Effect of rewetting degraded peatlands on carbon fluxes: a meta-analysis

Abstract

Numerous studies claim that rewetting interventions reduce CO2 and increase CH4 fluxes. To verify the claim, we conducted a systematic review and meta-analysis of the effects of rewetting on CO2 and CH4 fluxes and dissolved organic carbon (DOC). We identified 28 primary articles eligible for meta-analysis, from which we calculated 48 effect sizes for CO2 emissions, 67 effect sizes for CH4 emissions, and 5 effect sizes for DOC. We found that rewetting significantly decreased CO2 fluxes, with temperate zones showing the highest Hedges’ g effect size (−0.798 ± 0.229), followed by tropical (−0.338 ± 0.269) and boreal (−0.209 ± 0.372) zones. Meanwhile, rewetting increased CH4 fluxes, with the highest Hedges’ g effect size shown in temperate zones (1.108 ± 0.144), followed by boreal (0.805 ± 0.183) and tropical (0.096 ± 0.284) zones. In addition, based on yearly monitoring after rewetting, the CH4 emissions effect size increased significantly over the first 4 years (r2 = 0.853). Overall, the rewetting intervention reduced CO2 emissions by −1.43 ± 0.35 Mg CO2–C ha−1 year−1, increased CH4 emissions by 0.033 ± 0.003 Mg CH4–C ha−1 year−1, and had no significant impact on DOC. To improve the precision and reduce the bias of rewetting effect size quantification, it is recommended to conduct more experimental studies with extended monitoring periods using larger sample sizes and apply the before-after control-impact study design, especially in boreal and tropical climate zones.

Unraveling microbial processes involved in carbon and nitrogen cycling and greenhouse gas emissions in rewetted peatlands by molecular biology

“…Rewetting of drained organic soils is an effective measure to strongly reduce agricultural CO 2 emissions and to revert soil C sequestration in the short-term (Cabezas et al 2014 ; Nugent et al 2018 ). A recent meta-analysis by Darusman et al ( 2023 ) showed that rewetting reduced CO 2 emissions by 1.43 ± 0.35 Mg CO 2 -C ha −1 yr −1 on average, but the effects varied depending on climatic zone and nutrient status. Currently, CO 2 emission factors for rewetted peatlands are between − 0.34 and − 0.55 Mg CO 2 -C ha −1 yr −1 for boreal peatlands, − 0.23 and 0.5 Mg CO 2 -C ha −1 yr −1 for temperate peatlands, and 0 Mg CO 2 -C ha −1 yr −1 for tropical peatlands (Wilson et al 2016 ).…”

“…High nutrient concentrations in peat soils, particularly in temperate peatlands, generate larger CO 2 emissions from rewetted sites (Wilson et al 2016 ; Hemes et al 2019 ; Tiemeyer et al 2020 ). Additionally, vegetation can affect emissions by adding fresh plant residues to the soil (Rigney et al 2018 ) or by transporting O 2 to the peat through roots (Zhong et al 2020 ; Darusman et al 2023 ) thereby increasing peat decomposition and CO 2 emissions. These emissions are governed by the dynamics between CO 2 uptake by ecosystems, i.e., photosynthesis by plants and soil autotrophic microorganisms (both photo- and chemoautotrophic), and loss to the atmosphere from ecosystem respiration (Fig.…”

Pros and Cons of Strategies to Reduce Greenhouse Gas Emissions from Peatlands: Review of Possibilities

“…Peatland rewetting is performed in degraded and drained peatlands to restore hydrological conditions [29]. According to estimations, peatland rewetting is effective if the water table is 20-30 cm [29] below the peat surface throughout the year [29].…”

“…The water table is low at the drained peatland level; therefore, carbon dioxide (CO 2 ) emissions increase. In peatlands where drainage has been carried out, CO 2 is the main GHG emission [29]. It has been determined that drained peatland causes ~2% to 5% of the emissions of greenhouse gas (GHG) emissions and ~10% of CO 2 emissions in total [30].…”

“…However, there are some knowledge gaps and contradictive views on which strategies may be the most effective and appropriate [54,55]. Particularly, it is true for EU countries where peat is used for energy production [29,47,[55][56][57]. Existing peatland strategies do not always solve issues regarding the restoration and management of peatland in sufficient detail [49].…”