The Sixth Extinction: An Unnatural History by Elizabeth Kolbert

The sixth extinction referred to in the title  is of course the extinction Homo sapiens are bringing about through the agency of climate change. Situating our extinction in a cosmic context sets an entirely different tone from say, the panic engendered by the recent report from the U.N.’s Intergovernmental Panel on Climate Change. This is grown-up time. Take in the very big picture.

Setting the sixth extinction in its cosmic context tells you that the temperature change predicted for the next 100 years is similar to the range experienced during the last Ice Age, which left much of Canada buried under miles of ice. But as Kobert points out, while our “anthropocene epoch” is spewing carbon that took millions to years to bury, the temperature is changing ten times faster than it did at the end of the glaciation period.

Working through the devastation wrought by other cataclysmic events provides the perfect backdrop for understanding the implications of acidifying our oceans. Here’s a possibly incomplete list of what will be affected: metabolism of all kinds; enzyme activity; protein function; the availability of key nutrients like iron and nitrogen; how light passes through water; the passage of sound waves, making the oceans noisier; increased growth of toxic algae; photosynthesis; the reduction of carbonate ions, which hampers calcification; how compounds are formed by dissolving metals in ways that could be poisonous; and turning water corrosive. This is basic chemistry.

The anthropocene epoch probably won’t be as bad as the day the asteroid hit earth at the end of the Cretaceous Period but we’re reaching into the bottom of all possible bad days to make the comparison.

“On an ordinary day sixty-five million years ago, an asteroid six miles wide collided with the earth, releasing 100 megatons of TNT, or more than a million times of the most powerful H-bombs ever tested. Debris, including iridium from the pulverized asteroid, spread around the globe. Day turned into night and temperatures plunged. A mass extinction ensued.”

Kolbert is not simply shoveling our environmental failings into a great pile (as I have done here.) She is making long strings of connecting dots. As the planet warms the critters of the world will attempt to move north or up the slope. Any species that can’t cope with temperature variation is doomed: that would include most of what now live in the tropics. The huge diversity of tropical species that co-exist in complex interdependencies typically live within very short thermal and spatial ranges and they ultimately depend upon constancy. Well they’ll be gone.

The ones that do manage to move up the hill in search of cooler temperatures, they’ll be  invasives and not welcome anywhere, and if they do get to the top they’ll have lots of company because there is less space at the top than at the bottom.

Most species can’t move of course because our settlements are in the way, and the reserves we carved out at great cost to protect our charismatic species will be useless in the face of all pervasive climate change.

Where species aren’t killed outright, fragmented communities will survive and that means just a slower way of dying. Small environmental communities mean small populations of individual species, and small populations are particularly vulnerable to extinction.

Changes in land use affect air circulation so it is possible that if the Amazonian rain forests dry up or are cut down or die of some pestilence on a large enough scale, there may actually be no more rain.

For all the terrible evidence, this book doesn’t lash out at the pernicious obstinacy of our governments, or at our prestigious capacity to deny the facts staring us in the face or lament that the poor are bearing the brunt of our profligate use of fossil fuels. Instead Kolbert paints a picture of climate change as the (almost) inevitable result of our resourcefulness and our throwing arm. Other primates can’t play baseball or tennis or throw spears.*

Evidence is mounting that H. sapiens, emerging from east Africa 20,000 years evolved into “overkillers”, hunting down species, especially mega fauna at a rate that exceeded the prey’s ability to reproduce, so no evolutionary advantage possible. Getting big is a wonderful escape from predators (except from the likes of us) but it comes with the baggage of months or years in gestation.

The disappearance of the giant herbivores changed the landscape. They weren’t there to chew up the forests, which caused a build up of fuel, which caused fires, which favoured fire-tolerant plants—these would be grasslands that favoured upright runners with projectiles.

We did the same thing to Neanderthals and Denisovans except we had sex with them first. Neanderthals had good-sized brains, but they never got the hang of throwing things. That left them in dangerous proximity to the animals they were trying to bring down.

Kolbert makes the point that given all this killing, on so many continents and the number of species we’ve managed to finish off, you could argue that the anthropocene epoch began in the middle of the last Ice Age.

Kolbert concludes by describing our often-pathetic attempts to save the critters, lovingly tending to their needs, applying a lot of science to understanding their inner functioning. It is what makes us human, just as much as drilling oil wells.

Climate change will leave its own geologic traces, as will river diversions, monoculture farming, ocean acidification and the great spike in methane and carbon dioxide in the atmosphere.

“One hundred million years from now, all the great works of man will be compressed within a layer of sediment.”

The writing is so wonderfully wry, you want to squeal with pleasure at times, which seems entirely inappropriate given its message. But there it is. Human beings can hold two opposing ideas in their minds simultaneously and live to fight another day. It would be nice if we could call God into action to fix this place but it is really up to us.

* Scientific American ran an intriguing article on how well our anatomy is adapted to hunting in its April, 2014 issue. A flexible, taller waist allowed our ancestors to release a great store of torque power as they threw a spear. A less twisted upper arm bone and sideways-facing shoulder enabled humans to hurl with great accuracy and speed but compromised their ability to climb trees.  A long thumb and strong wrist provided a powerful grip. We also excelled at understanding social cues and could hunt in concert.

The Sixth Extinction: an Unnatural History by Elizabeth Kolbert, Henry Holt & Company, New York.

Correction: A correction has been made in the preceding blog concerning the Fair Elections Act. This is regarding the proposed transfer of the commissioner of elections’ powers from Elections Canada to the office of the Director of Prosecutions. See the third to last paragraph. My apologies.