For decades, environmental arguments against eating meat have been largely the preserve of vegetarian websites and magazines. Just two years ago it seemed inconceivable that significant numbers of western Europeans would be ready to down their steak knives and graze on vegetation for the sake of the planet. The rapidity with which this situation has changed is astonishing.
The breakthrough came in 2006 when the UN Food and Agriculture Organisation (FAO) published a study, Livestock's Long Shadow, showing that the livestock industry is responsible for a staggering 18% of all anthropogenic greenhouse gas emissions. This is only the beginning of the story. In 2008, Brazil announced that in the 12 months to July it had lost 12,000 sq km (of the Amazon rainforest, mainly to cattle ranchers and soy producers supplying European markets with animal feed. There is water scarcity in large parts of the world, yet livestock-rearing can use up to 200 times more water a kilogram of meat produced than is used in growing wheat. Given the volatile global food prices, it seems foolhardy to divert 1.2bn tonnes of fodder - including cereals - to fuel global meat consumption, which has increased by more than two and half times since 1970.
Vegetarians have been around for a very long time - Pythagoreans forbade eating animals more than 2,500 years ago - but even as the environmental evidence mounted, they didn't appear to be winning the argument. Today in Britain just 2% of the population is vegetarian.
Thankfully, a more pragmatic alternative to total abstinence now seems to be emerging. In September 2008, Dr Rajendra Pachauri, chair of the UN Intergovernmental Panel on Climate Change (IPCC), a vegetarian himself, called on people to take personal responsibility for the impacts of their consumption.
"Give up meat for one day [a week] initially, and decrease it from there," he said. "In terms of immediacy of action and the feasibility of bringing about reductions in a short period of time, it clearly is the most attractive opportunity." This week the Belgian city of Ghent met his demands by declaring Thursday a meat-free day. Restaurants, canteens and schools will now opt to make vegetarianism the default for one day a week,and promote meat-free meals on other days as well.