It felt like a political act to order an English breakfast last week after Lord Stern of Brentford’s remarks about a vegetarian diet being better for the planet. I happened to be staying at the Farmers’ Club, so the significance of the moment weighed heavily as I ordered up a defiant compromise: two poached eggs on toast with two rashers of bacon and a tomato on the side.

The former chief economist to the Treasury and the World Bank resembles at times a Methodist minister unable to temper sanctimony with wit. Since the Stern review on the cost of tackling global warming three years ago — a document that was never peer-reviewed and which drew some valid criticisms from within his profession — its author has taken it upon himself to go around making oracular statements about the magnitude of the task of reducing greenhouse gas emissions by 80% over 40 years. “I am not sure that people fully understand what we are talking about or the changes that will be necessary,” he said last week.

He may well be right. It is beginning to sink in that we may have to change the way we travel, eat and heat our houses in quite radical ways. But whether we shall feel inclined to do these deeply green things because we have been encouraged to do so by Stern is another thing altogether.

What upset many people last week was not that Stern took on our cherished meat-eating habits and the farming lobby, but the impression he gave that he understood the implications of what he was advocating rather less than those in the business of producing food.

Let’s examine his case for eating less meat. Official United Nations figures suggest that about 18% of greenhouse gas emissions come from livestock agriculture. Roughly a third of that is caused by methane belched by ruminants, a third comes from land-use changes such as clearing the rainforest for pasture and about a third is nitrous oxide from the use of fertilisers to grow more crops to feed them on.

What Stern appears not to have grasped is that different forms of livestock agriculture produce greenhouse gases in different measure and some do not produce them at all. As an extreme example, if you want to cut out methane and you live in Australia you can eat only kangaroo. Roos don’t belch methane.

Where a sense of injustice settles on the poor British beef or sheep farmer is that very little of the UN inventory of greenhouse gas production from livestock applies to him, particularly if he happens to graze sheep on the hills or to graze beef animals on permanent grass beside the rain-fed rivers of the west. Some 60% of British farmland is suitable only for growing grass. Since Neolithic times we have used livestock to turn inedible grass into food. And as a system there isn’t an awful lot wrong with it.

Graham Harvey’s book, The Carbon Fields, tells us that grazing permanent pasture with ruminants can actually be an overall carbon “sink” because of the vast root structures below ground which take up carbon efficiently every time they are grazed hard.

Compare this with the kind of “feedlot” cattle production favoured in the United States, in which you feed grain that could be eaten by humans to animals at a conversion rate of 8lb of grain to 1lb of beef. Nearly as inefficient is the way we currently produce pork or chicken by stuffing them full of grain. Do we want a food production system that is dependent on imported crops — including, please note, soya beans produced on cleared rainforest land in South America? I’m not sure we do. But if we want to get rid of it, we should be removing European Union subsidies and trade rules which encourage farmers to import commodity crops from intensive agricultural systems and we should stop institutions such as the World Bank, Stern’s former employer, lending money for feedlot production in the developing world. Surely this is where Stern should be concentrating his attention instead of telling us not to eat beef.

He is almost certainly right that we need to spend more time worrying about the carbon emissions that go into producing our food. He is right that it does seem pretty mad to feed about half the crops we produce to animals and that we eat more meat than is good for our health. He is right to say the Chinese acquisition of our taste for cheap meat doesn’t look good for the planet. But there are unsustainable forms of consumption closer to home that Stern didn’t dare get into. Pet food, for instance. A new book by a couple of New Zealanders has calculated that the meat diet of a medium-sized dog gives it the carbon footprint of two Toyota Land Cruisers and the average cat that of a Volkswagen Golf. I am not sure anyone here is ready to grill the labrador, but maybe it is time to go back to feeding pets scraps. It is certainly time to go back to feeding waste food, properly treated, to pigs.

Where I differ from Stern is that I am not sure people en masse will ever give up meat. Wouldn’t it be better to concentrate our efforts on making better use of waste, tackling the distortions of subsidy and trade and making food production more local?

The danger we must guard against in the new low-carbon religion, however, is being convinced by people who don’t fully understand what they are talking about to turn our backs on some of the most sustainable, ecologically friendly forms of agriculture we have.

Sunday Times 1/11/09