Seven Things to Know About the Sixth Mass Extinction

Coral Reef at Palmyra Atoll National Wildlife Refuge (Jim Maragos/U.S. Fish and Wildlife Service)
Coral reefs are the first major ecosystems that could be wiped out by human impacts. (Jim Maragos/U.S. Fish and Wildlife Service)

You gotta love an author who manages to turn complex scientific theories and millions of years of history into an easy-to-understand thesis -- even if that thesis is that humans are causing mass extinction. Elizabeth Kolbert’s book “The Sixth Extinction: An Unnatural History” centers around two ideas: that humans are witnessing a very high rate of species extinction and that we're causing much of it.

Kolbert joined KQED’s Forum to discuss her book and the disappearance of everything from the snails of the Hawaiian islands to bats in upstate New York. The topic isn’t a cheery one, but as Kolbert writes in the introduction, “If extinction is a morbid topic, mass extinction is, well, massively so. It's also a fascinating one.”

Here are highlights from the Forum interview, edited for clarity:

1. We Don't Know Yet How Bad This Extinction Will Be

“We are clearly at a time of very high extinction rates. Whether we rise to the level of the major – the five major – mass extinctions of the last half billion years certainly remains to be determined.  There have also been, somewhat oxymoronically, “minor” mass extinctions in the record. Where this extinction event is going to fit into that is obviously impossible to know when you’re in the midst of it. But increasingly you hear scientists comparing us to the asteroid that killed off the dinosaurs and many other groups.”

Trilobites went extinct in the mass extinction at the end of the Permian. (Kevin Walsh/Flickr)
Trilobites went extinct in the mass extinction at the end of the Permian. (Kevin Walsh/Flickr)

2. Based on Carbon Emissions, We May Be On Track For the Worst Mass Extinction, Ever


"The worst mass extinction in the history of the planet happened about 250 million years ago at the end of what’s known as the Permian period. And it’s believed that it was caused by this major burst of volcanic activity that emitted a lot of CO2 into the air and warmed the planet very radically and changed the chemistry of the oceans very radically.

And very soberingly, scientists have recently tried to figure out at what rate was CO2 being emitted at that point. And the best estimate that they can come up with – this is a pretty recent paper – suggests that we are pouring CO2 into the air faster than was poured into the air in the events leading up to the end of the Permian extinction. So you increasingly hear ‘We cannot rule out that kind of an outcome: the Permian,’ which was the worst mass extinction in history. I find that – even I, who wrote this book, and feel like I couldn’t be surprised by much anymore – find that, just extremely sobering and terrifying.”

3. Invasive Species Have Created a "New Pangea"

“Invasive species actually are implicated in, some people would say, the majority of extinctions we know about. Invasive species turn out to be really important.

Effectively about 250 million years ago all of the continents of the world were smushed together in this supercontinent that has been called Pangea. And then they drifted apart due to plate tectonics and we eventually got the world as we know it, with seven continents.

What we’re doing by bringing together all of the flora and fauna of the world just by transporting things around the world, in a biological sense, is erasing those boundaries between the continents and smushing them back together. So a term has been coined: the ‘New Pangea.’ We are creating the New Pangea. We’re bringing everything back together.

And that can have, it turns out, very devastating consequences. Often it has no consequences -- you move something around the world, it can’t make it in a new place so it just disappears, or it establishes itself and it doesn’t do any damage, it just sort of coexists with what was there before. But a certain percentage of the time, and even if it’s a very small percentage – [because] you are doing it over and over again, it obviously adds up  – a certain percentage of the time you bring together these evolutionary lineages that have been separated for tens of millions of years and very devastating things happen.”

Bats hibernating in a cave in New York with fungal growth on their faces. (Nancy Heaslip/NY Department of Environmental Conservation)
Bats hibernating in a cave in New York with fungal growth on their faces. (Nancy Heaslip/NY Department of Environmental Conservation)

4. White-Nose Syndrome, a European Fungus, Is Decimating North American Bats

“[The fungus] has been traced back to Europe – it came over quite possibly on someone’s shoe, or in their suitcase. It almost certainly landed somewhere in upstate New York, because that is where we first started to see these huge die-offs. It’s very devastating to bats, it gets on their skin, it irritates their skin. You can see it. It looks like the bats have been dunked in talcum powder or cocaine, some people have said.

What happens is that bats in the North Eastern U.S. hibernate during the winter. So they hang by their toes, their body temperature drops, their immune system shuts down and they really, really need to conserve energy. They are very small little creatures, they need that energy to get through the winter – there’s nothing to eat. And this fungus irritates them, they wake up, they fly around, there’s nothing to eat, they drop dead."

5. Coral Reefs Could Be the First Major Ecosystems to Disappear Because of Humans

“Many marine scientists believe that coral reefs will be the first major ecosystem to be done in by human impacts. So there will still be corals, but they will no longer be able to form these fantastic reefs that support a tremendous variety of species anywhere between half a million and something like nine million species spend part of their lives on coral reefs.

Changing water temperatures are really dramatically affecting reefs. Reefs have this interesting symbiosis going on. They have algae inside them, that feed them, that provide carbohydrates for them and that they get a lot of their energy from. And when water temperatures get too high this relationship breaks down, they expel [the algae] and they basically starve to death.

Coral bleaching events, which are happening more and more frequently because water temperatures are going up, those are already really reducing coral cover in a lot of parts of the world. So for example, in the Great Barrier Reef, which is the world’s largest reef, coral cover has declined by something like 50 percent just in the last few decades.”

6. The Chemistry of the Oceans Is Changing Radically

“If you talk to scientists – certainly if you talk to marine scientists – one thing that really, really worries them that has not gotten the press it deserves is this issue of ocean acidification. That’s the phenomenon where, when you pour CO2 into the air as we are -- there’s just no debate about that, we’re pouring about ten billion tons of carbon into the atmosphere every year just by burning fossil fuels -- a lot of it is going to end up in the oceans.

When CO2 dissolves in water it forms a weak acid. It forms carbonic acid … And it’s changing the chemistry of the oceans very radically."

7. There's No Saying What Will Survive This Extinction Event

"People are actively interested in this question precisely because we seem to be in another mass extinction event. What comes through? What tends to come through these extinction events? And they’ve found very very few rules. It’s very hard to say that there’s a rule. The dinosaurs were the dominate group on Earth for tens of millions of years and they all – every species of non-avian dinosaur dies out. Why is that? No one really knows."

You can listen to the complete interview below: