Thrice Removed
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Thrice Removed

The Sixth Extinction

On Elizabeth Kolbert’s book projecting data from past extinctions on to our current situation.

We’re in the midst of a mass extinction, but Elizabeth Kolbertis actually somewhat hopeful about it all. We are at a truly extraordinary moment of history in which we are cognizant of our own demise (except for those in denial) and, therefore, able to affect how it turns out if we can just get our act together!

This book has been on the NY Best Sellers list for four weeks for good reason. It’s full of scientific data, but it’s written conversationally. We get to know all the people involved in the research. They’re all pivotal to this engaging story.

Here are the facts in a nutshell:

There have been five mass extinctions so far. An extinction is exponentially different from a “fall.” It’s not just a civilization that’s being destroyed leaving ashes for another to rise up in. An extinction of a species means every single one is gone. And a mass extinction means many species are lost in a relatively short period of time — when we lose more species than we gain (extinction > speciation). Mass extinctions are “substantial biodiversity losses that occur rapidly and are global in extent” (16).

“Species are at a low risk of extinction most of the time. But this condition of relative safety is punctuated at rare intervals by a vastly higher risk. The history of life thus consists of long periods of boredom interrupted occasionally by panic” (16).

There is no one cause of mass extinctions: “As in Tolstoy, every extinction event appears to be unhappy — and fatally so — in its own way” (104). Here are the big five (but she doesn’t give much space to numbers 2 and 4):

1st: Ending the Ordovician period — 444 million years ago. Life was mainly in water, then 85% of marine species died off due to glaciation. Carbon dioxide levels dropped possibly due to the development of plant matter (early mosses) which absorbed the CO2 and then the ocean became more oxygenated. That chemical change in the ocean’s gasses coupled with the colder weather made the place inhospitable (103).

2nd: During the Late Devonian period — 370 million years ago. After this, reptiles started to gain ground.

3rd: Ending the Permian period — 252 million years ago. This was the most devastating — called “the great dying.” It was caused by an increase in carbon which acidified the oceans and, with the oxygen level dropping, most organisms probably suffocated. Reefs collapsed. It lasted maybe 100,000 years from start to finish, and eliminated 90% of all species on earth (104). The best explanation for this increased carbon is a massive burst of vulcanism in Siberia. “But this spectacular event probably released, on an annual basis, less carbon than our cars and factories and power plants” (123). This one is most similar to what we’re currently experiencing, but these days we like to do things much faster.

4th: At the end of the Triassic period — 200 million years ago. This ushered in the Jurassic period and the origin of birds and flowering plants.

5th: At the end of the Cretaceous period — 66 million years ago. This most recent one, the “K-T” extinction, wiped out the dinosaurs when an astroid hit the earth and incinerated everything nearby, then the dust created by the impact broiled anything left (86). This was followed by the dawn of the first Primates (our ancestors).

There was also an extinction of megafauna about 11,700 years ago (woolly mammoths, sabre-tooth tigers and the other creature from Ice Age), but that doesn’t rate as a mass extinction.

We’re always dealing with extinctions of individual species. During ordinary times, the millions of years between mass extinctions, we have “background extinctions.” It happens throughout history as species evolve and fight for resources. For the strongest species to survive, others have to go. As far as typical background extinction goes, we expect to lose about one species of mammals every 700 years and one amphibian species every 1000 years or so, worldwide (17).

Today, though, the amphibian extinction rate is about 45,000 times higher than the background rate. A third of all reef-building corals, fresh-water mollusks, sharks and rays, and a quarter of all mammals, a fifth of all reptiles, and a sixth of all birds are close to extinction (18).

Something that I can’t help notice is that one of humanity’s strongest survival traits, adaptation, is one that is leading us towards destruction. The extinction rate has been creeping up, and now we just accept that we’re losing many species of life every day as if it’s normal. We’re adjusted to this news to the extent that it doesn’t shock us the way it should — the way it needs to! A little too adaptable for our own good, I’d say!

White-nose syndrome.

The losses are happening worldwide, and one culprit is human travel. We unwittingly carry disease with us wherever we go that can destroy life in other parts of the world (like a fungus that doesn’t bother one species of bat, but completely obliterated another — the North American brown bat which used to be out there eating mosquitoes by the thousands).

But, people have a hard time processing disruptive information. This is a “paradigm shift discovery.” It’s hard to accept that catastrophes like this happen — and to us — and because of us.

We live in the newly-named Anthropocene Era — a “human-dominated geological epoch” in which we have transformed almost half the land surface of the planet, damned or diverted most of the world’s major rivers, added more nitrogen to the soil than is fixed naturally by all terrestrial ecosystems, removed more than a third of the fish, and used more than half the world’s readily accessible fresh water runoff.

“Most significantly, people have altered the composition of the atmosphere. Owing to a combination of fossil fuel combustion and deforestation, the concentration of carbon dioxide in the air has risen by 40% over the last two centuries, while the concentration of methane, an even more potent green-house gas, has more than doubled” (108). About a third of the CO2 that humans pump into the air is absorbed by the oceans. “This year alone the oceans will absorb two and a half billion tons of carbon…Every day, every American in effect pumps seven pounds of carbon into the sea” (114).

We’re altering the chemistry of the air and water, and that type of rapid change is what kick-starts mass extinctions. Most species manage within a small window of acceptable conditions, and we’re taking them outside this acceptable range.

“By burning through coal and oil deposits, humans are putting carbon back into the air that has been sequestered for tens — in most cases hundreds — of millions of years. In the process, we are running geologic history not only in reverse but at warp speed” (124).

The prediction of one scientist interviewed: “Under business as usual, by mid-century [35 years] things are looking rather grim” (132):

“It’s quite possible that by the end of this century, CO2 levels could reach a level not seen since…some 50 million years ago. Whether species still possess the features that allowed their ancestors to thrive in that ancient, warmer world is, at this point, impossible to say” (172).

All the coral reefs will dissolve, and they affect everything else in that delicate eco-system. It’s a chain-reaction that will affect us. “Warming today is taking place at least ten time faster than it did at the end of the last glaciation, and at the end of all those glaciations that preceded it.. To keep up, organisms will have to migrate, or otherwise adapt, at least ten times more quickly” (162). In one area of Peru, researchers have noticed the trees actually shifting location and dubbed it the “Birnam Wood scenario” (158).

Which species will go? According to Jared Diamond, “the main predictor of local extinction was ‘small population size’” (181). Species that totally died off in the past were ones that had only one or two offspring at a time and with a long gestational period. Kinda like us. “Which is why, with the exception of humans, all the great apes today are facing oblivion…By the time we’re done, it’s quite possible that there will be among the great apes not a single representative left, except, that is, for us.” (254). Wishful thinking. And the species that survive and flourish after we’re through are the ones with a speedy reproductive rate. They’re not talking cockroaches, but rats — giant rats (104).

Another interim problem is that the “world is changing in ways that compel species to move,” but it’s also “changing in ways that create barriers — roads, clear-cuts, cities — that prevent them from doing so….human activity has created an obstacle course for the dispersal of biodiversity” (189).

We’re creating a “new Pangea” that has more diversity in areas formerly bereft, but overall global diversity has dropped significantly (212). What we’re not destroying by altering the habitat — including the air and water — we are hunting to extinction. “Though it might be nice to imagine there once was a time when man lived in harmony with nature, it’s not clear that he ever really did” (235).

The first eleven chapters of the book all explain and compare what’s happening now to causes and effects of prior extinctions, but the ending is far more interesting. The last two chapters look at our psychology and potential for improvement.

We are the only primate that is driven to explore and take over new places, to venture “out on the ocean where you don’t see land” (251). Now that we’ve charted all of this planet, we have aims for another. No other animal does that (but viruses do), and Kolbert refers to it as a madness or a “Faustian restlessness.”

Faust signing his soul away.

But something else we do that no other primate does is collective problem-solving. Apes are great at solving puzzles, often faster than a 5-year-old. But they’re no match for a group of 5-year-olds working together. “When the children were given a hint about where to find a reward…they took it. The apes either didn’t understand that they were being offered help or couldn’t follow the cue” (249). And with “the capacity to represent the world in signs and symbols comes the capacity to change it, which, as it happens, is also the capacity to destroy it” (258). So things could really go either way at this point.

The final chapter chronicles the many projects people are currently undertaking to save species: keeping cells alive in a Frozen Zoo, banning DDT, passing the Endangered Species Act, saving condors by helping with lead poisoning, banning poaching, and performing “ultrasounds on rhinos and handjobs on crows” (265).

But, like so many books about the future of our species, the final rallying cry is, “People have to have hope” (263). Saying we need it isn’t the same as giving it to us. It’s suggesting, maybe, that we should live a bit in denial of the tragedy we’ve caused. Eleven chapters of bleak data followed by two chapters of hope might actually suffice for those who haven’t managed the paradigm shift towards understanding our potential for catastrophe. And I’m not convinced Kolbert doesn’t have huge doubts of her own. But I concur that it really doesn’t get us anywhere to just give up and resign ourselves to the end of our kind. If there’s a possibility that we have the ability to slow this thing down, then we’ll be remiss if we don’t continue to try in every way imaginable.

“Life is extremely resilient but not infinitely so. There have been very long uneventful stretches and very, very occasionally revolutions on the surface of the earth.” The causes of these events are varied incluing “one weedy species” (that’s us!). “The one feature these disparate events have in common is…rate of change. When the world changes faster than species can adapt, many fall out….What matters is that people change the world…..through: Our restlessness, our creativity, our ability to cooperate to solve problems and complete complicated tasks…..Having freed ourselves from the contraints of evolution, humans nevertheless remain dependent on the earth’s biological and geochemical systems. By disrupting these systems — cutting down tropical rainforests, altering the composition of the atmosphere, acidifying the oceans — we’re putting our own survival in danger….In pushing other species to extinction, humanity is busy sawing off the limb on which it perches…..Another possibility…is that human ingenuity will outrun any disaster human ingenuity sets in motion.”

We’ll see how it all play out then, shall we?



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Marie Snyder

Marie Snyder


I ramble endlessly about the environment, social injustices, and philosophy at