Consumers, on the other hand, have less access to the information required for making good choices when grocery shopping. Yes, in general it is better to eat plants rather than animal products, but this maxim is based on estimating the average effects of various foods. Still, not all packages of the same product, side by side on the grocery shelf, cause equal amounts of greenhouse gas. Indeed, the variations in producing any specific food may differ enormously.(2) For instances, if two bins of apples or potatoes come from different sources, they may have been grown, packaged, transported, and refrigerated in very different ways, so one bin of them may be a vastly better environmental choice than the other. Unfortunately, you cannot discover all those differences just by looking at the apples or potatoes. Indeed, your information is so limited that it is probably more efficient just to follow your national food guide and hope for the best. But here it’s worth discussing some examples of the complexities that may be involved.

Take the growing use of palm oil in food and household products. In Indonesia and Malaysia, jungles and carbon-rich peatlands are being replaced by monocultural plantations — palm trees — grown for their oil. Biodiversity is being destroyed as a result of the loss of habitat of thousands of animal and plant species. For instance, our cousins the Bornean Orangutans, as well as the Sumatran Rhino and Sumatran Elephant, may become extinct. Yet palm oil is in about half of all packaged products in grocery stores. It is in snack foods like ice cream, candy, and instant noodles. It is in laundry detergent, toothpaste and shampoo. Palm oil has become the most widely used vegetable oil on Earth.(3)

Or take almonds, for another complex issue. Almonds are a highly nutritious plant food that every dietary guide would promote. In fact, eating a handful of almonds four or five times a week will lower your blood pressure and cholesterol, if those are your problems.(4) Many people buy almond milk now as an environmentally friendly substitute for cow’s milk.

California’s Central Valley produces 80 percent of the world’s almonds(5) and, unfortunately, California has an ongoing shortage of water. Each nut takes a gallon of water to produce, and the orchards use almost ten percent of the state’s annual agricultural water – more than what the entire population of Los Angeles and San Francisco use.(6) So there is a trade-off between health and at least one environmental challenge. Should we be eating almonds? The national dietary guides do not mention either palm oil or almonds, so we are left to make these choices independently.

National diets always do reflect national cultures and traditions. Thus the 2019 Canadian guide does not urge people to drink cows’ blood, as the Masaai tribes in Africa do, almost painlessly collecting the blood without killing their cattle.(7) Nor does the Canadian guide yet recommend the consumption of insects or mealworms, though these are both extremely efficient end-products of converting garbage into high-quality protein.(8) (If you want to know what various bugs taste like without trying any yourself, read these reports).(9)

No one in the supermarket can help you select potatoes or apples wisely, but a growing field of science, Life Cycle Assessment (LCA), is beginning to quantify the average impacts of various foods on the levels of CO2 in the atmosphere, as well as the appropriateness of their land and energy use. They do this by summing up the multiple impacts throughout the “life cycle” of each food – before it is planted until it is finally consumed.

One such study by Carlsson-Kanyama compared the typical life cycle of carrots, tomatoes, potatoes, pork, rice, and dry peas consumed in Sweden. For example, when calculating the impact of pork, she counted up the effects of using electricity, fuel, and refrigeration coolants in producing and transporting fertilizers; crop farming; drying of crops for the pig food, extraction of oil, producing of fodder, rearing of pigs and storing their manure, slaughtering and cutting them, selling pork at the retailer, transporting to the consumer, cooking, cleaning, and disposing of the garbage. She also included the greenhouse gases emitted through producing and transporting the pesticides, seeds and manure, and producing of such inputs as machinery, buildings, equipment, and services. All of these numbers need to be added together to get a good estimate of pork’s greenhouse gas emissions, which can then be compared to similar estimates for other foods.

We are often advised now to “eat locally,” to avoid the greenhouse gas emissions that result from transporting food long distances. Carlsson-Kanyama found, however, that transporting the food to market is a fairly large component of the energy use, but a small component of the total greenhouse gas resulting from the pork industry. To be sure, energy consumption is important, and so is land use, but there are more factors involved in greenhouse gas emission figures. Indeed, some decisions along the supply chain may even require choosing between minimizing energy and greenhouse gas emissions.

Carlsson-Kanyama found that current food consumption patterns in Sweden and other developed countries exceed the level of sustainability by at least a factor of four. Regrettably, the prospects for achieving sustainable food consumption seem questionable.(10) She also showed that the greenhouse gas emissions were highest for pork and rice and lowest for potatoes, carrots, and dry peas.(11)

That pork is high will surprise no one familiar with current national diet guides, since it is the product of animals. And pork is a less serious source of greenhouse gas than beef or lamb, for pigs are not ruminants and therefore do not emit as much methane while living.

On the other hand, rice is also a high source of greenhouse gas, though it is a plant. Rice is cultivated in paddies that must be flooded at times during the growing season. This flooding creates an environment for microbes that produce a far more potent greenhouse gas than CO₂, methane, as well as large amounts of another serious gas, nitrous oxide. It had previously been estimated that 2.5 percent of human-induced climate warming can be attributed to rice farming. This is a serious challenge, since rice provides more calories to the global population than any other food.

Out of concern to reduce these emissions, some researchers recommend flooding rice paddies only intermittently. Unfortunately, new research indicates that this only worsens the matter, and that the impact of rice cultivation is twice as bad for global warming as previously believed.(12) Perhaps Swedes will change from eating rice to potatoes, peas, and carrots, but the culture of India uses rice as a staple, so the prospects for alternative food choices in Asia seem remote.

Millet – which is nearly as high in protein as wheat – may be the most climate-friendly grain, although its cultivation has declined worldwide over the past 50 years. It is a C4 plant, which means that it uses a different enzyme for carbon fixation than C3 plants (that is, most other grains), thereby improving water efficiency.(13) Other edible grasses related to millet are sorghum and teff.

Plants versus Animals

As noted already, national dietary guides are starting to advise us to eat fewer animal products and more plants. This trend is based on incontrovertible evidence that, on the average, producing the latter category of foods causes more environmental damage than the former. One definitive study showing this is by J. Poore and T. Nemecek,(14) whose meta-study compiled the results of 1530 previously published studies by 139 authors. After studying the environmental impacts of 40 food products from 83,700 farms and 1600 processers, packaging types, and retailers in 119 countries, they concluded that “impacts of the lowest-impact animal products typically exceed those of vegetable substitutes, providing new evidence for the importance of dietary change.” Or, as Michael Pollen famously urges us, “Eat food. Not too much. Mostly plants.”

Animals inevitably have considerable impact on the environment because they must consume large quantities of plants throughout their life cycle, while putting on enough weight to become our favorite protein, beef. How many plants? That depends on the method of farming. Cattle today in North America are generally kept in feedlots and fed corn or other grain. There are many serious environmental consequences of this system, including the fact that it takes about 7 kg of grain to produce 1 kg of live beef. For pork, the figure is about 4 kg of grain per kg of weight gain. For poultry it is just over 2, and for several species of farmed fish, it is less than 2.(15)

Why is this kind of beef worse than the other sources of meat? Partly because feedlot cows are fed grain instead of grass, and partly because, unlike pigs, chicken, or fish, they are ruminants. As the eminent scholar Google explains, “Ruminants include cattle, sheep, goats, buffalo, deer, elk, giraffes and camels. These animals all have a digestive system that is uniquely different from our own. Instead of one compartment to the stomach they have four. Of the four compartments the rumen is the largest section and the main digestive centre.” Actually, it is bacteria in the rumen that generates most of its greenhouse gas, methane, which is emitted from both ends of the animal.

Naturally, many scientists are searching for cost-effective ways of reducing ruminants’ methane emissions. The challenge seems to be largely a matter of reducing the microbes in the rumen section of the stomach. This can be done by various kinds of food additives. For example, British scientists fed their cows curry extract, but the animals rejected it. However, some California dairy cows are now given a small amount of red seaweed, mixed with their feed and molasses. Their breath is measured four times a day, and it contains 99 percent less greenhouse gas than when fed normally. A compound in the seaweed disrupts enzymes used by the microbes to produce methane.(16) If this additive turns out to be as cheap and effective as it seems, it may make California’s milk less a source of greenhouse gas, but without mitigating the many other bad effects of keeping cows in feedlots. Other researchers are experimenting by vaccinating cattle. Up to 70 percent reductions are found in methane emissions, and this system could be used on cattle grazing in pastures, not feedlots.(17)

Still, such promising innovations can solve only part of the problem, for the production of meat will still require animals — both ruminants and other herbivores — to consume amounts of plants that could instead feed larger numbers of human beings.

To solve that problem, work is well advanced toward producing meat commercially by cultivating cells in vats. A hamburger from such sources will never have been part of a living animal — a fact that may allay the moral concerns of vegetarians and vegans who object to eating meat because its production involves cruelty to animals. Some companies expect to bring cultured meat to the market by 2021.(18) Many advantages can be expected of this technology. Production will reduce the consumer’s exposure to dangerous farm chemicals such as pesticides and fungicide. The meat will not create antibiotic resistance, which has become a major threat to humankind because antibiotics are fed routinely to livestock. (See the article for plank number 16.) And the environmental impacts of cultured meat will be lower than slaughtered beef or lamb. If methane is produced in the vats, it can be captured and used as fuel, unlike the situation with cows’ burps.(19)

But even if the environmental damage of slaughtered meat can be reduced or even eliminated by culturing meat, many people will oppose eating it because they regard its consumption as harmful to human health. Here the evidence is less conclusive than when it comes to greenhouse gas emissions, or energy or land or water consumption.

Perhaps the most significant study of the health effects of meat-eating comes from a study by the European Prospective Investigation into Cancer and Nutrition, which followed half a million people in ten countries for more than 12 years.(20) The researchers found that eating moderate amounts of red meat had no effect on mortality. The lowest overall mortality rates were in those people eating up to 80 g a day. Non-meat eaters had a higher all-cause death rate. Apparently a low, but not zero, consumption of meat is beneficial for health. However, eating processed meat such as bacon, ham, or salami has a negative effect on health. Eating more than 40g a day of it increases rates of heart disease and cancer.(21)

Another important study is the Million Death Study, headed by Dr. Prabhat Jha, which began in 2002 to send researchers across India, knocking on doors to gather accounts of the symptoms and circumstances behind recent deaths. This mortality study has now reached 3.5 million homes and more than 23 million people. India is a particularly good location for studying the effects of meat-eating, since a large proportion of the population there have been lifelong vegetarians. Jha reports that when he compared those families with other non-vegetarians, he found that their mortality rates were equal, with one exception: vegetarian women die somewhat earlier than non-vegetarian women.

This does not mean, however, that vegetarianism is everywhere dangerous for women; it is probably a specific attribute of Indian culture that explains the difference. Indian women are expected to feed the males and children first and simply eat the leftovers themselves later. Unfortunately, it seems likely that their families consume most of the protein in vegetarian meals, so that the women receive insufficient amounts. In a different society, Jha thinks that vegetarians of both sexes probably have the same mortality rates as meat eaters.(22) His report does not mention any differences between types of meat. Perhaps processed meat is less frequently consumed in India than Europe, but in any case the aforementioned European study indicates that it is probably wise to eat less ham, salami, bacon, sausage, and cold cuts.

More cows, not less, please?

Despite everything noted above, even the most enthusiastic meat-eater cannot deny this hard fact: More people can be fed with a diet of plants than by running the same amount of plants through animals and then consuming their flesh. Since the human population is growing and land, water, and energy are limited, the era of livestock farming must end. The land must be used to grow more forests or crops for human consumption. People must become vegetarians or even vegans to save the planet.

Ah, not so fast! All of these arguments are true, and yet there are reasons for questioning the conclusion. Indeed, some rational experts insist that we world needs more cattle and other large animals, not less. They attribute the worst aspects of climate change to the loss of animal herds.

In the temperate and tropical zones, large amounts of land (about the size of Pennsylvania) are turning into deserts every year and no one knows how to stop the trend. In the Arctic, the situation is even worse; enormous quantities of methane have been frozen in the soil there for many thousands of years. It is thawing now and entering our atmosphere, where it may even lead to the extinction of humankind in a generation or two. In both of these situations, there is an argument that the solution is to send vast herds of big animals out to roam and eat grass.

Allan Savory is an expert on land management. His unusual views originated in Africa, where he observed the encroachment of desertification. Originally, he accepted the common notion that such degraded land needed a rest — that the problem was caused by overgrazing, so he began removing livestock from the pastures and hoping for the land to recover its fertility. Instead, he regularly saw the situation growing worse, with weeds replacing the drying vegetation.

But in earlier times there had been large herds of animals feeding on rich pastures of perennial grass. Because these animals had to protect themselves from predators, they stayed together in close herds, moving together from place to place as they consumed the local grass for a few days, stirred up the top layers of soil with their hooves, and left behind their manure and urine. This is what had kept the soil fertile, Savory concluded. But in modern times, no predators were near and ranchers let their cattle graze indefinitely in the same pasture, where they had no reason to stay together as close herds or to move frequently to different pastures. As a result, the land desertifies.

Savory recommends that ranchers re-create the situations that had kept the soil healthy before. He brings in large numbers of cattle, but uses electric fences to confine them close together in a particular area for just the right length of time before moving them to another pasture. They eat the weeds and fertilize the soil as they go, loosening the top layer a bit. This, Savory shows, can restore the whole landscape to fertility within a couple of years. Again, grass will grow there and sequester carbon, which is exactly what the world needs most right now.(23) And yes, the cattle do continue emitting methane from both ends. If Savory is right, this is a trade-off. Do the cows sequester more or less carbon than they emit? And how many cows would we need to restore the land that has already been degraded? It is clear, and Savory agrees, that over-grazing has destroyed much of the planet’s fertility. He insists that the question is not how many cattle should be kept, but rather how they are managed. Conventional ranching does not work.

Agricultural experts are divided in their opinion about Savory’s approach. There is no consensus on the matter and no easy way to ascertain which view is winning the debate. George Monbiot wrote a scathing article about Savory in The Guardian, but it was not evidently informed by research into the current findings.(24) Many experts concur with Savory’s claims and are recommending that the farmlands throughout the plains of North America be restored to the primeval perennial grasslands and that millions of bison allowed to graze again, perhaps with predators snacking on the perimeter of their herds. These researchers insist that global warming is being worsened by the land being covered today with monocultural cornfields for fattening cows in feedlots.(25) (See the essays about Platform for Survival planks number 12 and 14.) Moises Velaszuez-Manoff has published another interesting confirmation of Savory’s approach about a ranch in California.(26) Clearly, this solution is incompatible with the advice of the new national food guidelines to curtail the consumption of meat. If we are going to increase the number of cattle on the plane, whatever the rationale, they will be part of an economy that produces meat.

An even more ominous reason for increasing the world’s animal population is based on the work of a Russian father and son, Sergei and Nikita Zimov, who are creating the world’s first “Pleistocene Park” in the Arctic of Siberia.(27) They see their project as essential to saving humankind from global warming, since it is essential to keep the permafrost from melting and releasing the locked-up methane into our atmosphere. If that happens, there will be no way to save humankind.

The permafrost, nearly a mile deep in some places, extends across Eurasia and the other Arctic countries at the top of our planet. Nowadays there are trees in the Arctic, but during the Pleistocene period the land was covered in grass during the summer months, and snow in winter. Large herds of huge animals — notably the woolly mammoth — roamed and knocked over any sapling that might aspire to grow there. When human populations began living in the area, they killed the wild animals for food, and there may also have been other causes behind the extinction of those huge animals.

The Zimovs want to bring back herds of big animals and restore the land to grass. They have imported large herbivores and want millions more of them — musk oxen, reindeer, wild horses, bison — plus predators that can corral them into herds. They yearn for the restoration of mammoths(28) and hope that experts on genetics can bring that extinct species back into existence. (Harvard’s geneticist George Church is working to do exactly that, according to Ross Andersen, in his remarkable story about Pleistocene Park.(29)

Trees are dark and in the winter they absorb heat that is transferred into the soil. Grasslands are white with snow in the winter and stay colder – though the snow provides some insulation from the lowest temperature. In the past, ice caverns in the permafrost were six degrees below zero at all times of the year. Now they are only three degrees below zero, and in twenty years, if global warming continues, they will be above zero, so the microbes will come back to life and start producing methane, which will enter the atmosphere. This must not happen! There are now an estimate 750 gigatons of Carbon in the atmosphere, whereas the amount of carbon locked in the permafrost is about 1600 gigatons.

So how can that permafrost be kept frozen solid? If it were possible to push away all the blankets of snow, the soil would stay colder in the winter, but you cannot push enough snow to do that. Big animals could do so. Woolly mammoths and huge bison used to knock over the dark trees and keep the grasslands fertile. In the winter they kicked aside the snow to eat the frozen grass below. Like elephants (which are not ruminants but do eat astounding quantities of grass and emit lots of gas) the mammoths ate constantly and kicked aside enormous quantities of snow—enough to keep the soil frozen. According to the Zimovs, returning millions of huge animals to the wild will save the Arctic and thus possibly our civilization itself.

When the human population expanded, they did so by eating meat obtained by hunting down the huge animals that kept the Arctic a frozen grassland. Now the land is a forest and hardly any animals live there, except the ones that the Zimovs are importing.

Are they right to do so? At this moment, there is no certain answer. If the woolly mammoths come back, they will fart and belch, even while they knock down trees and keep the soil frozen. People will probably eat some of them too. Good luck to them. Good luck to us all.