A 2005 University of Chicago study shows that a standard vegetarian diet produces about 1.5 fewer metric tons of carbon dioxide per year. The impact is similar to that associated with switching from a Chevy Suburban to a Toyota Camry. Eliminating eggs and milk from our diets makes an even bigger difference.

The main problem is methane - one of the side products of digesting. And humans aren't the only smelly contributors to climate change. Cows are responsible for roughly triple the methane emissions of the American coal industry.

Land area and quality also have to be taken into account. As Cornell University scientists quoted in Slate (Vegans vs. Vegetarians, Oct. 23, 2007) point out, sometimes it is better to endure a modest carnivore, because cattle can graze on inferior land not suitable for crops. Obtaining more calories out of the land "means that less food needs be imported from elsewhere, thereby reducing the burning of fossil fuels".

What scientists and extreme environmentalists forgot to add is that breathing can be a problem as well. Every single day humans, not to mention other animal species inhabiting planet Earth, consume precious oxygen and produce lots of carbon dioxide. Therefore, apart from becoming either vegan or vegetarian, it may also be 'wise' to begin limiting our breathing.