Along with their obvious benefits, agriculture and food production have significant environment impacts: Carbon dioxide emissions result from the power requirements of farm machinery and from the transport, storage and cooking of food. Nitrous oxide (a potent greenhouse gas) is released from soils when they are tilled and fertilized. Methane (also a greenhouse gas) is released in large quantities through enteric fermentation. Indeed, food consumption is responsible for about 1/5 of all greenhouse gas emissions in the United Kingdom. It is also known that animal-based food products are responsible for a disproportionate amount of these emissions. Veganism is therefore often touted as being environmentally preferable to diets that include meat and dairy products.
To test this claim, researchers from Oxford collected data from 65,000 participants about their daily diet. They grouped each participant into one of six categories of food consumers: high meat (> 100 g/day), medium meat (50 – 99 g/day), low meat (<50 g/day), fish eaters, vegetarians and vegans. Finally, the researchers converted each participant’s daily food log into carbon dioxide equivalents per day.
They found that the average high meat diet produced about 2.5 times as many greenhouse gas emissions as the average vegan diet. Greenhouse gas emissions steadily decreased as meat consumption dropped. They also found that as people ate fewer animal-based products their diet was lower in saturated fat, higher in fiber and higher in fruit and vegetable intake.
Unfortunately, the authors also point out that the average British national consumes about 110 g/day of meat so that the majority of consumers are probably in the high meat consumer category. However, the authors also point out that if a consumer moves from a high-meat to a low-meat diet they can reduce their yearly carbon footprint by approximately the same amount as a return flight from London to New York.
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