ENVIRONMENTALISTS don’t like meat. It is not just—or even mainly—that some will not eat meat on moral grounds. Rather, greens say, meat has a big environmental hoofprint. It takes much more grain, land and water to fatten an animal to produce a pound of meat than it does to grow the same number of calories in the form of grain that is eaten directly (as bread, say). Animals also belch and fart forth remarkable quantities of greenhouse gases. The logical conclusion was drawn by Rajendra Pachauri, the chairman of the Intergovernmental Panel on Climate Change, who said “eat less meat; you’ll be healthier and so will the planet.”

New research in the current (special) edition of the Proceedings of the National Academy of Sciences (PNAS) shows that raising livestock does indeed chew up a disproportionately large share of the world’s basic resources. But it also suggests that reforming the livestock business, rather than rejecting it, is the way to go.

Livestock matters because it is the biggest land user in the world. More land is given over to grazing animals than for any other single purpose. About a third of the world’s crops are fed to animals, and they use a third of all available fresh water. Something like 1.3 billion people depend in some way on raising animals; animals provide a third of the protein in peoples’ diets and the business accounts for a third of global agricultural GDP. But meat is an inefficient source of calories. It accounts for 17% of global calorific intake, but uses twice that amount of land, water and feed.

Livestock also damages the environment. It accounts for between 8% and 18% of greenhouse-gas emissions, depending on how you account for changes in land use (when the Amazon is cut down for pasture, carbon emissions rise). Roughly a fifth of all the world’s pasture has been degraded by overgrazing. Livestock uses water inefficiently: you need about 15,000 litres of water to produce a kilo of beef but only 1,250 litres for a kilo of maize or wheat. And animals form a significant reservoir of diseases that affect humans; avian flu, the best known example, is far from an isolated case: 60% of human diseases are shared with animals and three quarters of new infectious diseases of people were first found in animals.

But a reduction in the size of the business isn’t going to happen soon, if ever. Urbanisation and rising incomes mean that more of the world is converging on European and American levels of meat consumption, which is roughly 100kg a year (80kg in Britain, 120kg in America). At the moment, most of Africa and South Asia eats less than 20kg of meat a year. Even if parts of India remain vegetarian, shifting patterns of demand imply worldwide meat consumption will double by 2050.

So the question is, what sort of livestock farming can satisfy the growing appetites, while using land, water and food crops more rationally? Environmentalists have an answer for that: small-scale, traditional pastoralism, of the sort practised for thousands of years. Such farming is, says Worldwatch Institute, a think-tank in Washington, DC, “essential to combat the destructive trend of factory farms.” The research in PNAS suggests this is back to front. Intensive livestock farming is more efficient and environmentally friendlier. It is essential to combat the destructive trend of traditional pastoralism.

The research by Mario Herrero of the Commonwealth Scientific and Industrial Research Organisation in Australia and colleagues starts by establishing a new data set on biomass use, meat production, feed efficiency, and other measures of livestock farming. It breaks this down by region, animal species, products (meat, milk, eggs and so on). This is vital because, even though the livestock sector is big, comprehensive, disaggregated data on it has been patchy.

The results confirm that efficiency in livestock varies hugely. Chickens and pigs convert grain into meat at rates of two or three to one (ie, it takes 2kg of feed to produce 1kg of chicken). The ratio for lamb is between four and over six to one and that for beef starts at five to one and goes as high as 20 to one. This has long been known. What is new are the amounts of greenhouse gases associated with the production of a kilo of protein by different animals. These vary even more widely: 3.7kg for chicken; 24kg for pork; and up to 1,000kg for cattle. The lower, more efficient ratios for chicken and pigs come about because they are kept in hated factory farms. Factory farming is good for the planet, if not for the animals.

The new research shows that there is an enormous spread of efficiency throughout livestock farming, not just between different animals. Milk is far more efficient than meat: it takes five times as much feed to produce protein in the form of meat than in milk. 

A cow in America or Europe will need to eat somewhere between 75kg and 300kg of hay and other dry matter for each kilo of protein. In most of Africa, she will need 500kg or more. On the dry rangelands of east Africa—in Ethiopia, Sudan and Somalia—the figure is up to 2,000kg, because the land is so poor. In these places, switching from traditional pastoralism to feeding cattle with grain would dramatically improve efficiency. It would also reduce greenhouse-gas emissions. Cattle on dry rangelands produce 100 times as much greenhouse gases as cattle in America or Europe for the same amount of protein. Cattle account for 77% of the greenhouse gases produced by livestock for 59m tonnes of beef each year. Pork and poultry produce 10% of the greenhouse gases, but 215m tonnes of meat.

Several lessons emerge from the new research. The advantages of white meat (chicken and pork) are even greater than was thought. Milk is more efficient as a source of protein than meat. And there are big opportunities for efficiencies in South Asia, South-East Asia, Africa and the Middle East, where 45-80% of pig and chicken farms are run by smallholders (compared with America and Europe, where 98% are run at industrial scale). There are risks, too, because industrial-scale livestock farming harbours some of the diseases that humans share with animals. But efficiencies in livestock farming imply better use of scarce basic resources such as land and water—which is environmentally essential.