Occupying merely 0.4% of the global land surface, drained peatlands emit ~2 Gt of carbon dioxide (CO2
) as a result of microbial oxidation of peat and peat fires, which account for ~5% of all anthropogenic greenhouse gas (GHG) emissions [1
]. These emissions constitute more than a quarter of the GHG emissions associated with Agriculture, Forestry, and Land Use (AFOLU) [2
]. After peatlands are drained, intense methane (CH4
) emission may occur from the drainage network and in small amounts after rains or snowmelt also from the intercanal spaces, and also nitrous oxide (N2
O) emission as well as dissolved organic matter (DOC) export with runoff water [3
Drained peatlands, especially when unused and abandoned, are extremely fire- prone [5
], because of the abundance of combustible material per unit area [6
], and susceptibility to fire increases with the intensity of drainage [8
As a result of progressive anthropogenic drainage, the planet’s peatlands have since 1960 changed from a net global sink to a net source of GHGs. Without action, GHG emissions from drained peatlands are projected by 2100 to consume 12–41% of the remaining GHG budget to keep global warming below +1.5–+2 °C [9
]. This illustrates the hitherto underexposed importance of drained peatlands for the implementation of the Paris Climate Agreement. The relevance of reporting and accounting for anthropogenic emissions from peatlands and wetlands directed the development of the 2013 Supplement to the 2016 Guidelines for National Greenhouse Gas Inventories: Wetlands [10
The most effective way to reduce GHG emissions from drained peatlands is their rewetting [11
]. The IPCC Special Report “Climate Change and Land” [12
] notes that peatland restoration targets the most carbon-rich lands and thus involves less area and less impact on land-use when considering climate change mitigation and adaptation measures. Peatland restoration, for example, requires three times less nitrogen compared to storing a similar amount of carbon in mineral soils [11
]. Restoring peatlands through rewetting may significantly reduce GHG emissions [13
], even in the case of increased CH4
], reduce peat fires [15
], and help restore biodiversity [17
], hydrological [18
] and other peatland ecosystem functions [19
]. However, when summarizing the various mitigation options, IPCC [12
] attributed only medium confidence to peatland restoration, likely due to a lack of scientifically validated data on the effectiveness of peatland rewetting.
Russia has the largest extent of peatlands worldwide [20
]. Peatlands occupy more than 8% and together with shallow peatlands (peat < 30 cm) more than 20% of the Russian territory [21
]. Most peatlands are preserved in their natural state, but more than eight million hectares have been drained for agriculture, forestry and peat extraction [23
]. Drained peatlands are mainly located in the European part of the country [24
], in the south of Western Siberia and in the Far East [23
]. Peat extraction has been the main driver of peatland drainage and degradation, especially milled peat extraction with intensive drainage, which is the dominant industrial method in Russia and many other countries. Peat mining has affected 0.85–1.5 [23
] or 0.9 million hectares [27
] of peatlands, 70% of which is attributable to milled peat extraction.
In the Soviet Union, cutover peatlands were normally recultivated for agriculture, less often for other purposes. However, after the decline of the peat industry in the early 1990s an increasing area of predrained and partially excavated areas was abandoned and no longer recultivated [5
]. As of 1 January 2000, the area listed under peat extraction in Russia was 242.3 thousand ha [28
]. The National Cadastre of Anthropogenic Sources and Sinks of Greenhouse Gases [29
] reported that from 2000 to 2007 this area had decreased from 261 to 219 thousand ha. However, due to the complex accounting of drained peatlands in the national economy [28
], these data are approximate. The reported areas are probably predominantly milling sites and include all sites that IPCC [10
] attributes to peat extraction, i.e., prepared (increasingly less due to the reduced opening of new deposits), under extraction, and abandoned after partial extraction without reclamation. Abandoned milling fields revegetate with difficultly and may stay bare for years, which makes them easily identifiable from satellite imagery [16
These milled peat extraction fields lose, depending on the hydrometeorological conditions, 1.6–4.7 tC ha−1
by microbial oxidation (irrespective of water and wind erosion). This means that the volume of peat mineralized in 10 years is comparable to the annual volume of peat extracted in industrial mining [33
]. The amount of organic matter available for microbial oxidation to CO2
is limited to the peat layers above the groundwater table and emissions may decrease over time, if the surface of the peatland subsides. According to some estimates, Russia is, after Indonesia and the European Union, the World’s largest GHG emitter from drained peatlands [34
]. At the same time, the significant areas of drained and abandoned peatlands represent a serious potential for reducing greenhouse gas emissions, in addition to the urgent tasks of reducing fire risk and enhancing climate change adaptation capacity by improving environmental safety.
As in many other countries, peatland rewetting in Russia was initiated by environmental NGOs, specially protected areas and other stakeholders and aimed at restoring peatland related biodiversity [23
]. According to the Water Code of the Russian Federation (2006) [36
] peatlands are “water bodies”, which after peat extraction should be rehabilitated primarily through rewetting (article 52 WC). After severe peat fires in central European Russia in 2002 and especially in 2010, the prevention of peat fires became the main driver for rewetting [5
]. In 2010–2013, more than 73,000 ha of fire-prone peatlands, i.e., a significant part of the peatlands in that region [37
], were rewetted in the Moscow Region (Figure 1
), which was at that time the most extensive peatland rewetting initiative in the Northern Hemisphere.
Long-term monitoring showed that the main goal of rewetting, the reduction in the number and extent of peat fires, has been achieved [16
]. However, it is also important to estimate the GHG emission changes resulting from rewetting. As official statistics on rewetted peatlands in Russia are lacking, it is, first of all, necessary to determine the areas that are rewetted to be included in the national greenhouse gas reporting of the Russian Federation to the UNFCCC [38
]. The purpose of this paper is to present such methodology and, using the example of rewetted areas in Moscow Region, assess the associated greenhouse gas emission reduction using emission factors proposed by the IPCC [10
]. In addition, using the example of one peatland site, we show the applicability of this approach to estimate the GHG emission reduction in a concrete peatland restoration project.
Due to the large uncertainties in the EFs, and especially those of methane, emission reduction has a large range of possible values, which can be approximated by a normal distribution (Figure 8
). Actual emission reductions from a concrete site may, with a probability of 95%, lie between the confidence limits. The calculated values were obtained by substituting the emission factors into Equation (1), and the mean values were calculated according to the distribution of random values. The calculated and average values differ from each other because of the asymmetric uncertainties of the emission coefficients. Therefore, the emission estimates made according to Equation (1) will also differ from the mean. Calculated values have to be used for the reporting, but to understand and forecast, we need to consider mean values as well.
If we assume that the rewetting of the drained peatlands took place at one point in time, we do not need to consider possible changes in the extent of rewetted areas. Without rewetting, annual GHG emissions would lead to an increasing climate burden over time, especially because of the accumulation of the persistent CO2
in the atmosphere [14
]. After rewetting, annual GHG emissions would remain lower, resulting in a cumulatively increasing positive climatic effect compared to the drained situation.
Calculations show that CO2
emission reductions for the Radovitsky Mokh peatland cumulatively have reached 29 thousand tons of CO2
in 2020, and will amount to almost 110 thousand tons of CO2
by 2050 (Figure 9
). If the increased CH4
emissions after rewetting are taken into account, GHG emission reductions for this single peatland have been over 17 thousand tons CO2
-eq. in 2020 and will be over 66 thousand tons CO2
-eq. in 2050.
These estimates are conservative. The focus on two clearly wet land cover classes disregards reduced microbial oxidation as a result of higher water levels (which linearly relate to CO2
]) in not fully rewetted subareas, the post-fire regrowth of (forest) vegetation, and the emission reduction from preventing further peat fires [16
Taking these aspects into account may significantly refine the methodology and the assessment results. The EFs of the Wetlands Supplement [10
] have meanwhile been updated [13
] and new measurements of greenhouse gas fluxes and runoff losses of dissolved organic carbon are emerging. The transition to regionally measured and elaborated CO2
O and DOC country/region specific Tier 2 EFs will allow additional improvements.
National and, if necessary, regional reporting of changes in GHGs emissions from peatland rewetting requires a methodology to assess the relevant area and the changes in GHGs and DOC EFs. In the absence of statistical accounting of rewetted areas in the Russian Federation, we have proposed an approach to identify effectively rewetted areas. We considered only areas that have been “permanently” watered of which the land category allocation (following 2013 Wetland Supplement [10
]) has been changed, i.e., areas with “wet grassland” and “water”. With respect to the IPCC land category before rewetting, we have assumed that they were ‘peatlands under extraction’, but (unused) agricultural land—‘grassland’ or ‘cropland’—may apply in other cases. As for forest land on organic soils, and primarily forest-drainage sites, rewetting and related changes of the water regime is not a priority [56
] and in Russia even legally forbidden.
Rewetting of abandoned drained peatlands, in addition to meeting the goals of peat fire prevention, improved environmental security and restoration of many of the ecosystem services of peatlands critical to humans, is an effective way to reduce greenhouse gas emissions from land use. As emissions from other sectors decline, the GHGs emissions associated with drained peatlands will increase in relative importance and may become key to keeping global warming below +1.5 to +2 °C. Given the areas of drained and abandoned peatlands in the Russian Federation, their rewetting represents an important but largely overlooked requirement for meeting the Paris Agreement commitments. The implication of that Agreement is that all CO2
emissions must be net zero in 2050, whereas CH4
O emissions have to be reduced, respectively, by 50% and 20% compared to 1990 [57
]. This will require substantial effort. The proposed approach is a first step in addressing the monitoring of rewetted unused drained peatlands and mire restoration at the country, regional and project level.