Volume 14, Number 47: 23 November 2011
In an Opinion article published in Global Change Biology, Hof et al. (2011) note that recent and projected climate change is assumed to be exceptional because of its supposedly unprecedented velocity; and they say that this view has fuelled the prediction that CO2-induced global warming "will have unprecedented effects on earth's biodiversity," primarily by driving many species to extinction, because of the widespread belief that earth's plants and animals are unable to migrate poleward in latitude or upward in altitude fast enough to avoid that deadly consequence, as well as the assumption that current climate change simply outpaces evolutionary adaptation. But are these assumptions correct?
The four biological researchers address this important question in stages. First, they present evidence demonstrating that "recent geophysical studies challenge the view that the speed of current and projected climate change is unprecedented." In one such study, for example, they report that Steffensen et al. (2008) showed that temperatures in Greenland warmed by up to 4°C/year near the end of the last glacial period. And they state that this change and other rapid climate changes during the Quaternary (the last 2.5 million years) did not cause a noticeable level of broad-scale, continent-wide extinctions of species. Instead, they state that these rapid changes appeared to "primarily affect a few specific groups, mainly large mammals (Koch and Barnosky, 2006) and European trees (Svenning, 2003)," with the result that "few taxa became extinct during the Quaternary (Botkin et al., 2007)." So how were the bulk of earth's species able to survive what many today believe to be unsurvivable?
Hof et al. speculate that "species may have used strategies other than shifting their geographical distributions or changing their genetic make-up." They note, for example, that "intraspecific variation in physiological, phenological, behavioral or morphological traits may have allowed species to cope with rapid climatic changes within their ranges (Davis and Shaw, 2001; Nussey et al., 2005; Skelly et al., 2007)," based on "preexisting genetic variation within and among different populations, which is an important prerequisite for adaptive responses," noting that "both intraspecific phenotypic variability and individual phenotypic plasticity may allow for rapid adaptation without actual microevolutionary changes."
So do these observations imply that all is well with the planet's many and varied life forms? Not necessarily, because, as Hof et al. continue, "habitat destruction and fragmentation, not climate change per se, are usually identified as the most severe threat to biodiversity (Pimm and Raven, 2000; Stuart et al., 2004; Schipper et al., 2008)." And since Hof et al. conclude that "species are probably more resilient to climatic changes than anticipated in most model assessments of the effect of contemporary climate change on biodiversity," these several observations suggest to us that addressing habitat destruction and fragmentation, rather than climate change, should take center stage when it comes to striving to protect earth's biosphere, since the former more direct and obvious effects of mankind are more destructive, more imminent and more easily addressed than are the less direct, less obvious, less destructive, less imminent, and less easily addressed effects of the burning of fossil fuels.
Sherwood, Keith and Craig Idso
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Hof, C., Levinsky, I., Araujo, M.B. and Rahbek, C. 2011. Rethinking species' ability to cope with rapid climate change. Global Change Biology 17: 2987-2990.
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