Wetland fluxnet synthesis for methane: understanding and predicting methane fluxes at daily to interannual timescales

Wetlands provide many important ecosystem services, including wildlife habitat, water purification, flood protection, and carbon metabolism. Our ability to manage these services and predict the long-term health of wetlands is strongly linked to their carbon fluxes, of which methane (CH4) is a key component. Natural wetlands emit approximately 30% of global CH4 emissions, as their waterlogged soils create ideal conditions for CH4 production. They are also the largest, and potentially most uncertain, natural source of CH4 to the atmosphere. To understand and predict CH4 fluxes across wetlands globally, we propose the first synthesis of CH4 flux tower data accompanying a global database of CH4 emissions. By taking advantage of the continuous and high-measurement frequency of flux measurements, our synthesis will provide novel insights into the controls and timing of wetland CH4 emissions for North America and globally. This database will also be used to parameterize and benchmark the performance of land-surface models of global CH4 emissions, providing a unique opportunity for informing and validating biogeochemical models. By developing the first global database of flux tower CH4 emissions and convening experts in CH4 flux measurements and modeling, we will 1) better characterize wetland carbon fluxes, 2) reduce uncertainties in the role of wetlands in the global CH4 cycle, and 3) provide metrics useful for safeguarding the many ecosystem services wetlands provide.

Additional support from the Moore Foundation.



Publications:
 

• Chang, K., Riley, W.J., Collier, N., McNicol, G., Fluet‐Chouinard, E., Knox, S.H., Delwiche, K.B., Jackson, R.B., Poulter, B., Saunois, M., Chandra, N., Gedney, N., Ishizawa, M., Ito, A., and others, 2023, Observational constraints reduce model spread but not uncertainty in global wetland methane emission estimates: Global Change Biology, v. 29, no. 15, p. 4298–4312, accessed March 25, 2025, at https://doi.org/10.1111/gcb.16755.
• Chang, K.-Y., Riley, W.J., Knox, S.H., Jackson, R.B., McNicol, G., Poulter, B., Aurela, M., Baldocchi, D., Bansal, S., Bohrer, G., Campbell, D.I., Cescatti, A., Chu, H., Delwiche, K.B., and others, 2021, Substantial hysteresis in emergent temperature sensitivity of global wetland CH4 emissions: Nature Communications, v. 12, no. 1, p. 2266, accessed July 6, 2023, at https://doi.org/10.1038/s41467-021-22452-1.
• Delwiche, K.B., Knox, S.H., Malhotra, A., Fluet-Chouinard, E., McNicol, G., Feron, S., Ouyang, Z., Papale, D., Trotta, C., Canfora, E., Cheah, Y.-W., Christianson, D., Alberto, Ma.C.R., Alekseychik, P., and others, 2021, FLUXNET-CH₄ : a global, multi-ecosystem dataset and analysis of methane seasonality from freshwater wetlands: Earth System Science Data, v. 13, no. 7, p. 3607–3689, accessed July 12, 2025, at https://doi.org/10.5194/essd-13-3607-2021.
• Knox, S.H., Bansal, S., McNicol, G., Schafer, K., Sturtevant, C., Ueyama, M., Valach, A.C., Baldocchi, D., Delwiche, K., Desai, A.R., Euskirchen, E., Liu, J., Lohila, A., Malhotra, A., and others, 2021, Identifying dominant environmental predictors of freshwater wetland methane fluxes across diurnal to seasonal time scales: Global Change Biology, v. 27, no. 15, p. 3582–3604, accessed July 6, 2023, at https://doi.org/10.1111/gcb.15661.
• Knox, S.H., Jackson, R.B., Poulter, B., McNicol, G., Fluet-Chouinard, E., Zhang, Z., Hugelius, G., Bousquet, P., Canadell, J.G., Saunois, M., Papale, D., Chu, H., Keenan, T.F., Baldocchi, D., and others, 2019, FLUXNET-CH4 Synthesis Activity: Objectives, Observations, and Future Directions: Bulletin of the American Meteorological Society, v. 100, no. 12, p. 2607–2632, accessed July 6, 2023, at https://doi.org/10.1175/BAMS-D-18-0268.1.
• McNicol, G., Fluet‐Chouinard, E., Ouyang, Z., Knox, S., Zhang, Z., Aalto, T., Bansal, S., Chang, K., Chen, M., Delwiche, K., Feron, S., Goeckede, M., Liu, J., Malhotra, A., and others, 2023, Upscaling Wetland Methane Emissions From the FLUXNET‐CH4 Eddy Covariance Network (UpCH4 v1.0): Model Development, Network Assessment, and Budget Comparison: AGU Advances, v. 4, no. 5, p. e2023AV000956, accessed March 25, 2025, at https://doi.org/10.1029/2023AV000956.
• Ouyang, Z., Jackson, R.B., McNicol, G., Fluet-Chouinard, E., Runkle, B.R.K., Papale, D., Knox, S.H., Cooley, S., Delwiche, K.B., Feron, S., Irvin, J.A., Malhotra, A., Muddasir, M., Sabbatini, S., and others, 2023, Paddy rice methane emissions across Monsoon Asia: Remote Sensing of Environment, v. 284, p. 113335, accessed March 25, 2025, at https://doi.org/10.1016/j.rse.2022.113335.
• Ueyama, M., Knox, S.H., Delwiche, K.B., Bansal, S., Riley, W.J., Baldocchi, D., Hirano, T., McNicol, G., Schafer, K., Windham‐Myers, L., Poulter, B., Jackson, R.B., Chang, K., Chen, J., and others, 2023, Modeled production, oxidation, and transport processes of wetland methane emissions in temperate, boreal, and Arctic regions: Global Change Biology, v. 29, no. 8, p. 2313–2334, accessed March 25, 2025, at https://doi.org/10.1111/gcb.16594.
• Yuan, K., Zhu, Q., Li, F., Riley, W.J., Torn, M., Chu, H., McNicol, G., Chen, M., Knox, S., Delwiche, K., Wu, H., Baldocchi, D., Ma, H., Desai, A.R., and others, 2022, Causality guided machine learning model on wetland CH4 emissions across global wetlands: Agricultural and Forest Meteorology, v. 324, p. 109115, accessed March 25, 2025, at https://doi.org/10.1016/j.agrformet.2022.109115.
• Zhang, Z., Bansal, S., Chang, K., Fluet‐Chouinard, E., Delwiche, K., Goeckede, M., Gustafson, A., Knox, S., Leppänen, A., Liu, L., Liu, J., Malhotra, A., Markkanen, T., McNicol, G., and others, 2023, Characterizing Performance of Freshwater Wetland Methane Models Across Time Scales at FLUXNET‐CH₄ Sites Using Wavelet Analyses: Journal of Geophysical Research: Biogeosciences, v. 128, no. 11, p. e2022JG007259, accessed March 25, 2025, at https://doi.org/10.1029/2022JG007259.

Rob Jackson (Stanford University)
Sara H Knox (Stanford University)
Lisamarie Windham-Myers (USGS Branch of Regional Research, Western Region)
Benjamin Poulter (National Aeronautics and Space Administration)

Participants:
Sheel Bansal (Northern Prairie Wildlife Research Center)
Jinxun Liu (USGS Western Geographic Science Center)
Benjamin Runkle (University of Arkansas)
Ankur Desai (University of Wisconsin)
William Riley (Lawrence Berkeley National Laboratory)
Rodrigo Vargas (University of Delaware)
Dennis Baldocchi (Univeristy of California, Berkeley)
Donatella Zona (San Diego State University)
Oliver Sonnentag (Université de Montréal)
Mathias Goeckede (Max Planck Institute for Biogeochemistry)
Masahito Ueyama (Osaka Prefecture University)
Torsten Sachs (GFZ German Research Centre for Geosciences)
Joe Melton (Environment and Climate Change Canada)
Annalea Lohila (Finnish Meteorological Institute)
Narasinha Shurpali (University of Eastern Finland)
Eric Ward (USGS Wetland and Aquatic Res. Center)
Zhen Zhang (University of Maryland)
Timo Vesala (University of Helsinki)
Eugenie Euskirchen (University of Alaska Fairbanks)
Karina Schafer (Rutgers University Newark)
Gavin McNicol (Stanford University)