Episode 5: A spore of hope

Humans face an existential problem: feeding billions of people in a warming world. But there's a ray of hope. And it all starts with microbes.

Photograph by Adaptive Symbiotic Technologies

Humans face an existential problem: feeding billions of people in a warming world. But there’s a ray of hope. And it all starts with microbes.


RUSTY RODRIGUEZ (MICROBIOLOGIST): One of the things that we had learned a long time ago is that you can do things in a laboratory that mean exactly nothing in the real world.

PETER GWIN (HOST): Rusty Rodriguez has seen some pretty cool things in the laboratory. He’s a microbiologist who studies the relationship between plants and microbes. And in the late 1990s, he and his team collected samples of grass from Yellowstone National Park, where the geothermal soils can get really hot.

RODRIGUEZ: And so what we found was that all of the plants in these hottest zones all had one dominant fungus that we could isolate from them.

GWIN: And when they heated up the grass in the lab without the fungus, the grass would wilt and die. So it seemed—at least in the lab—that the grass needed the fungus to stay alive in the hot soil. But to know for sure, they needed to get out of the lab. So they went back to Yellowstone to set up an experiment. On one side of a box, they planted the native grass with the fungus that lives inside it, and on the other side, they planted the grass without the fungus. And then they left—for a year. And when they came back, Rusty didn’t know what they would find.

RODRIGUEZ: The anticipation just during the hike, you know, I think it's only like a mile or two in, you know, it's not that far. But, you know, we were talking about, you know, well, gosh, I wonder what it’s going to look like. Do you think they survived? Is everything dead? Is this a disaster, you know, blah, blah, blah. And we got up there, and, you know, we threw our packs down, and we looked at the boxes—and we were all just silent.

GWIN: Something had definitely happened in the year they were gone. There were plants in the box.

RODRIGUEZ: What was going on through my head—because half the box was alive and half wasn't—it's like, I wonder which side that is.

GWIN: So they pulled out their books. Looked at the experiment. And then they were able to confirm it: The native grass that was planted without the fungus was deader than a doornail, and the grass planted with it wasn’t just alive, it was thriving.

RODRIGUEZ: It was like, Oh my God, it worked. This is incredible. You know, the fungus is required for heat tolerance out here.

GWIN: This discovery, it wasn’t just cool science.

RODRIGUEZ: This is a potential tool for mitigating impacts of climate change in natural communities and maybe even in agriculture. Who knows?

GWIN: Who knows? One thing is for sure: Rusty was excited to find out.

I’m Peter Gwin, and this is Overheard at National Geographic, a show where we eavesdrop on the wild conversations we have here at Nat Geo—and follow them to the edges of our big, weird, beautiful world.

This week: how to feed a growing population on a warming planet—with fungus. Yum.

More after this.

JOEL BOURNE JR (WRITER): So it's gonna be what I always consider—what many experts think—is the greatest challenge we've ever faced.

GWIN: Joel Bourne Jr. is the author of the book The End of Plenty: The Race to Feed a Crowded World. He also writes for Nat Geo.

BOURNE: The greatest challenge humanity has ever faced: to be able to sustainably feed everyone by 2050.

GWIN: So I’ve known Joel a long time, and I’ve never heard him say it quite like that before. In college he studied agronomy—the science of soil management and crop production.

BOURNE: You know, we subsist on this very thin layer of soil. You know what—six to eight inches of soil that provides all the protein, all the plant material that goes into all the feed that feeds all our livestock, and basically feeds the world. So even though we've got like 50,000 plants that we could eat on this planet, only three or four really provide the bulk of our calories.

GWIN: The big four: corn, wheat, rice, and soy. We mostly eat wheat and rice, while corn and soy we feed to livestock. Joel says those four basic crops make up about two-thirds of all the calories consumed by livestock and people.

BOURNE: And the big problem with that is the biggest driver of food demand, of course, is population growth.

GWIN: Right now there are nearly eight billion people on the planet. By 2050 the human population is predicted to increase by another two billion.

BOURNE: Second biggest driver is increased income, because as people get wealthier, move into the middle class, they tend to eat more meat, and meat is a multiplier for grain demand because we end up feeding a lot of our corn and our soy to hogs and cattle.

GWIN: So to meet demand, by 2050 we’re going to have to increase grain production a lot.

BOURNE: An enormous challenge for us in a time when climate change is suppressing our yields left and right all over the planet.

GWIN: As temperatures rise, it can cause all sorts of stress for crops, including water shortages and more pests and disease. And those stressors can diminish crop yields.

BOURNE: And the only way we can really make that up is either by boosting productivity, or by plowing under more acres. And, of course, that's what we've been doing.

GWIN: Joel says that for the last decade or so, the way farmers have grown more crops has been by planting more fields.

BOURNE: Typically that's at the expense of rainforests and standing forests, things that we really don't need to be chopping down.

GWIN: So, we’ve got big problems. And big problems? They require big solutions. That’s why scientists, engineers, and farmers are trying to make crops more resilient.

BOURNE: And of course, there are a lot of people working on just that—how to do that, how to make them more drought tolerant, how to make these crops more heat tolerant. And that's, you know, what we're going to have to do—and many of these crops—to adapt around the world.

GWIN: One of the people working to find solutions is microbiologist Rusty Rodriguez. You know, the guy who studied fungus in Yellowstone.

GWIN: So now I have to ask you the 101 question: is it fun-GUY or fun-JY?

RODRIGUEZ: You know, I—through my whole career I've heard it pronounced both ways. I go with fun-JY. But, you know, and then I save “fun guy” to describe myself at other times.

GWIN: Okay. Fair enough. I like that. That's a good sort of distinction. Fun-JY it is. That's how we'll roll.

GWIN: Rusty founded a small biotech company that’s developing microorganisms
to mitigate the impacts of climate change on crop production. Microorganisms like fungi.

GWIN: You know, the idea of a fungus. I mean, I'm an amateur gardener, and I have to emphasize the amateur. But usually fungus, you know, in my backyard is not a good thing for the plants there. It seems to be that way, you know?


GWIN: Yeah, Rusty says, some fungus is going to be bad for my garden, but not all fungus is the same.

RODRIGUEZ: It’s just that agriculture has focused on problems more than anything else. And so these things became problematic, just like in human health—animal health as well. People tend to think of microbes as being bad. That's why there's antimicrobial soaps everywhere. But the reality is that the vast majority of microorganisms are not detrimental, either to humans or animals or to plants.

GWIN: They can even be beneficial—like Rusty found in his Yellowstone experiments where the grass needed the fungus to survive in hot soil.

GWIN: So, I mean, this sounds a little bit like the whole kind of probiotic movement for humans. You know, in the past few years it’s been, you know, you're supposed to eat yogurt and drink, you know, things that have like, you know, the good bacteria for your gut biome, etc, etc., which I didn't even know I had until… Now I know, and I eat the yogurt, you know? But is this sort of kind of like that same notion for plants? I mean…

RODRIGUEZ: Absolutely. Here. Yeah. Yeah. It's the plant microbiome. And the plants cannot survive out there without these microbes. We can't survive without these microbes. It's a microbial world.

GWIN: Rusty says that’s how we evolved. All of us: Humans, plants, and animals. Because long before we existed, the world was one big microbial stew.

RODRIGUEZ: It was a microbial planet to begin with. And it still is. We just pretend it's not.

GWIN: So fungi are, you know, we’re comrades in arms basically on this rock revolving around the sun.

RODRIGUEZ: So, yeah, absolutely.

GWIN: Quick sum up there of the entire evolution of the planet. So.

RODRIGUEZ: If you take them away, you take us away. Let's put it that way.

GWIN: Rusty’s Yellowstone experiments showed that neither the grass nor the fungi could survive the heat on their own. They needed each other.

RODRIGUEZ: So although neither partner was heat tolerant, when they came together they formed a symbiosis and they communicated in such a way as to generate, if you will, thermal tolerance or heat tolerance.

GWIN: So basically, it's not that the fungi has this special power that it imbues the plant with. It's that the two of them together create a more—I mean, like this sounds like the plot of almost every movie—we’re stronger together. We can withstand...

RODRIGUEZ: It's true. And I mean—and this turns out to be very common in nature. This is how a lot of interactions go on with these plants.

GWIN: Rusty says how the plants and fungi communicate is not yet fully understood, but it’s clear they can achieve something together that they can’t achieve on their own. And since Yellowstone, Rusty has found symbiotic relationships between plants and fungi in all kinds of extreme environments: High up on Mount Everest, on military testing sites where the soil is polluted from explosives.

RODRIGUEZ: Anywhere where we can go into a habitat, identify what the stress is, we can now—for the first time in my life—have some predictive capabilities, saying see those plants over there? There's a fungus inside right now that's conferring tolerance to this stress.

GWIN: To be clear, the fungi can’t make the stress go away. But they can change how the plants react.

RODRIGUEZ: The best way I can explain it to you is that in both animals and plants, when they are confronted with stressful conditions or some stressor that hits them, what happens is that their metabolism goes out of balance.

GWIN: Stressed out plants start making chemicals that travel around and build up until the plant just can’t cope. But in plants protected by the right fungus, that switch doesn’t get flipped.

GWIN: So basically like whatever the fungi is saying is, don't freak out yet.

RODRIGUEZ: Yeah, pretty much. They're like the Xanax of the plant community.

GWIN: And he really does mean the “plant community.” Because that fungi that helped the grass survive the high temperatures in Yellowstone...

RODRIGUEZ: We threw onto tomatoes and watermelons and rice and wheat, corn, you name it, you know, with seeds we could buy easily. And it communicated the same way inside these plants. So when you put them in tomatoes, or into rice, or into corn, they became heat tolerant.

GWIN: Which is a really important quality for crops growing in a warming climate. But could fungi also make crops drought tolerant? As the climate changes, droughts have already become more common. Rusty says billions of dollars have been spent over the years trying to create more climate-resistant crops. But not many of those are drought resistant.

RODRIGUEZ: Crops can vary in their ability to deal with stresses. And there are more stress-tolerant crops than not. But the whole idea of breeding plants or genetically modifying them for that has not played out very well.

GWIN: Rusty and his team went looking for plants and fungi in more dry, hot places. They extracted the fungi from some grasses in Southern California and started using it to make a treatment to spray on seeds. His company’s seeds are now being used on millions of acres—on big farms in the U.S. and small farms in India. So far, Rusty says the results are promising. He says the treated seeds appear to be helping increase crop yields. So he and his team are going to keep experimenting and working with farmers.

RODRIGUEZ: For me, this boils down to, you know, the future of food security. And there always will be droughts. There's always going to be temperature extremes. But if we can generate climate-resilient crops, if we can get them to yield at higher levels, then there’s a ray of hope there.

GWIN: And writer Joel Bourne says we need every ray of hope we can get.

BOURNE: Anything we can do to make these crops more resilient is going to be critical.

GWIN: Because feeding a growing population on a warming planet isn’t going to be easy. And Joel says we’re not going to find a silver bullet.

BOURNE: We need every tool in the toolbox to try to nail this thing moving forward, to make sure everyone's reasonably fed.

GWIN: When Joel was studying agriculture in school in the 1980s, he thought genetically modified crops—or GMOs—could be a potential silver bullet. He says that’s what a lot of people thought back then.

BOURNE: They were going to be the miracle crops, right? I mean, we were going to create corn that did not need to have nitrogen fertilizer, so we'd never have to apply nitrogen again. You know, we were going to create crops that, you know, had all of these new nutrients in them so that we wouldn't have these micronutrient deficiencies in places around the world. We were gonna—you know, there were all these miracle things that they said these crops were going to do.

GWIN: But forty years later, Joel says those miracles haven’t panned out yet. It’s proven a lot more challenging to execute miracles. And also, there’s been a lot of resistance from consumers who don’t want their food to be genetically modified. One of the biggest benefits GMOs have provided to commercial farmers are the controversial Roundup-ready crops—crops grown from seeds that were genetically modified to be resistant to the herbicide Roundup.

BOURNE: It had a few nice benefits—saved a lot of more toxic pesticides from being sprayed—but because of the overuse and the mismanagement of those traits like, you know, like nature finds a workaround, right? It always finds a workaround. So now we've got Roundup-resistant weeds that you can spray all day long, and they'll eat Roundup like, you know, candy.

GWIN: Joel says that for decades the main thinking in agriculture has been that it doesn’t matter how healthy your soil is. As long as you can add water and fertilizer to it, you’ll be able to grow crops.

BOURNE: But what we're now understanding is that was very limited and that only goes so far—we've pretty much taken that as far as we can go. Now if we want to have better benefit, we've got to start looking at it more holistically and saying, look, it's—and again, this is stuff that the organic guys have been saying all along—you know, it's not just the plant. It's the soil. Healthy soils create healthy plants, create healthy crops, create healthy people.

GWIN: Solving this problem is not going to be easy. But Joel says he’s optimistic.

BOURNE: I am particularly optimistic about, you know, people like Rusty who are going off to the edges and really trying to help crops survive this new climate.

GWIN: And it’s not just Rusty who’s working on this.

BOURNE: I see young kids who are fired up to fix the world food problem. I mean, unlike anything I've seen since probably the early 1970s, when we really thought a lot of people were gonna starve. So there are a lot of people going into this space, whether it's organic, whether it's conventional, whether it's biotech, whether it's whatever—who are really going in to do public good, right, to do science as a public service. And I love that!

GWIN: And Joel says there’s something else we all can do to help: eat less meat.

BOURNE: Out of the 40 percent of the dry land on Earth that we commit to agriculture, two-thirds of it we use to feed our animals. So if everybody stopped eating animals, we would have two-thirds of the agricultural land to grow vegetables and crops and things like that. Makes perfect sense. But what I always tell people, it's kind of like trying to get your kids to eat spinach. It's like, great idea, really good for them. You know they need it. You know they want it. It's very difficult to do.

GWIN: Come on, spinach. Who doesn’t like spinach? Seriously though, as the grandson of a cattle farmer, I know it’d be difficult to take meat out of my diet entirely, but it is something to think about. Joel says there’s enough concern over this problem that he thinks it’s going to lead to even more investment in finding solutions.

BOURNE: Really. There's no other option—like we've got to figure it out. Or else we're going to see, you know, a world of pain and hurt no one wants to see. So I'm cautiously—I will say cautiously—optimistic. We're gonna figure it out. I just hope it happens sooner than later.

GWIN: Because, really, 2050 is right around the corner.

More after this.

GWIN: Microbes are everywhere! Learn about the ones in the depths of the Mariana Trench in the Pacific Ocean, and what they could tell us about life on one of Jupiter’s moons. And microbes have been around a long time! Check out the world’s oldest fungus fossils. And subscribers can take a look at how the tiny country of the Netherlands is pioneering the future of sustainable agriculture. And learn all about the trillions of microbes that live inside us!

All of this and more can be found in our show notes. Look for them in your podcast app.


Overheard at National Geographic is produced by Emma Jacobs, Brian Gutierrez, Jacob Pinter, and Laura Sim. Our editor is Ibby Caputo. Our fact-checker is Michelle Harris. Hansdale Hsu composed our theme music and engineers our episodes.

Special thanks to Jen Shoemaker and Adventure Scientists; Jerry Glover; Ricardo Oliva; and Toby Kiers.

This podcast is a production of National Geographic Partners. Whitney Johnson is the director of visuals and immersive experiences. Susan Goldberg is National Geographic’s editorial director.

And I’m your host, Peter Gwin.

Thanks for listening. Stay safe out there, and see y’all soon.


Microbes are everywhere! Learn about the bacteria living in the depths of the Mariana Trench, in the Pacific Ocean, and what they might tell us about life in outer space on one of Jupiter’s moons.

Microbes have been around a long time! Check out the world’s oldest fossilized fungus.

Also explore:

Read more about the “communication” between fungi and plants happening under our feet.

Listen to Nat Geo contributor Joel Bourne Jr. discuss his book, The End of Plenty.

And for paid subscribers:

How the tiny country of the Netherlands is pioneering the future of sustainable agriculture.

And learn all about the trillions of microbes that live inside us! 

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