Elizabeth Kolbert “The Sixth Extinction: An Unnatural History,” Henry Holt & Co., 2014, 271 pps
One of my MUST READ ratings:
Author Elizabeth Kolbert is a writer for The New Yorker and is considered one of the best science writers. In this book she describes that since the origin of life on earth 3.8 billion years ago, our planet has experienced five mass extinctions. The last occurred some 66 million years ago when a six-mile-wide asteroid collided with earth, wiping out the dinosaurs and about 75 percent of all plant and animal species. The 6th extinction, allegedly occurring as I write, is man-made and is primarily caused by climate change which threatens to eliminate 20 to 50 percent of all living species on earth by the end of this 21st century.
My Notes:
Pg. 6: There have been five great mass extinctions during the history of life on this planet. These extinctions led to a profound loss of biodiversity. The first took place during the late Ordovician period, some 450 million years ago, when living things were still mainly confined to the water. The most devastating took place at the end of the Permian period, some 250 million years ago, and it came perilously close to emptying the earth out altogether. The most recent—and famous—mass extinction came at the close of the Cretaceous period, it wiped out, in addition to the dinosaurs, the plesiosaurs, the mosasaurs, the ammonites, and the pterosaurs.
Pg. 11: Amphibians emerged at a time when all the land on earth was part of a single expanse known as Pangaea. Since the breakup of Pangaea, they’ve adapted to conditions on every continent except Antarctica. Worldwide, just over seven thousand species have been identified, the greatest number in the tropical rainforests.
Pg. 15: There is always a slow background extinction going on—about one species disappears every seven hundred years. Mass extinctions are different, there’s a crash, and disappearance rates spike. At these times, conditions change so drastically that evolutionary history counts for little. Today, amphibians enjoy the dubious distinction of being the world’s most endangered class of animals. It’s estimated that the group’s extinction rate is as much as forty-five thousand times higher than the expected background extinction rate. It is estimated that one-third of all reef-building corals, a third of all fresh-water mollusks, a third of sharks and rays, a quarter of all mammals, a fifth of all reptiles, and a sixth of all birds are headed toward oblivion.
Pg. 69: In the Origin, Darwin drew no distinction between man and other organisms. This equivalence was the most radical aspect of his work. Humans, just like any other species, were descended, with modification, from more ancient forebears. Even those qualities that seemed to set people apart—language, wisdom, a sense of right and wrong—had evolved in the same manner as other adaptive traits, such as longer beaks or sharper incisors. Darwin denied humanity’s special status.
Pg. 75: It 1980 it was established by the Alvarezes’ paper that on an otherwise ordinary day sixty-five million years ago, an asteroid six miles wide collided with the earth. Exploding on contact, it released energy on the order of a hundred million megatons of TNT, or more than a million of the most powerful H-bombs ever tested. Debris, including iridium from the pulverized asteroid, spread around the globe. Day turned to night, and temperatures plunged. A mass extinction (the 5th) ensued.
The asteroid arrived from the southeast, traveling at a low angle relative to the earth, so that it came in not so much from above as from the side, like a plane losing altitude. When it slammed into the Yucatán Peninsula, it was moving at something like forty-five thousand miles per hour, and, due to its trajectory, North America was particularly hard-hit. A vast cloud of searing vapor and debris raced over the continent, expanding as it moved and incinerating everything in its path. A triceratops in Alberta had about two minutes before getting vaporized. As the ejected debris fell back through the atmosphere, the particles incandesced, lighting the sky everywhere at once from directly overhead and generating enough heat to, in effect, broil the surface of the planet. On the land, every animal larger than a cat seems to have died out. (Pg. 86)
Addenda: Extinction is a relatively new idea in the scientific community. Well into the 18th century, people found it impossible to accept the idea that species had once lived on earth but had been subsequently lost. Scientists simply could not envision a planetary force powerful enough to wipe out forms of life that were common in prior ages.
Pg. 108: Owing to a combination of fossil fuel combustion and deforestation, the concentration of carbon dioxide in the air has risen by forty percent over the last two centuries, while the concentration of methane, an even more potent greenhouse gas, has more than doubled. The concentration of carbon dioxide in the air today—a little over four hundred parts per million—is higher than at any other point in the last eight hundred thousand years. By 2050 it is projected that the concentration will top five hundred parts per million, roughly double the levels they were in preindustrial days. This will produce an eventual average global temperature rise of between three and a half and seven degrees Fahrenheit, and this will, in turn, trigger a variety of world-altering events, including the disappearance of most remaining glaciers, the inundation of low-lying islands and coastal cities, and the melting of the Arctic ice cap.
Pg. 160: It is now generally believed that ice ages are initiated by small changes in the earth’s orbit, caused by, among other things, the gravitational tug of Jupiter and Saturn. These changes alter the distribution of sunlight across different latitudes at different times of the year. When the amount of light hitting the far northern latitudes in summer approaches a minimum, snow begins to build up there. This initiates a feedback cycle that causes atmospheric carbon dioxide levels to drop. Temperatures fall, which leads more ice to build up, and so on. After a while, the orbital cycle enters a new phase, and the feedback loop begins to run in reverse.
Pg. 162: Warming today is taking place at least ten times 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.
Pg. 231: When the chronology of extinction is critically set against the chronology of human migrations, man’s arrival emerges as the only reasonable answer to the megafauna’s disappearance.
Pg. 234: The Anthropocene is usually said to have begun with the industrial revolution. By this account, it’s with the introduction of modern technologies—turbines, railroads, chainsaws—that humans became a world-altering force. But the megafauna’s extinction suggests otherwise. Before humans emerged on the scene, being large and slow to reproduce was a highly successful strategy, and outsized creatures dominated the planet. Then, in what amounts to a geologic instant, this strategy became a loser’s game. And so it remains today, this is why elephants and bears and big cats are in so much trouble. 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.
Pg. 237: The Neanderthals lived in Europe for at least a hundred thousand years. For the most part, this was a time of cold, and for stretches, it was intensely cold, with ice sheets covering Scandinavia. Then roughly thirty thousand years ago the Neanderthals vanished. Increasing evidence leads to the conclusion that their bad luck was us. Modern humans arrived in Europe around forty thousand years ago and soon made their way to a region where Neanderthals were living, the Neanderthals in that region disappeared. It is also clear that humans had sex with the Neanderthals before they disappeared. As a result, most people alive today are slightly—up to four percent—Neanderthal. Specifically, Europeans and Asians share more DNA with Neanderthals than Africans.
Pg. 265: To the extent that we can identify the causes of past extinctions, they’re highly varied: glaciation in the case of the Ordovician extinction (430 million years ago), global warming and changes in ocean chemistry at the end of the Permian (250 million years ago), an asteroid impact at the very end of the Cretaceous (66 million years ago).
Addenda:
The earth’s water cycle is being dangerously disturbed, as warmer oceans evaporate more water vapor into the air. Warmer air holds more moisture (there has been an astonishing 4 percent increase in global humidity in just the last 30 years) and funnels it toward landmasses, where it is released in much larger downpours, causing larger and more frequent floods and mudslides.
The extra heat is also absorbed in the top layer of the seas, which makes ocean-based storms more destructive. Just before Hurricane Sandy, the area of the Atlantic immediately windward from New York City and New Jersey was up to nine degrees warmer than normal.
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