## 3 Literature Review
#### 3.1.2. Peatland Management and Restoration Strategies
A groundwater level that is too high will cause surface water to accumulate, forming lakes that, in turn, also hinder vegetation growth and negatively affect biodiversity [52] in peat bogs [65]. Therefore, the groundwater level must be continuously monitored. One can also use peat or wood for drain-blocking or dam construction. However, there is less information about the efficiency of using such raw materials in peatland rewetting [81]. The amount of GHG emissions reduction after rewetting can differ regarding peatlands' biological processes [5]. Also, emissions vary due to factors like vegetation, level and water table fluctuation, and land use history [5]. _Carbon dioxide (CO\({}_{2}\))_  
Based on the literature, it is estimated that CO\({}_{2}\) emissions will reduce after the water table level increases [29]. It is estimated that increasing the water table level by about 10 cm can reduce emissions of three tons of CO\({}_{2}\) equivalent ha\({}^{-1}\) yearly [30]. Some studies suggest that rewetting peatlands and restoring the hydrological conditions using dams or drainage blocking can reduce CO\({}_{2}\) emissions by 70%, and rewetting peatlands can reduce or even stop carbon loss [45]. As previously mentioned, GHG emissions after rewetting can vary, from strong sinks of ~8 tons of CO\({}_{2}\) equivalent ha annually to 0.71 tons of CO\({}_{2}\) equivalent ha annually [5]. For large emissions sources, it could be even 25 to 53 tons of CO\({}_{2}\) equivalent ha annually [5]. Studies in 2023 [29] showed that rewetting drained peatlands can reduce CO\({}_{2}\) emissions by 1.343 \(\pm\) 0.36 Mg CO\({}_{2}\) -C ha\({}^{-1}\) year \({}^{-1}\)[29]. For the EU, peatland mitigation potential through rewetting is estimated to be ~51-54 megatons of CO\({}_{2}\) equivalents annually [36]. The European Commission estimated that interrupting peat extraction would be possible to achieve an emission reduction of ~9 megatons CO\({}_{2}\) equivalent annually [5]. According to studies, rewetting can reduce annual CO\({}_{2}\) emissions in forested peatlands by as much as 15.4 tons of CO\({}_{2}\) equivalent per hectare, 25% lower than emissions before forested peatland rewetting [29]. If the rewetting of degraded grasses is carried out on peat soils, it is estimated that it is possible to reduce emissions by 20 tons of CO\({}_{2}\) equivalent per hectare annually. The rewetting of cultivated crops can reduce CO\({}_{2}\) emissions by even 30 tons of CO\({}_{2}\) equivalent ha\({}^{-1}\) annually. There is a reported annual reduction in GHG 773 tons CO\({}_{2}\) equivalent for a rewetted peatland in northeastern Germany [126]. From 1990 to 2019, roughly 150 hectares of drained organic soils were rewetted on forest land in Sweden. The cumulative decrease in emissions was 9.5 kilotons over two decades, but the factual numbers could be higher [127]. It is estimated that rewetting all organic soils in Denmark will result in a reduction of CO\({}_{2}\) emissions of about 4.1 million tons [127]. _Methane (CH\({}_{4}\)) emissions_  
Determinants of CH\({}_{4}\) emissions in naturally formed peatlands include the pH level of vegetation and soil, hydrological regime, and groundwater depth [40; 125]. As a result of the increase in water table level due to rewetting, methane forms a more potent greenhouse gas than CO\({}_{2}\)[49]. The radiation efficiency of CH\({}_{4}\) is substantially larger than that of CO\({}_{2}\)[125]. In drained peatlands, CH\({}_{4}\) emissions are low if the water level is less than 20 cm below the surface [39]. Rewetting may increase the CH\({}_{4}\) emissions and cause the input of nutrients in the short term [39]. Peatlands, after rewetting and sequestering CO\({}_{2}\), may emit up to 46% more CH\({}_{4}\)[25; 40]. The uncertainty in the scientific literature regarding emissions from rewetted peatlands is significant [29; 45; 83]. The 2014 Intergovernmental Panel on Climate Change (IPCC) Wetlands Supplement excluded emissions from rewetted drainage ditches.