Reasons for eating less meat range from the personal to the global. Many health risks--obesity, heart disease, strokes, diabetes, some cancers--fall as a person's meat consumption goes down. Most people ask, "How will I get enough protein?" Eating a varied diet is the answer. Plants provide plenty of protein; in fact, spinach has more protein per calorie than beef. The average American diet includes almost twice the FDA-recommended amount of protein. To feed everyone in the world the American diet, we'd need the resources of an extra Earth.
From an environmental point of view, meat production is a double whammy, increasing atmospheric pollutants even as it reduces (through deforestation, overgrazing, trampling, erosion, water pollution) the plant life that would help absorb them. Raising meat animals and the crops used to feed them takes up 30 percent of the planet's land and emits 20 percent of the world's greenhouse-gas pollution (more than transportation). And the volume producers of beef, pork, and poultry crowd their animals into cramped, unsanitary lots and barrage them with antibiotics to forestall resultant diseases; the flow of the drugs into our food and water supplies helps breed antibiotic-resistant supergerms.
Many wars--patriotic rhetoric aside--are about scarce resources: water, land, food, energy. Livestock farming increases incentives for conflict by consuming all of these--and inefficiently. Growing one calorie of meat takes two to five calories of feed--or, in the case of U.S grain-fed beef, 10 calories of feed. Diverting one-third of the world's grains to livestock and away from the humans who would happily eat them raises prices for those crops and brings hunger, malnutrition, or starvation to millions of poor people.
So how do we cut back? Convincing the world's meat-eaters that cattle, sheep, and pigs are our relatives may take more time than we have. But there's always the pocketbook route to changing behavior. Taxing meats with a surcharge that would go into a fund to care for people with meat-induced illnesses would be one approach. And ending the U.S. and international policies and subsidies that have made meat, especially beef, artificially cheap would drive meat-eating out of fashion in a hurry; one source estimates the true cost of a pound of factory-farmed beef at $815 a pound.
Less meat for the world's most privileged people? Sounds like a win-win-win: better health for people, animals, and planet.