How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

Species Assigned to Climate Envelopes in a Warming World
Sears, M.W., Raskin, E. and Angilletta Jr., M.J. 2011. The world is not flat: Defining relevant thermal landscapes in the context of climate change. Integrative and Comparative Biology 51: 666-675.

Climate alarmists have historically predicted catastrophic species extinctions based on the presumption that CO2-induced global warming will be so fast and furious that many species of plants and animals will not be able to migrate either poleward in latitude or upward in altitude rapidly enough to remain within the "climate envelope" to which they are accustomed.

What was done
In a study of this subject, Sears et al. analyzed how spatial heterogeneity can impact biological responses to thermal landscapes at scales that are more relevant to organisms than are the (much larger) scales implied by standard climate envelopes, which they did by examining the effects of topographic relief on the range of operative temperatures that are available for behavioral thermoregulation within various parts of an area described by a given climate envelope.

What was learned
The three researchers report that "empirical studies alone suggest that the operative temperatures of many organisms vary by as much as 10-20°C on a local scale, depending on vegetation, geology, and topography," while noting that even this variation in abiotic factors "ignores thermoregulatory behaviors that many animals use to balance heat loads." And through a set of simulations of these phenomena, they "demonstrate how variability in elevational topography can attenuate the effects of warming climates." More specifically, they find that (1) "identical climates can produce very different microclimates at the spatial scales experienced by organisms," that (2) "greater topographic relief should decrease selective pressure on thermal physiology for organisms that use behavior to avoid thermal extremes in heterogeneous environments," citing Huey et al. (2003), and that (3) "topographic diversity should buffer the impacts of climate change by facilitating behavioral thermoregulation."

What it means
The results of their analysis suggest, as Sears et al. describe it, that well-known relationships in biophysical ecology show that "no two organisms experience the same climate in the same way," and that "changing climates do not always impact organisms negatively." Hence, they conclude that "when coupled with thermoregulatory behavior, variation in topographic features can mask the acute effect of climate change in many cases," which renders the climate envelope approach to assessing species responses to climate change rather useless, if not even deceptive.

Huey, R.B., Hertz, P.E. and Sinervo, B. 2003. Behavioral drive versus behavioral inertia in evolution: a null model approach. American Naturalist 161: 357-366.

Reviewed 25 January 2012