Climate Change and Biodiversity. Thomas E. Lovejoy and Lee Hannah, eds. Yale University Press, New Haven, CT, 2005. 418 pp., illus. $65.00 (ISBN 0300104251 cloth).
If in the mind's eye one can envision all all the animals (including humans), the plants, and all the microbes in any ecosystem—managed and unmanaged, across any spatial or temporal scale, from soil pores to landscapes, from rural to urban, from the vast stretches of time behind us to those that lie before us—then one has come to grips with the extraordinarily complex concept of biodiversity. It may be surprising that so ungainly a concept has become a cornerstone of environmental ecology, but its success lies in its ability to accommodate the complexity and scope of modern environmental ecology.
Nowhere is its utility more evident than in the conceptual framework of the Millennium Ecosystem Assessment (2003), in which 1400 experts from 95 countries conducted a five-year, multi-scale, multisectoral assessment of Earth's environment. The assessment's framework explicitly links changes in biodiversity to changes in ecosystem services, which in turn lead to changes in human well-being. In a nutshell, by understanding biodiversity and the many drivers of its change, humans can better understand, and perhaps better manage, our environmental fate. Climate Change and Biodiversity, edited by Thomas E. Lovejoy and Lee Hannah, reviews one such driver—climate change.
Of all the well-known and dramatic drivers of biodiversity change, including habitat change, exotic species invasions, overexploitation, and pollution, why, one might ask, do we need a stand-alone volume on climate change? The answer, at least according to the preface of Climate Change and Biodiversity, is simple. Climate change is “threatening to accelerate the loss of biodiversity already under way due to other human stressors,” so much so that “it is now clear that climate change is the major new threat that will confront biodiversity this century” (p. x). Biodiversity, already being driven to staggeringly low levels by habitat change, invasions, overexploitation, and pollution, will be dealt its deathblow by climate change.
Lovejoy and Hannah organize their volume into six parts: (1) an overview of the issue and general introduction to climate change; (2) current, (3) past, and (4) future trends; and response options for (5) conservation biologists and (6) policymakers. I was immediately struck by a lack of coverage of biodiversity itself, and I also wondered why current trends in biodiversity responses to climate change are discussed before past trends. These oddities aside, the book's impressive lineup of 66 contributors represents a full spectrum of environmental ecologists (e.g., from academic institutions, agencies, and NGOs), a balance seldom achieved by such volumes. Not surprisingly, given the extreme heterogeneity of its authorship, the volume's 24 chapters and its sprinkling of case studies vary in quality, but collectively they provide excellent coverage of a complex topic. More surprising was the fair number of poor-quality figures (with excessive contrast, low resolution, or eclectic font usage, for example). No doubt some readers will be cheered by the now obligatory inclusion of several color plates of tiny Mercator projections of computer-generated visions of Earth.
While there is much to recommend this volume, there is cause for quibbling, which is a good sign, indicating that the book will serve well as material for lively graduate seminars. There are, however, two shortcomings worth mentioning. First, in spite of declarations throughout, the case for the primacy of climate change is never solidly developed. For example, chapters 3 through 6 review the brilliant work of Camille Parmesan, Terry L. Root, Lesley Hughes, Chris D. Thomas, and their many colleagues who have provided, in my opinion, unequivocal proof that the ranges, phenologies, and population genetic structures of many species of plants and animals have responded to climate change. These changes, however, are subtle in comparison with the horrific impacts other drivers are having on biodiversity. Parmesan acknowledges, for example, that “these trends may appear small compared to massive changes in species distributions caused by habitat loss and land use modification,” but nevertheless concludes that such changes could “alter species interactions, destabilize communities, and drive major biome shifts” (chap. 4, p. 53). Similarly, Thomas reviews convincing evidence that some species already show evolutionary responses to climate change, but concludes from only a small number of examples that, “directly or indirectly, climate change is likely to dominate the evolutionary process over the next century and more” (chap. 6, p. 83). It's not so much that I find these claims implausible, just that a biotic “signature” of climate change does not make it the primary driver of biodiversity loss.
The idea of climate change as a major driver of biodiversity change hardly needs selling. Sala and colleagues'article “Global Biodiversity Scenarios for the Year 2100” (2000) and the Millennium Ecosystem Assessment's Biodiversity Synthesis Report (2005), two independently authored (with the exception of the omnipresent Hal Mooney) expert opinion assessments, ranked climate change as second and third, respectively, among the top five anthropogenic drivers of biodiversity change. And the case for effective policy to mitigate the harmful effects of climate change on biodiversity has already been made in the Intergovernmental Panel on Climate Change's technical report of the same title as this volume (Gitay et al. 2002). What is needed now is to go beyond expert opinion and freehanded extrapolation.
The key to cinching climate change as the mother of all drivers, or, more aptly, the driver of drivers, is the enormous number of synergies between climate change and other drivers—the modus operandi of climate change as coup de grâce. This brings me to the book's second shortcoming. Synergies and feedbacks are both key components of the impacts resulting from climate change, and though they are alluded to in several places, the discussion of their role is never fully developed. I would have thought the dominant portion of such a volume would be devoted to these issues. The chapter by Drake and colleagues (chap. 18), however, is the only chapter devoted to synergistic effects. Although limited in depth and scope, no doubt for reasons of space, its review of many examples of synergistic effects, such as the impacts of climate change on burning, plant community composition, plant–microbe interactions, and vectorborne diseases (with a case study by LaPointe and colleagues on avian malaria in Hawaiian birds), goes a long way toward explaining why climate change is ranked so highly by independent expert assessment as a driver of changes in biodiversity. Allan, Palmer, and Poff's examples of complex feedbacks in freshwater systems (chap. 17) also provide good examples of synergies and feedbacks. These are what make climate change a real worry and a challenge for developing effective conservation strategies.
Quibbles aside, this volume, like its predecessor, Global Warming and Biological Diversity (Peters et al. 1992), will become the standard text on climate change as a driver of biodiversity change. The last chapters (pts. V and VI) make a strong case for two courses of action: bringing climate change more strongly into conservation planning (with some powerful examples using computationally intensive methods presented in chaps. 14 and 15) and getting on board with climate change mitigation. Though one might argue (and certainly I would) about the alleged primacy of climate change among the woes biodiversity faces, the fact remains that climate change is real, it's happening now, it needs to be dealt with, and this volume shows the way. In the penultimate chapter, Bob Watson states the challenge nicely: “Unless we act now to limit human-induced climate change, history will judge us as having been complacent in the face of compelling scientific evidence…. Leaders from government and industry must stand shoulder to shoulder to ensure that the future of the Earth is not needlessly sacrificed” (chap. 23, p. 385).