There really are more than two kinds of people in this world. It’s just that in addition to the two common ones, the third class is rare. There are those of us for whom slinging a hammock between two trees, draping first a mosquito net over it, then a rain fly, is as close to a definition of paradise as imaginable. There are those for whom this would be cruel and unusual torture. And, then there is Elizabeth Kolbert, who might have remained one of the latter, but has the pluck to sling her hammock and write about it.Walking through the forests of Panama, her guides point out the soldier ants, which leave their jaws in your legs after they’ve bitten. They look for, but do not find, the most venomous snakes, that “can really mess you up” and, eventually, the hammock site. “A slit in the bottom constituted the entryway, and … when I climbed into the thing, I felt as if I were lying in a coffin.” In this coffin, she has “vivid troubled dreams” of “bright yellow frogs”. Forest spirits do us — human actions are driving species to extinction at rates only seen five previous times in geological history.Kolbert is brave in another sense. Her main title is the same as the book by distinguished science writer Roger Lewin and famous anthropologist Richard Leakey, published in 1996. Kolbert is a staff writer at The New Yorker, a popular US magazine, and brings an essayist’s approach to the topic. Indeed, her book is a set of thirteen essays, with a three-page introduction and no summarising thoughts.About half the book is about geological extinctions — the five prior to the current one. These chapters cover familiar ground, with mastodons and ammonites, and familiar personalities — Cuvier, Lamarck, Lyell, Darwin, and more recently the father and son Alvarezes and their iridium layer.The remaining story of current extinctions is told well in essays on ocean acidification, fragmented forests, climate disruption, and the consequences of our carelessly moving plant and animal species to places where they do not belong.Kolbert captures the uniqueness of cloud forests. Her guide recommends that she pick out a leaf with an interesting shape. “You’ll see it for a few hundred metres and then it will be gone. That’s the tree’s entire range.”Kolbert is now getting used to fieldwork. Handed a handful of coca leaves and a pinch of baking soda, she finds they taste like “old books” — but the aches and pains of high altitude hiking in cloud forests soon vanish. (One of my perennial worries is to ensure that those I guide do not accidentally pack the coca tea bags from nightstands of good hotels in Quito when they return to the USA.) Spectacled bears have been through the campsite. Now, her visions are of Paddington Bear, the children’s story character, not of haunting frogs.The trees are moving uphill, too — or at least their descendants. The climate is warming fast enough that careful fieldwork readily documents their uphill dispersals. As they move, there is less room for each species and, perhaps in time, insufficient for their continued survival. Climate disruption — for it is more complex than mere warming — not only has the potential to exterminate species, but to eliminate species hitherto unaffected by the deforestation that disproportionately endangers lowland species.By the time Kolbert gets to the lowland Amazon, there is but the briefest mention of her hammock at the famous Camp 41 north of Manaus. (And she takes for granted the showers and toilets that may constitute my greatest contribution to tropical ecology: I chaired the committee that recommended their installation.) When noisy mating frogs wake her in the middle of the night, she enthusiastically steps out to look for them.The camp is the centre of the largest and most significant ecological experiment. As Kolbert explains, we live in a world where what habitats remain are usually in fragments, some small, some large. Nearly forty years ago, Tom Lovejoy recognised the global significance of fragmented landscapes and posed the critical questions: how many species will they lose and how fast will they lose them? Smaller fragments lose more species and do so more quickly. The experiments here, with their carefully designed fragment sizes, provide quantification that guides practical conservation actions elsewhere [1xConservation: forest fragments, facts, and fallacies. Pimm, S.L. and Brooks, T. Curr. Biol. 2013; 23: R1098–R1101Abstract | Full Text | Full Text PDF | PubMed | Scopus (4)See all References[1].Kolbert’s strength is in her essays. They are credible, well-selected and entertaining reads. Her weakness, alas, is the wider perspective. First, she does not attempt to justify why we should consider the present “the sixth extinction.” Bright yellow frogs may well haunt her dreams. Frogs have exceptional extinction rates — nearly 600 extinctions per million species per year. That’s some 6,000 times the background rate before human actions inflated it. How we derive these facts requires explanation and a story more remarkable than anything Kolbert presents.The International Union for Conservation of Nature compiles the Red List — the species that are in danger of becoming extinct or have already done so. It’s remarkable as the combined effort of hundreds of thousands of people, many of them amateurs, to compile data on the status of their favorite taxa. For amphibians, we know that there were 1437 species described by taxonomists before 1900. Of these, 18 are either extinct or presumed extinct. After 1900, taxonomists described 4967 species, for which 121 are extinct or presumed so. Following these newer discoveries from the time of their description allows an estimate of 587 extinctions per million species, per year. This contrasts to a background rate of about one extinction per ten million species, per year. These numbers attest to two other facts: first, the rate of species description is still increasing — new species (Figure 1Figure 1) are being found in places that were until recently inaccessible. Second, newly described species have very high rates of extinction and threat. They are rare — which is why we have only just found them — and in places where there is extensive habitat loss.Figure 1New species.Andinobate cassidyhornae is a recently described species of frog from the Western Andes of Colombia. It lives in forest protected by a land purchase made possible by SavingSpecies (www.savingspecies.org). (Photo: Luis Mazariegos.)View Large Image | View Hi-Res Image | Download PowerPoint SlideSecond, like too many others — such as diCaprio’s The 11th Hour or Call of Life: Facing the Mass Extinction — Kolbert details the problems, but none of the solutions. One wonders, were she to write about modern medicine, would she portray all physicians as telling us we are all going to die — which is true — but fail to notice that their profession greatly reduces mortality and disease? Tens of thousands of conservation professionals worldwide save species on the brink and are measurably reducing extinction rates. The fraction of the Earth’s surface now protected has increased steadily, while Brazil has massively reduced deforestation in the Amazon. From these and so many other stories, we surely conclude that the sixth extinction is not yet written. It’s a nightmare from which we can still escape.