The Sixth Extinction Chapter Summary

The Sixth Extinction: An Unnatural History details the continued loss of biodiversity that has occurred since the rise of mankind. Elizabeth Kolbert claims that we are now in the midst of a sixth mass extinction, and that, if precautionary measures are not taken, the loss of biodiversity would be catastrophic. Chapter one begins by describing the golden frogs in the town of El Valle de Antón, and how they were beginning to disappear. The frogs disappeared due to a fungus called Batrachochytrium dendrobatidis. This fungus has spread around the world at a lightning-quick rate, killing all sorts of amphibious organisms at an unnatural rate. The cause of the rapid spreading of the fungus has been theorized to be due to humans inadvertently spreading

it around the world or due to humans introducing infected bullfrogs to new ecosystems. Ultimately, the source is still human action, and, as a result, humans are to blame for the loss of the frogs.
Kolbert’s second chapter describes the concept of extinction. The concept of species going extinct was not always accepted as fact. It wasn’t until the discovery of the American mastodon that the concept of extinction was even considered. With the discovery of the bones, When the bones were discovered, many theories were constructed, such as that the bones were actually from multiple creatures, or that this was simply an undiscovered species and hadn’t been found. The discovery of other mysterious, lost species led to the concept of extinction, and the idea that the mammoth was indeed a species that, while it once was prevalent, no longer roamed the Earth. In chapter three, Kolbert writes about her visit to Iceland in which she learned about the loss of the great auk, a three foot tall bird reminiscent of a large penguin or puffin. She then proceeds to write the tragedy of the great auks, that being that they were regularly hunted and killed. The final moments of the great auk’s species can be tracked down, as they were captured and sold and their only egg was broken. The concept of human-caused extinctions wasn’t new, as Darwin wrote about how the Galápagos tortoises were dying out very rapidly due to overhunting. The extinction of species stems from events that drastically affect them, be them environmental changes to human meddling.
Chapter four of The Sixth Extinction begins with the theory of the iridium asteroid that crashed into the Earth and killed much of life in the Cretaceous period. The chapter then moves to Kolbert’s experience with ammonite fossils in Princeton, New Jersey. While the distinct spiral shape of ammonites is well-known and agreed upon, the exact shape and structure of the mollusk in the shell is heavily debated. Ammonites are then compared to nautiluses, living animals that heavily resemble ammonites, in terms of why one species was able to flourish, while the other was wiped out. Chapter five lays out the concept that ordinarily species go extinct at a gradual, slow pacing, unless of course there is a catastrophic event, such as human meddling or a giant asteroid, in which case the extinction process is expedited. The extinct species that Kolbert studies in this chapter is the graptolite, a long, thin, V-shaped marine animal. The extinction of grapolite is theorized to be due to a drastic change in the ocean. Kolbert additionally tells a theory that, in the future, rats will be the predominant race on Earth, overtaking even humans. This is all based on the fact that humans have too drastically changed the Earth’s composition and wherever humans go and change, rats are there to follow. Thus we are ushering in the Anthropocene, or the “age of humans,” a time period in which humans have wrecked up the planet to the point of no return.
In chapter six, Kolbert visits Castello Aragonese and learns that on the sea floor, there are high levels of carbon dioxide that are causing a decline in marine life. The high amounts of carbon originated around the time of the Industrial Revolution, in which fossil fuels were burned leading to an astronomical rise in carbon in the air and water. The carbon dioxide in the ocean is harming many of the organisms within its ecosystem, to the point that some sea creatures were losing their hard shells to erosion caused by the carbon dioxide. The more fossil fuels mankind uses, the more acidic and deadly the ocean is going to become for its organisms. Following this in chapter seven, Kolbert visits One Tree Island, right off the coast of Australia, where she learns about coral reefs and how they are slowly dying. The carbon dioxide in the water is eroding the calcium in the corals, however that is not the only threat that they face. The rising temperature is affecting the reefs, as the warmer water becomes, the more algae and plankton appear in the ocean, which would throw off the whole balance of the ecosystem. Slowly, the coral reefs are going to completely die, and there isn’t much that humans can do to stop it.
Chapter eight delves into the concept of the tropics, and how they are hubs of biodiversity.

However with the rising temperatures in the tropics, the plants and animals are moving to higher and higher altitudes. The most concerning issue is that the climate seems to be rising at an alarmingly fast rate. At this rate, some species will not be able to migrate quick enough to survive the sudden rise in temperature. Many, many species are going to die out thanks to the change in climate. In chapter nine Kolbert writes about the lack of undeveloped land that is left in the world. The little land that has remained undeveloped exist as small ‘islands’ within an ocean of developed land. In one of these land ‘islands,’ Kolbert discusses the decline in species of birds. These islands also have an overall lower biodiversity when compared to the surrounding land, which can be attributed to the severely limited amount of space and organisms that can live in the space. One of these islands, a rainforest, has an amazingly large amount of biodiversity. However due to the small space available, the biodiversity is dropping at a rapid rate. This is bad for the ecosystem as a whole, since if one organism goes extinct, all of the other species are affected in some

way.
Chapter ten opens with a shocking image: bats that one would expect to be hibernating show up dead on the ground, surrounded by the fungus that murdered them.

Kolbet then goes on the tell that this is due to invasive species: species that are introduced to an area where they are not native. This can lead to two outcomes: either the species will not be well suited for the new environment, and as such will die out very quickly, or the new species will flourish and the organisms that lived there before will be killed as they have no defense mechanisms to defend themselves. Humans are the leading cause of invasive species, as we transport organisms around the world. Kolbert then moves to chapter eleven in which she visits a zoo and finds a sumatran rhino that is one of five that are still living on the planet. These rhinos were once found all over the Himalayas, however when they began to become endangered, people swooped in to try to save the species. The people saved some rhinos, however the rhinos were unable to live under the various conditions that existed in the zoos. Eventually, they decided to artificially inseminate the rhinos, in hopes that the species would continue living. Kolbert then asks a question: why is it that giant animals go extinct so quickly? It is theorized that climate change could have killed many species, but the more likely answer is that humankind killed these giant animals. Prior to the rise of mankind, being a large creature was advantageous,

however once humans discovered these large, slow creatures, the power dynamic was shifted completely, and these creatures were easily hunted to extinction.
Chapter twelve focuses on the neanderthals, a species that, while very similar to modern humans, are still a different species. Neanderthals are different physically, however in actuality, neanderthal DNA is quite similar to human DNA, though some people have more in common with them than others. Eventually, however, the neanderthals could not continue to reproduce quickly enough, and as such, they died out. Kolbert’s final chapter begins at the ‘frozen zoo,’ a kab in which the final remains of an extinct species of bird are housed. When a species is nearing extinction, teams of scientists will do whatever it takes to save them, even going so far as to salvage the genetic remains, in hopes that one day, we can do something to bring them back. She then moves on to discuss the Anthropocene era, the Sixth Extinction. Kolbert shows that so many species are dying out, and who is to say that humans are not next? Right now, mankind should be trying to do what it can to salvage the life on earth and save the creatures. The responsibility falls to the humans.