wise use of mires and peatlands - Peatland Ecology Research Group

VALUES AND FUCTIONS OF MIRES AND PEATLANDS79Re-wetting of drained alder forests leads toincreased emissions of methane, but todecreasing nitrous oxide emissions.Climate change: The distribution of miresand mire types over the globe clearly reflectstheir dependence on climate. As mires areconcentrated in humid or cool regions, achanging climate can be expected to seriouslyaffect their carbon balance and radiativeforcing.Most climate models suggest that thenorthern regions, which contain most of theworld’s peatlands, will become significantlywarmer in the 21 st century - continental areas(though this is less certain) becoming drierand oceanic areas becoming wetter. Sinceboth net primary production anddecomposition are closely related to moistureand temperature, significant alterations in thecarbon dynamics of peatlands may result.Some researchers stress the importance ofalterations in the water table level, which mightincrease carbon accumulation in northernpeatlands but might create a greater sourceof carbon dioxide in the more southernpeatlands. Others stress the importance of arise in temperatures and suggest that a netloss of carbon will take place in northern fensbut a net gain in northern bogs.The behaviour of permafrost peatlands willalso be important, as both decomposition andnet primary production are acceleratedfollowing permafrost melt. In general,methane emissions from peatland ecosystemswill decrease with drying. Increasedtemperatures and thaw depth in wet tundraecosystems could, however, also increasemethane fluxes, especially when, as climatemodels indicate, precipitation at northernlatitudes increases.It may be concluded that there are still toomany uncertainties in the magnitude and thedirection of potential changes to arrive at afinal conclusion on the reaction of mires andpeatlands to global warming.Conclusion: The atmosphere and the ocean,and the interactions they have with livingthings constitute a complex dynamic systemwith many interconnections and feedbacks.This complexity explains the uncertainty andcontroversy about greenhouse gases andclimate change 184 . Most scientists believethat small changes in the “inputs” to theclimate system will result in small changes tothe resulting climate and that climate changewill take place gradually over a period of manydecades. If change is gradual, the overalleconomic impact on wealthy countries willprobably be modest. Because of thefeedbacks, the response of the climate to anincrease in greenhouse gases could, however,also be “nonlinear” meaning that a smallchange in an input might produce a majorchange in climate, such as might be broughtabout by a sudden change in the generalpattern of ocean circulation. If that happens,the economic costs to wealthy countriescould be very large, as much new investmentmight be needed in a very short period oftime.Whether it is fast or slow, climate change islikely to have greater economic impacts onpoor countries than on rich countries,because poor countries have less capacityto adapt to changes and because traditionallife styles depend more directly on a specificclimate. In the long run, if sea levelscontinued to rise, even developed countriesmight begin to experience serious costs, asmany of the world’s largest cities are in lowlyingcoastal locations.Because of this small but realistic risk of largeand negative effects of climate change, aprecautionary policy 185 should take intoaccount the climate regulatory function ofmires and peatlands, especially their role asmajor long-term stores of carbon.