The Sixth Extinction (book)
|Country||United States, United Kingdom|
|Subject||Conservation science, Wildlife, Epochs, Holocene extinction, The Anthropocene, Geology, Archaeology, Biology, Zoology, History of mass extinctions|
|Genre||Nonfiction popular science|
|Published||2014 (Henry Holt & Company)|
|LC Class||QE721.2.E97 K65 2014|
|Preceded by||Field Notes from a Catastrophe|
|Text||The Sixth Extinction (book) at the book publisher's website|
The Sixth Extinction: An Unnatural History is a 2014 nonfiction book written by Elizabeth Kolbert and published by Henry Holt & Company. The book covers past mass extinctions and demonstrates that the earth and humans are in the midst of a "sixth" mass extinction. She chronicles previous mass species extinction events, as well as specific species extinguished by humans thousands of years ago, such as the great auk; and she includes the accelerated widespread extinction of many species during our present time. Kolbert also describes prehistoric and historic ecologies surrounding prior and near-present species extinguishing events. The author received the Pulitzer Prize for General Non-Fiction for the book in 2015.
The target audience is the general reader, and scientific descriptions are rendered in understandable prose for the lay reader. The clear writing blends explanations of her treks to remote areas with interviews of scientists, researchers, and guides, without advocating a position, while maintaining objectivity. Hence, the sixth mass extinction theme is applied to flora and fauna existing in diverse habitats such as the Panamanian rainforest, the Great Barrier Reef, the Andes, Bikini Atoll, city zoos and the author's own backyard. The book also applies this theme to a number of other habitats and organisms throughout the world and its oceans. When researching the current mainstream view of the relevant peer reviewed science, she estimates flora and fauna loss by the end of this century to be between 20% to 50% "of all living species on earth".
- 1 Anthropocene
- 2 The author
- 3 Discovery
- 4 Summary of Chapters
- 4.1 Chapter 1: The Sixth Extinction
- 4.2 Chapter 2: The Mastodon’s Molars
- 4.3 Chapter 3: The Original Penguin
- 4.4 Chapter 4: The Luck of the Ammonites
- 4.5 Chapter 5: Welcome to the Anthropocene
- 4.6 Chapter 6: The Sea Around Us
- 4.7 Chapter 7: Dropping Acid
- 4.8 Chapter 8: The Forest and the Trees
- 4.9 Chapter 9: Islands on Dry Land
- 4.10 Chapter 10: The New Pangaea
- 4.11 Chapter 11: The Rhino Gets an Ultrasound
- 4.12 Chapter 12: The Madness Gene
- 4.13 Chapter 13: The Things with Feathers
- 5 Sources
- 6 Awards and honors
- 7 See also
- 8 References
- 9 External links
Kolbert equates general current unawareness of this issue to the previous widespread disbelief during the centuries preceding the late 1700s; at that time it was believed that prehistoric mass extinctions had never occurred. It was also believed there were no natural forces powerful enough to extinguish species en masse. Likewise, in our own time, the possible finality presented by this issue results in denialism. Human behavior disrupts earth's balanced and interconnected systems "putting our own survival in danger." Consequently, the earth systems currently affected are: the global atmosphere, the water cycle, the ocean's thermal or heat absorption, ocean acidity and coral reefs, soil moisture and drought conditions, plant destruction by pests or non-indigenous fauna or heat stress, heat regulation by the earth's ice, and so on.
The human species contributes to this disruption - even without intending to - because of our innate capabilities to alter the planet at this stage of our cultural evolution; for instance, we now have the ability to harness energy from beneath the earth's surface. Homo sapiens also has the ability to adapt relatively quickly to almost any environment on this planet's surface. Other species, however, have a hard time relocating to new, suitable habitats. They are unable to migrate ahead of current rapid ecological changes, or are hampered by artificial barriers such as roadways, cityscapes, and suburban sprawl, which cause increased discontinuity between viable habitats throughout world.
Elizabeth Kolbert, a science writer, is a staff writer at The New Yorker magazine, and is the author of Field Notes from a Catastrophe and several other books. Her writing focuses on the effects of humans and civilization on our planet’s ecosystem. She writes her experiences of various locations, as noted above. Previously, she was a reporter for the New York Times. Kolbert resides in Williamstown, Massachusetts with her husband and children, and she writes in her home office across from Mount Greylock in Massachusetts. Pertaining to this book, Kolbert has been interviewed by national news and media organizations.
Kolbert's decision to write this book followed first from a 2008 Proceedings of the National Academy of Sciences paper that she fortuitously read. This paper is entitled "Are We In the Midst of The Sixth Extinction." The second step toward writing this book came out of an article she wrote for the New Yorker magazine. This involved becoming aware of the condition of amphibians in Panama. She realized that she "hadn't scratched the surface, that there was a book there." 
Summary of Chapters
Chapter 1: The Sixth Extinction
The ancestors of the frogs crawled out of the water around 400 million years ago. 250 million years ago, frogs were the earliest representation of what would become the modern amphibian orders. Amphibians have been on Earth for longer than mammals or birds; they were even here before dinosaurs. Recently, it has been reported that the extinction rate of frogs is increasing. Based on observed extinction rates far beyond expected background extinction rates, we can predict that an event of a similarly catastrophic nature is headed our way. A decade ago, Panamanian golden frogs were plentiful in numbers and easy to find around Panama. However, within the past couple of years, the frogs started to disappear. Kolbert states that studies by the National Zoological Park in Washington, DC and a mycologist at the University of Maine have identified the reason for the increased mortality of Panamanian frogs as a type of Chytrid fungus. However, Chytrid fungi are not naturally found in Panama. This left a puzzling question: how did the fungus get to Panama? Evidence indicates that humans were instrumental in how the fungus traveled. Kolbert uses the frog-fungus relationship as a symbol of how humans are introducing invasive species to species who would normally have the proper distribution of alleles for their environment.
Chapter 2: The Mastodon’s Molars
Kolbert explains how fossils of the American mastodon (Mammut americanum) shaped Georges Cuvier’s views on catastrophism. According to Cuvier, there was no reason the mastodon should have died out. The mastodon was large enough to avoid predation, had large enough teeth to consume an abrasive diet, and had other phenotypes that should have increased its survival. Cuvier concluded there must be sudden and violent natural catastrophes that could cause mass extinction of viable species. Kolbert uses the mastodon as a symbol for the idea that catastrophe is an important mechanism of extinction.
Chapter 3: The Original Penguin
The great auk was a large flightless bird that lived in the Northern Hemisphere. It had a large, intricately grooved beak. When the first settlers arrived in Iceland, the auk population was probably in the millions. However, the settlers found the auks to be “very good and nourishing meat.” They also used their oily bodies for fuel and fish bait, and their feathers for stuffing mattresses. Kolbert uses the great auk as a symbol of how human overexploitation resources is an important mechanism of extinction.
Chapter 4: The Luck of the Ammonites
Kolbert explains that the main cause of the Cretaceous-Paleogene extinction event was not the impact of the asteroid itself. It was the dust created by the impact. The debris from the impact incinerated anything in its path. She states that it is impossible to estimate the full extent of the various species that died out due to this catastrophe. Kolbert explains that even though amniotes were ‘fit’ for their current environment, a single moment can completely change which traits are advantageous and which are lethal. 
Chapter 5: Welcome to the Anthropocene
Kolbert uses the extinction of graptolites and other clades to explain glaciation as a mechanism for extinction. When carbon dioxide levels in the air are high, there typically is an increased level in temperatures and in sea level. Right around the time graptolites went extinct, carbon dioxide levels dropped. Temperatures fell and sea levels plummeted. This caused a change in the chemistry of the ocean. This can cause a devastating impact on life forms. Kolbert states that human activity has transformed between a third and a half of land surface on the planet. We have dammed most of the major rivers of world, increased levels of nitrogen to levels higher than can be fixed naturally by terrestrial ecosystem, used more than half of the world’s readily accessible freshwater run-off, removed more than one third of the primary producers of the oceans’ coastal waters, and changed the composition of the atmosphere by deforestation and fossil fuel combustion. 
Chapter 6: The Sea Around Us
Since the beginning of the industrial revolution we have seen increasing levels of carbon dioxide in the atmosphere at an alarming rate. Studies show we have added approximately 365 billion tons by burning of fossil fuels and an additional 180 billion tons as a result of deforestation. We add another 9 billion tons or so a year, an amount that has been increasing 6% annually. Essentially, we have increased the concentration of carbon dioxide in the air to higher than it has been in the last several million years. Some of this carbon dioxide is being absorbed by our oceans to create carbonic acid. This is lowering the pH of our ocean and killing much of our marine life. Kolbert uses the drastic decline in life forms around the Castello Aragonese as a warning sign of what is to come if we continue to increase carbon dioxide levels in the atmosphere.
Chapter 7: Dropping Acid
Coral reefs support thousands of species by providing food and protection. Subsequently, many species have co-evolved with corals. Due to ocean acidification, it is very possible that corals will become extinct by the end of the century. Prior to the industrial revolution, underwater reefs had an aragonite saturation state between 4 and 5. However, if current emission intensities remain as they are today, by 2060, there will no longer be a region above 3.5. This will lead to an increase in energy needed for calcification. The same energy that will be expended on calcification is vital to recover from being eaten away by marine species and being battered by waves. Corals prove to be a symbol of ocean acidification as mechanism of extinction.
Chapter 8: The Forest and the Trees
Global warming is most commonly seen as a threat to cold-loving species. As temperatures rise, the ice at the North Pole and South Pole will melt. Any living thing that depends on the ice will be faced with extreme challenges that could ultimately drive them to extinction.  Kolbert points out that the poles are not the only places affected by global warming, and that other areas have much higher latitudinal diversity gradients. She discusses the work of scientists who have used measures of species-area relationship to model possible effects of global warming. The extent to which species are mobile and can relocate to new areas in response to shifting climate conditions is predicted to be a significant factor in possible species extinction. This has particular importance for trees and other plant species. Even more difficult to estimate is the extent to which ecological communities of species will be able to tolerate disruptive changes. Kolbert explains that climate change is a major force in mass extinction.
Chapter 9: Islands on Dry Land
Kolbert points out how everything in life is interconnected, and discusses the importance of patch dynamics. Over time, fragmentation of environmental areas leads to a decrease in the number of species in an area. This may occur in part because the size of such "islands" is too small to support a stable number of species members, in part because smaller populations are more vulnerable to chance events, and in part because the disconnection of islands makes it more difficult for species to reach and recolonize them. One researcher describes this as "an obstacle course for the dispersal of biodiversity.":189 Kolbert also notes that the life-forms and habits of many species can be highly specialized. She explains that one minor change can cause a domino effect in various ecological systems.  
Chapter 10: The New Pangaea
Kolbert points out there is an evolutionary arms race in which each species must be equipped to defend against their potential predators and to be more fit than their competition. A species has no defense if it encounters a new fungus, virus, or bacterium. This can be extremely deadly, as occurred in the case of American bats killed by the psycrophilic fungus Geomyces destructans. Another example of this occurred in the eighteen hundreds. The American chestnut was the dominant deciduous tree in the eastern forests. Then, a fungus (Cryphonectria parasitica) started to cause chestnut blight. It was nearly 100% lethal. The fungus was unintentionally imported to the U.S. Kolbert points out that global trade and travel are creating a virtual "Pangaea", in which species of all kinds are being redistributed beyond historical geographic barriers. This furthers the idea of the first chapter that invasive species are a mechanism of extinction.
Chapter 11: The Rhino Gets an Ultrasound
The Sumatran Rhino was once so abundant in numbers it was considered an agricultural pest. However, as Southeast Asia’s forests were cut down, the rhino’s habitat became fragmented. In the 1900s, the rhino population had been shrunk to just a few hundred. Today, there are only four living rhinos.  Kolbert uses the rhino to show habitat fragmentation as a mechanism of extinction.
Chapter 12: The Madness Gene
Europe was the home to Neanderthals for at least a hundred thousand years. Then, about 30,000 years ago, the Neanderthals vanished. Fossil records show that modern humans arrived in Europe 40,000 years ago. Within 10,000 years, Neanderthals were bred out. Through molecular sequencing, we have found that there is 1-4 percent Neanderthal DNA in all non-African humans. This indicates that humans and Neanderthals reproduced. Then the resulting hybrids reproduced. The pattern continued until Neanderthals were literally bred out. Kolbert states there is every reason to believe that Neanderthals would still exist if it weren’t for humans.
Chapter 13: The Things with Feathers
Kolbert concludes with the hope in humanity, pointing to various effects to conserve or preserve species. Whether meaning to or not, we are deciding which evolutionary pathways will be shut off forever and which can be left open to flourish.
Some sources for the book are: The Song of the Dodo by David Quammen, The Ghost With Trembling Wings by Scott Weidensaul, as well as reports from Edward O. Wilson, a biologist. The pioneering studies of naturalist Georges Cuvier and geologist Charles Lyell are also referenced . The book's title is similar to a 1995 book titie, The Sixth Extinction: Patterns of Life and the Future of Humankind by Richard Leakey and Roger Lewin. Also included are interview results from a forest ecologist, atmospheric scientist Ken Caldeira, wildlife and conservation experts, a modern day geologist, and fungus research in New England and New York state.
Awards and honors
- 2014 National Book Critics Circle Award (General Nonfiction) finalist
- 2014 Library Journal Top Ten Book
- 2015 Pulitzer Prize for General Non-Fiction
- http://www.pulitzer.org/citation/2015-General-Nonfiction Pulitzer citation
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