Carbon dioxide and methane emissions of Swedish low‐order streams—a national estimate and lessons learnt from more than a decade of observations

Abstract

Abstract Low‐order streams are suggested to dominate the atmospheric CO 2 source of all inland waters. Yet, many large‐scale stream estimates suffer from methods not designed for gas emission determination and rarely include other greenhouse gases such as CH 4 . Here, we present a compilation of directly measured CO 2 and CH 4 concentration data from Swedish low‐order streams (> 1600 observations across > 500 streams) covering large climatological and land‐use gradients. These data were combined with an empirically derived gas transfer model and the characteristics of a ca. 400,000 km stream network covering the entire country. The total stream CO 2 and CH 4 emission corresponded to 2.7 Tg C yr −1 (95% confidence interval: 2.0–3.7) of which the CH 4 accounted for 0.7% (0.02 Tg C yr −1 ). The study highlights the importance of low‐order streams, as well as the critical need to better represent variability in emissions and stream areal extent to constrain future stream C emission estimates.