I have come across quite a few people lately who are convinced that eating meat or dairy is bad for the environment. The logic behind this idea is that meat has an outsized environmental impact relative to the calories and nutrition that it provides. And the implicit conclusion is that a more plant based diet is good for the environment.

But thinking about the environmental impact of food in this way—meat is bad, plants are good—is useless. Many of the foods which these people probably think are great for the environment—basically all fruits and vegetables and especially kale, that icon of conscientious eating—are worse for the environment than meat. Usually much worse. Understanding the environmental impact of the food you eat is actually pretty straightforward. It mostly comes down to a simple rule of thumb:

The more a food costs per calorie, the worse it is for the environment.

To understand the logic behind this, first let's talk about some of the things that go into making the food we eat. We’ll start with plant based food. Broadly speaking, the ingredients are:

  • Land to grow the plants on
  • Water and fertilizer to feed the plants
  • Pesticides to increase yields
  • Labor and equipment to plant, harvest, process, and transport the crops
  • Fuel to run the equipment

Then, for meat, all of these same ingredients are required as a baseline, since animals eat plants to grow, plus we need some additional in each category to raise, slaughter, pack, and transport the animal. There are probably a few things that I'm leaving out, but that's okay, because this covers most of it and we're aiming for a rule of thumb here, not a dissertation on agricultural inputs.

Now, let's think about what happens if, for some reason, we need to use more of one of these ingredients to make the same amount of food. Obviously, the cost to produce that food goes up, too. Right?

Maybe that's not so obvious, so let's go through a hypothetical scenario. Imagine that we have a kale farm and it takes the following to produce 1,000 bunches of kale:

  • 1 acre of land
  • 10,000 gallons of water
  • 500 lbs of fertilizer
  • 50 lbs of pesticides
  • 200 hours of labor
  • 100 gallons of fuel
  • 20 hours of tractor time

Now let's see what happens as the amount of each ingredient that we need increases. Remember, this is a hypothetical situation; I have no idea how much of each of these inputs is actually required to grow 1,000 bunches of kale. But that's okay, because we don't care about the actual amount of raw ingredients required. We only care about the relationship between the cost of food and the amount of raw ingredients required to produce it.

For water, fertilizer, pesticides, labor, and fuel, it's rather obvious what happens if you need more of these to grow the same amount of kale: the cost to produce the kale goes up. If you need twice as much fertilizer, you'll have to spend twice as much on fertilizer. There's no getting around this, since you have to buy all of these items.

Land is a little bit more complicated. Let's imagine that, for some reason, it now takes 2 acres of land to grow 1,000 bunches of kale, instead of 1 acre. What happens to the cost to grow kale? Well, even if you already own the extra acre, it could have been used to grow a different crop, so the income that gets left aside as a result of not growing an acre of that other crop gets factored into the cost to grow the 1,000 bunches of kale. And if you didn't already own the land, you would have to buy or lease it. So, if land use goes up, cost goes up.

Tractor time is also a little bit more complicated. You could make the argument that a little more tractor time doesn't matter, since you already own the tractor. But it does matter. The useful life of heavy equipment is typically measured in hours of operation. So if you need more tractor time to grow those 1,000 heads of kale, you're using more of the tractor’s useful life. You may not pay the price now, but it's a real cost nonetheless.

Hopefully I've made a good case for the idea that, as the amount of raw ingredients required to produce a given food increase, so does the cost. Now I am going to make the case that the most important driver behind how much it costs to buy a food at the grocery store is the amount of raw ingredients required to produce that food. To do that, we will consider another hypothetical scenario.

Imagine you're a farmer and you've found a sweet niche selling an heirloom variety of eggplant. No other farmers are growing it, but it's a hit with consumers. As a result, you're able to sell these eggplants at a relatively high price. But a competing farmer notices that these eggplants are popular, does some calculations on expected yields, and figures out that you've got a pretty good thing going. The next season, your competitor also plants some of this heirloom eggplant variety. Now, grocery stores have two sources for these eggplants, so they're able to negotiate better prices from you. As a result, this heirloom eggplant variety goes from being abnormally profitable for you to just normally profitable.

This sucks for you, but welcome to the basic process of supply and demand under a free market economy; if there are markets or products which are unusually profitable, soon there will be competitors chasing after those profits and driving prices down in the process. Eventually prices reach an equilibrium that consists of the cost of production plus a reasonable amount of profit for engaging in the risk of running a business.

There are definitely exceptions to this, but farming and groceries are not them. It's just too easy for a grocery store to replace an expensive grower with a cheaper one. And it's just as easy for most consumers to shop at at whichever grocery store has the lowest prices. If you don't believe me, read the financial statements of huge grocery companies like Kroger or Safeway. Their margins are shockingly low.

So, the price you pay for kale at the grocery store is primarily a reflection of how much it cost to produce that kale. And how much it cost to produce is really just shorthand for how much land, water, fertilizer, pesticides, labor, fuel, and equipment went into making it. And the amount of land, water, fertilizer, pesticides, labor, fuel, and equipment that went into making it sounds an awful lot like its environmental impact.

But, in case you think I just pulled a fast one on you, let's consider each of these in turn:

  • Land used for agriculture is unavailable for wildlife.
  • Water used in agriculture is unavailable to support wildlife.
  • Fertilizer is either extracted from the environment or requires an energy intensive process to produce.
  • Pesticides inevitably end up contaminating the environment surrounding agricultural areas (just ask your local anti-GMO type for an earful on the topic).
  • Labor is people and all the food, fuel, and stuff that people consume definitely has an environmental impact.
  • Fuel extraction has a large environmental impact, as does the pollution that results from burning fuel.
  • Equipment manufacturing uses lots of energy and raw materials.

So the price of food is a rough indicator of its environmental impact. $2 of ground beef has twice the environmental impact as $1 of ground beef. $1 of chicken and $1 of kale have roughly the same impact. And $2 of ground beef has roughly twice the impact as $1 of kale. I say roughly because kale might require more land and fertilizer, whereas ground beef might require more labor and equipment, and those things are not exactly equivalent, but, again, we're going for a rule of thumb here.

Now, here's the important part:

One dollar’s worth of kale, ground beef, and chicken might have roughly the same environmental impact, but they do not provide the same amount of calories.

In fact, it's not even close. Here is a graph showing the number of calories that $1 buys when spent on kale, ground beef, and chicken (darker). It also includes a few common staples for some perspective (lighter).

Calories per $1, Selected Items

Prices were gathered from my local Fred Meyer in August, 2016. You can also check out an expanded chart which includes most common food items or the spreadsheet which the charts in this essay are based on.

This table really gets to the title of this article: kale is terrible for the environment. You can see it way down at the bottom of the chart, providing a mere 70 calories per $1. That’s 5x less calories per dollar than ground beef and 18x less than a whole chicken. Or, put differently, the environmental impact of a calorie of kale is roughly 5x greater than a calorie of ground beef and 18x greater than a calorie of chicken.

So, if your goal is to signal your virtue to your peer group—especially if your peer group is well educated, upper middle class white people—then kale probably can’t be beat. But if your goal is to minimize the environmental impact of the food you eat, then kale is a terrible choice. Just like pretty much every other fruit and vegetable.

Here’s a chart which shows the range of calories per $1 that each major food group provides:

Range of Calories per $1, by Category

Prices were gathered from my local Fred Meyer in August, 2016. You can also check out an expanded chart which includes most common food items or the spreadsheet which the charts in this essay are based on.

It’s plainly obvious that, of all the major food groups, fruits and vegetables have among the highest environmental impact per calorie. So, when I hear people saying that they are eating less meat because they want to reduce their environmental impact, all I hear is somebody who doesn't really know what they're talking about. Because when it comes to the environmental impact of your diet, what matters is the size of your monthly grocery bill, not whether your food came from plants or animals.

So if you give up eating meat, but your grocery bill is the same because you’re eating lots of salads and kale smoothies, then you haven’t really done the environment any good. Instead, you should be focused on shifting your diet away from high cost per calorie foods. So, more chicken, eggs & dairy (400–1200 cal/$), less seafood and steak (50–150 cal/$). More apples and bananas (200–600 cal/$), less blueberries and raspberries (35–65 cal/$). Include a grain or starch (1400–3000 cal/$) as a significant portion of most meals, cook with lots of butter and oil (900–5300 cal/$), and treat fruits and vegetables not as staples, but as what they really are: delicacies.

Now, since you’ve made it this far, I encourage you to take this rule of thumb and use it as a lens to look at the world around you. For instance, what does it imply about the environmental impact of:

  • Organic vs. non-organic food
  • Artisanal, locally grown vs. factory farmed food
  • Eating at restaurants vs. preparing your own meals

And this rule of thumb is not limited to food; it can be applied to all of your buying decisions.

I'll leave that discussion for another time and stop here, though.

Caveats and Limitations

Being a rule of thumb and not a rigorous scientific methodology, this way of quantifying the environmental impact of the food you eat has some limitations:

  1. It doesn't take into account externalities that occur while producing food. An externality is a cost which is external to the person or company that produces something. So, when runoff from a farm pollutes a river, that is an externality, because the cost of that pollution is borne by people in the community instead of by the farm. The big externality that probably comes to mind if you’re of the anti-meat mindset is methane emissions from cattle.

  2. It doesn't account for preferences you might have about different kinds of environmental impacts. You might care a lot about land use, but very little about labor or capital costs. Or vice versa. But this method boils all of those very different environmental impacts down into one opaque number. If you want to get specific, you'll have to do some research.

  3. It is probably not very useful across different time periods. The price of an input is a reflection of its relative scarcity at a given point in time and my intuition tells me that this can shift in strange ways over time. So, it's useful to compare the cost per calorie of apples to rice, but not useful to compare the cost per calorie of apples today to apples two years ago. In practice, I don’t think this limitation comes into play very often.

  4. It probably doesn't work very well across national boundaries. If you were comparing the cost per calorie of kale produced in Brazil vs. kale produced in the United States, it probably wouldn’t be a very useful comparison. Kale produced in Brazil would probably have a similar environmental impact to kale produced in the U.S., but it would probably cost much less because Brazil is less developed. Again, though, the purpose of this rule of thumb is to help you make decisions about what you eat, and this limitation doesn't affect that.

  5. The cost of fuel is not necessarily related to its environmental impact. As an example, imagine that the fuel cost in a head of kale comes to $0.10. If the price of oil gets cut in half (as it has in the last several years), then the cost of head of kale goes down by $0.05, even though the environmental impact of producing that head of kale stays exactly the same.

  6. Finally, some people give up eating meat because they have a moral objection to eating animals. I will readily admit that the calories found in $1 worth of beef is not really a good way to measure the welfare of the cow that it came from.

Thanks to Monika Radon-Jones and Guru Khalsa for reading drafts of this essay.