A strong mitigation scenario maintains climate neutrality of northern peatlands

Qiu, Chunjing; Ciais, Philippe; Zhu, Dan; Guenet, Bertrand; Chang, Jinfeng; Chaudhary, Nitin; Kleinen, Thomas; Li, Xinyu; Müller, Jurek; Xi, Yi; Zhang, Wenxing; Ballantyne, Ashley P.; Brewer, Simon; Brovkin, Victor; Charman, Dan; Gustafson, A. F.; Gallego‐Sala, Angela; Gasser, Thomas; Holden, Joseph; Joos, Fortunat; Kwon, Mi Hye; Lauerwald, Ronny; Miller, Paul A.; Peng, Shushi; Page, Susan; Smith, Benjamin; Stocker, Benjamin D.; Sannel, A. Britta K.; Salmon, Élodie; Schurgers, Guy; Shurpali, Narasinha J.; Wårlind, David; Westermann, Sebastian

doi:10.1016/j.oneear.2021.12.008

Cited by 19 publications

(18 citation statements)

References 80 publications

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“…Radiative forcing for our Moyarwood site under the five high priority shared socio‐economic pathways (SSP) scenarios further indicates the importance of keeping below the 2°C warming threshold, although as global temperatures continue to increase (IPCC, 2021 ), the very low GHG emissions scenario SSP1‐1.9 (and by extension the Paris Agreement targets) looks ever more challenging. While the appropriateness of Representative Concentration Pathway 8.5 (RCP8.5) as an emissions pathway has received some discussion in recent years (e.g., Hausfather & Peters, 2020a , 2020b ; Schwalm et al, 2020 ), it has been projected to lead to a decrease in peatland C sequestration at lower latitudes and a “decline phase” in mid‐latitude peatlands (Gallego‐Sala et al, 2018 ) and lead to a switch in the C sink function of northern peatlands (from net sink to source) (Qiu et al, 2022 ). Under the high (SSP3‐7.0) and very high emissions (SSP5‐8.5) scenarios in our study, the climate cooling effect of C sequestration at our study site is projected to plateau within a few decades of rewetting (Figure 8 ) and the climate warming impact of sustained CH 4 emissions is likely to predominate for the next two centuries.…”

Section: Discussionmentioning

confidence: 99%

Carbon and climate implications of rewetting a raised bog in Ireland

Wilson

Mackin²,

Tuovinen

et al. 2022

Global Change Biology

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Peatland rewetting has been proposed as a vital climate change mitigation tool to reduce greenhouse gas emissions and to generate suitable conditions for the return of carbon (C) sequestration. In this study, we present annual C balances for a 5-year period at a rewetted peatland in Ireland (rewetted at the start of the study) and compare the results with an adjacent drained area (represents business-as-usual). Hydrological modelling of the 230-hectare site was carried out to determine the likely ecotopes (vegetation communities) that will develop post-rewetting and was used to inform a radiative forcing modelling exercise to determine the climate impacts of rewetting this peatland under five high-priority scenarios (SSP1-1.9, SS1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5). The drained area (marginal ecotope) was a net C source throughout the study and emitted 157 ± 25.5 g C m −2 year −1 . In contrast, the rewetted area (sub-central ecotope) was a net C sink of 78.0 ± 37.6 g C m −2 year −1 , despite relatively large annual methane emissions post-rewetting (average 19.3 ± 5.2 g C m −2 year −1 ). Hydrological modelling predicted the development of three key ecotopes at the site, with the subcentral ecotope predicted to cover 24% of the site, the sub-marginal predicted to cover 59% and the marginal predicted to cover 16%. Using these areal estimates, our radiative forcing modelling projects that under the SSP1-1.9 scenario, the site will have a warming effect on the climate until 2085 but will then have a strong cooling impact. In contrast, our modelling exercise shows that the site will never have a cooling impact under the SSP5-8.5 scenario. Our results confirm the importance of rapid rewetting of drained peatland sites to (a) achieve strong C emissions reductions, (b) establish optimal conditions for C sequestration and (c) set the site on a climate cooling trajectory.

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Section: Discussionmentioning

confidence: 99%

Carbon and climate implications of rewetting a raised bog in Ireland

Wilson

Mackin²,

Tuovinen

et al. 2022

Global Change Biology

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“…The difference can be attributed to the management (harvest): Fens and bogs without harvest hardly showed the net CO 2 emissions with low WT, but grasslands and croplands showed net CO 2 emissions with low WT possibly because of different biogeochemical processes from natural peatlands, for example, disturbance and nutrient status (Evans et al, 2021 ). Nevertheless, we can further investigate whether natural peatlands can act as the net CO 2 source with extremely low WT by including more sites and more years with climate variability (Fenner & Freeman, 2011 ; Qiu et al, 2022 ).…”

Section: Discussionmentioning

confidence: 99%

“…In addition, drier peatlands with lower water availability can increase sensible heat flux, which can warm lower atmosphere (Göckede et al, 2017 ). Changing precipitation patterns can modify WT of peatlands in the local and regional scales (Qiu et al, 2022 ). Because of high uncertainty and large temporal and spatial variations in the relationship among temperature, precipitation, and peatland WT, it is challenging to forecast the direction and magnitude of C response of northern peatlands and their feedback with climate.…”

Section: Discussionmentioning

confidence: 99%

Lowering water table reduces carbon sink strength and carbon stocks in northern peatlands

Kwon

Ballantyne

Ciais

et al. 2022

Global Change Biology

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Peatlands at high latitudes have accumulated >400 Pg carbon (C) because saturated soil and cold temperatures suppress C decomposition. This substantial amount of C in Arctic and Boreal peatlands is potentially subject to increased decomposition if the water table (WT) decreases due to climate change, including permafrost thaw‐related drying. Here, we optimize a version of the Organizing Carbon and Hydrology In Dynamic Ecosystems model (ORCHIDEE‐PCH4) using site‐specific observations to investigate changes in CO2 and CH4 fluxes as well as C stock responses to an experimentally manipulated decrease of WT at six northern peatlands. The unmanipulated control peatlands, with the WT <20 cm on average (seasonal max up to 45 cm) below the surface, currently act as C sinks in most years (58 ± 34 g C m−2 year−1; including 6 ± 7 g C–CH4 m−2 year−1 emission). We found, however, that lowering the WT by 10 cm reduced the CO2 sink by 13 ± 15 g C m−2 year−1 and decreased CH4 emission by 4 ± 4 g CH4 m−2 year−1, thus accumulating less C over 100 years (0.2 ± 0.2 kg C m−2). Yet, the reduced emission of CH4, which has a larger greenhouse warming potential, resulted in a net decrease in greenhouse gas balance by 310 ± 360 g CO2‐eq m−2 year−1. Peatlands with the initial WT close to the soil surface were more vulnerable to C loss: Non‐permafrost peatlands lost >2 kg C m−2 over 100 years when WT is lowered by 50 cm, while permafrost peatlands temporally switched from C sinks to sources. These results highlight that reductions in C storage capacity in response to drying of northern peatlands are offset in part by reduced CH4 emissions, thus slightly reducing the positive carbon climate feedbacks of peatlands under a warmer and drier future climate scenario.

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“…As such, peatlands provide a critical ecosystem service of climate regulation through both biogeochemical and biophysical processes. While there is a concern that these climate regulation services may be weakened or even reversed as summer water deficits are predicted to increase substantially within the next century (Roulet et al, 1992; Granath et al, 2016; Helbig et al, 2020b; Qiu et al, 2022) due to future climate change, uncertainty exists on how predicted changes in climate will impact peatland ecosystems (Frolking et al, 2011; Loisel et al, 2021). Some modelling studies suggest that drier conditions may switch peatlands from a net carbon sink to a large net source (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, most long‐term WT drawdown studies are from peatlands drained for forestry and agriculture by ditching (e.g. Laiho et al, 2008; Sundström et al, 2000; Wells & Williams, 1996) which often results in WT drawdowns greater than predicted for northern peatlands under a future climate change scenario (Granath et al, 2016; Qiu et al, 2022; Roulet et al, 1992). As such, there is an important research need to examine the effect of multi‐decadal WT alteration effects on peatland vegetation composition (with a particular emphasis on shrub cover), peatland microtopography cover and the partitioning of evapotranspiration in order to better understand the water table–shrubification–evapotranspiration feedback.…”

Section: Introductionmentioning

confidence: 99%

Examining the peatland shrubification‐evapotranspiration feedback following multi‐decadal water table manipulation

Moore

Pypker

Hribljan

et al. 2022

Hydrological Processes

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Northern peatlands are globally important long‐term sinks of carbon due to their predominantly saturated conditions. However, these ecosystems are expected to become drier with climate change, potentially leading to shrubification. As such, the response of the shrubification–evapotranspiration (ET) feedback may be of critical importance to future peatland energy, water and carbon dynamics. We examined the effect of multi‐decadal peatland water table (WT) alteration at three adjacent sites with increasing depth to WT (WET, INTermediate, and DRY). In order to better understand the WT–shrubification–ET feedback, we measured peatland vegetation composition, microtopography and ET partitioning, where ET was measured at the ecosystem, microform, and leaf level using eddy covariance (EC), chambers and porometry, respectively. Averaged across microforms and WT treatments, there was a difference in the median measured leaf resistance (rleaf) between plant functional types ranging from 213 s m−1 for erect dwarf shrubs, 325 s m−1 for graminoids/sedges, and 520 s m−1 for prostrate dwarf shrubs. Scaled based on LAI, the low rleaf of erect dwarf shrubs dominated hummocks, where sites with a higher proportion of hummocks had lower median canopy resistance (rv) of 141, 133 and 130 s m−1 at the WET, INT and DRY sites respectively. Nevertheless, ET was highest at the WET site and similar between the INT and DRY sites, with greater evaporation from the moss surface at the WET site. Porometry and EC data along with a three‐source model were used to independently assess the evaporative contribution from the moss surface, which ranged from 17% to 40%. For moderate and persistent changes in WT from land‐use or climate change, our results suggest vegetation succession is minimal, but the microtopographic development and the concomitant differences in LAI for the various plant functional types is key to understanding changes in total ET and partitioning.

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A strong mitigation scenario maintains climate neutrality of northern peatlands

Cited by 19 publications

References 80 publications

Carbon and climate implications of rewetting a raised bog in Ireland

Carbon and climate implications of rewetting a raised bog in Ireland

Lowering water table reduces carbon sink strength and carbon stocks in northern peatlands

Examining the peatland shrubification‐evapotranspiration feedback following multi‐decadal water table manipulation

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