Numerous studies conducted on hundreds of different plant species testify to the very real and measurable growth-enhancing, water-saving, and stress-alleviating advantages that elevated atmospheric CO2 concentrations bestow upon Earth’s plants (Idso and Singer, 2009; Idso and Idso, 2011). In commenting on these and many other CO2-related benefits, Wittwer (1982) wrote that “the ‘green revolution’ has coincided with the period of recorded rapid increase in concentration of atmospheric carbon dioxide, and it seems likely that some credit for the improved [crop] yields should be laid at the door of the CO2 buildup.” Similarly, Allen et al. (1987) concluded that yields of soybeans may have been rising since at least 1800 “due to global carbon dioxide increases,” while more recently, Cunniff et al. (2008) hypothesized that the rise in atmospheric CO2 following deglaciation of the most recent planetary ice age, was the trigger that launched the global agricultural enterprise. In a test of this hypothesis, Cunniff et al. designed “a controlled environment experiment using five modern-day representatives of wild C4 crop progenitors, all ‘founder crops’ from a variety of independent centers,” which were grown individually in growth chambers maintained at atmospheric CO2 concentrations of 180, 280 and 380 ppm, characteristic of glacial, post-glacial and modern times, respectively. The results revealed that the 100-ppm increase in CO2 from glacial to postglacial levels (180 to 280 ppm) “caused a significant gain in vegetative biomass of up to 40%,” together with “a reduction in the transpiration rate via decreases in stomatal conductance of ~35%,” which led to “a 70% increase in water use efficiency, and a much greater productivity potential in water-limited conditions.”
Posted on: Fri, 31 Jan 2014 16:22:52 +0000
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