The “sixth global extinction” has already begun, and its cause is humanity

    05 Sep 2021

    Elizabeth Kolbert’s book, “The Sixth Extinction: An Unnatural History,” was a “hit” in 2014 among the nature conservation community. The author received the Pulitzer Prize for General Non-Fiction for the book in 2015. Its title will intrigue those unfamiliar with the most recent theories of mass extinction.

    Kolbert (born 1961) is an American journalist, author, and visiting fellow at Williams College. She is best known for her book “The Sixth Extinction…,” and as an observer and commentator on environmentalism for The New Yorker magazine. Like “The Sixth Extinction,” her writing and other books, such as “Field Notes from a Catastrophe” and “Under a White Sky,” often explore the crisis faced by humans in the Anthropocene.

    Let me describe in brief the content of the book, with the necessary spoilers.

    The popular science essays tell us about the struggle of scientific concepts, starting from the 17th century. It wasn’t always the generally accepted point of view that species, in principle, are capable of extinction. The author clearly shows that this opinion prevailed only through the efforts of Georges Cuvier at the beginning of the 19th century. Then scientists debated whether an extensive array of species could disappear in a short period (the classic of biology Charles Darwin disagreed with this opinion). Further, the scientific community recognized the hypothesis of catastrophic extinctions, but there were disputes about the nuances. For example, could an asteroid be the cause of a speedy extinction?

    By the way, the “asteroid” hypothesis is relatively young; scientists published the first article with its presentation in 1980.

    The Alvarez hypothesis posits that the mass extinction of the non-avian dinosaurs and many other living things during the Cretaceous-Paleogene extinction event was caused by the impact of a giant asteroid on the Earth. Evidence indicates that the asteroid fell in the Yucatán Peninsula, at Chicxulub, Mexico. The hypothesis is named after the father-and-son team of scientists Luis and Walter Alvarez, who first suggested it in 1980.

    After reading the critical chapters of Kolbert’s book, it becomes clear that we humans are an analog of that very asteroid. We are here and now causing damage to the planet’s ecosystems, comparable to the previous “five great extinctions.”

    In general, the book will not open fundamentally new secrets for the audience curious about paleontology and zoology, but it structures a lot in mind.

    Colbert writes that we realize the very idea of extinction very early: we all played with plastic dinosaurs as children and at some point began to recognize that these animals no longer exist.

    Six ideas from the book “The Sixth Extinction”

    The scale of the transformations we are witnessing now is difficult to assess without a broader context. Probably, for this reason, the author resorts to excursions into the distant past.

    Thus, five global quantitative and qualitative changes in biodiversity have taken place on Earth before. Why now we talk about the sixth extinction and associate it with human activity? What makes Homo sapiens actions so unique, commensurate with the effect of a falling asteroid (because of which dinosaurs began to die out)?

    The author refers to Nobel Laureate P. Krutzen. He introduced the term “Anthropocene” to denote the modern era in which humans dominate.

    What grounds do we have to talk about a particular era?

    Krutzen notes that:

    ·        humanity has changed from a third to a half of the land area;

    ·        humanity blocked most rivers or changed their channels;

    ·        fisheries take more than a third of the primary output of coastal ocean waters.

    Thus, our activity not only changes the world but also transforms it.

    What are the consequences?

    We are destroying certain species of animals and changing the course of evolution: the future development of biodiversity depends on which animals survive now; they will be the new starting point. The evolutionary tree changes shape because whole branches disappear from it. In emotionless scientific terminology, this is formulated as “the human tendency to redistribute life.”

    The extermination of animals is not limited to hunting or fishing. (Although the author gives examples of barbaric poaching, e.g., the extermination of the Great auk). Indirect effects on populations can be even stronger. For instance, traveling between continents, people involuntarily carried with them different species of rats. Getting into a new environment and not coming into contact with the usual predators, rats quickly began to reproduce – and destroy the local flora and fauna. As a result, forests and endemic animals were affected even on remote islands, where people did not think to settle. They did not hunt or built something – it was enough for travelers to stop the ship on the island for a short time.

    None of us also thought that humans transported from continent to continent a fungus called Bd, which destroys whole species of frogs. It causes the disease chytridiomycosis in amphibians.

    Using the example of some Panamanian frogs, Kolbert shows the rate of extinction: animal species may become extinct before biologists have time to discover and describe them. Extinction is happening so fast that we don’t even always notice the loss!

    Coral reefs (common to the inhabitants of the Arabian Gulf) may not survive the Anthropocene. Different researchers call different dates of disappearance. Some argue that reefs will live to the maximum by the end of the 21st century; some give them even less time.

    Coral reefs are considered one of the ecosystems most vulnerable to climate change and other anthropogenic impacts, with predictions that 60% of the world’s coral reef area will be lost by 2030 (Hughes et al., 2003), or worse, and reefs will suffer near-total destruction – with precedent in the geological past (Pandolfi & Kiessling, 2014).

    Not only can corals themselves disappear, but also mollusks, fish, starfish, and other reef fauna. More than a hundred species of crustaceans alone can live on one m² of coral reefs! And they are all in danger of extinction if the corals die.

    One day, human civilization will also move into the realm of paleontology interest: “In 100 million years, everything we consider great human creations – sculptures and libraries, monuments and museums, cities and factories – will be compressed into a layer of sediment, not much thicker than cigarette paper.”

    You may found the list of a few species exterminated by humanity here.

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