Last year one in five of Swedish young women became vegetarian because of climate change. Some might think that this is excellent news. We hear a lot that we should all eat less meat, ideally become vegetarians. The complex problem of food and sustainability has been reduced to the simple statement that vegetables are all good and meat overall bad. Unsurprisingly, such black and white statements are oversimplifications. One of the simplifications is the issue of methane and whether or not it is part of the carbon cycle, as I’ve previously written about here.
Another simplification is how the climate impact of food is calculated. Many calculations are based on how much CO2 is released per kilogram of the food. This, however, has been criticized by research that shows that calculating CO2 per volume, calorie or even nutrient will give different results. The researchers conclude that “the sustainability of alternative diets, matched for energy and nutrient adequacy, can only be made on the basis of calories and nutrient contents and not per gram of weight”. Surprisingly, if you calculate climate impact per calorie, lettuce appears worse than bacon. Basically, how we calculate the climate impact of food makes a big difference. Like, Gunnar Rundgren I believe that there’s a point in calculating emission per nutrient density.
Taking nutrients into account when calculating climate impact is important because, as Rockström has pointed out, food is both a key factor in the health epidemic as well as the climate. Half of Swedish female adolescents have iron deficiency, one in three women in general. It is well known that iron from meat type of sources is absorbed more easily (25%) than from vegetable sources (5-10%). Research on diets and climate change acknowledges that reduced meat in diets is especially problematic for young women for this reason.
If we encourage women with iron deficiency to become vegetarians, we’d better be sure it is beneficial for the climate.
I am not so sure it is and I’ll use the following example with two high impact foods to illustrate why. Lamb is generally viewed as the meat with the highest climate impact. Rice, because of methane emissions, is among the highest climate impact grains. A Swedish lamb provides a carbon footprint of 16 kg CO2-equivalent per slaughtered kg lamb. A kilo of Thai rice provides between 1.34- 3.57 CO2-e per kg. Let’s say 2.4 kg CO2-e/kg.
Calculating emissions according to weight, yes lamb (16/kg) is much worse for the climate than rice (2.4/kg). You can eat six times as much rice and still release less CO2.
However, we have all heard about empty calories. What’s important is not only how much we eat but the nutrients the food provides us with. And we have to consider a woman’s recommended daily intake of iron, around 15 mg (9 mg for men). So here’s the issue. You would have to eat 3.2 kg rice a day to get the daily iron allowance. And considering the sort of iron and its lower absorption, it is even more. If you instead eat lamb, maybe even liver, 300g/day is enough. Of course, in reality no one would rely on a single food to provide all the necessary iron but the figure shows how efficient liver would be in doing so.
So to get your recommended daily intake of iron, what is the climate impact? For Thai rice the climate impact is at least 7,68 kg CO2-e. For Swedish lamb liver it’s 4,8 kg CO2-e.
Now, you might say, young Swedish women know about empty calories and would go for broccoli rather than rice. Still lamb liver is more efficient than broccoli in delivering iron per kg CO2-e. You would have to eat more than 2,3 kg broccoli to get the recommended daily intake. In climate impact that’s (using the example of UK broccoli) ca 5,3 kg CO2-e.
My message is really this. We have to consider nutrient content and absorption instead of climate impact per weight or calorie. When we consider nutrient content and absorption, we may find that going vegetarian is not a good idea. Instead, eating small amounts of nutrient dense food, like lamb liver, helps young women to maintain their health.
It is more climate friendly to eat small amounts of nutrient dense foods than eating large quantities of empty calories.
The nutrient argument was highlighted by researchers with connections to the Swedish dairy industry in 2010. While we of course have to be wary of industry motives, I still believe the overall idea of considering nutrients in relation to climate impact is a sound idea. And the general lesson here is that how we calculate affects the results we get.
On the picture: grazing sheep on the west coast of Norway, are they really that bad for the climate? It depends on how you calculate.