Rose-Tinted Ecology

PLoS Biology | http://biology.plosjournals.org This important book relates much the most optimistic treatise on conservation that I have ever read: many would say naively optimistic. I should say from the outset that I genuinely fear that Michael Rosenzweig’s theories and examples are less broadly applicable than he argues. And yet I want to believe that he is right. If he is right, the conservation of biodiversity, and ultimately of humanity, may be easier— much easier—than many of us worry. Win-Win Ecology is a splendid read, interspersing excellent science with engaging erudition and humour. It’s structured in an unusual fashion, which is unsurprising, because it is an unusual book. Rosenzweig spends his first seven chapters winning the reader over with examples of what he terms “reconciliation ecology”:—“sharing our habitats deliberately with other species.” These are delightfully eclectic, ranging across species and space from coral reef gardening in the Red Sea to the red-cockaded woodpeckers (Picoides borealis) on Florida’s Eglin Air Force Base—although the exciting news that Bachman’s warblers (Vermivora bachmanii) persist on Eglin (p. 30) is, sadly, extremely unlikely. However, the examples are also selective. They are all very small scale: the evidence that they can be generalized across the landscape to deliver us a reconciled planet is slim. Chapter 5, the one chapter which addresses broad-scale issues—economically and environmentally perverse subsidies— does so from a “what-if” perspective, rather than by reporting actual successes. Even more worryingly, they are heavily Americocentric: Rosenzweig occasionally ventures outside the United States to Europe and Israel, but beyond that, his examples are sparse and shaky. The remaining five chapters of the book go from the specifics to the generalities; they address the science behind reconciliation ecology. Rosenzweig’s argument is a simple one, founded on a huge quantity of empirical and theoretical evidence. Human-driven habitat loss, he demonstrates, is leading inexorably to species loss; if those species are to survive, we must therefore allow them access to those portions of the planet that we have appropriated. This logic is undeniable, even if, in a bizarre reversal of the general mood of the book, this science actually veers towards pessimism. Rosenzweig’s claim that, over evolutionary time, there is a linear relationship between the number of species in an area and the size of that area is dubious (most ecologists would argue that this relationship is a power function, implying that relatively few species are lost until most habitat has been lost). And his estimate of the extent of the planet already co-opted by people—95%—is high (of course, none of the planet is pristine any longer, but numerous studies suggest that half of the planet’s natural habitat Book Review/Science in the Media