The Kingdom of Rarities Read Free

deterioration.
    Many conservation biologists target “saving rare species” as the ultimate aim of their work. Yet rarity, as a phenomenon in nature, can take many forms, not only among species, although that is central, but also in the building blocks of the natural world: genes, populations of species, habitats, assemblages, and ecological and evolutionary phenomena. Species, with few exceptions, are made up of populations distributed across the landscape. Saving only one population of each rare species simply as a token gesture would be of little ecological value, especially where those species play a role in maintaining a given ecosystem’s integrity. So an essential goal is to conserve multiple populations of species and the genetic, ecological, and behavioral features that these building blocks contain. Conserving dispersed populations and their genetic variabilitygives species a better chance of adapting to and persisting amid changing conditions, such as a rapidly changing climate or invasion of their homeland by introduced species.
    Buried within the species extinction crisis is another, less publicized calamity: the increasing rarity of species populations. These losses of populations, as well as in some cases entire species, have led biologists to sound warning after warning. The eminent biologist E. O. Wilson, for example, pronounced in a speech in early 2000 that “biodiversity cannot afford another century like the last one. We are about to lose thousands of species a year, especially in rainforests.” Wilson could have extended the depth of the problem, if risking the simplicity of his message, by adding a phrase whose meaning has gone unnoticed by the general public: we have been losing
populations
of species faster than we have been losing species themselves.
    These two concerns—rarity of species and paucity of particular populations—merge when it comes to those species whose entire earthly existence is represented by a single population, as a result of either natural forces or human encroachment. Who are these singleton species, and how many of them are now close to the abyss of extinction?
    In 2003, several colleagues and I put together a paper for the
Proceedings of the National Academy of Sciences
to address this question, name those species, and suggest how their imminent extinction might be prevented. Our work on the paper, which was published in 2005, sparked the scientific basis for this book, an interpretation of the evolutionary and contemporary aspects of rarity. We focused our effort on a subgroup of relatively well known but threatened vertebrates, our fellow creatures with backbones—birds, mammals, reptiles, amphibians (fishes are yet to be analyzed). We postulated that certain of these species were already so uncommon that they would be extinction’s next dodo birds unless action were taken to prevent their disappearance.
    To begin, we turned to the gold standard for evaluating rarity of wild species, the International Union for Conservation of Natureand Natural Resources (IUCN) and its famed Red List of Threatened Species, which ranks species on the basis of sizes of remaining populations. The IUCN assigns the category “endangered” or “critically endangered” to species whose numbers have plummeted toward extinction. We then went a step further. “Let’s name the rarest of the rare, those species whose entire global range is limited to one population at a single site,” my colleague John Lamoreux suggested. He was proposing that we limit our survey to such species as the Bloody Bay poison frog, which hails from the last patches of rain forest on the island of Trinidad, the only place on Earth where it can be found.
    Once a species such as the Bloody Bay poison frog is restricted to a single dot on the map, if one or another of several catastrophes strikes—if the spot is plowed, burned, flooded, drained, paved, polluted,