Methane emissions from tank bromeliads in neotropical forests.

Methane is a potent greenhouse gas1. Methane concentrations above neotropical forests—the tropical forests found in Mexico, Central America, South America and the Caribbean—are high according to space-borne observations. However, the source of the methane is uncertain2,3. Here, we measure methane fluxes from tank bromeliads—a common group of herbaceous plants in neotropical forests that collect water in tank-like structures—using vented static chambers. We sampled 167 bromeliads in the Ecuadorian Andes, and found that all of them emitted methane. We found a diverse community of methane-producing archaea within the water-containing tanks, suggesting that the tanks served as the source of the methane. Indeed, tank water was supersaturated with methane, and 13C-labelled methane added to tank water was emitted though the leaves. We suggest that the bromeliad tanks form a wetland environment conducive to methane production. In conjunction with other wetlands hidden beneath the copy surface, bromeliads may help to explain the inexplicably high methane levels observed over neotropical forests.