Last fall, UC Berkeley hosted Half-Earth Day, a symposium to explore the idea of setting aside 50 percent of Earth’s lands and oceans for conserving biodiversity. The Half-Earth concept was conceived by E.O. Wilson, the eminent biologist, two-time Pulitzer Prize winner, and noted myrmecologist (that’s someone who studies ants). As Wilson wrote in the January/February 2016 edition of Sierra:

“Only by committing half of the planet's surface to nature can we hope to save the immensity of life-forms that compose it. Unless humanity learns a great deal more about global biodiversity and moves quickly to protect it, we will soon lose most of the species composing life on Earth. The Half-Earth proposal offers a first, emergency solution commensurate with the magnitude of the problem: By setting aside half the planet in reserve, we can save the living part of the environment and achieve the stabilization required for our own survival.”

The ambitious goal—which Wilson calls a “moonshot—has galvanized conservationists. Many environmental organizations, including the Sierra Club, are now calling for preserving 30 percent of wild nature by 2030 as a stepping stone toward the Half-Earth goal.

On the eve of the UC Berkeley gathering, I got the opportunity to sit down with Professor Wilson at the Graduate Hotel in Berkeley. Here’s part of our conversation.

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Sierra: I'm curious what your feelings are about the reception of the “Half-Earth” idea. Are you in any way surprised by how people have responded? 

E.O. Wilson: I was surprised when it first was presented in my book, Half-Earth, in 2016. At that time, I expected that it probably would get a lot of opposition and dismissal, for no other reason that it's just too much—too far, too fast. But when I arrived at the quadrennial meeting of the International Union for Conservation of Nature, in Honolulu, where I expected to receive either dismissal or a lot of objections and so on, I found almost universal enthusiasm. 

What the book had done was just suggest that [the biodiversity crisis] was a big complicated problem that could be solved in one stroke. I called it a “moonshot.” Because conservation efforts around the world had consisted of targeted procedures to save a species here or there, or to save a habitat here or there. And the aggregate of all of this was supposed to be the protection that nature needed—if [the procedures] were intense and wide enough to carry it through. But we knew even then, in 2016, that only about one-fifth of the species on the International Union for Conservation of Nature “Red List”—that is, species in some immediate danger of going extinct—had had the slide toward extinction slowed by all these efforts around the world. I think most of us realized that we were achieving many victories in a losing war. And now seemed appropriate, to me at least, that we go for a moonshot and try to see if we could do it all at once. 

For folks who haven’t read the book, why half? Why not 35 percent or 65 percent? I mean, it's got a certain kind of equitable elegance to it—fifty-fifty—but why half from a biological or ecological standpoint?

I arrived at that figure partly for the reason that you just intimated—that it's easy to remember. And half was, as it turns out, a hefty object to lift. But it would go far to solve the whole problem worldwide. In particular, from my theoretical measurements of what we knew about extinctions and the extinction process, [half] would be enough to save probably more than 80 percent of all the species on Earth, maybe 85. Now, when I arrived at this figure, I went back and thought about the theory that a young professor at Princeton University, Robert MacArthur, and I devised almost 50 years previously. I was a young professor at Harvard, and I decided to see if we could work out a projection of how area affects the numbers of species, because we were interested in what determines the variety of life on an island—a small island, a medium-sized island, and so on. And we recognized eventually that what we were doing applied to nature reserves as well.

This is the idea of island biogeography?

That is correct—the theory of island biogeography. And it has one result, which is immediately relevant at the present time. At this period, about 15 percent of the land has been put into reserves explicitly to try and protect the animal and plant species that are there, the biodiversity that is there. Fifteen percent of the land, and about seven and a half of the sea. (And that figure for the sea is, primarily, not open ocean but territorial waters.) So this 15 percent and seven and a half percent—what would it do for us if we stuck with those figures? And it turns out that we would do much better than we thought we were doing [because of] the theory of island biogeography. That is based on the actual measurements that show that the number of species on an island (or in a reserve) increases as the fourth root—you know, the fourth times to the figure—of the area increases. If that is true, then saving about 10 percent of an area where you want to protect fauna and flora would allow you to save as much as 50 [of the species]. So then I started thinking, we need a moonshot. We need to do one big thing that people could get together on that would solve the problem. And I said to myself, well OK, how much should we be ready to really fight for? And it occurred to me that 80 percent or maybe 85 percent sounds pretty good. So, how much land would that be? Half. 

What I'm hearing is that the Half-Earth concept is, in a way, island biogeography scaled to an island that's floating in space. 

Yeah, the figure of one-half came out of island biogeography. Actually, it’s more than just a guess. From databases, I knew that if we could save one-half of a given reserve, then we were somewhere in the vicinity—at least a prediction—that 85 percent of the plants and animals would be saved. 

Given that we're still pretty shy of the one-half goal, what needs to happen politically, globally to fulfill this vision? The numbers I'm hearing thrown around are trying to get to 30 percent by 2030 and 50 percent by the middle of this century. There's the political angle, and there's also the scientific angle. You've written about how little we know about the entire planet and all of its many inhabitants. Is there more research that needs to be done to also inform this? 

Well, we have to start somewhere. I like to quote John Kennedy, when he announced that we were going to put a man on the moon in a decade. He did not say in his famous speech, “We will, by the end of this decade, make significant progress toward putting a man on the moon and bring him home.” He said, “We will put a man on the moon and bring him back in by the end of this decade.” So it was really important, in my mind, that we do a similar thing: We will put half of the surface of land that contains substantial amounts of native-born flora and fauna in reserve for nature. And keep it that way. And we will save the great majority of species on Earth. 

When I look at the landscape of environmental politics, it seems to me that climate change sucks a lot of air out of the room. And yet there's this twin crisis of the extinction emergency. Do you sometimes get the sense that this other twin crisis is not getting as much attention? 

Well, there is the possibility that our struggle to halt destructive climate change is going to make most of the people around the world very conscious of changes on the planetary level that need to be stopped, and species extinction is in that category. . . . Let me just suppose there are three great crises of the environment. What we will see soon—it is on the horizon—is a second great environmental crisis, and that's a shortage of freshwater. It's a shortage of freshwater that is rapidly growing, that's causing some of the most tragic humanitarian problems . . . in North Africa, and also in Central America, where climate change has destroyed a lot of the agriculture. A great many of the people who are hoping to come to this country are coming to basically avoid that problem. OK, that's a second great environmental crisis that we are now beginning to be aware of, and it’s going to get worse and worse.

And the third is the one that you and are seated here together to talk about—and that is the mass species extinction. Even if you were to say, “Well, we can do with fewer kinds of plants and animals”—God forbid we would ever take a position of indifference of that kind—but even if we did, then we would have to take into account the collapse of ecosystems. When you take out enough species—particularly the ones that we call the keystone species, the ones that have a big, positive impact on the rest of the ecosystem—you'll have a substantial possibility of seeing a complete collapse of the ecosystem. And then you have one of those irreversible impacts of human activity. 

When you look at the literature, are there [species extinctions] that really keep you up at night? I'm thinking like the American chestnut—something that so many other species depend on. Are there other species that you really worry about, or let's say a genus? 

I specialize in ants, right? And believe it or not, there are species of ant that are endangered. And so I've mounted my own expeditions out of Harvard, to assess their status and to figure out how we can prevent these species from going extinct. One was in Sri Lanka. Ants that used to be dominant in the age of dinosaurs, they make up an entire family, the Aneuretinae.

I rediscovered them on the island of Sri Lanka and proposed what needs to be done to keep this ancient lineage alive. I also recently went to the country of Vanuatu—used to be the New Hebrides, near the Solomon Islands in New Guinea—because it was there that a species of bull ants—a big, hard stinging ant and the only species of that kind ever known outside of Australia, where the type is very common—had been discovered on New Caledonia and then apparently disappeared around the 1880s. I mounted an expedition to find it on far-off Vanuatu just to make sure that something that interesting still might be saved. And we found it. And we prescribed what it needs to keep that alive. 

Now, one species of ant on a place most people have never heard of—it's not exactly earthshaking. But the era that we have to create ahead of us is going to have to include action and research of that kind, in multiplicity. I mean, lots and lots of people involved in order to keep the whole planet and all the plants and animals in it. The role of each one could be important. We just haven't worked out what their importance might be. We should be able to save them long enough to understand them, and then find out how—species by species and reserve by reserve—we can hold on to them.

The fate of a single ant species on a single island, and the question of what is it good for, takes us back to your point about indifference—which is that we want to preserve these species, not just for their potential ecosystem services or their functions to us. They've got a right to exist in and of their own selves.

True. They are precious in themselves. And moreover, we need to study them all eventually, in order to understand how the living world works. We need case after case of the study of rare species, of common species, of species on the equator, species of the far Arctic. And we need to be constantly adding that knowledge and putting it together to determine where life came from, where we came from, and what we need to be preserving in order to make Earth a livable, habitable place—a planet to be our home. 

You're well known as being a synthetist—taking many different topics, themes, combining them. And you’re also known as a great scientist in your own field of studying ants. This makes me think about your book Letters to a Young Scientist. What's the push-pull between the microscopic view and the telescopic view?

That book, Letters to a Young Scientist, has in some ways been my most successful book, because, in part . . . well, let me put it this way: It’s so American. The book could be titled How to Be a Success in Science. It's a book that tends to challenge—although I don't do it very explicitly in the book—the whole concept of STEM, which now dominates teaching. STEM: science, technology, engineering, and mathematics.

I'm very uneasy about telling young people who are enthusiastic about going into scientific studies and being part of the future of technology, telling them, “Oh, to be a success and get that job, you need to go into science. Oh, and by the way, if you're going into science, and say, biology, especially, you're going to need chemistry. You gotta study chemistry. And while you’re at it, says the STEM philosophy, to really understand the chemistry you need to remember that chemistry is based on physics. So plan on learning some physics; at least take a few courses of it. And while you're at it, I have to remind you that most sciences have a mathematical foundation. So don't be afraid of math. You've got to plunge in and learn some math. And once you’ve got all that stuff going, why, then you'll be ready to go on and become a junior scientist.” 

I think that's sort of the mood that we're creating now. And I'm against that vigorously. I think they got it backward. I think that kids should do the best they are able, and their mentors can help them to become scientists right away. And then as they develop enthusiasm, this would include, for example, going out and studying an ecosystem anywhere and finding out what species are there and what they're doing. Or going out and looking for a rare species of frog that’s known to exist in the area. This is the kind of thing that gets kids going and excited. And once they get moving—like one who has been planted in front of a piano and so loves hammering those keys that in six months you’ve got to buy that kid a piano, and then give him or her the lesson—this student that you begin that way is going to believe you when you say, “Well, now let's talk about what physics you need and what chemistry you need.” 

It seems to me that's equally applicable to the citizen scientists and the hobbyist naturalists—follow your passion and the findings will come, the insights will come.

That's quite correct. There are so many people who find the greatest satisfaction in their lives to go out and enjoy nature. And as they do, become amateur field biologists—learning the birds, learning the frogs, learning the different species of flowering plants, and so on. This is a rapidly growing activity, of people brought back into science and enjoying every bit of it. And even contributing to science, by finding species, seeing the behavior of organisms—birds, for example, or grasshoppers or ants—that are very interesting. Then those findings get picked up by the active scientists.

You had boyhood experiences of being out in the woods, fishing, watching birds, and watching insects. Young people today have less of that access. This is really just musing, maybe we're way out on a limb here, let’s say we accept your biophilia hypothesis that we've got this instinctive trait for an affinity for wild nature. As an increasingly urban species, what if there's an epigenetic on-off switch? You know, might this be a trait that could atrophy? 

I'm not sure about that. Actually, we see in biophilia something like a true human instinct that's acquired and manifested following a period of learning. Actually, what we inherit as an instinct is a propensity to learn one thing and not another. So it's called program learning, gene culture co-evolution—that phrase is the key to understanding the relationship between heredity and learning in human behavior. 

For example, when we have a free range of options to follow, as a species, to select certain environments and surroundings, this leads automatically—depending on the degree of freedom we have as to where we live and what our income is and so on—to a propensity to select certain environments to live in. Experiments conducted around the world discovered that people choose to live in an environment that has the following traits:

You’re on a rise. You have behind you a wall, a cliff wall, or a dense forest. You're looking out over grassland, dotted with copses trees. In other words, you're looking out over a savanna. And you have your place of residence next to a body of water—all those things together. And that's what experiments have shown, that’s what people around the world prefer, that combination. And this, of course, when we were evolving as a species, was what gave our very, very different distant ancestors more safety and comfortable living. To live a little on a rise, where we can see animals we will hunt and enemies coming. Grasslands where the big animals live, which provide a good deal of our food to the extent that we’re carnivorous. Then, of course, water. Water that provides not just living but transportation and food, particularly in times of drought and hardship on the land. 

In terms of what we’re evolutionarily developed for, you’ve pointed out that species that work well together—ants and termites and humans—are the species that have taken over the planet. And yet, our knack for cooperation also seems increasingly—according to a lot of metrics—self-destructive. I'm wondering, what are the other kinds of evidence of cooperation that you see that leave you more hopeful? 

[Long Pause] That’s a very interesting question. Let me just think. [Pause] What sort of cooperation do I see? Perhaps you could say intrinsic, to human instinctive behavior?

I would say all cooperation except war, or other forms of violent inter-group activity. I believe the evidence is quite strong—and now we're about to get into another subject altogether—that the human species, through the Australopithecines and first direct human progenitors, all the way through primitive forms of like Homo erectus and the Neanderthals has been marked by an evolution that included, as a driving force, competition between groups. Competition of group against group, with cooperation constantly increasing as a result of the competition. Because groups that are more cooperative among the members have been, I believe, a driving force of evolution. 

The way it can be expressed: Within groups, selfish members beat altruistic members. But altruistic groups beat groups of selfish members. And that is a driving force that I think has been extremely important in the formation of what we consider us. It’s the best trait of the human species. 

This conversation has been edited for clarity and length.