A “peatland” is an area with a naturally accumulated layer of peat at the surface. Peatlands occupy about 384.220 km2 of the EU area and are mainly concentrated in Fennoscandia and the northwestern and Baltic countries. Around 23% of the EU peatland is in Finland, and around 19% is in Sweden. Vast peatland zones have been drained since the middle of the 20th century for intensive forestry (e.g. 1/3 of the Finnish forests are on peat soils) and, as a result, about 50% of the EU peatland area (up to 90% in Germany) is currently degraded.
Drained peatlands currently produce approx 7% of the official EU greenhouse gas emissions, being by far the largest source of emissions from agricultural land use and forestry, and their protection through conservation and sustainable management is crucial to avoid significant GHG emissions. In exploited peatland forests, planted trees sequester carbon in living biomass and litter, but their drained soils release substantial quantities of it to the atmosphere, and drainage ditches may emit considerable amounts of CH4. Nitrous oxide emissions may also be significant if fertilisers are applied. Moreover, drained soils are prone to forest and peat fires that release massive quantities of CO2 and some CH4 to the atmosphere.
In temperate and boreal peatlands, forestry abandonment and peatland rewetting are the best option for safeguarding C stocks in the long run, since by maintaining the water table close to natural levels (i.e. close to or short below ground surface), CO2 uptake by growing peat will almost compensate for moderate CH4 emissions over time.
However, where abandonment is not a realistic goal in economic terms, forest management should be oriented to conserving carbon stocks. Among the existing management options to reduce carbon losses while allowing economic exploitation of peatland forests is “Continuous Cover Forestry” (CCF). CCF should replace rotation forestry, consisting of clear-cutting followed by site preparation by furrow ploughing and further natural regeneration or tree planting.
In peatland forests, current management by clear-cutting exposes soil to higher temperatures, which potentially increases microbial activity and soil respiration. However, at the same time, removing all trees reduces transpiration and causes the water table level to rise, which in turn reduces aeration and slows down peat decomposition and CO2 emissions from soil. Although raising the water table level also increases CH4 emissions, critical factors in the final GHG balance will be the effect of raising water table on CO2 /CH4 emissions, on plant biomass production, and on increased litter input in the long run. A continuous tree cover will also keep the water table at a level which allows the new tree seedlings to survive and trees to grow, and will reduce nutrient and sediment exportation from forest plots.
However, in the long run, the final use of the harvested wood will define the mitigation value of exploited peatland forests, and therefore, this evaluation should be performed within the framework of the whole life cycle of forest exploitation.