Human-emitted nitrogen helps in forest growth

Small doses of human-spewed nitrogen — emitted by cars, factories and farm chemicals — can help forests grow more and absorb climate-warming carbon dioxide, researchers reported on Wednesday. But a little nitrogen goes a long way and too much can be damaging, said Beverly Law, a professor of forest science at Oregon State University and co-author of a study on the phenomenon in the journal Nature. “It’s not, ‘if a little is good, a lot is better,’” Law said. “It can reach a point where there is saturation of the effect of increased growth.” Law stressed that the level of nitrogen that can actually nourish a forest and help it suck up the greenhouse gas carbon dioxide is about 10% of what is annually applied to farmlands.