Inland waters are a significant natural source of methane (CH₄), a potent greenhouse gas. However, existing emission models were primarily developed for solute-poor ecosystems and may not accurately represent salt-rich systems. This study combines field surveys and eddy covariance measurements to demonstrate that salinity restricts microbial CH₄ cycling in the Canadian Prairies, a region with high density of salt-rich inland waters. Existing models overestimated CH₄ emissions from ponds and wetlands by several orders of magnitude due to the exclusion of salinity as a factor. While less significant for rivers and larger lakes, salinity interacts with organic matter availability to influence CH₄ patterns in small lentic habitats. The study estimates that excluding salinity leads to an overestimation of emissions from small Canadian Prairie waterbodies by at least 81%, a substantial amount comparable to other major national emission sources. These findings suggest a global overestimation of lentic CH₄ emissions, and that widespread salinization of inland waters should be considered in future emission projections.

Cynthia Soued, Matthew J. Bogard, Kerri Finlay, Lauren E. Bortolotti, Peter R. Leavitt, Pascal Badiou, Sara H. Knox, Sydney Jensen, Peka Mueller, Sung Ching Lee, Darian Ng, Björn Wissel, Chun Ngai Chan, Bryan Page, Paige Kowal