The Sixth Extinction and Our Unraveling World

Brenna Miller    

Welcome to History Talk the podcast that brings together a panel of experts to discuss current events in historical perspective. I'm your host, Brenna Miller.

 

Jessica Vinas-Nelson  

And I'm your other host, Jessica Vinas-Nelson. In the last few years serious discussions about manmade climate change and its present impacts have dominated the headlines. Much of this discussion has centered around issues that directly impact human life, such as extreme weather events, the consequences of pollution for human health, and changes in the practice of agriculture. But an increasingly urgent issue has also been the impacts of climate change on animal and plant life and diversity.

 

Brenna Miller

In recent years, there have been increasing warnings about the threat of a sixth extinction, in which manmade climate change could wipe out a significant portion of plant and animal species on Earth. Estimates suggests that by the end of the century, we may lose as much as 25 to 50% of all species on Earth. How likely is such an event? How far has it gone already? And what will be its consequences? Today, we've invited two guests to discuss the past, present and future of diversity on earth, and what we can learn from past extinctions. And if there's anything that can be done to address extinction in the future.

 

Jessica Vinas-Nelson     

Via phone, we have Elizabeth Kolbert, journalist and author of "Field Notes From a Catastrophe" in 2006, and the 2015 Pulitzer Prize winning book, "The Sixth Extinction: An Unnatural history".

 

Elizabeth Kolbert   

Hi.

 

Brenna Miller    

And in the studio with us, we have Sam White, an associate professor at The Ohio State University specializing in environmental history, and recent author of "A Cold Welcome: The Little Ice Age and Europe's Encounter with North America".

 

Dr. Sam White     

Hello.

 

Brenna Miller    

Thank you to both of you for joining us today. So our first question is, how exactly do historians and scientists define the sixth extinction? And why is it referred to specifically as the sixth? And Elizabeth, if you want to go ahead and start with that question?

 

Elizabeth Kolbert   

Well, anything that sixth obviously implies five earlier events. And that is exactly why we are discussing the sixth extinction because there have been five, what are called major mass extinctions in the history of multicellular life. So over the last half billion years or so, and the most famous of these extinction events, is the event that in the dinosaurs, which was probably caused by an asteroid impact. And then each one of these events, what defines these events is just they're periods of time relatively short periods of time on a geological scale, when the diversity of life on Earth, for some reason plummeted. And we just see that in the fossil record. And so we don't have a fossil record of today. So it gets a lot more complicated when we look at present day extinction rates. But the idea is basically that we have very elevated extinction rates. So elevated, that they're on the same scale that we would have expected to see during previous mass extinction events.

 

Brenna Miller    

Sam, do you have anything to add?

 

Dr. Sam White     

There's not a cut and dry definition for what constitutes a mass extinction. The five that we usually identify as the five big ones are simply the, you know, peaks of what were probably smaller extinction events as well. And in comparing our present-day situation to those, it is difficult, because it is hard to find exact rate of extinctions. And to compare the count of extinctions we have to the way we count extinctions or loss of biodiversity in the geological record. However, it is clear that the rate of animals and plants going extinct now is much higher than it usually has been over geological time.

 

Brenna Miller    

So even though it's hard to compare to the earlier ones, what makes the sixth extinction different from past extinctions? and how is the sixth extinction happening exactly by habitat destruction, pollution?

 

Dr. Sam White     

So I think what, of course, makes it interesting to us is that it's what we're presently living through, and that we appear to be the principal driver of this accelerated rate of extinction and loss of biodiversity. And it obviously has many causes. And what maybe most worrying is that it's not any one of those that we can separate, but really the combination of all of them that catalyze each other. So to take two major drivers to extinction, we have, for instance, loss of habitat and climate change. Well, either one of those is probably going to drive a certain amount of biodiversity loss. But with the two together probably drive more than either would independently. Because as we lose habitat to, for instance, deforestation, the conversion of natural grasslands to pasture, or the expansion of huge areas, such as cities and suburbs, we make it more difficult for species to adapt by migration. So even if they were able, in other circumstances to persist through global warming by migration, we've now potentially blocked those routes.

 

Brenna Miller    

So in contrast to something like a possible asteroid driving the extinction, the dinosaurs were looking at not one big event, but a lot of smaller ones contributing to it.

 

Elizabeth Kolbert   

Well, I think even if people look at the asteroid impact, you know, and we'll never know what happened in the aftermath of that impact. But there were a lot of potential drivers there to, you know, most things were not necessarily killed by the impact, per se, and they weren't even necessarily killed by the immediate aftereffects of the impact, which may have included, you know the basic setting of much of the world on fire. But they there were potentially long, longer term impacts, you know, blocking the sun for quite a long time with all the dust in the atmosphere and things like that. So there are potentially, you know, even multiple drivers during that extinction event, which was very, very catastrophic event. But even so, there were probably a lot of different drivers.

 

Brenna Miller    

So both of you take a really long view of history on a geological timeline. So why is it important to look at present climate change in this longer view? And how is it useful for understanding the sixth extinction?

 

Elizabeth Kolbert   

So one, one thing I did want to say is that, you know, we have to look at what does this look like in the very long context of the history of life? And the very disturbing thing is when we do that, when we look at, okay, how's the atmosphere changing? How's the climate changing? How are the chemistry of the oceans is changing? Then we find that they're, they're changing very dramatically, even if you know, against this backdrop of the long history of life, and it's very hard to find analog, going back through, you know, 10s of millions of years to what's going on right now. So, you often find in the scientific literature, the phrase, no analog, we're going into a no analog future. And that if you're a creature, you know, another creature, not a human creature that looks very, very, very scary to you.

 

Dr. Sam White

So I guess we should back up and talk a little about the this idea of the Anthropocene. So this is really two things we should keep in mind. One is that there is a formal proposal to rename the current geological epoch that we live in the Anthropocene to say that we've essentially entered in a new epoch. And there could be any number of possible starting dates for that, from what I understand from talking people involved at the most likely would probably be actually around 1950 would probably with sometimes known among environmental historians as the great acceleration as mass consumerism in rapid population growth really accelerated our environmental footprint. However, in thinking about the Anthropocene, it's also been a way for environmental historians and other people in history and in Earth history to think about the human impact on the environment over a longer timescale because others have proposed other possible start dates. So this does help us see a longer history here to the possible sixth mass extinction, we could take back to say, human, you know, colonization of the earth, and the extinctions that have brought about in the late Pleistocene, through the impacts of, you know, converting land to agriculture, after the Neolithic Revolution, and through, you know, impact some early modern periods for industrialization. I think that helps us see how many dimensions there might be to this concept of the Anthropocene. That while climate change is often, first and foremost, on our minds, it is just one dimension of our much larger much more diverse environmental impact that we've been having. And that has been with us for quite some time, although certainly accelerating over the last 50 years or so.

 

Jessica Vinas-Nelson

So when exactly, then did the threat of the sixth extinction really take off? And have we already witnessed any consequences of losing diversity in nature?

 

Elizabeth Kolbert   

Well, I'm, I think that the same way that as Sam alluded to, there are multiple proposed start dates for the Anthropocene. There are also different time frames in which you could look at the sixth extinction. And there's a big wave, or wave, I shouldn't really say, as humans moved around the planet, these are some measures for good surprises in a megafauna extinction, until people arrive at different parts of the world, they encountered, often these very big animals that were very slow to reproduce, and those animals are not there anymore. You know, in North America, there are lots of them there were mammoths, there were mastodons, we don't have those anymore. And once again, you know, there's debate over why that's the case. I am convinced. And I think many, many people who have studied this issue are convinced that humans drove those extinctions. If you look at the timing of them, when humans arrived in Australia, we get a wave of extinctions when humans rise North America, we get a wave of extinction when humans arrive in Madagascar, we get a wave of extinctions. And that seems like too much to just be coincidence. So it's possible that quite possible that this, you know extinction event, which many millions of years from now will look very, very, very rapid you won't even be able to tell you know exactly when it started. That that it really started, you know, 10 10s of thousands of years ago.

 

Jessica Vinas-Nelson     

Are there any other animals who have done something like that? A predatory species or something on the same level?

 

Brenna Miller    

Or are humans unique?

 

Jessica Vinas-Nelson     

Yeah, or unique, in our destruction.

 

Elizabeth Kolbert   

I know, there's sometimes an analogy drawn to the very earliest photo synthesizers, two billion years or so ago, who, over, you know, long, long, long, long period of time changed our atmosphere, the atmosphere didn't have any oxygen in it. And its sort of synthesis merged, evolved. And these creatures photosynthesize the way we got an atmosphere that's filled with oxygen. And for creatures that don't like oxygen. That was a disaster. And it's sometimes called the oxygen Holocaust. And that is potentially the only analog in the history of life on this planet. But even so, it's a pretty, it's a pretty weak analog. So I think that the, the very basic answer is no, you know, no creature has ever done this. And one other thing I'll just say is, you ask the question I didn't fully answer before, which is, you know, have we already seen the impact of as the creatures going extinct. And so in the case of the of the megafauna, you know, there, there are all sorts of impacts, there are all sorts of, you know, plants that relied on the megafauna, for example, to spread their seeds around that are sort of these orphan plants that that don't really do very well anymore. Or some cases, maybe even they're gone at this point. So these effects are ones that we don't necessarily notice. Because, you know, we're not very good at noticing these things. We move things around the world, you know, all the time, and most of our landscapes are made up of creatures and of plants that we moved here, that people moved here. So, you know, we're not really very, very good at sousing out the impact of these extinctions on other creatures. But undoubtedly, there has been many, many, impact, already.

 

Dr. Sam White

I would follow up on that by bringing up an important concept that the college's environmental historians bring up a lot which is the shifting baseline syndrome, that the fact that unless our loss of biodiversity, or the disappearance of a species has taken place very rapidly, within one human generation, we tend not to notice it, because we mentally shift our expectations about the environment or about species abundance. So this is particularly well known, for instance, in patterns of overfishing, that we really have biologically impoverished oceans, especially when it comes to the species that we once most enjoyed catching and eating. But we didn't always see how much we were losing and how quickly because each generation of fishermen quickly adjusted their expectation. And each generation consumers adjusted their expectation to the smaller catches to eating what used to be considered trash fish, because they were all that became available as we essentially ate our way down the traffic level from the big carnivores being like to, you know, smaller species of fish that once would have been considered not even worth the time.

 

Brenna Miller    

So one of the things is that it's really hard to tell exactly how much diversity we've lost to this point. But is there any way that we have a sense of how far the sixth extinction has gone? And in general, what are the anticipated consequences for life on Earth, and especially for humans, since that seems to be what most people really care about. If it goes unchecked?

 

Elizabeth Kolbert   

I mean, the way that we've looked at sort of how far it's gone is complicated, because we don't have the record of the present, we only have the present and we don't even know how much, how many species there are on Earth right now right, even within an order of magnitude. Some people would say that it so there's a lot of species that, you know, we just haven't catalogued yet. Probably the vast majority of species on Earth, which are not, you know, charismatic animals, they're not panda bears they're not porpoises. There are, you know, mollusks and insects, and they're pretty poorly studied. So what we do, or what scientists do, is they look at the groups that we have studied, so take you know, mammals of birds, or groups that we pretty rarely encounter new species, occasionally we do, but pretty rarely so we think we have a pretty good handle of how many mammals there are on Earth right now. And then we look at how fast they're going extinct. And we find they're going extinct really, really fast. And when you look through all those, you know, pretty well known and well cataloged groups, you find very high extinction, extinction rates that are so high that if they continue just for another few hundred years, say 500 years or so which in geologic front of nothing, you would get to mass extinction rate fatality rate, and in terms of what the impact of this are going to be there, you know, they're, they're unspeakable, I suppose on one level, they're certainly from the perspective of all the other life on Earth they're, you know, apocalyptic. From our perspective, what does this mean to humans? That's a that's a pretty difficult question to answer, because we have proved over and over again, that we can survive the extinction of lots of creatures, because once again, we've done that. But the question of whether there's a certain point where ecosystems just unravel as the systems that we depend on, and they're all part still a big biological system that we don't exactly even understand whether that just leads to some kind of ecological collapse that has very dire consequences for us. You know, I certainly wouldn't want to risk that personally. But that is exactly what we're doing right now.

 

Dr. Sam White

I would add that perhaps even the rate of extinctions that we're experiencing might not capture the full magnitude of what we're doing, probably the most profound kind of impact we're having is the way in which we are replacing so much wild animal biomass, with domesticated and human biomass. So in other words, we may be that we managed to preserve enough Savannah to keep a small fraction, a few percent of the original population of lions alive or we managed to hold on to a few breeding families of condors, but we've already replaced the vast majority of their numbers, with ourselves in our habitats, you know, including our cities and farms and our domesticated animals, including, you know, grasslands set aside for cattle, for instance. So we may be reducing many species beyond the point at which they could provide the same ecosystem services or serve the same function within a healthy ecosystem as they did before.

 

Elizabeth Kolbert

I think Sam makes a really good point. And another sort of corollary to that, that I just like to add is, you know, and I wrote a, you know, a book called "The Sixth Extinction". So I am perhaps, you know, part of the problem here. But also, when we look at extinction rates, we're not really just looking at population crashes. So for an animal to be considered extinct, it has to be, no one has seen one for 50 years, that's sort of the technical definition of it, or the definition in scientific circles. But when we go out, and we just look at what has happened to, you know, populations of animals, are there still some around. They're not, it's not considered extinct, yet. We see, you know, just terrible loss, so you know, as sort of Sam was alluding to, we were just replacing a lot of the biomass so extinction rates, you know, I I completely agree, they don't entirely capture what's going on here. Because we really need to look at populations. And when we do that, and there was just a big study on that recently, you know, those, in some ways, even more dire, those figures.

 

Jessica Vinas-Nelson

So to be a bit cavalier here, though, life on Earth has survived past extinctions. Why should we worry about a sixth extinction?

 

Dr. Sam White     

It's really a question of timescales. You know, species, global biodiversity, does rebound after mass extinctions. But that took millions of years. And we just don't have millions of years.

 

Elizabeth Kolbert

Yeah. And I think I think, you know, when you say why should we worry? That's a very interesting question. Because right as Sam is suggesting, we won't be around, at that point, biodiversity, might may rebound. But the other point is, if we're one of the species that is gone, you know, as you alluded to, we seem to be particularly concerned about our own future. Well, you know, that that sort of curtains for us too.

 

Jessica Vinas-Nelson

Who is more likely to adapt to the changing circumstances, us or plant and animal species?

 

Elizabeth Kolbert

You know, I mean, if we could all just adapt to whatever humans, you know, blew at us, then we wouldn't be in the situation that we're in right now. Now, you know, there are all sorts of questions as to what kinds of species are, you know, particularly sort of extinction vulnerable, and, you know, they tend to have all the characteristics that you would, that you would think they have very small ranges, they're endemic to, you know, one particular place. But, you know, some creatures will make it through history as our guide, they will be species that were very widespread to begin with, so maybe, you know, humans are very widespread, so maybe will be one of them. But the defining characteristics of a mass extinction you know that lots and lots and lots of species go extinct in all different groups. So you know, from the very tips of the tree of life to, you know, to the root.

 

Jessica Vinas-Nelson

So, despite having a best-selling book titled "The Sixth Extinction", do you think most Americans or people around the world are even aware of the threat of a sixth extinction?

 

Elizabeth Kolbert

Well, I think that people are aware, you know, to the extent that people are aware of anything these days, they're aware that there's a lot of species, iconic species that are threatened, you know, take your kids to the zoo, and you're just bombarded. I used to find taking my kids to the zoo, you know, really, one of the most depressing things you could do, because here were all these fantastic creatures. And it was awesome literature says he would enter the label on the aquarium or whatever, about how terribly endangered these creatures were in zoos are repositories for a lot of biodiversity that increasingly doesn't exist anywhere else. And they're often very involved in conservation, I should add. So I think it's hard to avoid, you know, these days, the sense that there's a lot of loss out there, but do people put it all together and the big picture and say, Wow, something big and huge and really unusual is going on, I don't think so I think all of us, you know, who are alive today, grew up in a time of biodiversity loss. So we're sort of used to things like, oh, something's gone extinct. That doesn't strike us as that weird, but really, it should be basically impossible for you in the course of your lifetime to see a species go extinct, that just should not happen.

 

Dr. Sam White

Yes, I partially agree with that. I think what captures public attention is the threat to charismatic megafauna threat to polar bears threat to elephants, or lions. And those animals are often so few and number that actually at the time that they do go extinct, they no longer played a major role in ecosystems that they were not particularly abundant in the wild. And so people see their loss as something sort of sentimental or aesthetic, what what's troublesome is that people don't see the much greater biodiversity loss that that's going on all around us day by day in species that they had never heard of. And that may play significant roles and ecosystems that may provide vital ecosystem services or be the linchpin of an ecosystem. I think another point which often rather surprises my students, as I teach environmental history, is the extent to which we have replaced most mammalian and avian biomass in the world. What tends to really shock my students much more so than giving numbers of extinctions or pointing out major past extinction, such as the passenger pigeon, is just simply showing them estimates that for instance, we have now replaced more than 90% of the world's mammalian biomass with humans and their domesticated animals, that the figure is just so overwhelming. This is really an ongoing struggle, that we need to keep finding different ways to address different problems.

 

Brenna Miller    

So is there anything that people can do at this point to halt or slow mass extinction and mitigate its effects in the future? Are there practical actions that people can take on an individual level to help address this problem?

 

Dr. Sam White     

So it's a difficult question, because I'll start by saying, probably the most important thing you can do is vote, because this will largely be a policy issue. But in thinking about just what you can do on a personal level, I guess they're really two kinds of actions that you can take one with the actions focus specifically on avoiding current threats to endangered species, the kinds of actions avoiding the kinds of actions that directly affect endangered species. So for instance, trying to avoid fish that are not certified by the Stewardship Council or for that matter, trying to avoid meat consumption altogether, since it tends to have a larger environmental footprint. And of course, avoiding any kinds of purchases that would directly contribute to poaching of endangered species, for instance, don't purchase ivory don't purchase any animal parts of many which are already illegal, of course, under the international treaty under the CITES treaty, but that really is only a part of it. Because as we talked before, there are so many drivers of the global massive extinction event that may be occurring. And really to minimize your role in that, you would have to minimize your environmental impact in so many ways, you would want to, for instance, minimize your carbon footprint, by minimizing your energy use, especially any energy use that comes from burning fossil fuels, you'd want to physically take up less space, if you could, by living, you know, in the city, rather than on more land you would want to minimize any kinds of, you know, purchases of goods that may in the process of production or distribution involve taking up more energy or producing more greenhouse gas. So I think what it really gets to is, as with so many other environmental issues, that they are all tied together, because our environmental impact the accelerating rate, environmental changes, largely driven by home or economic activity or economic activity as consumers and producers, that makes it very hard for an individual to maintain the current standard of living in still have a reasonable environmental footprint.

 

Brenna Miller    

So then turning to the bigger picture about how we act on national and on and on a global scale. Are their current US environmental policies that address the six extinction in any meaningful way? And is it possible to address the sixth extinction on sort of a country-by-country basis? Or do we need a global consensus on how to how to manage this problem?

 

Elizabeth Kolbert

Well, I, there's you know, there's a lot of different ways to answer that question. The first, and the immediate one that comes to mind is you have environmental policy right now in 2017 is you know, is just a disaster. The current Trump administration is undoing whatever progress was made in terms of curbing carbon emissions and trying to limit climate change there are huge policy changes, you know, that are being in favor of exploitation of our public lands, which are the only real big tracks left we have of habitat for a lot of species. So, you know, we're actually actively moving in, in the wrong direction, right, right now, as we speak, now, if we took a bigger picture, and we are abstracted ourselves from the politics of the moment, one of the big things that that we could do that would require international cooperation would be to put aside big tracts of land that are still intact, and some of them in North America, a lot of them are in the tropics. And we would have to as a as a society, as it as a world decide those are places that we want to leave intact, because the climate is changing, we're not stopping that we can limit it, but we're not stopping it right now. I think that, you know, one of the best bets we would make as a planet is to is to criticize land whereas many species as possible to get through this very, very difficult time that we've imposed on them. And a lot of these rain forests and areas that are very, very, very biodiverse are in developing parts of the world, they would presumably need to be compensated say, for putting that land aside. So as a globe, we would have to kind of, you know, step up to the plate. Now, is there any sign that that's happening? The short answer is no. But could it happen? Yes, it is possible that is in the realm of the possible.

 

Dr. Sam White

From a historical perspective, what's peculiar is that on the one hand, America has been often a leader in policies designed to protect endangered species. Whether this goes all the way back to say, or the hunting laws or later the national parks and movement and national forests movement into the late 19th century, or national Wilderness Act 1960s, endangered Species Act, America has often been at the lead in those kinds of environmental initiatives and continues to take part in some international initiatives such as the Convention on International Trade and endangered species. Yet on the other hand, America has often been a laggard in the kind of environmental policies that more indirectly affect when species are impacting biodiversity. You know, we've traditionally had a very energy intensive and land extensive style of growth. We are not necessarily as concerned about our impacts on landscape survive diversity overseas and our consumption here in America. And of course, now we are an international laggard on policies to address climate change. And I would also be, you know, cautiously optimistic that while we can't completely stop the biodiversity loss we've had, we could potentially slow this biodiversity loss considerably through active international policies, and there have been some promising steps. It would otherwise might seem a gloomy situation, such as, for instance, countries, including America that have set aside larger marine reserves designed to protect marine biodiversity.

 

Brenna Miller    

Well, we'll wrap it up on that note, thank you to our two guests, Elizabeth Kolbert Pulitzer Prize winning author of "The Sixth Extinction" and OSU Department of History Environmental historian Sam White.

 

Jessica Vinas-Nelson

Thanks, everyone. This episode of History Talk podcast was brought to you by Origins: Current Events in Historical Perspective an online publication of the public history initiative, and the Goldberg Center and the history department at the Ohio State University in Columbus and Miami University in Oxford, Ohio. Our main editors are Steven Conn and Nicholas Breyfogle. Our executive producer is David Staley, our audio and technical advisor is Paul Kotheimer. Our audio producers and hosts are Brenna Miller and Jessica Vinas-Nelson. Song and band information can be found on our website. You can find our podcasts and more on our website origins.osu.edu on iTunes and on Soundcloud and as always, you can find us on Twitter and Facebook. Thanks for listening