Elevated concentrations of CO₂ may double methane emissions from mires

The potential impact of an increase in methane emissions from natural wetlands on climate change models could be very large. We report a profound increase in methane emissions from cores of mire peat and vegetation as a direct result of increasing the CO 2 concentration from 355 to 550 μol mol −1 (a 60% increase). Increased CH 4 fluxes were observed throughout the four month period of study. Seasonal variation in CH 4 flux, consistent with that seen in the field, was observed under both ambient and elevated CO 2 . Under ambient CO 2 , methane fluxes rose from 0.02 μol m ‐2 s −1 in May to 0.11 μol m −2 s −3 in July before declining again in August. Under elevated CO 2 methane fluxes were at least 100% greater throughout the experiment, rising from 0.05 μol m ‐2 s −1 in May to a peak of 0.27 μol m −2 s −1 in July. The stimulation of CO 4 emissions was accompanied by a 100% increase in rates of photosynthesis from 4.6 (± 0.3) under ambient CO 2 to 9.3 (± 0.7) μol m −2 s −1 . Root and shoot biomass were unaffected.