Global warming has been called the world's gravest environmental threat and humankind's "greatest challenge". Going vegan is one of the most effective ways to fight global warming. A recent United Nations report concluded that a global shift toward a vegan diet is necessary to combat the worst effects of climate change.
Carbon dioxide, methane, and nitrous oxide together cause the vast majority of global warming. Raising animals for food is one of the largest sources of carbon dioxide and the single largest source of both methane and nitrous oxide emissions.
Burning fossil fuels (such as oil and gasoline) releases carbon dioxide (CO2), the primary gas responsible for global warming. Producing one calorie from animal protein requires eleven times as much fossil fuel input—releasing eleven times as much carbon dioxide—as does producing a calorie from plant protein. Feeding massive amounts of grain and water to farmed animals and then killing them and processing, transporting, and storing their flesh is extremely energy-intensive. In addition, enormous amounts of carbon dioxide stored in trees are released during the destruction of vast acres of forest to provide pastureland and to grow crops for farmed animals. On top of this, animal manure also releases large quantities of carbon dioxide.
According to the University of Chicago, a vegan diet saves more tons of CO2 (compared to a meat-eating diet) than driving a hybrid car does (compared to a standard sedan). Additionally, a German study conducted in 2008 concluded that a meat-eater's diet is responsible for more than seven times as much greenhouse gas emissions as a vegan's diet.
More methane and nitrous oxide is produced by the billions of chickens, turkeys, pigs, and cows who are crammed into farms each year than any other source. The methane is produced, both during digestion and from the acres of cesspools filled with feces that they excrete. Scientists report that every pound of methane is more than 20 times more powerful than carbon dioxide at trapping heat in our atmosphere. The EPA shows that animal agriculture is the single largest source of methane emissions in the U.S.
Nitrous oxide is about 300 times more potent as a global warming gas than carbon dioxide. According to the U.N., the meat, egg, and dairy industries account for a staggering 65 percent of worldwide nitrous oxide emissions.