Peatland protection and restoration are key for climate change mitigation

Abstract

Peatlands cover only about 3% the global land area, but store about twice as much carbon as global forest biomass. If intact peatlands are drained for agriculture or other human uses, peat oxidation can result in considerable CO2 emissions and other greenhouse gases (GHG) for decades or even centuries. Despite their importance, emissions from degraded peatlands have so far not been included explicitly in mitigation pathways compatible with the Paris Agreement. Such pathways include land-demanding mitigation options like bioenergy or afforestation with substantial consequences for the land system. Therefore, besides GHG emissions owing to the historic conversion of intact peatlands, the increased demand for land in current mitigation pathways could result in drainage of presently intact peatlands, e.g. for bioenergy production. Here, we present the first quantitative model-based projections of future peatland dynamics and associated GHG emissions in the context of a 2 °C mitigation pathway. Our spatially explicit land-use modelling approach with global coverage simultaneously accounts for future food demand, based on population and income projections, and land-based mitigation measures. Without dedicated peatland policy and even in the case of peatland protection, our results indicate that the land system would remain a net source of CO2 throughout the 21st century. This result is in contrast to the outcome of current mitigation pathways, in which the land system turns into a net carbon sink by 2100. However, our results indicate that it is possible to reconcile land use and GHG emissions in mitigation pathways through a peatland protection and restoration policy. According to our results, the land system would turn into a global net carbon sink by 2100, as projected by current mitigation pathways, if about 60% of present-day degraded peatlands would be rewetted in the coming decades, next to the protection of intact peatlands.

Peat depth as a control onSphagnummoisture stress during seasonal drought

“…For example, while deep pristine peatlands will likely be resistant and resilient to drought, shallow peatlands such as younger and/or slow‐accumulating peatlands (Vardy et al, 2000), recently restored peatlands (Granath et al, 2016), and organic soils under moss and lichen mats on the upland rock barrens (Hudson et al, 2020; Moore et al, 2019) will be more vulnerable and conservation and potential adaptive management efforts may be necessary to maintain the carbon storage function of these sites. Given that peatland restoration has been emphasized as an important nature‐based solution to mitigate climate change (Humpenöder et al, 2020), our research also highlights the vulnerability of peatland restoration efforts in situations where the peat and moss layer are shallow (Grand‐Clement et al, 2015).…”

Committed and projected future changes in global peatlands – continued transient model simulations since the Last Glacial Maximum

“…Degradation following past land-use conversion will continue to release large amounts of carbon over decades to come (Leifeld and Menichetti, 2018). Given prompt action, this committed and additional carbon loss could be partly mitigated with largescale restoration and re-wetting efforts (Warren et al, 2017;Nugent et al, 2019;Günther et al, 2020) in conjunction with strong protection policies (Humpenöder et al, 2020;Wibisana and Setyorini, 2021).…”

Drought years in peatland rewetting: rapid vegetation succession can maintain the net CO<sub>2</sub> sink function

“…The CO 2 flux time series was also used to infer the start and end of the carbon uptake period (CUP) as a proxy to derive drought effects on plant phenology. In addition, we deployed a simple GEP light-use efficiency model (Hunt, 1994;Gower et al, 1999) to further elucidate the biophysical mechanisms that control photosynthetic CO 2 uptake during periods of drought. This interdisciplinary long-term approach, including ecosystem-scale monitoring of vegetation development and greenhouse gas exchange, allowed us to track the response mechanisms of a rewetted fen to a severe drought event and thereby to infer insights into the resilience of this novel ecosystem in times of more frequently upcoming climate extremes.…”