People want to be good. They want to save the Earth, or at least maybe just destroy it a little more slowly. The problem is, they don’t know how. They don’t really have any idea about how much energy their appliances are using, or how much energy it takes to make the food they eat, and thus don't know the greenhouse gas impact of using those appliances or eating that food.

If only they knew, the hope goes, they (we) would change their (our) destructive ways. “Those who believe that reducing meat consumption effectively reduces greenhouse gas emissions are much more likely to intend to reduce eating meat,” according to a paper just out in Nature Climate Change.

A study done in 2010 indicated that people knew that refrigerators and dishwashers use more energy and emit more greenhouse gases than light bulbs. But they had no real sense of the true emissions numbers, nor the magnitude of the difference between high- and low-emitting appliances.

This new paper describes a similar analysis, substituting food for appliances. It found pretty much the same thing—food impacts were even more badly underestimated than appliances. Although most people (around a thousand were sampled) knew that red meat was more energy intensive than, say, apples, the impact of red meat was still underestimated by the widest margin.

For the record... The food system is currently estimated to contribute somewhere between 20 and 30 percent of global greenhouse gas emissions, and raising cattle accounts for much of that. Animal feed is grown using fertilizer that's manufactured with natural gas. It is hardly an efficient process; since it takes 38 kg of plant-based protein to generate 1 kg of beef, most of the feed becomes manure and methane. The beef (like many other foods) must be refrigerated and transported, processes that also rely on fossil fuels. And carbon-sequestering forests are often burned to make way for pastures for grazing or growing crops.

This study was undertaken because researchers thought it was important to know how consumers perceive the environmental impact of their food choices. Ideally, interventions can be designed to show them the error of their ways, and then they’ll be able to make informed decisions. Would that actually work, though?

To find out, the researchers did a smaller study, this one of 120 people. This indicated that if people were told about the magnitude of the environmental impacts of beef production—like if there was a label on the product telling them—that they’d eat less beef. The participants were paid to participate in the study, and once they arrived they were asked to spend part of their payment on cans of beef or vegetable soup.

Some of them were shown cans of beef soup that had a carbon label, and these participants bought fewer of them than those in the control group. Thankfully, the researchers acknowledge that “knowledge alone is often insufficient to change behavior... our promising observations warrant replication outside a laboratory setting.”

This has been tried before—and it didn’t work. Ten years ago, the British supermarket giant Tesco pledged to have carbon labels on all 70,000 food items it carried, displaying their carbon footprints. About 500 labels and five years later, they shelved the plan. Not because people didn’t change, but because it was just too complicated to figure out the environmental impact of most foods. This is the same reason why these researchers think people underestimate it.

Maybe labels would help, but you shouldn’t need one to remember that meat production, in particular, is energy intensive. Eat less of it.

Nature Climate Change, 2018. DOI: 10.1038/s41558-018-0354-z (About DOIs).