Of all the animals that humans eat, none are held more responsible for climate change than cows. Cows not only consume more energy-intensive feed than other livestock, they also produce more methane, a powerful greenhouse gas.
But grass-fed cows may have the opposite effect.
Grass is a perennial. If cattle and other ruminants are rotated across pastures full of it, the animals' grazing will cut the blades, spurring new growth, while their trampling helps work manure and other decaying organic matter into the soil, turning it into rich humus. And healthy soil keeps carbon dioxide underground and out of the atmosphere.
Currently, 99 percent of U.S. beef cattle live out their last months on feedlots, where they are stuffed with corn and soybeans. Much of the carbon footprint of beef comes from growing grain to feed the animals, which requires fossil-fuel-based fertilizers, pesticides, and transportation.
Even though grass-fed cattle produce more methane than conventional ones (high-fiber plants are harder to digest than cereals), their net emissions are lower because they help the soil sequester carbon.