By some estimates, the world’s food system is responsible for one-quarter of humanity’s greenhouse gas emissions.
It happens because forests get cleared to make room for farms and livestock. Cows and rice paddies emit methane, a potent greenhouse gas. Fossil fuels are burned to power farm machinery, make fertilizer and ship food.
Anyone focused on the climate effects of diet should keep a few broad things in mind.
First, beef, lamb and cheese tend to have the biggest effects on emissions by far — creating the most greenhouse gases per gram of protein — in part because cows and other ruminants are more resource-intensive to raise. Pork, chicken, eggs and many types of fish typically have smaller effects on emissions (though they can create other environmental concerns). Plant-based foods usually produce the fewest emissions of all.
So the most straightforward way of reducing diet-related emissions is to consume less meat and dairy and more plants. It’s especially the case if you live in the United States, where red meat consumption is much higher than in many parts of the world.
According to a World Resources Institute analysis, if the average American simply replaced a third of the beef they eat with lower-emissions pork or poultry or legumes, their food-related emissions would fall 13 percent. Moreover, a number of studies have found that people who currently eat a meat-heavy diet could shrink their food-related footprint by one-third or more by going vegetarian.
It sounds like a no-brainer, but the other big way to shrink the climate effect of your diet is simply to waste less food. According to some estimates, Americans throw out roughly 20 percent of the food they buy.
Other popular strategies are less clear-cut, at least when it comes to greenhouse gas emissions.
Studies differ on whether grass-fed beef, for instance, is any more climate friendly than conventional feedlot beef, although some argue it’s better for animal welfare. Organic crops tend to require more land than traditional crops, which could lead to more emissions if such farming results in more deforestation.
As for debates over locally grown produce, or paper vs. plastic bags, those are relatively small in the grand scheme of things, since transportation and packaging are a sliver of food’s climate effects.
And, of course, there are other concerns besides climate change.
For example, when compared with meat, wild fish can be a lower-emissions option. But that comes with a caveat: The world is already catching about as much wild fish as it possibly can. Most fisheries are being fished at their maximum sustainable level, while others are being overexploited. So more people switching to fish could require, among other actions, increasing the number of sustainable fish farms worldwide.
— Brad Plumer
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Your Questions About Food and Climate Change, Answered