Costs and cures

Before they vanish. Saving nature's populations—and ourselves. Ehrlich, P. R., Ceballos, G., and R. Dirzo. 2024. Johns Hopkins University Press, Baltimore, MD. xxiv+348 pp. US$29.95 (hardcover). ISBN 978-1-4214 4969-2. The 3 authors of this book are known for their forceful presentation of the biodiversity crisis, which have been summarized in influential books and articles (e.g., Dirzo et al., 2014; Ehrlich, 1968), and for the terms they have coined, such as biological annihilation and defaunation. They have been pivotal in bringing the alarming state of nature to a wider audience. Therefore, with saving nature and ourselves in the subtitle, I hoped to not only get up-to-date information on the state of the world but also learn how biodiversity loss is detrimental to humans (“The Costs,” Chapter 11) and how we can rectify the problem (“The Cure,” Chapter 12). Not only should a general summary be informative for those working in conservation science, but it is essential to communicate both the costs of loss and the benefits of preservation to a wider audience. This book partly succeeds in these endeavors. Despite the title of Before They Vanish, much of the content is about the vanished. It is an accounting of the disappeared and disappearing, largely by example. Sometimes written in emotional terms and describing personal experiences, the ethics of human exploitation regularly surface. Consternation and exasperation reach their highest levels when describing the slaughter of gorillas and elephants, given the great intelligence and complex societies of these remarkable species. The book's tone is gloomy and doomy, appropriate for readers of this journal, but perhaps not the best way to encourage a broader audience. The authors state that this is a popular book, and all the illustrations are of animals and plants rather than data. It is most likely to be useful to researchers and teachers seeking examples. The first two-thirds of the book provide what is essentially an annotated summary of the International Union for Conservation of Nature's Red List. Mammals, birds, other vertebrates, invertebrates, and plants all get their own chapter. These are followed by an interesting chapter on microbes. Each is richly illustrated with examples, personal anecdotes, references to the primary literature, and, in many cases, inferences about how the decline of the species may be detrimental to us. With sections perhaps written separately by the different authors, there are regularly similar or identical statements separated by as little as a paragraph. Perhaps this is a tactic to bring home the message, but it is certainly an unusual writing style and sometimes a little disconcerting, especially when statements are contradictory. About nature's rarest mammal, the vaquita (Phocoena sinus), one paragraph says 12–15 individuals remain and the next mentions 10–13 individuals. In one place, we are told that feral cats kill several million birds globally, elsewhere the more accepted estimate of low billions in North America alone is presented. These are not isolated examples, and readers ought to check the impressive list of the referenced primary literature if exact figures are important. The 3 summary chapters on drivers, costs, and cures are key. In the drivers chapter, the authors summarize the classic threats (climate change, habitat loss, pollution, overharvesting, and invasive species) and mention interesting examples. More controversially, they are convinced that human population size is the critical ultimate cause and even state “When you have more than one child you are…participating in the causes of the 6th mass extinction.” Consequently, it is a surprise that they do not emphasize the fertility declines across the world (and population movement to cities) that give us hope for a better future, albeit only decades from now (Sanderson et al., 2018). Increasing consumption driven by the rise in income is given secondary importance to population, but the authors do accept that they (and you and I) are personally contributing to species loss through an extravagant lifestyle. Impacts of wealth should have been given greater emphasis. The growth of wealth is proceeding apace as inequality across the world is declining in some countries and increasing in others. As people get ever richer, there is no evidence that the incremental increase in environmental impacts is slowing (see figure 12.5 in Price [2022]). The hope is that technological advances will reduce impacts even as consumption increases. The authors accept that major threats to the future of life are nuclear war and climate change. Persuasive books have made the case that these threats indeed loom large (Lynas, 2020, 2025). But this book is about the impacts of biodiversity loss. Many statements are made along the line of “We are utterly dependent on the integrity of our too-little understood life-support systems.” Can such statements be justified? The costs chapter lists 3 main reasons why we should be concerned. Most prominent are ecosystem services, which include provisioning of clean water, CO2 sequestration, and so forth. Next, much is made of quality of life more generally, including benefits from being surrounded by nature (something that has clearly affected the authors and which they wish others to experience). Finally, many benefits lie hidden in the many unexplored species, exemplified by drugs, such as penicillin. Here, as in the drivers chapter, several crucial themes remain undeveloped. First, while acknowledging that loss of species may lead to further decline, more needs to be made of probabilities and uncertainty. The authors state that the loss of elephants and lions (and blue whales and pandas) would not lead to the end of humanity, but we really do not know. Indeed, throughout the book the laudable emphasis is on how intertwined species are. It starts with an excellent example, describing how the 19th century fur trade led to a decrease of sea otters, which led to a rise in sea urchins and a consequent increase of the urchin's consumption of kelp. That chain is thought to have contributed to the extinction of Steller's sea cow (Hydrodamalis gigas), along with hunting (Estes et al., 2016). One can imagine tipping points on a grander scale. Second, simplification of communities and the associated rise in the abundance of a few species make them and us particularly prone to disease. In my experience, this threat hits home with those who need to be persuaded. Third, species diversity per se increases many positive aspects of ecosystems. According to Tilman et al. (2019), “Greater plant diversity is now known to lead to greater net primary productivity, greater root mass, greater use of limiting soil nutrients, greater rates of accumulation of soil organic carbon and organic nitrogen, greater ecosystem stability, greater resistance to invasion by exotic plant species, greater insect diversity, and lower incidences of species-specific plant diseases.” What are the cures? Time is short, so immediate action is required. The cure chapter touches on a few possibilities that have been raised, including de-extinction, translocation, captive breeding, and removal of invasive species. The authors note that these are impractical, unlikely to happen, or both, and will make only a small contribution. They criticize several politicians and are especially harsh toward President Trump, for their actions against nature. However, most successful politicians note that the economy motivates the public. Many conservationists consider our best bet to be the preservation of large reserves. These have the potential to usher a large fraction of biodiversity through this century's traumas and at the same time to provide immediate economic benefits. In the ocean, fishing catches increase when they abut protected areas (Roberts et al., 2001), and on land the tremendous increase in ecotourism may make reserves more profitable than agricultural uses, as has been shown in the Peruvian Amazon (Kirkby et al., 2010). Predicting what will happen over the next few decades is almost impossible. But we can be sure the environment will be very different; the natural world could be devastated or it could be improving. We should be adding optimism to the mix, especially because it is only the improving case that seems worth contemplating. Although the inciteful observation by Wiens (2016) that range shifts in response to climate change implies many populations at the trailing edge have gone extinct (as described in the book), it also means that many areas at the advancing edge have been colonized. There are more whales in the sea and tigers in India than there were 50 years ago. Soon we will be able to grow food in labs, freeing up land (Monbiot, 2022). None of this diminishes the dire state of the world, but perhaps with some effort the sixth mass extinction can be averted.