How does rising atmospheric CO2 affect marine organisms?

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Effects of Warming on the Terrestrial Vegetation of Antarctica
Green, T.G.A., Sancho, L.G., Pintado, A. and Schroeter, B. 2011. Functional and spatial pressures on terrestrial vegetation in Antarctica forced by global warming. Polar Biology 34: 1643-1656.

The authors write that "there is growing interest in the distribution of terrestrial organisms in Antarctica because of the potential use of biodiversity as an indicator or predictor of the effects of climate change," with the particular value of Antarctica in this regard being "its relative pristine nature with almost no anthropogenic influences on the present distributions of terrestrial vegetation," as well as "the relative simplicity of the vegetation itself being composed only of bryophytes and lichens with the exception of the presence of two vascular plants in the Antarctic peninsula."

What was done
Green et al., as they describe it, looked at "the relationship between temperature and the occurrence of mosses, lichens and hepatics [liverworts] within Antarctica ... by using published information, particularly the key paper of Peat et al. (2007), melding this with climate data and then applying performance data from ecophysiological studies to probe how organisms respond, or have responded, to the severe Antarctic climate."

What was learned
The four researchers first determined that the terrestrial vegetation of Antarctica could be divided into two zones: (1) the micro-environmental zone south of approximately latitude 72°S, where "biodiversity (richness and location) is uncoupled from the macro-environment and is, instead, determined by the occasional coincidences of warmth, water, light and shelter," and (2) the macro-environmental zone lying north of 72°S, where "biodiversity (richness, cover and growth) is strongly positively linked to mean annual temperature." And in this latter zone they found that "species numbers increase at about 9-10% per °C (24.0, 9.3 and 1.8 species for lichens, mosses and hepatics, respectively), probably due to improved water availability through increased precipitation and longer active period allowing greater productivity, completion of metabolic processes and a switch from survival to growth strategies."

What it means
As a result of their findings, Green et al. make a few predictions about "what is likely to happen to Antarctic vegetation if temperatures increase," among which they predict that (1) "there will be an increase in biodiversity at the rate of around 9-10% of present total species numbers per 1°C rise in mean temperature," (2) "there will be an equivalent southward movement of species in the macro-environmental zone," (3) "there will be a southward extension of the macro-environmental zone at the approximate rate of around one degree latitude per 1°C increase in mean annual temperature," and (4) "at any particular site in both micro- and macro-environmental zones, an increase in annual growth rate of crustose lichens is expected." Thus, it would appear that Antarctica is poised to get somewhat "greener" if air temperatures continue to rise, due to whatever it may be that might propel them upwards.

Peat, H.J., Clarke, A. and Convey, P. 2007. Diversity and biogeography of the Antarctic flora. Journal of Biogeography 34: 132-146.

Reviewed 7 March 2012