Review of Inheritors of the Earth: How Nature is Thriving in an Age of Extinction by Chris Thomas

This post briefly considers Chris Thomas’s new book Inheritors of the Earth: How Nature Is Thriving in an Age of Extinction. As the subtitle suggests, the book seeks to challenge the “pessimism-laden, loss-only view of the world” (p.9) that Thomas believes is currently dominant in conservation and ecology. In contrast, the book emphasises the “biological gains of the human Epoch” (p.8). Thomas argues that the creation of new animal and plant species is a core “evolutionary signature of the Anthropocene epoch” (p.8) – i.e., not only species extinctions – and that, in the long run, speciation caused by evolutionary processes will exceed the number of extinctions. He asks a related question: “is the prognosis really as bad as the doom-laden message of biological decline?” (p.5).

It is important to note that this book isn’t a Pollyanna-ish everything-is-fine style book. Thomas clearly emphasises the current high level of species extinctions and the human-caused changes which influence biodiversity. He states that a major extinction event “is in full swing” (p.4), though he suggests it’s premature to judge it to be the sixth mass extinction event. As a Professor of Conservation Biology at the University of York (link), and an elected Fellow of the Royal Society, the author is an influential scientist who is well-placed to comment on key biodiversity and conservation trends.

Yet the underlying message of the book is that the narrative of biological loss and extinction isn’t the whole story. Thomas presents what he considers to be a broader and more balanced perspective, informed by an understanding of evolutionary processes which “sets today’s challenges in their appropriate historical context” (p.5) and a range of interesting case studies which examine the fate of different species and various parts of world where he’s done fieldwork. He argues that – along with the losses – human impacts have initiated a major period of evolutionary change including more rapid speciation processes (e.g. creation of new species). A related question posed by the book is “whether we are on the brink of a sixth major genesis of new life” (p.117). (Spoiler alert: Thomas argues there is strong evidence of this but it will take a long time to unfold so we can’t say for sure).

He further contends that there are good reasons to believe that over the long run (over evolutionary timeframes) biodiversity on Earth will increase as a consequence of human activities – quite the contrarian position. Centrally the book is an attempt to challenge the current “paradigm of biological decline” (p.5).

The book has four main parts:

• Part 1: Opportunity, which outlines the attempt to consider both gains and losses along with some key points of contention in conservation debates and practice;
• Part 2: New Pangea, which examines ecological changes that have resulted from the four major human-caused impacts which Thomas argues are the major threats to terrestrial biodiversity: killing animals for food and other products (Chap 2), habitat destruction for agriculture and cities (Chap 3), climate change (Chap 4), and the biological invasions that take place when species are transported to new parts of the world (Chap 5);
• Part 3: Genesis Six, which shifts to considering an evolutionary perspective and considers whether we are on the brink of a sixth major genesis of new lifeforms; and
• Part 4: Anthropocene Park, which “concentrates on our attitudes towards the biological world and our strategies to protect it” (p.201). The final two chapters propose a new conservation philosophy, and then present speculations on the long-term consequences of the evolution of Homo Sapiens for biodiversity on planet Earth (entitled ‘Epilogue: One million years AD’).

I do not have the scientific training to provide a scientific review of the book’s core claims and the associated arguments and evidence that Thomas presents. It will be interesting to read book reviews appearing in relevant journals. Instead, here I want to briefly consider a few aspects of the book.

One of the most interesting things about this book is that it nearly wasn’t written. As he explained in an interview (link) Thomas was concerned about how his arguments would be interpreted (e.g. potential ‘hijacking’ of the book’s messages by those wanting to continue with business-as-usual). Thomas “nearly didn’t put fingers to keyboard” because of such concerns (link).

This made me wonder whether other scholars are self-censoring for fear that more balanced or broader perspectives could hamper environmental action and/or result in them coming under attack. This is a plausible hypothesis that could be worth investigating.

On this general theme, other reviewers have judged the book and author to be fearless and courageous given its contrarian messages. From a sociology of science perspective it’s interesting to note that Thomas only started to write it after his scientific career was well-established as a full tenured Professor and an elected Fellow of the Royal Society. Thomas doesn’t have to worry about his career/job security.

A further interesting aspect to consider is the apparent tension between the scientific perspective that Thomas is seeking to encourage and the public attitudes to the biological world which are given expression in conservation debates and inform environmentalists. For example:

• Thomas questions the tendency to “set ourselves apart [from nature] to act as referees and arbiters of how nature should be” (p.19). Related to this he argues that humans are part of the nature and therefore “anything we do [e.g. building cities, introducing species to new parts of the world, etc.] is also a natural part of the evolutionary history of life” (p.230);
• He argues that “there is no correct state of nature” (p.19) and there is no non-arbitrary baseline against which to measure progress/loss. This view suggests peoples’ ideas about how nature should be are, in essence, arbitrary value judgements; and
• Thomas critiques our tendency to “accept without question that species are [currently] found where they should be” (p.85). He further critiques the ways people often interpret the natural world: “We think of the new vegetation and reefs that developed at the end of the last ice age, and of the Greenland lemmings living in Greenland, as the way that the Earth is ‘meant to be’. However, while there are plenty of reasons why we would wish to reduce the rate at which humans alter our planet’s climate, there is no logic in defining past change as good and natural and at the same time describing more recent change and future change to the distribution of species as regrettable and unnatural” (pp.85-86). (Compare these statements to public activism on the future of the Great Barrier Reef).

I reflected on this in many ways because, as an environmentalist, I have sometimes adopted the viewpoints that Thomas critiques. However, my mind most strongly turned to Steven Yearley’s examination of the relationship between science and green movements (see his book The Green Case and this paper). Inheritors of the Earth could be interpreted as supporting Yearley’s arguments – particularly his argument that science is less of an ally to green movements than is commonly assumed – and as a critique of dominant environmental arguments. It seems unlikely that Thomas’s view will gain much traction in the Australian context given debates tend to concentrate on threats to ecosystems judged to be valuable (e.g. the Great Barrier Reef) and also tend to presume that such ecosystems are currently the way they’re ‘meant to be’ and are where they should be.

Consideration of this point is further suggested by other claims made in the book. For example, Thomas states that “more species like it hot than cold, and so the overall consequence of a warmer climate is to raise biological diversity in many parts of the world” (p.6).  Given that environmentalists tend to be in favour of maintaining (or improving) biodiversity, the apparent implication is that environmentalists should be in favour of global warming.

Perhaps more than anything Thomas wants us to rethink the current “default position” of treating change as inherently negative (p.231). He contends that scientists have developed new understanding of nature that tells us that “any attempt by humans to keep things just as they are is utterly pointless” (p.84). Related to this Thomas also aims to persuade conservationists and ecologists that in the Anthropocene we need to be more open to unconventional ways of maintaining and promoting biodiversity. He passionately calls for more creative approaches to biodiversity conservation which don’t seek to achieve stasis and don’t view pre-human environmental conditions as inherently better (how nature is ‘meant to be’).

A final intriguing aspect of the book that I wish to emphasise is Thomas’s suggestion that biodiversity management and monitoring approaches overly focus us on bad news and have too narrow scope – emphasising the loss of species and not giving equal attention to other biological processes such as hybridisation of species, speciation processes (evolutionary processes), and new opportunities for species to take advantage of novel ecological situations. This points to knowledge practice biases, something that may also be worthy of investigation. Thomas states multiple times that credible data shows that biodiversity gains have occurred in virtually every country and island studied during the period of human influence, and implies that such evidence is currently inadequately considered. Policies such as the Convention on Biological Diversity are criticised on related grounds.

Overall, I found the book to be an informative and fascinating read. It reminded me of other books like Rambunctious Garden (by Emma Marris) and The Big Ratchet (by Ruth DeFries), both of which in quite different ways also challenge the strongly pessimistic environmental narratives which are currently dominant. In the case of Inheritors of the Earth Chris Thomas usefully points out that the current trend of “declaring the Anthropocene to be the sixth mass extinction is somewhat premature” (p.244). Additionally, as I suggested earlier in this review, how the book is received by environmentalists and conservationists will tell us something about the relationship between the biological sciences and green movements.