Viability of enhancing methanotrophy in terrestrial ecosystems exposed to low concentrations of methane

Methane is a potent but relatively short-lived greenhouse gas, with anthropogenic and natural sources and rapidly increasing atmospheric concentrations. Hence, it is an important target for reducing emissions and increasing sinks, as doing so could notably reduce rates of climate change in the near-term. This includes potentially enhancing methanotrophy, a microbial process of methane oxidation that occurs broadly in aquatic environments, in soils and on foliar and bark surfaces. Methanotrophy can be an important sink where it intercepts relatively high concentrations of methane produced from within soils or water bodies, but when methanotrophs are exposed to only ambient atmospheric methane concentrations (about 2 ppm), methane oxidation occurs at very slow rates. Here we present an assessment of possible strategies – including introduction of exogenous microbes to soils and plant tissues, improved tillage and nutrient management in agriculture, and reforestation – to enhance rates of methanotrophy for removal of atmospheric methane, where the low concentration constrains the energy available to support methanotrophic growth. The microbial process of methane oxidation is slow due to energy limitations in environments exposed to low methane concentrations, but understanding limiting factors may help to enhance rates of atmospheric methane removal, according to a review of ecological and evolutionary aspects.