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Improved Estimations of Methane Emissions from Wetlands Using a Bottom-Up Approach

A lush wetland area, with low bushes rising from the water, under a blue sky

Source: AGU Advances

Methane is one of the most important greenhouse gases globally, second only to carbon dioxide in terms of its warming effects in the atmosphere. A large portion of natural methane emissions comes from wetlands, although exactly how much is unclear. Figuring out the magnitudes and locations of wetlands’ methane contribution more precisely is crucial for improving our understanding of climate change.

A challenge arises from conflicting wetland methane emission models, hindering trend evaluation. To address this, additional data analyses could enhance understanding of global methane emissions and decrease uncertainty in climate projections.

McNicol and colleagues utilized information from 119 site-years of data collected from 43 wetland locations included in the FLUXNET-CH4 global eddy covariance methane flux database. This database was compiled by the Global Carbon Project in collaboration with AmeriFlux and the European Eddy Fluxes Database Cluster. The researchers employed this data to develop a random forest model ensemble that could estimate total methane emissions from wetlands across the globe. The outcomes of their analysis generally aligned with those of existing models on methane emissions, but showed discrepancies in the tropics, highlighting the need for improved data and modeling techniques for methane sources in tropical wetlands.

Similar to previous research, the latest findings suggest that approximately 68% of methane emissions from wetlands occur in tropical regions. However, there are discrepancies in the specific locations within these regions where the emissions originate. For instance, the new model suggests that the semiarid monsoon Sahel contributes three times more methane than previous models based on GCP data have shown. Conversely, the model found much lower levels of emissions from wetlands in humid tropical forests such as those found in the Amazon, Congo, and Indonesian archipelago.

According to the authors, inadequate coverage of tropical regions and an overrepresentation of certain ecosystems in current methane monitoring systems may contribute to differences in data on tropical methane emissions.

The scientists propose that the amount of methane produced by tropical wetlands with high humidity and seasonal wetness may be inaccurately estimated in various models for methane emissions. Combining the results from these models could improve predictions of future methane release and the expected level of warming.

—Nathaniel Scharping (@nathanielscharp), Science Writer

Reference: Scharping, N. (2023), Improved Estimates of Wetland Methane Emissions from a Bottom-Up Approach, Eos, 104, Published on September 13, 2023.

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