Editing IPCC:AR6/WGIII/Chapter-7 (section)

==== 7.4.2.7 Peatland Restoration ====

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'''Activities, co-benefits, risks and implementation barriers.''' Peatland restoration involves restoring degraded and damaged peatlands, for example through rewetting and revegetation, which both increases carbon accumulation in vegetation and soils and avoids ongoing CO 2 emissions. Peatlands only account for about 3% of the terrestrial surface, predominantly occurring in boreal ecosystems (78%), with a smaller proportion in tropical regions (13%), but may store about 600 GtC or 21% of the global total soil organic carbon stock of about 3000 Gt ( [[#Page--2011|Page et al. 2011]] ; [[#Leifeld--2018|Leifeld and Menichetti 2018]] ). Peatland restoration delivers co-benefits for biodiversity, as well as regulating water flow and preventing downstream flooding, while still allowing for extensive management such as paludiculture ( [[#Tan--2021|Tan et al. 2021]] ). Rewetting of peatlands also reduces the risk of fire, but may also mobilise salts and contaminants in soils ( [[#van%20Diggelen--2020|van Diggelen et al. 2020]] ) and in severely degraded peatlands, restoration of peatland hydrology and vegetation may not be feasible ( [[#Andersen--2017|Andersen et al. 2017]] ). At a local level, restoration of peatlands drained for agriculture could displace food production and damage local food supply, although impacts to regional and global food security would be minimal ( [[#Humpenöder--2020|Humpenöder et al. 2020]] ). Collaborative and transparent planning processes are needed to reduce conflict between competing land uses ( [[#Tanneberger--2020b|Tanneberger et al. 2020b]] ). Adequate resources for implementing restoration policies are key to engage local communities and maintain livelihoods ( [[#Resosudarmo--2019|Resosudarmo et al. 2019]] ; [[#Ward--2021|Ward et al. 2021]] ).

'''Conclusions from AR5 and IPCC Special Reports (SR1.5, SROCC and SRCCL); mitigation potential, costs, and pathways.''' Large areas (0.51 Mkm 2 ) of global peatlands are degraded of which 0.2 Mkm 2 are tropical peatlands ( [[#Griscom--2017|Griscom et al. 2017]] ; [[#Leifeld--2018|Leifeld and Menichetti 2018]] ). According the SRCCL, peatland restoration could deliver technical mitigation potentials of 0.15 – 0.81GtCO 2 -eq yr –1 by 2030–2050 ( ''low confidence'' ) ( [[#Couwenberg--2010|Couwenberg et al. 2010]] ; [[#Griscom--2017|Griscom et al. 2017]] ) '''(''' Chapters 2 and 6 of the SRCCL), though there could be an increase in methane emissions after restoration ( [[#Jauhiainen--2008|Jauhiainen et al. 2008]] ). The mitigation potential estimates cover global peatlands and include CO 2 , N 2 O and CH 4 emissions. Peatlands are highly sensitive to climate change ( ''high confidence'' ), however there are currently no studies that estimate future climate effects on mitigation potential from peatland restoration.

'''Developments since AR5 and IPCC Special Reports (SR1.5, SROCC and SRCCL).''' The most recent literature and reviews indicate with ''high confidence'' that restoration would decrease CO 2 emissions and with ''medium confidence'' that restoration would decrease net GHG emissions from degraded peatlands ( [[#Wilson--2016|Wilson et al. 2016]] ; [[#Ojanen--2020|Ojanen and Minkkinen 2020]] ; [[#van%20Diggelen--2020|van Diggelen et al. 2020]] ). Although rewetting of drained peatlands increases CH 4 emissions, this effect is often outweighed by decreases in CO 2 and N 2 O emissions but depends very much on local circumstances ( [[#Günther--2020|Günther et al. 2020]] ). Restoration and rewetting of almost all drained peatlands is needed by 2050 to meet 1.5°C–2°C pathways which is unlikely to happen ( [[#Leifeld--2019|Leifeld et al. 2019]] ); immediate rewetting and restoration minimises the warming from cumulative CO 2 emissions ( [[#Nugent--2019|Nugent et al. 2019]] ).

According to recent data, the technical mitigation potential for global peatland restoration is estimated at 0.5–1.3 GtCO 2 -eq yr –1 ( [[#Leifeld--2018|Leifeld and Menichetti 2018]] ; [[#Griscom--2020|Griscom et al. 2020]] ; [[#Bossio--2020|Bossio et al. 2020]] ; [[#Roe--2021|Roe et al. 2021]] ) (Figure 7.11), with 80% of the mitigation potential derived from improvements to soil carbon ( [[#Bossio--2020|Bossio et al. 2020]] ). The regional mitigation potentials of all peatlands outlined in [[#Roe--2021|Roe et al. (2021)]] reflect the country-level estimates from ( [[#Humpenöder--2020|Humpenöder et al. 2020]] ).

Climate mitigation effects of peatland rewetting depend on the climate zone and land use. Recent analysis shows the strongest mitigation gains from rewetting drained temperate and boreal peatlands used for agriculture and drained tropical peatlands ( [[#Ojanen--2020|Ojanen and Minkkinen 2020]] ). However, estimates of emission factors from rewetting drained tropical peatlands remain uncertain ( [[#Wilson--2016|Wilson et al. 2016]] ; [[#Murdiyarso--2019|Murdiyarso et al. 2019]] ). Topsoil removal, in combination with rewetting, may improve restoration success and limit CH 4 emissions during restoration of highly degraded temperate peatlands ( [[#Zak--2018|Zak et al. 2018]] ). In temperate and boreal regions, co-benefits mentioned above are major motivations for peatland restoration ( [[#Chimner--2017|Chimner et al. 2017]] ; [[#Tanneberger--2020a|Tanneberger et al. 2020a]] ).

'''Critical assessment and conclusion.''' Based on studies to date, there is ''medium confidence'' that peatland restoration has a technical potential of 0.79 (0.49–1.3) GtCO 2 -eq yr –1 (median) of which 0.4 (0.2–0.6) GtCO 2 -eq yr –1 is available up to USD100 tCO 2 –1 . The large land area of degraded peatlands suggests that significant emissions reductions could occur through large-scale restoration especially in tropical peatlands. There is ''medium confidence'' in the large carbon stocks of tropical peat forests (1956–14,757 tCO 2 -eq ha –1 ) and large rates of carbon loss associated with land cover change (640–1650 tCO 2 -eq ha –1 ) ( [[#Goldstein--2020|Goldstein et al. 2020]] ; [[#Novita--2021|Novita et al. 2021]] ). However, large-scale implementation of tropical peatland restoration will likely be limited by costs and other demands for these tropical lands.

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