Litter decomposition as a potential natural source of methyl bromide

We assessed the potential significance of global litter decay as a new source of atmospheric methyl bromide. We combined information on the global distribution and quantity of litter decay, litter bromine content, and the halogen-methylating ability of wood-rotting fungi to produce a spatially explicit estimate of CH₃Br emission from litter decay. The uncertainties are large and the potential methyl bromide source varies greatly in response to assumptions made, including those regarding the efficiency of bromine utilization and release. Our best estimate of the potential flux from woody litter, 0.5 - 5.2 kT yr^-1, is unable to account for the entire "missing source." Additional possible fluxes from regions of inadequate data and from nonwoody litter may raise this total. This proposed decomposition source is of potential interest to budget calculations and should be experimentally characterized and quantified.