text: Jin et al . write that the bioavailability of iron to terrestrial plants "is often limited (Guerinot and Yi, 1994), particularly in calcareous soils, which represent 30% of the earth's surface (Imsande, 1998)," and they thus conclude that "Fe nutrition in plants is likely to be affected by the continued elevation of atmospheric CO 2 , which, in turn, will affect crop production." And as their work strongly suggests, those important effects should be highly beneficial, while even wider biospheric benefits are suggested by the work of Sasaki et al . (1998), who have demonstrated that both the ferric reductase activity and Fe uptake capacity of the marine alga Chlorococcum littorale cultured in Fe-limited media have been significantly enhanced by elevated CO 2 concentrations. References