Review: The Song of the Dodo: Island Biogeography in an Age of Extinction by David Quammen.
Island biogeography is a study that has proven itself indispensable to mainstream ecology, evolutionary biology and conservation by providing edifying ideas, theories and models. For this reason, it has received a renewed surge of interest for its relevance to habitat fragmentation. The author, David Quammen, grasps his reader’s attention in the first two chapters by introducing the subject matter with an illustrative metaphor. Conceding to the historically ‘dry’ nature of the topic, the author leaves nothing to the imagination, but rather safely bridges the gap between theory and misconception by drawing on vivid examples and giving faces to eminent names.
He reveals his partiality for island biogeography and passion for research when he describes islands as “natural laboratories of experimentation” and the study thereof as “full of cheap thrills”. He raises several exclusively
biological terms- relaxation to equilibrium, faunal and floral collapse, ecosystem decay, which he explains fully through his island-hopping journey. Aided by an excellent glossary however, Quammen’s narrative excludes no one, providing almost a crash-course in population genetics and conservation biology.
In chapter II, Quammen presents the questions and topics central to island biogeography and clearly signposts the ‘journey’ for the reader. These first chapters revisit the birth of island biogeography and its, often unwitting pioneers- Linnaeus, Darwin, Wallace and their protégés. Quammen speaks of the trials and tribulations most of these eminent thinkers endured in founding this scientific field. In describing the spectacular life found on islands, he highlights their dichotomies, which may lead to such diversity. In observing island life, Wallace proposes a novel formula to account for its diversity: isolation + time = speciation. Quammen, unequivocally siding with Wallace, points out how negligent Darwin was to allow this insight to evade him during his visits to the Galapagos Islands. This is not the last time the reader will be humoured by the author’s jovial ridicule of this great scientist as he re-tracks the journeys of these 1800’s naturalists.
Possibly one of the most pivotal, and reiterated, tenets in the book is first defined in chapter I with Wallace’s words, “every species has come into existence coincident both in space and time with a pre-existing closely allied species”- this describes Quammen’s “yin” of evolution. He guides the reader onwards, describing phenomena that ultimately result in the swansong of so many island species- Founder effect, endemism, predator-prey interactions, genetic drift, habitation fragmentation, and inbreeding. Quammen aptly terms this the “yang” of evolution.
The following chapter begins to explain why island life is often so extravagant in comparison to mainland life. The flightless dodo, dwarf elephantids and giant reptiles are but a few of the results of being marooned on an island. Quammen mentions a list of reasons for the propensity of islands to harbour such impressive morphologies- loss of dispersal ability, and defensive adaptations, size change, adaptive radiation etc. Befittingly, he concludes that islands resemble each other only in their bizarre distinctiveness, as evolution attempts to find solutions to exact energetic efficiency.
Another law central to island biogeography is alluded to, where Quammen again counts the tallies against Darwin in his mock-competition against Philip Darlington who happened upon the empirical truth regarding islands- “Limitation of area often limits both number and kind of species of animals in isolate faunas”. This is known simply as the species-area relationship. After briefly recapping insular characteristic, we move on to island community characteristics. The reader progresses to add ‘disharmony’ and ‘impoverishment’ to the list of insular vocabulary. Quammen notes that, of all the attributes species tend to exhibit, extinction is by far the most representative of island life. “Islands are where species go to die”. The poignant idea that “islands are where species go to die” resonates through all the pages of the novel.
Rarity unto Death (chapter IV) delves into the precursory factors leading to extinction. Quammen uses the example of the Tasmanian tiger and draws on Jared Diamond’s work to provide reasons why apex predators, habitat specialists and small populations are particularly susceptible to extinction. He alludes to the persistence of a species and how abundance, as in the passenger pigeon, sometimes does not preclude a species from extinction. This species, so gregarious and bountiful, was driven to extirpation because it had been deprived of an essential ecological asset- its abundance.
Quammen explores predator-prey interactions in his visit to Southern Guam and elaborates on the extent to which imbalance is brought into entire communities when a single ecological interaction is disrupted. He describes what is termed “trophic collapse and trophic cascades” when he meets the arachnid population explosion in a very intimate way.
A central tenet to conservation biology first originated in the late 1800’s when Johann Forster noticed how species’ abundances respond to area. Chapter V touches on isolation and the infringement of human enterprise on the natural environment. He contrasts “sample” and “isolate” population and tells how human infrastructure increasingly drives even large, safe populations along this perilous path to rarity. Quammen reproachfully emphasises the brutal truth that humanity is at war against other species.
This concept developed into what is known as the species-area relationship. Phillip Preston established a model- “Preston’s Bell”- to describe how rarity relates to area and why conservation efforts would be thwarted if one attempted to replicate an entire reserve on a small scale.
‘The coming thing’- chapter VI, sees the integration of models and mathematics into ecology as it moved away from a purely descriptive nature. Robert MacArthur, amongst other prominent fathers of the field, believed that pertinent patterns and predictions could be derived if the study ‘grew a quantitative backbone’. He asserts that mathematics was integral to understanding how evolutionary processes and ecological stresses shape biological communities. Equilibrium Theory of Island Biogeography was such a concept, which transformed the field of ecology. This theory describes the colonization and extinction patterns of metapopulations, and highlights the specific implications to island ecosystem composition. MacArthur and Edward Wilson authored this ingeniously logical idea, asserting that species composition is dependant only on two variables- distance from mainland and size. With this, they brought insular biogeography into the limelight of ecology and conservation, as those factors reveal how an ‘island’ ecosystem may become impoverished through ‘relaxation to equilibrium’.
Quammen enters the realm of habitat fragmentation while exploring the Amazon. He poses a crucial question that echoes Lovejoy’s enquiry- “is there a quantifiable relationship between insularization and doom?” This speaks to minimum critical sizes of conservation areas and elicits the SLOSS (Single Large or Several Small) debate. Namely, is one single large reserve better able to conserve species as opposed to several smaller reserves? Daniel Simberloff and Diamond are the main opponents in this scientific combat. Quammen explores this in detail, providing the reader with the opposing evidence, yet not explicitly offering an answer as no universal blueprint exists that can be applied to all conservation efforts.
In chapter VIII Quammen introduces the reader to the concept of minimum viable populations, using the Indri, one of the largest extant lemurs, as an example. That is, how large is a population required to be, to buffer against the four types of uncertainty: demographic, environmental, genetic and natural disasters. He leads the reader through some basic genetics such that one can fully comprehend the dangers faced by small populations. Quammen refers to conservation guidelines (e.g. 50/500 rule) and cautions against assigning a minimum requirement as this may in fact consign a species to extinction.
The penultimate chapter epitomizes the poignancy of the entire book. “The World in Pieces” not only describes the physical state of the earth’s ecosystems, but also conveys the desperate situation that besets our earth. Moreover, it describes the discord in the will, as well as the manner, to conserve. However dismal the situation might be, and despite the numerous conservation ‘rules’ provided, Quammen chooses the example of the kestrel to illustrate how no species is irredeemable. The chapter leaves the reader with the dire knowledge that, as long as humans continue to fragment the environment, species will continue to face the perils of isolation and ‘island’ life.
In chapter X, Quammen- on the last stretch of his discovery to Aru, manages to culminate the essence of extinction through the example of the “cenderawasih” (Paradisaea apoda). At a time when extinction did not cause concern, Wallace voices a perceptive truth of how humans, for all their ‘intellect’, fail to leave any virgin part of this world unscathed from intrusive meddling. The author touches on the rates of extinction in the geological past, reiterating the ominous forecast of Simberloff, who believes that the spectacular ‘evolution’ of man has triggered possibly the greatest biological demise this earth has seen.
Throughout the book, Quammen clarifies some common misconceptions- whether fundamental (adaptive radiation) or perceptions or opinions of earlier scientists (paying particularly attention towards Darwin’s reputation), that have been perpetuated for convenience sake. He applauds scientists such as Pat Wright, an avid primatologist- who pursue their obsession to find answers to questions that the environment poses, despite the difficulties encountered.
Even as a not-so-prolific reader, one is wiser and more deeply concerned. , “Biology can be no more alive and riveting as in this recollection of the perceived ‘unutilized facts of biogeography’ that Quammen has given life to”. Through his book, I believe he is able to comfort Wallace’s lament of how an overarching apathy for acquiring knowledge beyond immediate reach tends to permeate the general population. I believe Quammen renders these wonders, which are often “too distant and alien beyond imagining” accessible to even readers, of no previous knowledge of our natural world and the dangers it faces.