Most people would agree that it is important to conserve wildlife and the environment it lives in. But can you clearly articulate why? Defending Biodiversity brings together an ecologist and two philosophers to critically examine the arguments environmentalists often put forward in favour of biodiversity conservation. Because, as they point out, a lot of these arguments are not very strong, and sometimes conflict with each other, or with other parts of what environmentalists wish to achieve. Now, before you get all worked up, all three authors strongly believe that biodiversity ought to be conserved, and this book is not an attack on environmentalists or biodiversity conservation. They are careful to avoid being unnecessarily controversial with this book. Rather, they want to help environmentalists improve and strengthen their arguments and to become more persuasive in debates.

After some definitions and an overview of the environmentalist agenda (i.e. those things that environmentalists want to achieve), the book is split into two parts. The first half analyses arguments of instrumental value (i.e. the usefulness of biodiversity to humans), while the second half analyses arguments of intrinsic value (i.e. the value of biodiversity in and of itself, without considering its usefulness).

I found the first half of the book easily accessible and understandable, as this takes a look at the empirical data in favour of conservation. Four arguments are examined: ecosystem functioning and stability (e.g. soil fertility or air quality that is provided by functional, highly biodiverse ecosystems), the precautionary principle (when in doubt, let’s err on the side of caution and conserve a species), agricultural and pharmaceutical benefits, and nature-based tourism.

There has especially been a lot of empirical work done on ecosystem functioning, but closely examining the data shows that most work is done on artificially created grassland communities that are very species-poor. It is very hard to extrapolate from these findings, and they have little relevance to support the idea of more biodiversity supporting better ecosystem functioning (this is just one of a raft of problems the authors highlight).

The precautionary principle is often touted in favour of proper ecological risk assessments or quantitative cost-benefit analyses. Furthermore, the precautionary principle is usually invoked to stop something from happening (usually human action that could lead to biodiversity loss), without ever asking what the benefit is from said action, and the cost if said action is prevented.

Agricultural and pharmaceutical benefits only apply to a very small number of plants that are already well protected, leaving much biodiversity out of the picture. And as far as nature-based tourism is concerned, the link between biodiversity and the enjoyment people get out of it is weak.

I only highlight some of the findings that struck me as particularly relevant or surprising, but the authors analyse each topic in much more detail. Furthermore, in many cases, a corollary of each argument is that if you apply it consistently, it would suggest actions that many environmentalists would oppose. For example, the idea that biodiversity supports ecosystem functioning could be an argument for species introductions, or causing local extinction of a species if it benefits the ecosystem. Actions most environmentalists would baulk at.

“Most people would agree that it is important to conserve wildlife and the environment it lives in. But can you clearly articulate why?”

The second half examines arguments that biodiversity has intrinsic value. I’ll be honest with you, this is where the book largely lost me. Now, I have no formal background in philosophy. The introductory chapter to this section is aimed at people like me who are not familiar with how ethical theories and principles are defended. The different chapters look at sentientism (the idea that the lives of all sentient animals, including humans, have intrinsic value), biocentric individualism (the lives of all organisms, sentient or not, have value), ecoholism (ecological wholes such as species and ecosystems have intrinsic value), Aldo Leopold’s land ethic (his book A Sand County Almanac has had a large influence on modern environmentalism), and the importance of aesthetic value. Here, too, the authors provide analyses of what some of the weak points are of each of these arguments, but I feel ill-equipped to summarise them.

The overall conclusion is that none of the arguments that environmentalists normally put forward address all the points on their agenda. Combining arguments doesn’t necessarily make things better as some of them are in conflict with each other. This does leave me wondering how we can improve our arguments in favour of biodiversity conservation. The book doesn’t provide clear answers. Largely, I think, because these answers are not yet apparent. Where the instrumental values are concerned, reading between the lines, Defending Biodiversity highlights what sort of research we would need to do, and what sort of data we would need to gather in order to answer such questions. For the intrinsic values debate the authors highlight that theories have not been fully developed yet, and that this is still an area of ongoing effort.

The academic discipline of environmental ethics, which examines the ethical arguments of how humans ought to treat the natural environment, has been around for a few decades. This book seems to me to be the first to try and build a bridge to the practical discipline of biodiversity conservation practised by environmentalists. My impression is that this book would be an excellent textbook for a course on environmental ethics, where you read each of these chapters and discuss them in a group setting, led by an environmental philosopher. I could see how, in such a setting, a biologist like myself with little formal training in philosophy could get more out of it. As it stands, reading it is interesting, but the book feels like an opening salvo. It highlights many problems, which is valuable, but it provides few answers or directions to better answers. I understand that this book wants to engender reflection, but I’m a bit worried that practising biologists and conservationists reading the book will finish it feeling lost for both answers and a way forward.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

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