From G2 section of today's Guardian (Thursday 7th June 2007).

Quote The Guardian

Meat.
According to a report published last year by the United Nations Food and Agriculture Organisation, the global livestock sector generates more greenhouse gas emissions than all forms of transport. It warned: “The environmental costs per unit of livestock production must be cut by one half, just to avoid the level of damage worsening beyond its present level.” The key is that the livestock sector produces a much larger share of greenhouse gases that are more harmful than CO2, such as nitrous oxide (296 times more impact than CO2) and methane (23 times more impact).
“At the very least, people need to think about cutting down their meat and dairy consumption to help the environment,” says Justin Kerswell, campaigns manager at the vegetarian campaign charity Viva. “The meat-based diet most people eat is completely unsustainable, but we are starting to see people make the shift. The amount of vegans in the UK has increased 10-fold in the past 10 years and is now around one million.”