Identifying the main drivers of the spatiotemporal variations in wetland methane emissions during 2001–2020

Abstract

Wetlands act as an important natural source of global methane (CH 4 ). The emission rate of wetland CH 4 is jointly affected by climate change, carbon dioxide (CO 2 ) fertilization, and wetland distribution. In this study, we implemented a wetland CH 4 emission module into the Yale Interactive Biosphere (YIBs) model to quantify the spatiotemporal variations of global wetland CH 4 emissions in 2001–2020. Site-level validations showed that the YIBs model reasonably captures the seasonality and magnitude of CH 4 emissions at 28 out of 33 sites with significantly positive correlations and low relative biases. On the global scale, the YIBs predicts an annual mean wetland CH 4 emission of 147.5 Tg yr −1 in 2000–2017, very close to the estimate of 147.9 Tg yr −1 from the ensemble of 13 process-based models. Global wetland CH 4 emissions showed a positive trend of 0.74 Tg yr −2 in the past 2 decades, leading to an increase of 7.4 Tg yr −1 (5.2%) in 2008–2017 than 2000–2009. Climate change and CO 2 fertilization accounted for over 70% of global wetland CH 4 emission changes. Among them, the impact of CO 2 grew steadily and became the dominant factor after the year 2008. The most significant changes in wetland CH 4 emissions were located in the tropical regions following the perturbations in temperature that drives the ecosystem productivity. We found limited changes in CH 4 emissions over high latitudes because of the moderate variations in wetland area fraction. The rise of wetland CH 4 emissions poses an emerging threat to the global warming and likely escalates the tropospheric air pollutants.