The United States is a nation of meat eaters. The average American eats roughly 97 kilograms (214 pounds) of meat – including beef, pork, chicken, and sheep – per year, compared to a global average of around 34 kilograms (75 pounds), and with all that agriculture comes a significant cost to the environment.
Many argue that if we all became vegan, it would help solve climate change, so a group of researchers decided to put this to the test. They calculated what would happen if the entire population of the notoriously carnivorous US gave up meat and its associated products and dined solely on plants. The results are not quite as straightforward as you might expect.
Feeding 320 million is a carbon-intensive activity, particularly when so much meat is consumed. On average in the US, it takes 7 kilograms (15 pounds) of corn to produce just 1 kilogram (2.2 pounds) of meat. Growing that corn costs energy, while the animals themselves are also significant sources of greenhouse gases. Around 9 percent of greenhouse gas emissions in the US in 2015 were due to agriculture, and it's thought that livestock contributed about half of this.
So if everyone in the US stopped eating meat overnight, you would think that greenhouse gas emissions from this sector would immediately fall by at least half. Well, the study published in Proceedings of the National Academy of Sciences found that this wasn’t quite the case, as emissions would fall by a slightly lower 28 percent. This is around 2.5 percent of the US’s total greenhouse gas emissions.
This is due to a number of factors. One is that there is a lot of waste from crops, be it corn stalks or potato waste, which while not being suitable for human consumption, is fine to feed to animals. So without these critters to hoover it up, the waste would likely be burned for energy, releasing around 1.8 million tonnes (2 million US tons) of carbon in the process.
Next up, providing enough plant-based sustenance for such a large population would cause a huge spike in the demand for fertilizer. As the supply of natural manure from all the feedlots declined, farmers would have to increasingly rely on man-made fertilizers, which could end up pumping another 21 tonnes (23 million US tons) of carbon into the atmosphere.
The authors also note that there would likely be another significant impact on people’s health. They predict that, as seen currently in vegans, there would be an increase in deficiencies of key nutrients such as calcium, vitamins A and B12, and some fatty acids.
So while there would be a net benefit, it is not as clear-cut as many would like to believe, although it is still true that eating less meat has other environmental benefits.