"If one cares about the environment, one must care about eating animals ... Someone who regularly eats factory-farmed products cannot call himself an environmentalist without divorcing that word from its meaning."

Jonathan Safran Foer, Eating Animals

The numbers look pretty unarguable. So much so that - as a senitive meat-eating, trying-hard green - I have to ask if Safran Foer is being too soft: can any meat-eater at all call themselves an environmentalist?



Livestock agriculture produces more greenhouse gas emissions than every train, truck, car and aeroplane put together. The resources consumed by one average omnivore in pursuit of animal protein would nourish as many as 10 vegetarians (there's lots of argument about this stat - some would put the ratio higher). So, shift people's diets and the planet can support more people – in fact, it will quite easily deal with the 9.2 billion at which population is currently forecast to peak in about 40 years' time, even with the threat to agriculture that climate change poses.

If the omnivores you convert are the usual guzzlers of cheap industrial meat that populate the rich world, all the better. Because production of their protein is particularly demanding on fossil fuels – for fertiliser, processing, transport and so on.

So, it's better for the planet if you're a vegetarian, right? You don't have to be a vegan fundamentalist (before the climate change deniers start venting) to hold this view: Lord Stern, former chief economist at the World Bank and a pretty mainstream figure who now advises the British government on climate change, told the Times in October: "Meat is a wasteful use of water and creates a lot of greenhouse gases. It puts enormous pressure on the world's resources. A vegetarian diet is better." And what is Stern diet? "Not strict vegetarian," apparently.

Therein are the makings of a defence for meat eating. Clearly vegetarians who eat soya, chickpeas, lentils, rice and other imported foods are not as green as a Fife dieter eating locally grown turnips, kale and oats. Ask a preachy vegetarian to audit their food sourcing and they may not come out much cleaner than what Safran Foer calls a "selective omnivore".

It is argued that the average rich world vegetarian may not consume much less of the planet's resources than the average moderate omnivore: a report last week for the Worldwide Fund for Nature (download pdf) on the impact of food production pointed out that highly processed vegetarian meat substitutes or foods made of imported soya (as in tofu) might actually use more arable land and resources than their beef or dairy equivalents. Deforestation in the developing world to grow cheap soya for human and animal feed is a major issue in climate change.

Fish-eating - which Safran Foer stated in Tuesday's Guardian is as, if not more, cruel than meat eating - may not be a much greener option either. Already 50% of the fish and shellfish eaten globally is produced by aquaculture, much of it intensive and ecologically often dodgy - for instance in the tropical prawn industry. Farming carnivores like salmon is fairly disastrous ecologically, and involves a similar waste of food resources to meat - it takes 3-5kg of other fish to produce 1kg of salmon.

But as a committed carnivore I have to acknowledge that if I want my grandchildren ever to enjoy a perfect entrecôte steak I must address my habits now: all this nonchalant animal protein-munching cannot go on. Meat in the developed world needs to be seen as more of a luxury and less of a staple.

Food is responsible for 30% of the UK's greenhouse gas emissions (according to the new WWF report) and a large proportion of that is from livestock farming. The average Briton eats 50g of animal protein a day: a chicken breast or a lamb chop. That's much less than countries like the United States, but it is still 25-50% more than the average person needs for healthy nutrition. The main reason that world food production must rise by 50% in the next 50 years (the UN FAO's projection) is not the increase in population, but the increase in meat eating as poorer countries develop.

Which is why I am trying to embrace the 'drop meat once a week' notion. One day off the red stuff? Not so great a hardship, really. And if you eat local meat, sustainably produced, rather than Brazilian rainforest fed burgers, that will help. Also, I don't want to see livestock farming disappear - it shaped the countryside we know.

Or you could simply have fewer children - the most planet-unfriendly thing you can possibly do is produce more animal-gobbling, methane-emitting, fossil fuel squanderers. The only other carnivore option is to eat the dog and then the goldfish. After that, it's roadkill only.