Eating less meat - what it can do to reduce carbon emissions

21/7/2010 New Scientist IF YOU’RE a typical westerner, you ate nearly 100 kilograms of meat last year.This was almost certainly the costliest part of your diet, especially in environmental terms. The clamour for people to eat less meat to save the planet is growing ever louder. “Less meat = less heat”, proclaimed Paul McCartney in the run-up to last December’s conference on global warming in Copenhagen. And this magazine recently recommended eating less meat as a way to reduce our environmental footprint.

If less is good, wouldn’t none be better? You might think so. “In the developed world, the most effective way to reduce the environmental impact of diet, on a personal basis, is to become vegetarian or vegan,” says Annette Pinner, chief executive of the Vegetarian Society in the UK.

It seems like a no-brainer, but is it really that simple? To find out, let’s imagine what would happen if the whole world decided to eliminate meat, milk and eggs from its diet, then trace the effects as they ripple throughout agriculture, the environment and society. The result may surprise you.

In 2008 the world consumed about 280 million tonnes of meat, 700 million tonnes of milk and 1.2 billion eggs, according to the UN Food and Agriculture Organization (FAO). Environmentally speaking, this came at an enormous cost.

All agriculture damages the environment - think of all those felled forests and ploughed-up prairies, all the irrigation water, manure, tractor fuel, pesticides and fertiliser. Agriculture produces more greenhouse gases than all methods of transport put together, and contributes to a host of other problems, from nitrogen pollution to soil erosion.

Livestock farming does the most damage. In part, that is because most livestock eat grain that could be used to feed people. As little as 10 per cent of that grain gets converted into meat, milk or eggs, so livestock amplify the environmental impact of farming by forcing us to grow more grain than we would otherwise need.

As a rough measure of how much more, consider that livestock consume about a third of the world’s grain crop. So as a first approximation, a vegan world would need only two-thirds of the cropland used today. That’s only part of the story, of course: meat and milk make up about 15 per cent of calories eaten by humans, so we would need to eat more grain to compensate for their loss. Altogether, switching to a vegan diet would reduce the amount of land used for crops by 21 per cent - about 3.4 million square kilometres, roughly the size of India.

Such a reduction would have a huge effect on the environmental impact of farming. Take nitrogen pollution, which can lead to eutrophication in lakes. As a small-scale illustration, environmental scientist Allison Leach of the University of Virginia in Charlottesville calculated that if everyone at her university cut out meat from their diet, it would reduce the university’s nitrogen footprint - the amount of nitrogen released to the environment from all activities - by 27 per cent. This is largely because of reductions in fertiliser use and the amount of nitrogen leaching from manure. If everyone went a step further and eliminated dairy products and eggs as well, Leach found that the university’s nitrogen footprint would fall by 60 per cent.

It’s not just in terms of nitrogen that livestock impact the environment. Global statistics are hard to come by, but in the US at least, livestock account for 55 per cent of soil erosion and 37 per cent of pesticide use. As well as that, half of all antibiotics manufactured are fed to livestock, often as part of their normal diet, a practice that is leading to antibiotic resistance in bacteria.

That’s not all. Livestock are also a major source of greenhouse gases. Much of this comes in the form of methane - an especially potent greenhouse gas - produced by microbes in the guts of grazers such as cattle and sheep, and eventually belched out to the atmosphere. Livestock farming also accounts for a lot of carbon dioxide, mostly from forests being cut down for pasture, or when overgrazing and the resulting soil erosion causes a net loss of carbon from soils. When you add all this together, livestock account for a whopping 18 per cent of all greenhouse gas emissions as measured in CO2 equivalents, according to Livestock’s Long Shadow, a 2006 FAO report. Eliminating livestock would certainly make a big difference in efforts to control global warming.

Just how big a difference depends on what replaces the livestock and the land it grazes. Certainly, where pastures revert to forests - particularly in areas like the Amazon basin, for example, where 70 per cent of deforested land is now pasture - the regrowing forest will sequester huge amounts of carbon. The American plains, too, would accumulate carbon in their soil if grazing stopped. But in sub-Saharan Africa, any reduction in methane from domestic grazers is likely to be at least partially offset by increased emissions from wild grazers and termites, which compete with livestock for food. “It’s certainly worth someone spending some time to look at that,” says Philip Thornton, an agricultural systems scientist with the International Livestock Research Institute.

Hidden costs
A meat-free world, then, would be greener in many ways: less cropland, more forest and, presumably, more biodiversity; lower greenhouse gas emissions; less agricultural pollution; less demand for fresh water - the list goes on. Clearly, if meat, milk and eggs were on trial for crimes against the environment, the prosecution would have an easy ride. And that says nothing of animal-welfare issues.

But wait. If everyone opted to give up meat there would be significant costs, too. It is true that most livestock today are fed grain that people could otherwise eat, but it doesn’t have to be so. For most of human history, cattle, sheep and goats grazed on land that wasn’t suitable for ploughing, and in doing so they converted inedible grass into edible meat and milk. Even today, a flock of sheep or goats can be the most efficient way to get food from marginal land. In a world where more than a billion people don’t have enough to eat, taking such land out of production would only contribute to food insecurity. Moreover, for semi-arid or hilly land, modest levels of grazing may cause much less ecological damage than growing crops.

Even pigs and chickens, which lack the digestive machinery to eat grass, don’t need grain. Instead they can subsist on leftovers and whatever they forage. “Your household pig was your useful dustbin,” says Tara Garnett, who heads the Food Climate Research Network at the University of Surrey in Guildford, UK. “You give your leftovers to the pigs, they deal with your rubbish, and you get meat.” Fed in this way, livestock represent a net gain of calories and protein in the human diet while dealing with some of the estimated 30 to 50 per cent of food that goes to waste - a benefit that a meat-free world would have to do without. Most pig and chicken farms are missing a trick here, since the animals eat commercial, grain-based feeds.

You give your leftovers to the pigs, they deal with your rubbish and you get meat
Another downside would be the disappearance of animal by-products. A meat-free world would have to replace the 11 million tonnes of leather and 2 million tonnes of wool that come from livestock farming every year. Not only that, many farmers would miss the manure, though the use of animal fertiliser is less important than it once was. “Manure has become a minor source of nitrogen in all major agricultural countries. It’s not unimportant, but it accounts for probably less than 15 per cent of total nitrogen,” says Vaclav Smil, an environmental scientist at the University of Manitoba in Winnipeg, Canada.

Even ardent vegetarians acknowledge that dairy products and even meat may be a good thing in poorer countries. “Whilst there’s no doubt that considerable reduction of meat consumption would have an environmental benefit, we do have to be careful about saying it would be the best solution if the whole world went vegetarian,” says Pinner. For as many as a billion of the world’s poorest rural residents, an animal or two may represent their only realistic hope for a little extra income, and a little bit of animal protein can make a big difference to a marginal diet.

What if we decided on a vegetarian, rather than vegan diet? After all, milk and eggs are very efficient ways of producing animal calories, second only to factory-reared broiler chickens. Unfortunately, an exclusively lacto-ovo livestock system simply doesn’t work well in practice.

“It’s difficult to switch to a no-meat but milk diet, because you cannot produce milk without meat,” says Helmut Haberl, a social ecologist at the Institute of Social Ecology in Vienna, Austria. Dairy cows must calve every year to keep producing milk, and only half their offspring will be female. While many vegetarians see moral reasons not to kill and eat the males - or retired dairy cows - there is surely no practical reason to waste so much meat. Similar arguments apply to chickens kept for eggs.

So even though a meat-free world sounds good on paper, it is likely that a utopian future will still have some animal products in it. And we are talking meat, not just milk and eggs. The real questions, then, are how much meat do we want, and how will we produce it?

The answers depends on how you approach the question. The most straightforward is to assume that the world will continue to demand ever more meat. That is certainly how things are going at the moment (see “Wealth = meat”).

Under this scenario, the goal will have to be producing the most meat at the lowest environmental cost. That means fewer free-range cattle and sheep grazing in bucolic pastures and more animals, especially chickens, packed into feedlots or high-density enclosures. “If you’re going to keep some livestock systems, I think the ones you’ll want to keep are the intensive ones,” says Walter Falcon, an agricultural economist at Stanford University in California.

Indigestible grass
That’s because pasture grazing is inherently inefficient. Animals burn large amounts of energy roaming about the landscape feeding on relatively indigestible grasses. They grow more slowly than feedlot animals and, as a result, emit more methane over their lifetime. A beef cow in a US pasture, for example, emits 50 kilograms of methane per year, compared with just 26 kilograms in a feedlot, according to Livestock’s Long Shadow.

But even a feedlot cow is a much less efficient meat producer than an industrial pig or chicken. While these eat a largely grain-based diet and thus compete directly with humans for food, they are relatively good at converting feed into flesh while producing little or no methane. This keeps their environmental cost down: a kilogram of industrial chicken meat represents greenhouse gas emissions equivalent to just 3.6 kilograms of CO2; a kilogram of pork, 11.2 kilograms; and a kilogram of beef, 28.1 kilograms, according to an analysis by Bo Weidema of sustainable development consultancy 2.-0 LCA based in Aalborg, Denmark.

Of course, such intensive operations cause other problems as well, notably the disposal of large amounts of manure. In theory - and increasingly in practice - much of this manure could be used to generate biogas and subsequently electricity. If all US livestock manure were processed in this way, it could reduce greenhouse gas emissions by about 100 million tonnes annually, equivalent to 4 per cent of the emissions from electricity generation (Environmental Research Letters, vol 3, p 034002). With the right incentives, intensive livestock farms could cause much less environmental damage than they do today.

There is another alternative, though: treat livestock as part of the ecosystem. Garnett envisions returning animals to their original role as waste-disposal units, eating food leftovers and grazing on land not suitable for crops. “In that context,” she says, “methane emissions per animal will be higher, but overall emissions would be less because there would be fewer animals.”

Fewer animals means less meat of course. Just how much less, no one really knows. As a first approximation, Garnett notes that about half of global meat production comes from intensive animal-only farms, and none of these would be allowed under the ecological approach. What is left would be those ranches where animals graze on marginal land and are not fed grain - about 10 per cent of the total today - and a larger number of mixed farms where the livestock feed off crop residues, milling wastes and other leftovers.

Such a future would require a major adjustment in food preferences. People would need to eat less meat, especially in the meat-hungry west. Not only that, but we would also have to change the kind of meat we eat. “You are not going to get your fat, heavy-breasted chickens by feeding them household scraps and letting them peck for worms. You are going to get a much scrawnier animal,” says Garnett.

Would people really accept pricey free-range beef and scrawny barnyard chickens perhaps once or twice a week? Certainly most do not today, opting for price and abundance over environmental impact. But change happens. Given the deforestation, soil erosion, water pollution and greenhouse gas emissions that will result if worldwide meat production continues to rise, some people are already choosing to eat less meat. And the message is definitely less, not none. For best results, meat should be medium-rare.

Wealth = meat
Persuading the world to eat less meat looks like a tough task. In country after country, as people become wealthier they eat more meat. Between 1980 and 2002, per capita meat consumption in developing countries doubled to 28 kilograms per year, and is projected to rise to 37 kilograms per year by 2030.

That is still less than half what the average person in the developed world eats today, and demand is still rising. In the west, people ate nearly 8 per cent more meat per capita in 2002 than they did in 1992.

When you add this to the growing population, the United Nations’ best guess is that by 2050, the world will need to more than double its production of meat - an increase that would be environmentally disastrous.

Bob Holmes is a consultant for New Scientist based in Edmonton, Canada
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