In a grassland, you see little blades of grass. So it feels just, like, weird to think, oh, it's storing all this carbon. Can you, like, describe what's happening under the surface?
ROSEN: Yeah. So - few people said this to me. They describe grasslands as the inverse of the rainforest. What we see at the surface is just these little blades of grass, you know, not higher than our knee, or, in the tallgrass prairie, maybe as tall as our shoulders. But underground is this huge network of roots that can go 6 to 8 feet deep. Some of the prairie flowers can go up to 20 feet deep.
ROSEN: But really, like, it functionally lives underground. And that's why it's so resilient and so interesting because it's got all these - all of its storage organs, like, for the plants, the things that it needs to survive the winter or to bounce back after a fire or grazing, that's all underground, so it's safe. And then they're photosynthesizing all the time. They're producing all these sugars, and then they're pumping carbon underground all the time. You know, it looks like there's nothing there, but it's just that what's there is invisible to us because it's below ground, but it's very much there.
SCOTT: So by one estimate, only 10% of these native grasslands remain, which I think will come as a surprise to a lot of people. I mean, if I'm driving through the country and I look out the window, it looks like I'm surrounded by grasslands and fields. So how is what I'm seeing out the window or on a bike ride different from these old native grasslands that used to cover the continent?
ROSEN: Yeah. So it's really hard for an untrained eye to tell the difference. And when I was first going on these reporting trips and going out to prairies, I'm like, I don't know, tell me what I'm looking at. Like, it looks like grass to me. But yeah, let's start with an agricultural field. So that's really different because what was there before has been completely removed. The soils have been tilled, and then, you know, pastures are often seeded with nonnative grasses that are good for animals to eat, and they've often been plowed and seeded. So those look very different.
Really, if you go out into an old-growth grassland with someone who knows what they're looking at, what they will show you is a diversity of native grasses and, maybe even more than that, a diversity of forbs, which are wildflowers and the other plants that live amongst the grasses. And there really can be a huge diversity of those in old-growth grassland.
SCOTT: And what are we losing when we've plowed those grasslands and replaced it with either cropland or nonnative grasses for livestock?
ROSEN: Well, on a very practical level, we're losing a lot of carbon, and you lose a ton of the biodiversity, both of the plants and the animals that would live there. But I think on a more sort of philosophical level, a lot of these grasslands are hundreds to thousands of years old. So they're ancient, and they have been developing to become what they are over long, long periods of time that far exceed sort of human timescales, the same way that an old-growth forest does. And so we're basically coming in and wiping that out without really understanding, you know, what was there and why it might have been important.
And there also used to be the idea that, like, well, we can always get more grass back. But now what scientists are realizing is they're very, very different types of ecosystems. So you're not going to get it back any time in our lifetime. And again, it's really more on the timescale of an old-growth forest - hundreds of years.
SCOTT: And speaking of forests, I mean, there is now some really big, in some case, international campaigns to plant more trees with the idea that, you know, it's one of the most perfect ways to pull carbon out of the atmosphere. Some of the places that have been targeted for tree planting include grasslands. I'm curious - what do the grassland ecologists think about these efforts?
ROSEN: The grassland ecologists are very alarmed at these efforts. There's a lot of concern that, again, because grasslands appear empty, they seem like an easy place to go out and put some trees. That really damages the grassland. You're actually taking carbon that's very safe underground, and then you're putting it in a tree that can burn. And then the other thing is that a lot of these plantations, they're not forests. Like, you're not going in and planting a biodiverse forest of native tree species; you're planting a monocrop of nonnative, commercially valuable tree species.
SCOTT: Trees that will probably be logged at a certain point, releasing that carbon.
ROSEN: Yes. That's the other thing, is that you're not trading a pristine grassland - an ancient, pristine grassland for a beautiful, vibrant forest, you know? You're trading this old, irreplaceable ecosystem for a plantation.
SCOTT: So I'd love to circle back to where we began - you walking out in the Southern Plains Land Trust's prairie - because that is one of the spots in the country that is actually selling carbon credits to preserve grasslands. Can you tell us a little bit about how that works and some of the other efforts that are taking place to, you know, really protect or utilize grasslands as part of our all-in strategy to confront climate change?
ROSEN: Yeah. So again, I guess getting back to this whole trees-versus-grass thing, trees have been part of the carbon credit picture from the beginning. Something like 80% of the offsets in California's market are from forest management. But just in the last five or 10 years, there started to be carbon credits for grasslands. So if you've got a grassland that's intact, you can sell carbon credits from basically promising not to plow it or develop it. So, like, in the case of the Southern Plains Lands Trust, they basically have to protect it for 150 years at least.
There's some really interesting research about putting compost on grasslands. There's studies that show that if you increase the diversity of plants in our restored prairie, you can store more carbon. So there's a bunch of things that people are exploring to sort of see if we could increase the amount of carbon that these landscapes can hold. But for now, really, a huge one is just leaving the grasslands that exist in place.
There's growing awareness that grasslands are in trouble. So there's a lot of conservation groups that have been trying to build momentum for grassland protection. And the Senate recently introduced a North American Grasslands Conservation Act. So there are things happening at a high level that could benefit grassland conservation.
SCOTT: Julia, I can't thank you enough. Like, I kind of want to just go lay in my lawn but, really, more so drive out somewhere where I can be in knee-high grass and lay in it and watch it sway above me and think about all the things that are happening below me underground.
ROSEN: Do it.
SCOTT: Thanks for talking with us.
ROSEN: Yeah, thanks for having me. This was great.
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SCOTT: Julia Rosen gets so much deeper into the science and history of grass in her article for The Atlantic. We've got a link to it in our show notes. And a special thanks to Nicole Rosmarino from the Southern Plains Land Trust for recording gorgeous prairie sounds for us.
This episode was produced by Rebecca Ramirez and Thomas Lu. It was edited and fact-checked by our senior supervising editor Gisele Grayson. And Neisha Heinis was the audio engineer. Beth Donovan is our senior director of programming, and Anya Grundmann is our senior vice president of programming. I'm Aaron Scott. Thanks as always for listening to SHORT WAVE, the daily science podcast from NPR.
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