Climate-driven increase of natural wetland methane emission offset by human-induced wetland reduction in China over the past three decades

Abstract:

Both anthropogenic activities and climate change could dramatically affect the biogeochemical processes of natural wetland methanogenesis. Chinese natural wetlands vanished considerably during recent decades mainly due to human activities. Quantifying possible impacts of changing climate and wetland area on wetland methane (CH₄) emissions in China is important for improving our knowledge on CH₄ budgets locally and globally. However, their respective and combined effects are uncertain. We incorporated changes in wetland area derived from remote sensing into a dynamic CH₄ model of TRIPLEX-GHG to quantify the contributions of both human-induced and climate change to methane emissions from natural wetlands of China over the past three decades. Here we found that under the conditions of climate change, human-induced wetland loss contributed 34.3% to the CH₄ reduction (0.92 Tg CH₄), and climate change only contributed 20.4% to the CH₄ increase (0.31 Tg CH₄), suggesting that the decrease of CH₄ emission due to human-induced wetland area reductions has offset the climate change induced increasing of CH₄emission at the national scale. Wetlands in northeastern China made the greatest contribution to national wetland CH4 emission variation under both climate change and wetland area dynamics conditions, followed by the Qinghai-Tibet Plateau (QTP), where the emissions mainly controlled by climate change. Temperature was a dominant controlling factor for wetland CH4 emission in the northeast (high latitude) and Qinghai-Tibet Plateau (high altitude) regions, whereas precipitation had a considerable influence in north China. Ignoring the dynamic change of human-induced wetlands loss may result in great uncertainties in quantifying global wetland CH4 emissions.