There have been five major extinction events since the evolution of complex animals. Each time, the planet underwent changes so acute and so rapid—in geological terms—that most living things were killed off before they could adapt. As our understanding about the so-called “Big Five” events has grown, we’ve come to realize that we’re now in the midst of a sixth extinction. The cause, scientists say, is us.

Human behavior is disrupting the very biological systems on which we rely. Chief among a list of culprits are deforestation, habitat fragmentation, ocean acidification, and climate change.

To address the college’s role in climate change, Williams is pursuing an ambitious set of initiatives set forth in fall 2015. Work is under way to achieve carbon neutrality by 2020 through goals that include reducing emissions, investing in sustainable design and building practices, and developing renewable energy projects. e college is also investing in its educational mission, making climate change a campus-wide theme of inquiry for the 2016-17 academic year.

In this spirit, just before the start of the fall semester, Williams Magazine brought together three faculty members whose research and work intersect with this year’s theme, Confronting Climate Change. Leading the conversation was Nicolas Howe, assistant professor of environmental studies and former journalist, who studies the cultural and religious dimensions of environmental problems. He was joined by geosciences professor Phoebe Cohen, who’s using the fossil record to study the second mass extinction at the Late-Devonian period 375 million years ago, and Elizabeth Kolbert, Williams’ Class of 1946 Environmental Fellow-in-Residence, co-chair of Confronting Climate Change, and Pulitzer Prize-winning author of e Sixth Extinction: An Unnatural History (Henry Holt & Co., 2014). e three explored how the planet is changing, what can be learned from past extinction events, and how Williams is informing the conversation about global climate change.

NICOLAS HOWE: Why do so many scientists think that we’re in the midst of a mass extinction?

ELIZABETH KOLBERT: The evidence is extremely simple. e background extinction rate is usually very slow. So if one mammalian species goes extinct in a human lifetime, something weird is going on. If many species go extinct, as we are now seeing, then something very weird is going on. We are learning more and more about what happened during past extinctions through the work Phoebe does, for example, looking at the fossil record. And researchers are monitoring the rate at which species are moving through various categories of extinction: “vulnerable,” “threatened,” “near extinct,” and “extinct.” Based on what scientists know from past extinctions, they project that if we continue at this pace with well-studied groups, we’ll reach mass extinction rates—loss of 75 percent of all species on earth—within a few hundred years. at’s incredibly fast.

PHOEBE COHEN: Most mass extinctions take thousands of years. at’s the temporal window over which we’re allowed to see them, based on the limits of the rock record. But you can only truly say that there’s a mass extinction after it’s already over.

HOWE: What can we learn from past mass extinction events? How quickly can nature rebound afterward?

COHEN: The answer to how quickly the planet can rebound has to do with what’s causing the extinction and how quickly that cause goes away. e two best-studied extinction events are the Cretaceous-Paleogene (K-Pg) and the Permo-Triassic. During the K-Pg, a giant rock fell out of the sky, there’s evidence of increasing volcanic activity, and the dinosaurs—among many other living things—went extinct. It was relatively sudden and mostly due to external factors. As a result, the rebound was faster. During the Permo-Triassic, there was warming, high CO2, and toxic gasses being released into the ocean and atmosphere because of volcanism. at extinction took longer to happen, and it took way longer to recover from, because it was as if the whole planet was sick, internally.

HOWE: So what makes the current situation fundamentally different?

KOLBERT: The Permo-Triassic is the worst mass extinction that we know about—and probably the worst since complex life began. It ended the Paleozoic Era and began the Mesozoic Era. Recent research indicates that a huge CO2 release took place over thousands of years. But on an annual basis, less CO2 was being released back then than what we’re currently releasing now, which suggests that we’re pushing the system really, really fast. We don’t have the distance of 250 million years to understand how that will turn out.

If we continue at this pace…we’ll reach mass extinction rates–loss of 75 percent of all species on earth, within a few hundred years. That’s incredibly fast. -Elizabeth Kolbert

HOWE: What might the world look like after a mass extinction?

KOLBERT: One possibility is that we’re creating a world of insects. Most of the world’s species are invertebrates, and they’re poorly catalogued. But they may be less prone to extinction, because they have very fast generation times and produce a lot of young. They can evolve pretty quickly compared to, say, pandas.

COHEN: Cosmopolitan species that can survive in many types of different environments, like rats, also tend to survive most extinctions.

HOWE: And a number of researchers are optimistic about the possibility of cosmopolitan species repopulating the world.

The Big Five Extinctions

1 END-ORDOVICIAN EXTINCTION; 444 million years ago; 86% of species lost
The cause was probably a short, severe ice age, potentially triggered by the uplift of the Appalachian Mountains, which lowered sea levels. Exposed silicate rock drew CO2 out of the atmosphere, chilling the planet.

2 LATE-DEVONIAN EXTINCTION375 million years ago; 75% of species lost
One of the least understood extinctions, it’s thought that the deep roots of newly evolved land plants stirred up the earth, releasing nutrients into the ocean. This triggered algal blooms that depleted oxygen in the water.

3 PERMO-TRIASSIC EXTINCTION; 251 million years ago; 96% of species lost
Causes include an eruption in what is now Siberia that blasted CO2 into the atmosphere; bacteria- releasing methane; rising global temps; and ocean acidification, stagnation, and oxygen depletion that released poisonous hydrogen sulfide.

4 END-TRIASSIC EXTINCTION; 200 million years ago; 80% of species lost
To date, no clear cause has been identified. But mounting evidence suggests global climate and ocean disturbances, similar to those seen at the Permo-Triassic, played roles.

5 CRETACEOUS- PALEOGENE EXTINCTION; 66 million years ago; 76% of species lost
Volcanic activity and climate change put many species under stress. An asteroid impact eliminated them and the dinosaurs.

KOLBERT: We’re mucking with some pretty basic geochemical and biological systems that have been functioning a certain way for quite a long time. When we’re driving our cars, we’re running organisms that were alive 100 million years ago through a motor and combusting them. We’re reversing a process that took many tens of millions of years to run in one direction— and we’re running it backward, very fast. We don’t know how that’s going to turn out.COHEN: That’s right. The fossil record bears that out, to some extent. It’s interesting to think about how quickly the earth will rebound once the cause of the mass extinction goes away. So if we kill o a bunch of things and then all fly to Mars and leave the earth alone for a while, the rebound will probably be relatively fast. But we’re not going anywhere as a species, so the cause of the current mass extinction will persist. at means the extinction will likely be prolonged, and the recovery will take longer—more like the Permo-Triassic extinction event.

HOWE: Has the window slammed shut in terms of averting a disaster?

COHEN: The window to avoid the worst—or at least to avoid things that may affect billions of people—may already have closed. But I don’t think we’re at a point where both of the poles are going to melt or sea levels will rise tens of meters. Our energy systems are changing and will continue to change.

KOLBERT: Researchers have looked at the time it might take to transition our energy systems. If we had 100 years to switch from fossil fuels, we could do it. And we probably will make that transition in 100 years. But you can put a lot of carbon into the air in that amount of time. It’s not clear you can take it out.

COHEN: It begs the question of what’s natural. We’re never going to return to a previous state. The earth will be different, even if we all stop driving cars and begin sucking CO2 out of the atmosphere immediately. As an earth historian, I find learning about past mass extinctions comforting. In retrospect, they’re just small moments in the history of the planet. Life will persist in new and interesting ways that we can’t even imagine, long after we are gone. That thought doesn’t make me any less motivated to create change now, but it helps me sleep a little better at night.

KOLBERT: Certainly the issue of climate change is much more top of mind than it was, and it’s only going to be more so as California burns and Louisiana floods. It’s getting very hard to avoid the issue.

COHEN: July was the hottest month on record, ever.

How do 10 billion people live lightly on the land? –Phoebe Cohen

HOWE: As one way to avert a mass extinction event, biologist E.O. Wilson proposes setting aside roughly half the planet as a permanent preserve. ere are also e orts to do assisted migrations and de-extinction (also known as resurrection biology) through selective breeding or cloning.

KOLBERT: There are scientists who have the cells of the last three of some now-extinct species—usually animals, but also plants—in the refrigerator. But first let’s start with keeping things alive. There are bighorn sheep in Yosemite for the first time in 100 years. (The federally endangered species was re-introduced to Yosemite and Sequoia national parks in March 2015 as part of a complex, multiyear recovery effort.) The Endangered Species Act of 1973 demands that we do this work to conserve species and the ecosystems they depend upon. But as more and more species need that kind of help, the question of where you put your resources is pressing. Wilson’s proposal makes a lot of sense, but it’s easier said than done.

COHEN: It’s politically challenging. And while habitat restoration or habitat protection might actually be useful in the long run, neither addresses the underlying problem.

HOWE: Is it possible the answer to mass extinction may be one of the oldest in the environmentalists’ playbook? at is: Live as lightly on the land as you possibly can, and don’t play Russian roulette with evolution.

COHEN: How do 10 billion people live lightly on the land? What does that look like?

KOLBERT: All of these questions are relevant for the Williams students of today. We have at least two sets of values that are profoundly in conflict. One is eliminating poverty, bringing as many people as possible to the kind of standard of living we enjoy. It seems only equitable. But it’s also an ecological catastrophe if you consider our impact on the planet. So you’re faced with saying that anyone above a certain standard of living— one that we’d consider pretty minimal—had better radically reduce their consumption, or resigning yourself to a terrible ecological outcome. It’s very, very difficult to thread that needle. How do you engage students in thinking about these questions?

COHEN: My intro-level course is the most important course I teach, because I’m getting students who aren’t necessarily going to become geosciences majors. It’s not a course explicitly about climate change, but we talk about how the planet’s system works, and, at the end of the semester, we talk about how part of that system is us, screwing up the system. Empowering them with an understanding of how the earth works and what we’re doing to it is really important in a time when climate science denialism is still rampant.

HOWE: This is the first generation to grow up with climate change as a public fact, even if the scientists have understood it for a really long time. ere’s no before and after climate change for our students. e environmental studies students already care. My dream would be to get the students who don’t yet care to take environmental studies.

KOLBERT: These issues—climate change, mass extinction—present a fundamental challenge even to the humanities. This question of what does it mean to be human needs to be revisited. What are the defining characteristics? One of them turns out to be that we’re capable of—and in the process of—completely changing the world.

COHEN: I’m excited to see climate change as a campus- wide conversation this year as opposed to one that’s primarily happening within environmental studies or geosciences. It needs to be something all our students are learning about and exposed to thinking about. It’s not just about the mechanics of CO2 or saving pandas or growing your own food. It’s bigger than that.

HOWE: Having a sustained conversation is essential. That’s the most important aspect of Confronting Climate Change—the duration of it, and the fact that there are going to be a variety of speakers addressing the issue in various ways, from economic, legal, and scientific standpoints.

KOLBERT: A useful outcome of Confronting Climate Change would be understanding where our emissions really come from. If you ask students what they think should
be done to reduce the college’s emissions, they say things like: “Let’s unplug all the dorm-room refrigerators.” I’m deeply opposed to mini-fridges. They’re inefficient. But if you actually run the numbers, it turns out that they’re a trivial part of Williams’ energy footprint. So the next step is digging down and seeing what the numbers are. And when you do that for your own life—or for the Williams life, collectively—you find things that are upsetting.

COHEN: I hope institutionally that this inquiry leads to a bigger commitment to energy efficiency and changing our energy sources. It’s something we’ve talked a lot about. We’re building our new buildings very efficiently. But we still have a lot of old buildings on campus. Figuring out what to do with those buildings isn’t as exciting as, say, pursuing Living Building status for the Class of 1966 Environmental Center. But the old buildings matter a great deal.

KOLBERT: The question of how many buildings matters.

HOWE: We’re looking at both big and small changes that will make a difference. But many of the people we’re bringing to campus, including Bill McKibben (an author, educator and environmentalist), would argue that, without a broad-based social movement that’s global in scale, we’re not going to be able to avert a catastrophe.

COHEN: It’s hard for me to envision that social movement. It’s conceptually challenging.

Having a sustained conversation is essential. That’s the most important aspect of confronting climate change.–Nicolas Howe

KOLBERT: One could argue that we’ve never voluntarily done social change on a global scale before.

HOWE: Certainly not to give up something. Large social movements have always been about getting more of something—whether it’s rights or political freedom.

KOLBERT: Theoretically you could frame it in such a way that we are getting something.

COHEN: A future.

HOWE: You have to throw everything at the wall that you possibly can: new technologies, better scientists, more scientific research, social movements, policies. A good outcome of a focus on climate change this year would be that every student, no matter what their interest is, no matter what their career plans are, understands that they have a role to play.

KOLBERT: And that they have a stake. Every student graduating from Williams now will feel severe effects in his or her lifetime.

COHEN: Climate change is only part of the full extinction story. Our food systems come into it, as do the way we build our homes and move around the world. It comes down to showing students how it’s all connected, so they can go out into the world and make informed decisions and—we hope—bring about change. Many of my students are choosing careers that in some way involve climate change. It seems like it’s a more normalized way of thinking. We do a good job of showing students that there are lots of different ways they can be involved.