49 pages • 1 hour read
Elizabeth KolbertThe Sixth Extinction: An Unnatural History (2014)
Nonfiction | Book | Adult | Published in 2014A modern alternative to SparkNotes and CliffsNotes, SuperSummary offers high-quality Study Guides with detailed chapter summaries and analysis of major themes, characters, and more.
Chapters 10-11Chapter Summaries & Analyses
Chapter 10 Summary: “The New Pangaea: Myotis lucifugus”
Kolbert opens this chapter by describing the hibernation processes of bats. This species prepares to hibernate in the late fall months by dropping their body temperature roughly 60 degrees; then “[i]ts heartbeat slows, its immune system shuts down, and the bat, dangling by its feet, falls into a state close to suspended animation” (193). When a group of wildlife biologists from Albany, New York conducted a bat census in a cave near the city in March 2007, they found nearly all the bats dead. Panicked, they brought back carcasses to test and photographed the few live bats remaining.
Upon examination, it looked like the bats had “been dunked, nose first, in talcum powder” (193), something these scientists had never seen before. The biologists reached out to colleagues, but no one had any idea what could have killed off so many bats. Al Hicks, the group’s supervisor, hoped that it was a one-off situation, but by the next winter, the situation had only worsened. Thirty-three bat caves in four different states contained dead bats covered in the powdery substance. Kolbert notes that “in some hibernacula, populations plunged by more than ninety percent” (194).
Over the next two winters, the powdery disease continued to spread, appearing in five more states one year, then three more states the year after that. Scientists eventually determined that the powder is a cold-loving fungus (psychrophile) that was inadvertently brought to America from Europe. The fungus at first had no name aside from its genus, but because of its impact on the bat population, scientists called it Geomyces destructans.
Before humans accidentally, or in some cases purposefully, carried different species to other parts of the world, species travel was limited by topography, especially oceans. Geographical barriers explain why different varieties of species (sometimes related, sometimes not) have been found on either side of oceans, mountains, and major rivers. Darwin called this process “geographical distribution” (196), although scientists would not recognize some of the implications of this process until the late nineteenth century.
Then, in the early 1900s, Alfred Wegener, a German meteorologist, argued that the continents must have shifted at some point, breaking apart and separating from each other over the course of time. This concept was called “continental drift,” and although Wegener was mocked for his theory during his lifetime, future proof showed that due to plate tectonics, he was right.
Because of the rapidity and mass of human transportation, species are now being carried all over the world, and at such a fast rate that in many places “non-native plants now outnumber native ones” (198). A supertanker or a passenger jet can not only defeat the forces of geographic separation; they can also introduce thousands of different species to new environments.
Kolbert teams up with Hicks to go on a bat census count near the Adirondacks. They travel down into an abandoned mine shaft that the bats have used as their home. The resident bats included small-footed, little brown, and Indiana bat varieties. Some of the bats are found with the white fungus on them; their necks are snapped and then the bodies placed in plastic baggies to be taken back for testing. Kolbert states that no direct reason has yet been found for why the fungus kills bats, except that it disrupts the bats’ hibernations by eating away at their skin. The irritation prompts the bat to use fat stores that were meant for hibernation, and then the bats fully wake up and fly outside looking for insects to eat. Because it is winter, there are no insects available, and the bats end up starving to death.
Kolbert explains that when a new organism appears in a stable environment, it can do one of two things: it dies because it cannot survive the new culture, or it survives and then produces a whole new generation of “invasive species,” a process known as “establishment.” The spread of invasive species threatens to cause the extinction of many native species in various environments. The success of invasive species may also be due to a relocation away from predators (“enemy release”).
Kolbert provides an example in the brown tree snake, which was transported from northern Australia to Guam by boat. Unaccustomed to snake species, the birds of Guam were not prepared for the destruction this snake would cause. The snake destroyed most of the island’s native birds, some of whom had to be kept in a captive breeding program to stave off extinction. The brown snake also decimated the island’s bat populations; of the three native species, only one remains today.
Hicks and his bat researchers suspected an invasive species was behind the abrupt and mysterious bat deaths. They determined, based on the mortality rate and the locations where the fungus spread, that it was probably brought into the Albany area via a commercial cave featuring underground boat trips that entertains 200,000 visitors each year.
The New Pangaea is a concept posed by biologists that states that the way in which species have been transported around the world was also a way of recreating the one supercontinent that existed at one time on the planet. Considering that the most invasive species on earth has been humanity, the “establishment” of new species in environments unfamiliar to them has existed for thousands of years. Ultimately, scientists believe this process will result in “total global homogenization” (212). The world’s species will become less complex, and far more deficient in nature and quality.
Kolbert visits the Albany bat caves again a year later, only to see the same mortality results due to the fungus. The scientists note that the bat population cannot procreate quickly enough to make up for the stunning devastation done to their numbers. Since her last visit to the caves, Kolbert states that the fungus has spread to Canada, as well as twenty-two other American states. The little brown bat that had been so ubiquitous is now an endangered species in states like Vermont.
Chapter 11 Summary: “The Rhino Gets an Ultrasound: Dicerorhinius sumatrensis”
At the Cincinnati Zoo, Kolbert is introduced to Suci, a Sumatran rhino born at the zoo in 2004. The Sumatran rhino is the smallest of the five remaining rhino species. As the oldest rhinos, the Sumatran’s genus stretches back twenty million years, making the Sumatran the “closest living relative to the woolly rhino” (217). The Sumatran rhino is a shy loner who hides in dense undergrowth. Procreation only happens if the female, an induced ovulator, releases an egg when she senses an eligible male nearby.
For Suci, there are no males nearby, so Dr. Terri Roth, the zoo’s director of Conservation and Research of Endangered Wildlife, has been working to inseminate the rhino artificially. Kolbert watches with a crowd of zookeepers as Roth checks to see if Suci, who was given a hormone injection to stimulate ovulation the week before, has in fact ovulated. After a few minutes of examination, Roth declares that Suci had not ovulated. The entire crowd is disappointed by the news.
The Sumatran rhino originated in the Himalayas through India and Myanmar, and on the islands of Sumatra and Borneo. The rhinos’ habitats shrank as the deforestation of Asia’s forests began, leading to a severe decrease in population. By 1984, the species was headed toward extinction, and so captive breeding programs were established around the world to prevent the total loss of these rhinos.
The captive breeding programs ran into difficulty immediately, with some of the rhinos contracting illnesses spread by flies, some injured during their captures, and others dying from tetanus. Worse, none of the captive rhinos were breeding. Unfortunately, the rhinos had only been fed hay in the programs, a roughage on which Sumatran rhinos cannot live. Their dietary requirements include branches and fresh leaves. Because the seven rhinos sent to America were at seven different zoos, the odds of sustaining the breed seemed faint at best.
As a final attempt to save the species, two rhinos from the Los Angeles and Bronx Zoos were sent to Cincinnati, where one surviving male bull lived. Roth was brought to the Zoo to manage and save the species, a tall order because, as Roth says, “[i]t’s a very complicated species” (219). After months of hypothesis, Roth realized that the female needed to sense the male nearby for ovulation to occur. Finally, the male rhino impregnated the female, but she miscarried five times.
When the female rhino became pregnant again, Roth gave her liquid hormone supplements and created more shaded areas for both animals. This treatment was effective, and the female gave birth to a calf, followed by two more, including Suci. One of the young calves was sent back to Sumatra and fathered another calf there. While the breeding success has been heartening, thus far these are the only Sumatran rhinos born in captivity. Kolbert soberly notes that “humans have brought the species so low that it seems only heroic human efforts can save it” (220).
The Sumatran rhino scenario has been repeated with other rhino species, including the Javan, the Indian, and the black rhino. Again, humans are at the heart of their decline in numbers and endangered statuses. Poachers kill rhinos for their horns, which they sell on the black market for $20,000 a pound. Other animal species, like Asian and African elephants, as well as some large cats, are in similarly dire straits.
Kolbert revisits Suci and reflects on the “advantages of being oversized” (224), wherein large species, like adult rhinos, have no natural predators. At various times in Earth’s history, large animals have ruled the earth, including the dinosaurs, the woolly rhinos, cave bears, grizzly-sized beavers, mastodons, mammoths, and giant elk. Even small islands were home to larger beasts such as dwarf hippopotamus, giant lemurs, and elephant birds. All these species died out, and in ways that seem eerily similar to the ecological circumstances currently observed around the world.
During her trip to the Big Bone Lick, Kolbert considers past scientists’ views that natural climate change causes extinction. If this stance is valid, then the human impact on climate is deeply alarming because of it has sped up the process. If, instead, it is human activity that is causing climate warming and species extinction, then the current world circumstances are devastating to animal life. Kolbert argues that the second of these theories—human fault—is the correct one. There are too many examples in the geological records of large species going extinct at precisely the same time that humans arrived in those areas. More evidence continues to be found that many previous extinctions could not have been caused directly by climate change, but only by a change driven by humankind.
Some scientists still question this proof, arguing that a primitive people could not have wiped out entire species of large animals. But John Alroy, a paleobiologist at Macquarie University, Australia, points out that most larger animals didn’t begin reproducing until their teens, and often only had single offspring after a lengthy gestation period. In other words, the length of time needed to procreate worked against the larger species once humans appeared on the scene and killed them—what Kolbert refers to as the “overkill hypothesis” (233).
Although the Industrial Revolution is looked to as the period where humans became a “life-altering force” (234), Kolbert argues that humans have always been “life-altering,” from the moment they first emerged. This is the reason why large animals still in existence, like Suci the Sumatran rhino, are facing extinction.
Chapters 10-11 Analysis
Where does the responsibility lie for the extinction of species: with natural ecology or humanity? Kolbert provides a few different examples that, paired with information provided by scientists, indicate that humanity is at fault for the rapid climate change that leads to species extinction.
In Albany, New York, Kolbert sees firsthand the damage done to once prolific bat species that were exposed to a deadly fungus brought to the area via water. The fungus originated in Europe, demonstrating that human transportation has caused a mixing of species all over the globe. Unfortunately, many of these mixes end up being deadly for one or more species, as native species are not equipped to handle a disease or another animal that is not natural to their environment.
Kolbert notes that, ironically, man has caused a mixing of species not unlike what the world was like originally, when there was a single continent. This phenomenon is referred to by scientists as the New Pangaea, and it may result in fewer species of a less complex order.
In Chapter Eleven, Kolbert discusses how many large species went extinct or nearly extinct at different points in history. While some scientists believe that earlier extinction events were caused by natural climate change, Kolbert believes that humans are responsible, as many large species disappeared at the same time that humanity was coming to power in their region. For this reason, rhinos like Suci and other large animals have gone extinct or face extinction.
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