How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic


Methane Emissions from Peatlands in a Warmer World
Reference
Strack, M., Waddington, J.M. and Tuittila, E.-S. 2004. Effect of water table drawdown on northern peatland methane dynamics: Implications for climate change. Global Biogeochemical Cycles 18: 10.1029/2003GB002209.

Background
The authors introduce their study by noting that climate models predict evapotranspiration will increase in a CO2-accreting atmosphere due to rising temperatures, which should lead to lowered water tables in high northern latitudes. This prediction literally cries out for an analysis of how lowered water tables will impact peatland emissions of methane (CH4), which is the atmosphere's next most important greenhouse gas after CO2; and in a theoretical study of the subject, Roulet et al. (1992) calculated that for a decline of 14 cm in the water tables of northern Canadian peatlands, due to climate-model-derived increases in temperature (3C) and precipitation (1mm/day) predicted for a doubling of the air's CO2 content, CH4 emissions would decline by 74-81%.

What was done
In an attempt to obtain some experimental data on the subject, at various times over the period 2001-2003 Strack et al. measured CH4 fluxes to the atmosphere at different locations that varied in depth-to-water table within natural portions of a poor fen in central Quebec, Canada, as well as within control portions of the fen that had been drained eight years earlier.

What was learned
The Canadian scientists report that "methane emissions and storage were lower in the drained fen." The greatest reductions (up to 97%) were measured at the higher locations, while at the lower locations there was little change in CH4 flux. Averaged over all locations, they determined that the "growing season CH4 emissions at the drained site were 55% lower than the control site."

What it means
That both theoretical and experimental approaches to evaluating the response of peatland CH4 emissions to the changes in climate predicted for a doubling of the air's CO2 content yield substantial reductions in CH4 emissions is just one of many powerful pieces of evidence that the biosphere is programmed to resist warming influences that could push it into a thermal regime that might otherwise prove severely detrimental to its well being. Other examples of biologically-induced negative feedbacks to potentially dangerous climate changes may be found in our Subject Index under the heading Feedback Factors (Biophysical).

Reference
Roulet, N., Moore, T., Bubier, J. and Lafleur, P. 1992. Northern fens: Methane flux and climatic change. Tellus Series B 44: 100-105.

Reviewed 29 December 2004