Animal-based food, especially beef, produces more greenhouse gases than plant-based food because of the emissions released through its production, mostly at the farms and ranches where the animals are raised.
Grazing animals, especially cows, consume a lot of land, and in major beef-producing countries, especially the tropics, swathes of the rainforest are cut down to graze animals or to grow feed for those animals. That means forests that normally store carbon instead release carbon.
Ruminants, especially cows, also emit a lot of methane when they burp. (About 95 percent of the methane they emit comes from burps.) Methane and nitrous oxide, both potent greenhouse gases, are also released through their manure, and nitrous oxide is released from the use of nitrogen-based fertilizers, which are widely used to grow crops to feed livestock.
While beef is especially greenhouse-gas producing, animal-protein in general uses more resources through the production process, largely because of feed.
“What we can see pretty clearly is the big gap [in emissions] between plants and anything that’s animal based,” said Edwina Hughes, who helps run a program at the World Resources Institute (WRI) called the Cool Food Pledge, which encourages companies to assess the impact of the food they serve.
For example, Hughes said, producing beef uses 20 times the land and releases 20 times the greenhouse gas emissions, per gram of protein, than producing beans.
The food system, in total, is a major contributor of greenhouse gases, producing about 35 percent of global emissions, according to the Food and Agriculture organization of the United Nations. Animal-based food accounts for two-thirds of that amount.
Researchers at WRI have calculated that, in order to curb climate change, consumers and producers need to cut about 67 percent of the climate impact of the food system by 2050. Along with major reports from the IPCC and United Nations, they have emphasised the need to shift toward lower-impact, plant-based diets.
“We need to rebalance our plates,” Hughes said.