Townsend says some scientists had hoped that excess reactive nitrogen levels might actually reduce greenhouse gases by stimulating plant growth, which locks up carbon dioxide. But, he says, “It doesn’t seem likely that it’s going to play a dominant role.” Although the jury is still out, Tilman adds, “there isn’t very good evidence that nitrogen deposition actually does lead to increased carbon removal and storage.”
Although more reactive nitrogen means more growth, it also changes which of the species in an ecosystem thrive. For example, in grasslands that received increased nitrogen, Tilman says, “the species composition changed to plants that had litter that decomposed more quickly. And because it decomposed more quickly, there was actually no net storage of carbon with added nitrogen.”