Glob. Biogeochem. Cycles 21, GB4013 (2007)

The amount of the greenhouse gas methane that is soaked up by soil microbes — the soil methane sink — is greatest in temperate forests, a new study finds.

In the study, Laure Dutaur and Louis Verchot of the International Centre for Agroforestry in Nairobi, Kenya, considered 318 estimates of local methane sinks taken from 120 field studies. Previous extrapolations of the global soil methane sink from local data ranged from 17 to 44 million tonnes of methane per year and suffered from high error margins. But by attributing some local variation to different environments, Dutaur and Verchot narrowed the figure to 22 ± 12 million tonnes per year.

The consumption of methane depends more on ecosystem type than on climatic zone or soil texture, they found — the forest floor being the most methane-hungry of ecosystems — though the sink data reflect a combination of all three factors. But the estimates of forest sinks also varied the most, pointing to a need for more detailed research. Identifying the environmental influences on sinks could help to explain fluctuations in atmospheric concentrations of methane, which remain poorly understood.