Recent increases in annual, seasonal, and extreme methane fluxes driven by changes in climate and vegetation in boreal and temperate wetland ecosystems
[1];
[2];
[2];
[7];
[10];
- University of Groningen (Netherlands); Stanford University, CA (United States); Universidad de Santiago (Chile)
- Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
- US Geological Survey, Jamestown, ND (United States). Northern Prairie Wildlife Research Center
- Stanford University, CA (United States); University of Illinois Chicago, IL (United States)
- University of British Columbia, Vancouver, BC (Canada) McGill University, Montreal, QC (Canada)
- Stanford University, CA (United States); University of California, Berkeley, CA (United States)
- Universidad de Santiago (Chile)
- Stanford University, CA (United States)
- Chinese Academy of Sciences (CAS), Beijing (China)
- NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
- Stanford University, CA (United States); Precourt Institute for Energy, Stanford, CA (United States)
Climate warming is expected to increase global methane (CH4) emissions from wetland ecosystems. Although in situ eddy covariance (EC) measurements at ecosystem scales can potentially detect CH4 flux changes, most EC systems have only a few years of data collected, so temporal trends in CH4 remain uncertain. Here, we use established drivers to hindcast changes in CH4 fluxes (FCH4) since the early 1980s. We trained a machine learning (ML) model on CH4 flux measurements from 22 [methane-producing sites] in wetland, upland, and lake sites of the FLUXNET-CH4 database with at least two full years of measurements across temperate and boreal biomes. The gradient boosting decision tree ML model then hindcasted daily FCH4 over 1981-2018 using meteorological reanalysis data. We found that, mainly driven by rising temperature, half of the sites (n = 11) showed significant increases in annual, seasonal, and extreme FCH4, with increases in FCH4 of ca. 10% or higher found in the fall from 1981–1989 to 2010–2018. The annual trends were driven by increases during summer and fall, particularly at high-CH4-emitting fen sites dominated by aerenchymatous plants. We also found that the distribution of days of extremely high FCH4 (defined according to the 95th percentile of the daily FCH4 values over a reference period) have become more frequent during the last four decades and currently account for 10–40% of the total seasonal fluxes. The share of extreme FCH4 days in the total seasonal fluxes was greatest in winter for boreal/taiga sites and in spring for temperate sites, which highlights the increasing importance of the non-growing seasons in annual budgets. Our results shed light on the effects of climate warming on wetlands, which appears to be extending the CH4 emission seasons and boosting extreme emissions.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Biological and Environmental Research (BER); National Aeronautics and Space Administration (NASA)
- Grant/Contract Number:
- AC05-76RL01830; SC0023084; NNH20ZDA001N
- OSTI ID:
- 2282265
- Report Number(s):
- PNNL-SA-190015
- Journal Information:
- Global Change Biology, Vol. 30, Issue 1; ISSN 1354-1013
- Publisher:
- WileyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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