Active afforestation of drained peatlands is not a viable option under the EU Nature Restoration Law.

The EU Nature Restoration Law (NRL) is critical for the restoration of degraded ecosystems and active afforestation of degraded peatlands has been suggested as a restoration measure under the NRL. Here, we discuss the current state of scientific evidence on the climate mitigation effects of peatlands under forestry. Afforestation of drained peatlands without restoring their hydrology does not fully restore ecosystem functions. Evidence on long-term climate benefits is lacking and it is unclear whether CO2 sequestration of forest on drained peatland can offset the carbon loss from the peat over the long-term. While afforestation may offer short-term gains in certain cases, it compromises the sustainability of peatland carbon storage. Thus, active afforestation of drained peatlands is not a viable option for climate mitigation under the EU Nature Restoration Law and might even impede future rewetting/restoration efforts. Instead, restoring hydrological conditions through rewetting is crucial for effective peatland restoration.

Water pollution risks by smoldering fires in degraded peatlands.

Climate change may increase the overall susceptibility of peatlands to fire. Smoldering fires in peatlands can cause substantial emissions of greenhouse gases. It is, however, less clear how smoldering affects the soil pore water quality. In this study, soil samples were collected from agricultural fen and disturbed bog study sites in Germany and Lithuania to quantify the effect of peat burning on pore water composition. The samples were air dried and smoldered under ignition temperature (approximately 200 °C) with different durations (0, 2, 5, and 10 h). Pore water samples were extracted from the soil to determine dissolved organic carbon (DOC) concentrations, dissolved organic matter (DOM) fractions, fluoride, extractable organically bound fluorine (EOF), and sulfate concentrations. The results showed that soil smoldering changes the peat pore water chemistry and that changes differ between fens and bogs. The smoldering duration is likewise influential. For fen grasslands, 2 and 5 h of smoldering of peat caused a >10-fold increase in DOC (up to 1600 mg L-1) and EOF concentrations. The fluoride (up to 60 mg L-1) and sulfate concentrations substantially exceeded WHO drinking water guidelines. In contrast, the temperature treatment decreased the DOC concentrations of samples from raised bogs by 90 %. The fluoride concentrations decreased, but sulfate concentrations increased after smoldering of the bog samples. DOC, fluoride, and sulfate concentrations of bogs varied significantly between the smoldering duration treatments. For all peat samples, the extracted DOM was dominated by humic-like substances before smoldering, but the fraction of low molecular weight substances increased after smoldering combustion. In conclusion, smoldering alters the biogeochemical processes in both peatland types and possibly impair the water quality of adjacent water resources especially in fen peat landscapes.

To store or to drain - To lose or to gain? Rewetting drained peatlands as a measure for increasing water storage in the transboundary Neman River Basin.

Agriculture continues to place unwanted pressure on peatland functionality, despite international recognition calling for their conservation and restoration. Rewetting of peatlands is often the first step of restoration that aims towards improving the delivery of ecosystem services and their benefits for human well-being. Ongoing debates on peatland restoration in agricultural landscapes raise several issues based on the valuation of benefits achieved versus the costs of peatland restoration. Using the transborder Neman River Basin in North-Eastern Europe, this study aimed to quantify and evaluate the gains provided by peatland rewetting. To achieve this, this study estimated i) possible changes in water storage capacity from peatland restoration, ii) the value of expected benefits from restoration and iii) costs of restoration measures at the overarching basin level. Applying multiple assumptions, it was revealed that rewetting drained peatlands in the Neman River Basin could increase water retention by 23.6-118 M m3. This corresponds to 0.14-0.7% of the total annual Neman River discharge into the Baltic Sea. Unit increase of water retention volume due to rewetting ranged between 69 and 344 m3·ha-1. The estimated water retention value ranged between 12 and 60.2 M EUR·year-1. It was also shown that peatland rewetting at the scale of Neman River Basin would cost from 6.8 M and 51.5 M EUR·year-1 depending on the selected scenario. Applying less expensive rewetting measures (non-regulated outflow from ditch blocks), the economic gains (as water storage ecosystem service of rewetted peatlands) from rewetting exceed the costs of rewetting. Thus, rewetting peatlands at a river-basin scale can be considered technically and economically efficient measures towards sustainable management of agricultural landscapes. The novel methodology applied in this study can be used when valuing trade-offs between the rewetting of drained peatlands and leaving them drained for the uncertain future of wetland agriculture.