Laughing Gas Biggest Threat to Ozone Layer, Study Says

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For instance, millions more cases of skin cancer caused by UV exposure are expected to occur over the 21st century due to the CFC-depleted ozone layer, according to the World Health Organization.

What's more, nitrous oxide is also a greenhouse gas, which means it traps heat and fuels global warming. (See global warming fast facts.)

"That's why cutting nitrous oxide emissions is a win-win situation in terms of greenhouse gases and ozone depletion," said John Daniels, a co-author of the new study in tomorrow's Science.

Farmland Squeeze

Modern farming practices are responsible for most of the rise in human-generated nitrous oxide. (Take a pollution quiz.)

Nitrous oxide is also released to a lesser degree by sewage and transport, including vehicle exhaust, said Detlef van Vuuren of the Netherlands Environmental Assessment Agency in Bilthoven, who was not involved in the new study.

But as populations climb and incomes rise, so does the use of chemical fertilizers and meat eating—contributing to the release of more nitrous oxide.

The growing population is also putting a squeeze on the world's existing croplands, so changing what we eat would make a big difference, van Vuuren said.

"Eating less meat would reduce not only the number of [farm] animals," he said, "it also requires less fertilizer for feed production."

Researchers are also testing different ways of growing food that might release less nitrous oxide, such as farming without tilling fields to prevent nitrogen in the soil from escaping.

Another approach is to add a form of charcoal called biochar to soils, enriching croplands and reducing the need for fertilizers.

(Read about other sustainable agriculture projects.)

Taking such measures may "reduce [overall] emissions by 30, maybe 40 percent," van Vuuren said.

But "I don't see ways to easily reduce them to zero."

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