Roughly two-thirds of all emissions of atmospheric methane — a highly potent greenhouse gas that is warming planet Earth — come from microbes that live in oxygen-free environments like wetlands, rice fields, landfills and the guts of cows.
Tracking atmospheric methane to its specific sources and quantifying their importance remains a challenge, however. Scientists are pretty good at tracing the sources of the main greenhouse gas, carbon dioxide, to focus on mitigating these emissions. But to trace methane’s origins, scientists often have to measure the isotopic composition of...