Methane Is a Potent Greenhouse Gas That Has Been Rising Rapidly in Recent Years, But Pinpointing Its Sources Is Difficult

Wild deer release millions of tonnes of methane annually, a new study finds, though their total contribution is tiny compared with domesticated livestock. Methane is a potent greenhouse gas that has been rising rapidly in recent years, but pinpointing its sources is difficult. Like cows, wild ruminants such as deer, moose and llamas rely on bacteria to break down fibrous plants, releasing methane in the process.

Theresia Yazbeck of the Max Planck Institute for Biogeochemistry in Jena, Germany, and colleagues combined global wild animal population estimates with methane emission estimates based on body mass and diet. Their calculations, published in the Journal of Geophysical Research: Biogeosciences, suggest wild ruminants release around 3m tonnes of methane annually, with more than half coming from just six deer species. That is a small fraction of the over 600m tonnes of yearly global methane emissions and some 38 times less than domesticated livestock emit.