Warning over'huge overloadof nitrogen'

Nitrogen is essential for life, but too much of it can pollute rivers and coastal seas, increase global warming, and erode the ozone layer.

Between 1960 and 2000, the use of nitrogen fertilisers to enhance crop yields rose by 800 per cent.

Excessive nitrogen squeezes oxygen out of lakes, rivers, and coastal waters, leading to the death and decline of numerous aquatic species, said the scientists. Through chemical reactions, it also causes the potent greenhouse gas nitrogen oxide to be released into the atmosphere.

“No phenomenon has probably impacted the nitrogen cycle more than human inputs of nitrogen into the cycle in the last 2.5 billion years,” said Professor Paul Falkowski, from Rutgers University in New Jersey.