2005 might well be remembered as the year that hybrid cars "broke through" into the mainstream with the Toyota Prius leading the pack. It's true that these cars could offer great benefits to society if more drivers replaced their old gas guzzlers with their fuel-efficient cousins.

However, if you really want to have a positive impact on the environment, you would do well to start by reconsidering what you eat rather than what you drive, say Gidon Eshel and Pamela Martin of the University of Chicago.

The two recently compared the environmental savings of switching to a vegan diet versus switching to a hybrid vehicle and - guess what?- the tofu won. Eshel and Martin studied the amount of fossil fuel needed to cultivate and process various foods, including running agricultural machinery, providing food for livestock and irrigating crops. They also factored in emissions of methane and nitrous oxide produced by cows, sheep and manure treatment.

The typical US diet, about 28 per cent of which comes from animal sources, generates the equivalent of nearly 1.5 tons more carbon dioxide per person per year than a vegan diet with the same number of calories, say the researchers.

By comparison, the difference in annual emissions between driving a standard car and a hybrid car, which runs off a rechargeable battery and gasoline, is just over 1 ton.

There are those of us for whom sliced tofu just doesn't cut it, so to speak. If you don't want to go vegan or even vegetarian, choosing less-processed animal products and poultry instead of red meat can help reduce greenhouse gasses. And, of courses, always buy locally produced foods when possible.

Source: New Scientist magazine, 17 December 2005