Arecent survey of published ecologists and evolutionary biologists suggests that the more a person knows about climate change, the higher he or she estimates its magnitude and the greater risk he or she perceives it poses to biodiversity (Javeline et al. 2013). Scientists reporting to be the most knowledgeable about climate change anticipated 0.6 degrees more warming within the twenty-first century than the least knowledgeable scientists did and expected 5 percent more species to go extinct and more than 20 percent more species to change their ranges under climate change than did less knowledgeable scientists. These findings suggest that greater expertise confers greater concern about the climatic changes that confront human and natural systems.
This is one reason among many for which Eric Post's recent book, Ecology of Climate Change: The Importance of Biotic Interactions, has an important role to play. It can increase understanding among budding and established biologists by serving as a reference and tutorial. The book covers the role of climate in past extinction, the potential for climate to shift phenology and life histories, how warming alters populations and communities, and the effect of climate change on the global carbon cycle and carbon storage in the biosphere. Post reviews much of the relevant literature, with an emphasis on his own study system in Greenland and his own interest in large animals and the Arctic. The book is also focused on density-dependent processes and stability theory and includes several models to explore how climate change might affect population dynamics and the coexistence of species. Its relatively lengthy text is useful for aspiring climate change biologists who want to make inferences about climate in ecological processes using models, field experiments, and meta-analyses.
Ecology of Climate Change purports to be focused on species interactions, but it is not until page 167 that Post defines what he means by this emphasis. His concept of interaction relies on density dependence as a key regulatory process. Interactions among species may or may not be density dependent, however, or the effects of species interactions may occur at densities at which density-dependent effects are relatively weak (Ziebarth et al. 2010). That Post pays lesser attention to these possibilities reflects a particular tradition in community ecology.
The author's synthesis raises several intriguing questions. For example, is there an “ecology” of climate change, a general theory that allows us to combine direct (physiological) and indirect (interaction-mediated) effects of climate change and make projections? What is the relative importance of different perspectives of ecology in building this new theory? In which cases do interactions among species rise above ecophysiological processes that are often more conducive to experimentation and measurement? Post offers surprisingly few predictions about how climate change will alter the face of the planet, other than extending basic observations of advancing phenology and changing distributions and abundances. The book is not targeted at managers or decisionmakers, and no management solutions or conservation actions are suggested.
Several provocative ideas in the book could lead to specific predictions, however. One example is the author's claim that “lateral” communities dominated by interspecific competition may be stabilized by climatic variability (e.g., Adler et al. 2006), whereas “vertical” communities dominated by trophic interactions are destablilized or perturbed by changing conditions (e.g., Post and Forchhammer 2001). Post suggests the latter using a model and stability analysis but calls on further research to test the generality of his claim. A key challenge will be delineating when a community is more lateral or more vertical in character.
A second provocative example is Post's call for ecosystem ecologists and global biogeochemists to include animals in carbon accounting—animals that we know can have a strong influence on plant productivity through top-down processes (e.g., Kurz et al. 2008). Drawing an analogy to megafaunal extinctions in the Pleistocene, Post emphasizes that ecologists fail to include animals in carbon cycling models at our collective peril. Models that include herbivore control of productivity, for example, could lead to significantly less carbon storage than do models that include only plant growth, and this could imply a warmer world overall.
A number of important issues receive little or no treatment in Ecology of Climate Change: The biogeography of adaptive genetic variation within and among species stands out as one example. We know that these processes can hinder or promote ecosystem transformation, depending on the circumstances (Pelini et al. 2009, Hoffmann and Sgrò 2011). Post also has relatively little to say about the geography of climate change, such as climate-mediated dispersal or other processes of geographic range change (e.g., Schloss et al. 2012). This leaves room for other authors.
No volume can provide the definitive answer on a topic as broad and complex—or as important—as climate change ecology, but Post's contribution is a useful start.