Headwater streams are natural methane sources but face anthropogenic disturbances like land use change and climate warming. Intensified agriculture since the 1940s increased fine sediment export, impacting stream methane. This study reveals widespread excess fine sediment in UK streams, increasing streambed organic matter and tripling methane emissions. While streambed methane production strongly responds to organic matter, warming's effect is comparatively modest. Separating natural and human-enhanced emissions shows that catchment management targeting excess fine sediment could mitigate stream methane emissions by about 70%.

Yizhu Zhu, J. Iwan Jones, Adrian L. Collins, Yusheng Zhang, Louise Olde, Lorenzo Rovelli, John F. Murphy, Catherine M. Heppell, Mark Trimmer