PAUSE for a moment the next time you pass a farm. It looks pretty green on the surface, doesn't it? Take away the diesel-guzzling machinery and pesticides, and farms would be green in every sense, you might think. No wonder some see agriculture as the answer to global warming, as the rush to produce biofuels illustrates.
But appearances can be deceptive. In fact, farming contributes more to global warming than all the world's cars, trains, ships and planes put together. And the single biggest problem with farming is not carbon but nitrogen.