Termite mounds mitigate half of termite methane emissions.

Termites are responsible for ∼1 to 3% of global methane (CH ₄ ) emissions. However, estimates of global termite CH ₄ emissions span two orders of magnitude, suggesting that fundamental knowledge of CH ₄ turnover processes in termite colonies is missing. In particular, there is little reliable information on the extent and location of microbial CH ₄ oxidation in termite mounds. Here, we use a one-box model to unify three independent field methods-a gas-tracer test, an inhibitor approach, and a stable-isotope technique-and quantify CH ₄ production, oxidation, and transport in three North Australian termite species with different feeding habits and mound architectures. We present systematic in situ evidence of widespread CH ₄ oxidation in termite mounds, with 20 to 80% of termite-produced CH ₄ being mitigated before emission to the atmosphere. Furthermore, closing the CH ₄ mass balance in mounds allows us to estimate in situ termite biomass from CH ₄ turnover, with mean biomass ranging between 22 and 86 g of termites per kilogram of mound for the three species. Field tests with excavated mounds show that the predominant location of CH ₄ oxidation is either in the mound material or the soil beneath and is related to species-specific mound porosities. Regardless of termite species, however, our data and model suggest that the fraction of oxidized CH ₄ ( f _ox ) remains well buffered due to links among consumption, oxidation, and transport processes via mound CH ₄ concentration. The mean f _ox of 0.50 ± 0.11 (95% CI) from in situ measurements therefore presents a valid oxidation factor for future global estimates of termite CH ₄ emissions.
Competing Interests: The authors declare no conflict of interest.