The Sixth Extension focuses on the topic of climate change, but unlike other books on the subject it is more scientific thus explores other subtopics such as mass extinctions and natural selection. In her analysis, Kolbert gathers multiple evidence on human impact on and relationship with the planet since their existence. Exploring the five mass extinctions that have already occurred and the sixth one also known as Anthropocene that is imminent and threatens Earth systems and biological life. Humanity is the main villain in this looming threat as human activities have played a negative role in the ecosystem and its impact is more visible currently. Through details on endangered species and extinct species, Kolbert links the phenomena of human activity and developments to such ecological changes.
Kolbert also delves into Darwin’s theory of extinction and prehistoric extinction events to compare catastrophism. The book highlights the five mass extinctions as caused by catastrophes including asteroid collisions, volcanic eruptions, or ice ages. The fossils of American mastodons prove that certain species did not suffer extinction from a gradual change in ecological systems but by catastrophism. After siting the mechanism behind extinction and natural selection through sudden catastrophes Kolbert attaches the same mechanism to human exploitation of species. For instance, the original penguin known as the great auk that is extinct due to overexploitation by humans for resources. In the same vein, she attributes the reducing number of particular organisms such as Panamanian golden frogs to human interference and activities.
Through her research and information conveyed Kolbert attributes the reduction of biodiversity to habitat loss caused by humans. Human developments have led to the limited movement of organisms thus if their habitat becomes unsuitable relocation is near to impossible. Furthermore, the loss of flora and fauna from activities also contribute to the loss of habitat for endangered organisms. The industrial activities have emitted carbon and chemicals to the ecosystem quicker than species can adapt to the changing bionetworks. Human activity has disrupted ecosystems by affecting the atmosphere, heat absorption, ocean acidity, and water cycle. Thus revolving back to the current issue of climate change that has reached unprecedented levels hence threatening the upsurge of the sixth extinction.
