Activity by organisms such as lichens, fungi and algae accounts for nearly half of the land-based conversion of atmospheric nitrogen into a chemical form that is useable by most plants, reports a study published online this week in Nature Geoscience. Because bio-available nitrogen often limits plant growth, this process could be crucial for carbon sequestration by plants.

Ulrich Poeschl and colleagues re-analysed published data on the spatial coverage of organisms that synthesize their own food from inorganic substances with the help of sunlight, such as lichens, fungi and algae. Based on their analysis of data on fluxes of carbon and nitrogen in a range of ecosystems, they estimate that these organisms contribute about 7% of the net primary production of the terrestrial vegetation, in addition to their role in the nitrogen cycle.