By Brian Harrison

The Sixth Extinction: An Unnatural History
By Elizabeth Kolbert

Over the past half a billion years of earth’s history there have been five mass extinctions in which the diversity and reach of life forms have been greatly reduced. To some, there is a sense that we may be living in what may be called the sixth extinction. Many believe that this extinction could have a much greater impact than the fifth extinction, which wiped out the dinosaurs. Ms. Kolbert has written an engaging tome in which she looks at more than a half dozen different disciplines tracking impacts on various species throughout the world. 

Too often we take the accepted scientific standards as clearly and obviously determined, as if someone saw the light and the new scientific principle was clearly understood and accepted by all. However, each and every scientific gain goes through a period of struggle, challenges and modifications before it is able to stand its ground. Ms. Kolbert begins her discussion with the beginning of modern human’s first sense of understanding that there had been animals and/or reptiles which had once existed but were no more. Arrival at this first recognition, rising from the work of Georges Cuvier in France, was at significant odds with the uniformitarian view of Charles Lyell (i.e., “The present is the key to the past”). While Lyell and Cuvier where contemporaries, Lyell could not see any evidence of cataclysmic events which may have altered past geologic events or affected species. Charles Darwin, while much younger, was still somewhat contemporaneous with Lyell and Cuvier. His view of evolution, as those that did not change and/or modify died out naturally, was in stark contrast to the view of mass extinctions. These first four chapters provide a wonderful insight into how scientific thought is modified and changed as new data is discovered and our scientific world view is expanded.

Ms. Kolbert extends her discussion further into how the discovery of the Iridium signature at the end of the Cretaceous Period was initially identified by Walter Alverez and his father. Their view of an asteroid impact causing a mass extinction at the end of the K-T boundary was initially laughed off and viewed as almost nonsensical. However, with increasing evidence from areas around the world and re-evaluation of thousands of drilling cores from ocean sediments it was postulated that an asteroid had impacted the Yucatan Peninsula in Mexico at the K-T boundary and thus one very plausible explanation of the K-T extinction.

Ms. Kolbert assesses the theories of the causes of the past extinctions to understand the driving forces that affected and changed existing life. The discussion of the end-Ordovician extinction is thought to have been caused by large scale glaciation and the end-Permian extinction by warmer climates and high climatic CO2 levels. Ms. Kolbert introduces us to the idea of the sixth extinction through her discussion of how humans have changed the rates of processes of everything from CO2 interactions with the oceans, transformation of one-third of the world's land surface, high fertilizer production impacting nitrogen fixation, damming and diverting of natural rivers, moving/introducing species from one continent to other continents essentially overnight, etc. This human impact has led to a call to change this time to be known as the Anthropocene Epoch.

Much of the remainder of the book is an in-depth, on-site experience consulting with some of the leading researchers on species impacts around the world. She spends time looking at tree impacts in South America, impacts of sea vents off-gassing volcanic gasses near Italy, loss of the aruk (i.e., somewhat similar to the South American penguins) in the Northern hemisphere, coral impacts in the Great Barrier Reef, impacts to bats in northwestern U.S. and Sumatran rhino breeding in Cincinnati. Each one of these experiences includes discussion on the impacts of change and rates of change on our existing biodiversity. The last one great extinction of species focuses on the extinction of the Neanderthals and megafauna and discussion if humans had any role in the process.

In summary, Ms. Kolbert looks at humans, not as consciously deciding to eliminate or reduce diversity, but more as an evolutionary group that has a collective ability to change its environment. One of her most evocative statement is that, “With the capacity to represent the world in signs and symbols comes the capacity to change it, which, as it happens, is also the capacity to destroy it.” Ms. Kolbert’s book is an effort of tracing a possible extinction and to place it in the broader complex of this world’s history. This extinction has its own novel cause, not an asteroid nor glaciation but the effects of “one weedy species” (i.e., man) and the end results have not been fully written but will leave an impact for millions of years to come.

BOOK CORNER: This section will be included each month in the Volunteer Newsletter. While we have written the first version, it is our hope that someone will come forward, identify an interesting book (i.e., science, history, new exhibit theme, etc.), and develop a report on such book. Please contact Brian Harrison with future ideas or new books. Thank you.