METHANE EMISSION FROM WOOD-FEEDING TERMITES IN AMAZONIA

The contribution of termites to the global methane budget has been controversely discussed in the last decade. We measured methane emissions from nests of wood-feeding termite species (Nasutitermes spp.) of primary and secondary forests of Amazonia. The methane emission rates from single termite nests varied in a broad range between 0.01 and 9.4 mg CH4 hour-1 nest-1 (average = 2.0 +/- 2.4 mg CH4 hour-1 nest-1), as termite colonies vary considerably in size (biomass). Consequently, data given as methane emission per nest are unsuitable for interspecific comparison. In seek for an appropriate unit the methane flux was related to the biomass of the termites dwelling in the nest. On this basis, the variation between the methane emissions of the nests was far lower (0.4 - 4.9 mug hour-1 g termites-1). Biomass-related methane emission rates averaged 3.0 +/- 1.3 mug hour-1 g termites-1, which means that Amazonian termites release significantly (at p = 0.01 %) more methane than species from other regions. By extrapolating these emission rates to the estimated global biomass of termites we calculated a total emission of 26 Tg CH4 year-1, which represents about 5 % of the annual methane flux from all sources to the world atmosphere. Termites are unlikely to contribute essentially to the global budget of the ''greenhouse gas'' methane.