Summary and Analysis of The Sixth Extinction: An Unnatural History: Based on the Book by Elizabeth Kolbert
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Summary and Analysis of The Sixth Extinction: An Unnatural History: Based on the Book by Elizabeth Kolbert
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This short summary and analysis of The Sixth Extinction: An Unnatural History by Elizabeth Kolbert includes:
- Historical context
- Chapter-by-chapter overviews
- Detailed timeline of key events
- Important quotes
- Fascinating trivia
- Glossary of terms
- Supporting material to enhance your understanding of the original work
About The Sixth Extinction by Elizabeth Kolbert:
Our planet has endured five events of mass extinction, from centuries of catastrophic heating and cooling to the asteroid that fell to earth and ended the Cretaceous Period. We are currently facing the sixth extinction, and this time the human species is to blame.
Elizabeth Kolbert travels the world and meets with scientists who are grappling with the ecological outcomes of human activity. Her Pulitzer Prize–winning modern science classic tells the stories of thirteen different species that have already disappeared or are on the brink of extinction as a result of human activity.
A captivating blend of research and historical anecdotes enlightens readers about the unintentional consequences of our behaviors, from climate change and global warming to invasive species and overexploitation.
The summary and analysis in this ebook are intended to complement your reading experience and bring you closer to a great work of nonfiction.
Product Details
| ISBN-13: | 9781504044172 |
|---|---|
| Publisher: | Worth Books |
| Publication date: | 02/14/2017 |
| Series: | Smart Summaries |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 30 |
| Sales rank: | 556,238 |
| File size: | 2 MB |
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Summary and Analysis of The Sixth Extinction: An Unnatural History
Based on the Book by Elizabeth Kolbert
By Worth Books
OPEN ROAD INTEGRATED MEDIA
Copyright © 2017 Open Road Integrated Media, Inc.All rights reserved.
ISBN: 978-1-5040-4417-2
CHAPTER 1
Summary
Prologue
About two hundred thousand years ago, a new, not yet named species appeared on the earth in Africa. Although not particularly swift or strong, they were resourceful. Before long, they had crossed rivers, mountain ranges, and oceans without difficulty, adapting to various climates through innovation. More than one hundred thousand years passed. They traveled to faraway lands, bringing a host of germs and animals with them. The ecosystem that greeted them was forced to adapt, but often it was unable to, and other species died. Another one thousand years passed and this species, human beings, inhabited every corner of the globe. They discovered how to use energy from deep in the ground, which alters the atmosphere and the climate. Some animals adjusted by moving — up into the mountains, into deeper water, to the poles — but thousands of species were unable to survive. No other animal has altered life on earth in the way humans have.
The planet has experienced five other periods of enormous change that resulted in mass extinctions. This is the story of the sixth. In the first part of her book, Kolbert discusses creatures that are already extinct and the history that led to our understanding of these mass extinctions. The second part of the book is concerned with the present, and looks at the catastrophic changes happening in the rainforests, the reefs, the mountains, and even our own backyards.
Chapter I: The Sixth Extinction
Kolbert dedicates her first chapter to the modern plight of the golden frog (Atelopes zeteki). Once abundant in Panama's rainforests, golden frogs now serve as the figurehead for the worldwide endangerment of all amphibians. In 2002, scientists, researchers, and local Panamanians noticed a drastic decline in golden frogs, and by 2004, efforts were underway to preserve the existing population in captivity and to hunt out the cause of their disappearance. Amphibians survived millions of years, dating back to before the dinosaurs, across virtually every habitat, from rainforest to desert to the Arctic Circle. However, their recent disappearance has occurred irrespective of geography and across nearly all species.
As the title suggests, there have been five mass extinctions, the first being 450 million years ago. At the center of the present sixth extinction is the exceptional fact that it is unintentionally caused by one species: us. Kolbert reveals the mysterious amphibian-killer to be a microscopic fungus called Bd, which disrupts normal functioning of the creatures' skin, resulting in the equivalent of cardiac arrest. Human activity is accountable for the global distribution of Bd, which is now so widespread across the planet that scientists believe it is impossible to repopulate the golden frog and other threatened amphibians in the wild.
Need to Know:The Sixth Extinction opens with the recent and rapid death of amphibians, which is caused by human activity and is occurring at a rate forty-five thousand times higher than the baseline. Once thought nearly impervious to extinction, amphibians are now the world's most endangered class of animals.
Chapter II: The Mastodon's Molars
Extinction theory dates back to the eighteenth century and French scientist Georges Cuvier, who famously studied the fossilized remains of the American mastodon. Cuvier gained renown for suggesting extinction as a widespread phenomenon, and for sensationally asserting "the existence of a world previous to ours," an idea that captivated the Age of Enlightenment and the likes of Thomas Jefferson. While not able to refine a theory of the extinction in his own lifetime, Cuvier did catalog the remains of forty-nine extinct species, including the cave bear, the giant sloth, and the pterodactyl. He also advanced the notion of catastrophism, that a cataclysmic event could cause the end of a species. As for the American mastodon, its demise resulted from humans hunting megafauna during the ice age thirteen thousand years ago.
Need to Know: Kolbert paints a picture of New World intellectuals sitting atop fossils of undiscovered species while still ignorant of their own symbiotic relationship to the natural world. Once Cuvier arrived at the turn of the nineteenth century, the "previous" world of extinct fauna gained much interest and scrutiny.
Chapter III: The Original Penguin
Cuvier's theory of extinction became overshadowed by its great scientific cousin, Charles Darwin's theory of evolution. Darwin and his contemporary, geologist Charles Lyell, criticized Cuvier and other catastrophists by asserting the primary cause of extinction to be natural selection, the same gradual mechanism behind evolution — not catastrophic events. Kolbert recounts a notable extinction that occurred within Darwin's own lifetime. The great auk was a three-foot-tall, flightless bird that inhabited rocky shores throughout the North Atlantic. Its population numbered in the millions until contact with Scandinavian settlers in the tenth century. The most notable extermination of the great auk occurred near Newfoundland, where numerous expeditions exploited a colony of one hundred thousand auks in the span of two centuries, initially to feed malnourished settlers and eventually for the lucrative feather trade. This overexploitation led to extinction in 1844, when the last known pair of auks were haphazardly strangled and their last egg was cracked by three men off the coast of Iceland.
Need to Know: Kolbert traces the prominence of extinction in scientific literature alongside the study of evolution and its primary engine, natural selection. While the auk and the dodo were killed off by humans due to overexploitation, prominent scientists of the day could not recognize mankind's connection to extinction.
Chapter IV: The Luck of the Ammonites
While studying plate tectonics in the late 1970s, renowned geologist Walter Alvarez and his father, Nobel laureate and physicist Luis Alvarez, discovered a thin layer of iridium, an element found abundantly in asteroids. This iridium layer was found in various sites around the world and served as a geological marker for an abrupt global event. The Alvarezes suggested this marker corresponded with the mass extinction of the dinosaurs sixty-six million years ago, wherein vaporized iridium dust created by an asteroid's impact incinerated nearly everything on the earth's surface in a matter of minutes.
Kolbert joins modern geologists in New Jersey to study ammonites, a class of marine creatures that did not survive the great asteroid's impact, along with three-quarters of all species. Like the great auks, which could not outrun humans, ammonites and countless other species on the planet endured millennia of natural selection but could not escape the asteroid.
Need to Know: Our current understanding of the end of the Cretaceous period and the previous mass extinction is a recent discovery. This shift in thinking among the scientific community solidified that evolution through natural selection may equip flora and fauna to thrive, yet one dramatic change to the environment can cause widespread extinction.
Chapter V: Welcome to the Anthropocene
Mass extinctions began more than 450 million years ago, when fossil records indicate severe changes in climate occurred. These catastrophic changes were caused by the sharp rise and fall of atmospheric CO levels and altered the course of life on our planet. Too much carbon dioxide leads to increased temperatures and rising sea levels, and when carbon dioxide levels drop, temperatures fall and oceans are absorbed in ice, a process called glaciation. The first mass extinction, the end-Ordovician, was a period with such extreme glaciation that ninety percent life on earth did not survive.
Humans have dominated the natural processes of the planet, altering nearly half of all dry land, damming or diverting most major rivers, using more than half of the world's fresh water runoff, and changing the atmosphere through deforestation and fossil fuel combustion. The past two centuries have shown a forty percent increase in atmospheric CO levels and a doubling of the concentration of methane, an even more potent greenhouse gas.
Need to Know: Aside from the asteroid event that ended the Cretaceous period, the previous four mass extinctions have been tied to global cooling and warming events that triggered the end of most life on earth. Today, human activity has caused similarly drastic changes in atmospheric conditions.
Chapter VI: The Sea Around Us
Since the beginning of the Industrial Revolution, the burning of fossil fuels (coal, oil, and natural gas) has added approximately 365 billion metric tons of carbon dioxide to the atmosphere, and deforestation has contributed an additional 180 billion metric tons. As this process continues, the total concentration of carbon dioxide has reached the highest levels in the last eighty million years. In nature, where ocean meets air, gases from the atmosphere are absorbed and dissolved. When carbon dioxide dissolves in water, it forms carbolic acid, which lowers the pH level, resulting in a precipitous decline in the pH of the planet's oceans. Many marine species rely on a delicate balance in pH for calcification of shells and coral, so they are highly susceptible to ocean acidification. On a global scale, based on current rates of CO release, marine biologists predict entire marine ecosystems are on pace to "crash" due to ocean acidification.
Need to Know: Kolbert outlines the process of ocean acidification, which results from the rapid increase in atmospheric carbon dioxide levels. Human civilization has produced a historic level of carbon emissions which threaten nearly all marine life.
Chapter VII: Dropping Acid
Kolbert visits Australia's Great Barrier Reef, where coral cover has declined by fifty percent in the past thirty years. Coral reefs — part animal, part vegetable, part mineral — are a unique ecological structure responsible for providing food and protection to hundreds of thousands of marine species. Their construction and growth requires aragonite, a crystal form of calcium carbonate, which disintegrates under acidic conditions. Therefore, as carbon emissions persist, lowered pH inhibits the natural regeneration of coral. Rising ocean temperatures also disrupt equilibrium between coral and other species within the reef, leading to "coral bleaching" and eventual death of coral colonies. Scientists predict "reefs will be the first major ecosystem in the modern era to become ecologically extinct," likely in the next fifty years.
Need to Know: Coral reefs harbor half a million other species, yet they are highly susceptible to ocean acidification caused by carbon emissions. Large swaths of coral have already been lost around the world and may soon disappear, eliminating a vital ecosystem from the world's oceans.
Chapter VIII: The Forest and the Trees
The ecological diversity of the tropics is much greater than toward the earth's poles, a relationship known as the latitudinal diversity gradient. This diversity mimics coral reefs, where trees are the primary organisms supporting the life of forests. Plants themselves rely on other organisms for survival — birds disperse seeds and combat harmful insects, and helpful insects pollinate. This relationship, called the species-area relationship, has been studied by scientists to predict the extinction risk of global warming in regions like the Andean Amazon. Since tropical plant species are more sensitive to altitude and changes in temperature caused by global warming, they suffer when this delicate balance collapses. While some plant species thrive from increased carbon dioxide levels, their general lack of mobility threatens their survival amid increased temperatures. It is predicted nearly one-fourth of all tropical plant species will be fated to extinction in less than forty years. Beyond that, it is impossible to predict how plants, ill equipped to adapt to sudden change, will be able to survive.
Need to Know: Global warming threatens cold-loving species as much as tropical species. The vast and delicate ecological diversity of the tropics is just as fragile; 24% of all species will become extinct by 2050 due to global warming and climate change. Prominent scientists have called the scenario "apocalyptic."
Chapter IX: Islands on Dry Land
Humans have directly transformed more than half of the planet's fifty million square miles of ice-free land, and the remaining, untouched land has been separated by pipelines, ranches, hydroelectric projects, and more. Kolbert visits a group of scientists who study the effect of this fragmentation in the Brazilian Amazon by intentionally isolating plots of land into twenty-five acre "islands" of pristine rainforest surrounded by cleared scrub. Fragmentation separates species into smaller populations unable to support a stable number of members who can insulate themselves against natural calamities. Subsequently, species members outside of the islands cannot reach the dwindling survivors to recolonize. This phenomenon exacerbates extinction. Kolbert illustrates how one species of army ants lives in association with hundreds of other species. This level of interdependence has led scientists to estimate that the planet's tropical rainforests lose nearly five thousand species every year due to fragmentation.
Need to Know: As humans fragment the natural environment, small populations of isolated species become especially vulnerable.
Chapter X: The New Pangaea
Kolbert joins scientists in the northeastern United States to study the dwindling population of little brown bats, which have fallen victim to white-nose syndrome, caused by an invasive species of fungus accidentally imported from Europe by humans. While native species have always been threatened by foreign species — from fungus and bacteria to plants and rodents — modern travel and global trade have accelerated this process by accidentally transporting flora and fauna around the world. In effect, humans have removed important geographic boundaries to create a "New Pangaea." As various species are redistributed into non-native territories, they often thrive at the expense of local populations who are unable to adapt. Victims of this phenomenon range worldwide and include the American chestnut, the Central American wolfsnail, and the Guam flycatcher. From 2007 until 2013, it is estimated that white-nose syndrome has spread to twenty-two states and five Canadian provinces, killing more than six million bats. In less than ten years, the little brown bat has become an endangered species.
Need to Know: While humans have fragmented land and isolated species, they have also introduced invasive species as a potent mechanism of the sixth extinction. The increased pace and volume of global trade has precipitated the extinction and steep decline of numerous species, such as the little brown bat.
Chapter XI: The Rhino Gets an Ultrasound
Of all the endangered species humans work to save, large animals are the most visible and most vulnerable. Kolbert takes readers to the Cincinnati Zoo, where zoologists attempt to breed the Sumatran rhino, whose ancestors were victims of habitat fragmentation in the rainforests of Southeast Asia during the last century. Humans have been a major threat to populations of megafauna like rhinos and the moa of New Zealand since well before the industrial age. These outsized creatures once dominated the food chain, but ten to fifteen thousand years ago, as humans began to hunt large animals for food, "'the rules of the survival game' changed." Many large animals' primary evolutionary weakness in the face of human civilization is a long gestation period, which prevents repopulation at the same rate of decline.
Need to Know: With fewer than one hundred members worldwide, the Sumatran rhino is another example of the threat posed by fragmentation, and efforts to save the remaining population outside of its natural habitat are proving futile. While prevailing theories of the Anthropocene suggest the impact of humans began with the Industrial Revolution, our species has threatened the populations of megafauna like the rhino since the Stone Age.
Chapter XII: The Madness Gene
For nearly one hundred thousand years, Neanderthals ranged from Europe to the Middle East and shared many traits with humans: constructing tools, building shelters, fashioning clothing, and caring for members of their tribe. Thirty thousand years ago, Neanderthals disappeared. Archaeological records indicate humans made contact with Neanderthals in various regions, and molecular sequencing projects show the genetic code of modern humans is one to four percent Neanderthal, evidence the two species interbred and cohabitated. Paleogenticists like Svante Pääbo study why humans overtook Neanderthals to become the dominant species. One theory is humans' desire to disperse and explore, leading our species to venture across land bridges and open water to places like Australia and the Americas. Pääbo and others investigate our genetic code to isolate this behavior, without which Neanderthals and many other species would still exist.
(Continues...)
Excerpted from Summary and Analysis of The Sixth Extinction: An Unnatural History by Worth Books. Copyright © 2017 Open Road Integrated Media, Inc.. Excerpted by permission of OPEN ROAD INTEGRATED MEDIA.
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Table of Contents
Contents
Context,Overview,
Summary,
Timeline,
Cast of Characters,
Direct Quotes and Analysis,
Trivia,
What's That Word?,
Critical Response,
About Elizabeth Kolbert,
For Your Information,
Bibliography,
Copyright,