Many years ago, I stood in a cave on the Isle of Arran, off the west coast of Scotland. As I gazed up at the roof of the cave, I saw a blanket of fossils of marine invertebrates. This was a death assemblage of a now extinct species. The sight of these fossil species brought home the reality of extinction, something that has stayed with me. I have read many good books addressing different aspects of climate change, but I had seen fewer well-argued, scientifically sound books about the biodiversity crisis. So, I was delighted to review The Sixth Extinction as I was already aware of Elizabeth Kolbert’s previous work.

Testimonials on the covers of The Sixth Extinction encourage the reader to look inside. Recommendations such as ‘compelling’, ‘meticulous’, ‘remarkable’ and ‘a big story of our age’ make you want to know more. Opening the book is the first step on a journey through a remarkable, alarming story.

Elizabeth Kolbert is a journalist and author who is currently a staff writer at the New Yorker. She has established a reputation for being a science writer up there with the best. The Sixth Extinction received the Pulitzer Prize for General Non-Fiction in 2015.

The book opens with a prologue. Some argue nowadays that books should not begin with a prologue, but this one disproves that view. It introduces a species, a land animal, which emerged two hundred thousand years ago. We then realise that this ‘land animal’ is indeed our species. That land animal plays a critical role in the Sixth Extinction. This brief prologue sets the scene magnificently.

Each of the thirteen chapters of the book are underpinned by exemplary scientific narrative amplified by Kolbert’s own involvement in elements of each story being told. She recounts her travels through Panama, France, Iceland, Italy, Australia, Peru, Brazil, Germany and, of course, the USA in her quest to understand the nature of extinctions past and present. Each location provides an ecotype of the extinction story to be told. On one hand, the style could be considered a travelogue of extinctions; on another, it is a record of explorations for scientific verification.

Chapters I to IV address extinctions through geological time, ie. the Big Five. A mass extinction is one that is characterised by substantial biodiversity losses and is global in its extent. The contention of the book is that we are living through a sixth mass extinction event, although it remains to be seen whether this one will reach the scale of the previous Big Five. Understanding the Big Five helps us to set the proposed Sixth Extinction in context.

Chapter I relates a sobering tale of contemporary frog death in Panama. We learn that amphibians are the world’s most endangered class of animals. This chapter introduces the reader to the concept of ‘background extinction rate’. This is the yardstick against which it can be determined whether any extinction is unusual or to be expected. The extinction rate for amphibians is forty-five thousand times higher than the background rate. Scientists use different metaphors to describe mass extinctions, but Kolbert describes them as ‘long periods of boredom interrupted occasionally by panic’. It is estimated that a third of sharks and rays, a quarter of all mammals, a fifth of all reptiles and a sixth of all birds are headed for extinction. Such data helps the reader to realise the urgent need for writing the book.

Through Chapters II to IV we are invited to explore developments in geological thinking and, specifically, the concept of extinction. We are introduced to some of the big names in geology: Cuvier, Lyell and Darwin among others. From Chapter V onwards the story is set in the present day with losses of individual species exemplifying the scale of modern extinction. The reader is introduced to the Anthropocene, argued to be the geological age that we now live through and defined by human-induced ecological degradation. Despite the time since the publication of this book, arguments persist as to whether Anthropocene should be accepted as a term. The core of this uncertainty among geologists, including those who define the geological time scale, is whether the evidence for human impact can be identified in rocks and sediments to show a fundamental change. More importantly, the actual date for the start of this period continues to be debated. This is in part, again, due to the need for the identification of sites which can demonstrate evidence for the abrupt change in key environmental markers. However, this does not diminish the evidence for human impact on biodiversity at this time.

Chapters VI to XIII take us on a journey through impacts of CO2 emissions on marine environments, on coral reefs; of global warming impact on tree distributions; on the stability of Amazonia; on species introductions; and of Neanderthals and DNA. Each chapter incorporates case studies of species which provide evidence to support argument for a sixth extinction. It is perhaps ironic, however, that Kolbert must have clocked up many miles in her journeys in search of evidence for her book, contributing carbon emissions that are part of the story of some extinctions. This paradox was highlighted by Sir David Attenborough in 2019 acknowledging that in order to communicate the impact of humans on the environment, climate journalism often involves participating in the problem.

Sound research is critical for any science book. Kolbert not only identifies which key scientists are researching elements of her story, but she also visits them to gain personal insight. Her capacity for ‘showing not telling’ permeates the text so that the reader can share in the excitement of her reporting.

This is an excellent book aimed at the general reader who has an interest in science. It is well written, readable and highly enjoyable. Kolbert’s style is relaxed, informative and, at times, humorous. It will appeal to any reader interested in human impact on the environment. Some content is, at times, disturbing, but such is the nature of this extinction. The work is underpinned meticulously by appropriate research. A detailed bibliography allows the reader to pursue some of the key themes further. I feel that some content of the early chapters may challenge those with little earth science/geology knowledge, but attentive reading of these sections will be worthwhile.

The original hardback version of the book was published in 2014 and probably completed sometime before that. It is timely for an update to explore further possible species at risk of extinction.

The prologue of The Sixth Extinction concludes with the author’s hope that readers will have ‘an appreciation of the truly extraordinary moment in which we live’. I defy any reader not to have that appreciation after reading this book. The final chapter of the book makes the sobering statement:

Having been alerted to the ways in which we’re imperilling other species, can’t we take action to protect them? Isn’t the whole point of trying to peer into the future so that, seeing dangers ahead, we can change course to avoid them?

Given that humans are implicated in the extinctions of the Anthropocene, surely there is a moral imperative here. This book provides much for the reader to reflect on.

Jennifer Jones

Jennifer Jones is a writer, children’s author and scientist based in north-west England. With a BSc (Hons) in Geography and Botany, and a PhD in soil geochemistry both from the University of Liverpool, she is currently an Honorary Research Fellow at Liverpool John MooresUniversity. Jennifer is passionate about the natural world and loves communicating that passion to school groups and the public. She tries hard to convince people of the joys and wonders of soil.

The Sixth Extinction: An Unnatural History by Elizabeth Kolbert

Jennifer Jones