Rewetting of Cutaway Peatlands: Are We Re‐Creating Hot Spots of Methane Emissions?

Abstract

Hot spots of CH 4 emissions are a typical feature of pristine peatlands at the microsite and landscape scale. To determine whether rewetting and lake construction in a cutaway peatland would result in the re-creation of hot spots, we first measured CH 4 fluxes over a 2-year period with static chambers and estimated annual emissions. Second, to assess whether rewetting and lake creation would produce hot spots at the landscape level, we hypothesized a number of alternative land use scenarios for the peatland following the cessation of peat extraction. Using the results from this study and other studies from literature, we calculated the global warming potential (GWP) of each scenario and the respective contribution of CH 4 .The results showed that hot spots of CH 4 fluxes were observed as a consequence of microsite-specific differences in water table (WT) position and plant productivity. CH 4 fluxes were closely related to peat temperature at 10 cm depth and WT position. Annual emissions ranged from 4.3 to 38.8 g CH 4 m 22 yr 21 in 2002 and 3.2 to 28.8 g CH 4 m 22 yr 21 in 2003. The scenario results suggest that lake creation is likely to result in the re-creation of a hot spot at the landscape level. However, the transition from cutaway to wetland ecosystem may lead to a reduction in the GWP of the peatland.

Organic sediment formed during inundation of a degraded fen grassland emits large fluxes of CH<sub>4</sub> and CO<sub>2</sub>

“…by raising the local groundwater table, is currently being implemented in Germany with the explicit goal of reducing GHG emissions (Höper et al, 2008). Rewetting principally reduces CO 2 emissions but can often lead to a sharp increase in CH 4 release, as confirmed by field studies in fen (Hendriks et al, 2007;Wilson et al, 2008) and bog ecosystems (Tuittila et al, 2000;Drösler, 2005).…”

“…It has previously been shown that this layer releases large quantities of nutrients and dissolved organic carbon once waterlogged conditions have been re-established in peat (Zak and Gelbrecht, 2007). Furthermore, primary production and the deposition of plant litter in the top layer may increase CH 4 emissions under anoxic conditions (Tuittila et al, 2000;Juutinen et al, 2003;Wilson et al, 2008), as labile organic matter is a prerequisite for anaerobic CO 2 and CH 4 formation (Glatzel et al, 2004;Segers, 1998;Conrad, 1989). Raising the water table not only affects GHG exchange but also the vitality and composition of the vegetation (Drösler, personal communication;Clymo, 1984).…”

Peatlands, their economic value and priorities for their future management – The example of Ireland

“…There are, though, significant avoided costs. For instance, Wilson et al (2009) estimate that losses from drained industrial peatlands could be as much as 11 tonnes t CO 2 -eq per hectare per year, equal to a cost of €220 per hectare on the basis of global warming potential. On rewetting losses are reduced by around 9 tonnes CO 2 -eq.…”

Benchmarking Environmental Impacts of Peat Use for Electricity Generation in Ireland—A Life Cycle Assessment

“…Cutaway peatland restoration has been shown to reduce CO2 emissions [20], and even restore the carbon sequestration capacity compared to the original cutaway [21]. However, the return of anoxic conditions in the peatland results in an increase in CH4 flux, with 100 ha of restored wetlands emitting CH4 emissions of 105 tonnes of CO2-equivalents (CO2-eq) per year [22]. Restored peatlands are likely to contribute CH4 emissions of the same magnitude as natural peatlands [20].…”

“…However, there can be considerable losses of soil carbon from the residual peat which continues to decompose [15,19]. In terms of CH4, afforested peatlands are likely to be a modest sink; however, considerable emissions are more likely from drainage ditches [22].…”