The Sixth Extinction | Elizabeth Kolbert

Summary of: The Sixth Extinction: An Unnatural History
By: Elizabeth Kolbert


Get ready to dive into the fascinating and alarming world of ‘The Sixth Extinction: An Unnatural History’ by Elizabeth Kolbert. This book will take you on an illuminating journey through the history of species extinction, exploring the underlying causes and alarming current trends. You will encounter the background extinction rates and be introduced to the concept of mass extinctions like the one happening right now. Furthermore, the book delves into the human impact on these extinctions, from modern transportation networks to industrialization and even our early evolutionary history. As you venture into this enlightening summary, prepare for an eye-opening experience about the fragile ecosystems we inhabit and our responsibility for their survival.

The Human Role in Species Extinction

Species extinction is not a new phenomenon. Historically, environmental changes have triggered mass extinctions, leading to the disappearance of many animals. Although the background extinction rate for mammals is slow, the actual extinction rate today for endangered classes such as amphibians is estimated to be 45,000 times higher. Humans are responsible for species extinction through modern transportation systems that introduce new organisms into habitats and by directly wiping out species and changing their habitats. To address this issue, it is crucial to reflect on the history of evolution and extinction.

Understanding Species Extinction

The concept of species extinction is a relatively new one. During the 19th century, French naturalist Georges Cuvier theorized that animal species could disappear through environmental catastrophes. British geologist Charles Lyell, however, later proposed that extinction occurs at the same pace as environmental changes. It was only in the 1980s that Walter Alvarez, a geologist, unearthed new information that supported Cuvier’s theory of extinction catastrophe. He discovered an abnormal amount of iridium, a rare metal commonly found in meteorites, in a layer of earth. Based on this discovery, Alvarez proposed impact theory; he suggested that a ten-kilometer-long meteor hit the earth many millions of years ago. As a result, catastrophic climate change led to the rapid extinction of many species of dinosaurs. Current research has shown that four out of the “big five” mass extinctions occurred due to climate change caused by shifts in the earth’s orbit, resulting from the gravitational pull of other planets in our solar system. Humans have also played a role in species extinction, but how exactly?

The Devastating Effects of Industrialization on Biodiversity

Our world is rapidly approaching a sixth mass extinction due to the rapid changes that industrialization has wrought on our environment, with carbon dioxide emissions being one of the main culprits. The oceans are becoming dangerously acidic due to increased levels of carbon dioxide caused by industrialization, leading to a reduction in biodiversity. Acidification is most harmful to calcifiers, or organisms that have external shells or skeletons that protect them from predators. As the oceans grow more acidic, the levels of calcium and carbonate ions, the building blocks of shells, decrease, putting organisms that can’t develop protective shells at risk of extinction. Additionally, carbon dioxide is also contributing to global warming and causing cold-climate species to face extinction as their habitats disappear. Despite their ability to migrate to colder climes, species are dying before they find a suitable place to live due to unprecedented warming rates caused by human activities.

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