About ten years ago, science writer Ferris Jabr started contemplating Earth as a living planet rather than a planet with life on it. It began when he learned that the Amazon rainforest doesn't simply receive the rain that gives it its namesake; rather, it helps generate that rain. The Amazon does that by launching bits of biological confetti into the atmosphere that, in turn, seed clouds.

He began looking for other ways life changes its environment, which led to his new book Becoming Earth: How Our Planet Came to Life. He talks to host Regina G. Barber about examples of how life transformed the planet — from changing the color of our sky to altering the weather.

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This episode was produced and fact checked by Berly McCoy and edited by Rebecca Ramirez. The audio engineer was Kwesi Lee.

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BARBER: ...From NPR. About 10 years ago, science writer Ferris Jabr came across a fact he never heard before that blew his mind.

FERRIS JABR: The Amazon rainforest does not simply receive the rain for which it is so famous. It actually generates about half of the rain that falls on its canopy every year.

BARBER: It may seem straightforward that trees and other plants pull water from their soil then release what they don't need into the air, but Ferris says it's not that simple...


BARBER: ...That the process actually involves the entirety of life within the forest.

JABR: So the Amazon is continually spewing these invisible plumes of tiny biological particles.

BARBER: Think pollen grains, fungal spores, microbes, bits of leaves.

JABR: They get swept up into the atmosphere, and they become the particles on which water vapor condenses in order to form clouds. So because they're continually lofting all of this water vapor and all these biological particles into the atmosphere, they're dramatically accelerating the water cycle.


JABR: So the more the rainforest is growing and thriving, the more rain it is stimulating. And then the more rain that is falling back to the forest, the more it can grow.

BARBER: And the more it can influence ecosystems elsewhere. When Ferris learned that the Amazon forest actually changes the rain cycle, not only above its canopy but on other continents, it started to change the way he thought about life on Earth.

JABR: Because I had always been taught that life is subject to its environment, not the other way around, and here were living things changing the weather on the scale of an entire continent.

BARBER: So he started looking for other examples of how life changes its surroundings, which led him to write his new book "Becoming Earth: How Our Planet Came To Life." It explores the idea that life doesn't just live on Earth, life is Earth.

JABR: The basic concept of the world being alive is truly ancient. We see that in religion mythology going way, way back.

BARBER: From the Aztecs to the ancient Polynesians and many other Indigenous cultures.

JABR: But within Western science, this idea that we can think of Earth as a living entity has been very controversial for a long time.

BARBER: Since the 1960s, when James Lovelock and then later Lynn Margulis developed their versions of the idea.

JABR: That was severely criticized and ridiculed by many mainstream Western scientists, especially within evolutionary biology, because they did not like this idea of Earth being alive and being conflated with an organism.

BARBER: But now that's starting to change with new research that's come out in the last few decades.

JABR: It suggests that wherever life emerges, it inevitably transforms its home planet and that together, life and the greater planetary environment do form a single highly interconnected system.

BARBER: Today on the show, what it means to consider Earth a living planet. From bacteria-caused rainfall to the delicate balance of wildfires and oxygen, we look at how the environment shapes life and how life shapes the environment. I'm Regina Barber, and you're listening to SHORT WAVE, the science podcast from NPR.


BARBER: OK, Ferris, let's dig into this idea of a living Earth. Like, what does it mean? And how is it different from a planet with life on it?

JABR: Right. So one of the biggest revelations for me when writing this book is to stop thinking of life as something that simply inhabits the planet or resides on the planet's surface and to think of life as a literal physical extension of the planet.


JABR: A tree is a beautiful metaphor for our living planet because by mass or volume, the majority of a tree is actually dead tissue. It's dead wood that is structural but contains no living cells, and there's just thin strips of living tissue here and there ringed in lace throughout that dead wood. Well, Earth is similar in that, you know, the majority of it is inanimate rock and water and air, but it has this beautiful flowering skin of life that in some ways sustains this larger living system.


JABR: All life forms are, by definition, systems. They are networks of smaller components, some of which are animate and some of which are inanimate. And so in that regard, the Earth is no different. It's just that it is the largest of all of those systems. It's all the other ecosystems combined into the largest known living system.

So what we call life emerged from Earth. It is made of Earth. And then life loops back to profoundly transform the larger planetary environment. And we can recognize that system itself as the largest known living entity 'cause it demonstrates what seems to be the most fundamental characteristic of life at all scales, which is a capacity to regulate itself, to preserve itself, to endure. Somehow, we have to account for Earth's incredible resiliency through time. The fact that Earth has remained alive for more than 4 billion years is truly astonishing.

BARBER: Right. And to illustrate kind of, like, how this feedback is happening, you go through a bunch of examples in your book. One that really stuck out to me is how bacteria can cause rain. Like, how does this work?

JABR: Yeah, I'm fascinated by this capacity of microbes to change the weather and to stimulate rain and snow and hail, in fact. So, you know, there are - there's microbes all over the surface of the planet, both on land and in the ocean. And they're continually swept into the atmosphere by powerful winds, by storm currents. And in addition to the living microbes themselves, there's also all kinds of, you know, bits and pieces of life. Just biological confetti, you know, gets up in the atmosphere, and they become seeds for both clouds and then for ice crystals within the clouds. And there's one microbe that's particularly special, pseudomonas syringae. It has on its surface, on its cell surface, proteins that act as a template to organize water molecules into a solid ice crystal. And it's the most effective so-called ice nucleator that we've ever discovered.


JABR: It's so effective that it's actually used worldwide on ski slopes to create artificial snow. So we...


JABR: Yeah, we spray water into the air with the proteins from these microbes, and they freeze the water. You know, they help freeze the water and turn it into snow.

BARBER: That's so cool. Another cool example is how life, quote, dyed the sky blue. I love that imagery. Like, what did the sky look like before it was blue?

JABR: Right. So if we go back into Earth's ancient history, you know, more than 3 billion years ago, Earth probably had a hazy orange sky. You know, it was probably full of carbon dioxide and methane, and it had essentially no free oxygen in it. And so Saturn's largest moon, Titan...


JABR: ...Has a sort of - yes, it has a smoggy orange atmosphere that maybe resembles what Earth's ancient atmosphere used to look like for similar reasons.

BARBER: Cool. OK, and - but tell us why it's blue then.

JABR: Right. So when life started to oxygenate the atmosphere - and this began maybe 2 1/2 billion years ago with cyanobacteria inventing photosynthesis, you know, using sunlight and water and then releasing oxygen as a byproduct, and then later continued with algae and land plants. So this long process of oxygenating the atmosphere completely revolutionized the chemistry of the entire planet and, in doing so, shifted the color of the sky towards the blue end of the spectrum.

So, you know, most times today, when somebody asks, why is the sky blue, the most common answer you hear is well, it's because the atmosphere most effectively scatters the shortest wavelengths of lights.

BARBER: It's called rayleigh scattering, and it's something I taught many, many times.

JABR: Well, there you go. Then you probably know much more about it than I do. And so, you know, my understanding is, like, that is why when we look up the sky, we see blue because it's those shortest wavelengths that are getting scattered.


JABR: But that depends entirely on the chemistry of the atmosphere. If you have a different proportion, different concentrations of different molecules in there, they're going to scatter different wavelengths of light, and that was the case back in Earth's ancient atmosphere until life changed the picture.

BARBER: Let's give the planetary scientists something, too. There's also a lot to do with volcanoes, but, you know...

JABR: Yes. That's true. My book is kind of, you know, really focused on life, but, of course, geology is the second half of that picture, and it's always...

BARBER: Right.

JABR: ...There as well.

BARBER: Right, right. OK. The next one that we're going to talk about is this, like, relation between, like, fire and life. So, like, this coevolution of wildfire and plant life. I can kind of see how these are - two are connected, but can you, like, break it down for me?

JABR: Absolutely. So for a long time in earth's history, the level of oxygen in the atmosphere fluctuated really wildly. For example, if we go back roughly 300 million years, the level of atmospheric oxygen was somewhere between 30- to 35% compared to about 21% today. And back then, we had massive raging wildfires unlike anything we've seen.

And so something seems to have shifted about 200 million years ago and especially in the past 50 million years where the level of atmospheric oxygen is a lot more stable than it used to be. It's hovering around that 21%. And so scientists have long struggled to explain that stability, and what they're converging on now as a possible answer is the coevolution of fire at terrestrial plant life.


JABR: So the basic idea is that if oxygen levels get too high and you have these raging wildfires, they're going to burn down huge tracts of terrestrial vegetation. So when that happens, oxygen levels start to dip back down again, right? So it's the stabilizing feedback built into the system.

BARBER: So with all of these examples, like, happening all at the same time, like, what makes Earth living? Like, how do we put all of these things in a conversation? Like, what's the sum of all of these?

JABR: Right. So the way I think about it is life is looping back to change the planet really profoundly. So together, earth and life are forming this single system, this tightly interconnected, tightly coupled system. And this system as a whole demonstrates a capacity to regulate itself, to regulate the planet's climate, to endure, you know, to have resilience. These are the characteristics that we associate with living things. So we can think of this, you know, system as a whole as the largest known living entity.

BARBER: Yeah, I'm really intrigued by this, like, idea that Earth will balance its system out. But like how the fire example took millions of years, humans may not be around for that balancing act, like, to see what happens.

JABR: Absolutely. Yeah, so the planet seems to have this innate capacity to regulate its climate to some extent. It can pull itself back from these extreme hothouse states or these deep freezes. But the process by which that happens is so slow that it is simply not relevant to human societies or even to any particular species most of the time. And we definitely cannot rely on that planetary balancing act, and, you know, we have to intervene and, you know, correct the severe imbalance that we've introduced.

But it is astonishing that the planet, that the Earth system as a whole, kind of has this innate, albeit very slow and limited, capacity to keep itself, you know, in a more temperate climate and a more habitable zone.

BARBER: What do you think the implications of changing this mindset will be, like, if we do start thinking about Earth as a living thing?

JABR: I think there are some really important implications of this kind of conceptual shift. You know, I think the first thing to recognize is that in some ways, we're like all other life. Life changes its environment all the time. So we're the most recent chapter in this really long, coevolutionary saga.

But in other ways, we're highly unique compared to other life-forms because we're really the only creatures on the planet that can consciously understand and deliberately change the entire Earth system as a whole. And so all life is participating in this system, but when we're actually aware of our actions and their consequences, that gives us a unique privilege and responsibility and, I would even argue, a moral obligation not just to each other as people, as humans, but to the larger living entity, the larger system that we are a part of.

I think there's an immense difference between thinking of ourselves as inhabitants of the planet or, quote, "passengers on spaceship Earth" versus being literally continuous with the planet. So to save the planet is literally to save ourselves.


JABR: We are all extensions of Earth, and everything we do is looping back to change the planet in some way, so we are empowered in that sense.


BARBER: Ferris, thank you so much for talking to us today. I've started to think about Earth differently just in this conversation. So thank you so much for sharing your book with us.

JABR: Thank you so much. It's a pleasure to be here.

BARBER: Ferris' book, "Becoming Earth: How Our Planet Came To Life" is out tomorrow, June 25. See our episode notes for a link to the book. This episode was produced and fact checked by Berly McCoy, edited by our showrunner Rebecca Ramirez, and the audio engineer was Kwesi Lee. Beth Donovan is our senior director, and Collin Campbell is our senior vice president of podcasting strategy. I'm Regina Barber. Thanks for listening to SHORT WAVE from NPR.

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.

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