Tradeoff of CO2 and CH4 emissions from global peatlands under water-table drawdown

The climate impact of water-table drawdown in peatlands is unclear as carbon dioxide emissions increase and methane emissions decrease due to drying. This study shows decreasing water-table depth results in net greenhouse gas emissions from global peatlands, despite reducing methane emissions. Water-table drawdown across peatlands increases carbon dioxide (CO2) and reduces methane (CH4) emissions. The net climatic effect remains unclear. Based on global observations from 130 sites, we found a positive (warming) net climate effect of water-table drawdown. Using a machine-learning-based upscaling approach, we predict that peatland water-table drawdown driven by climate drying and human activities will increase CO2 emissions by 1.13 (95% interval: 0.88-1.50) Gt yr(-1) and reduce CH4 by 0.26 (0.14-0.52) GtCO(2)-eq yr(-1), resulting in a net increase of greenhouse gas of 0.86 (0.36-1.36) GtCO(2)-eq yr(-1) by the end of the twenty-first century under the RCP8.5 climate scenario. This drops to 0.73 (0.2-1.2) GtCO(2)-eq yr(-1) under RCP2.6. Our results point to an urgent need to preserve pristine and rehabilitate drained peatlands to decelerate the positive feedback among water-table drawdown, increased greenhouse gas emissions and climate warming.

Automated summary

The impact of water-table drawdown in peatlands on climate is uncertain, as studies show conflicting results regarding the net greenhouse gas emissions despite the reduction in methane emissions. However, observations from 130 sites globally suggest a warming effect of water-table drawdown. Predictions indicate that water-table drawdown driven by climate drying and human activities will increase CO2 emissions and decrease CH4 emissions, resulting in a net increase in greenhouse gas emissions by the end of the twenty-first century under certain climate scenarios. Urgent action is needed to preserve and restore drained peatlands to slow down the positive feedback loop of water-table drawdown, increased greenhouse gas emissions, and climate warming.