Eating for the climate
Reframing the debate about ethical diets
by Matthew Evans
IF THERE'S ONE area in which the battle for the food dollar has met the battle for the climate head on, it's meat. In particular, meat from grazing animals. Those who believe we should all abstain from eating meat have found the ultimate enemy in ruminants, or livestock whose digestive system releases methane, a potent greenhouse gas. According to the author of one scientific paper, the single best thing you can do for the environment is stop eating meat. His quote has appeared in headlines around the world and been used to energise plant-­based food proponents.
The problem is, it isn't the best thing you can do.
In 2018, Science published a paper by Joseph Poore and Thomas Nemecek, 'Reducing food's environmental impacts through producers and consumers', that examines the impact of eating meat on agricultural land. When asked about the paper after its release, Poore was quoted as saying: 'A vegan diet is probably the single biggest way to reduce your impact on planet Earth, not just greenhouse gases, but global acidification, eutrophication, land use and water use.' He added, 'It is far bigger than cutting down on your flights or buying an electric car.'
But Poore and Nemecek's paper doesn't look at anything other than food. Not coal. Not fugitive emissions from fracking or natural gas extraction. Not petrol. Not the embedded energy in steel or concrete. It doesn't actually look at flights and electric cars. The meta-analysis relies on consolidated data with a median reference year of 2010, including a life-cycle carbon accounting system that allows for emissions from livestock, but not carbon cycling in pasture and the earth that grows it. It compares carbon emissions, but not capture, and a great range of new research has been done in this field.
The Poore and Nemecek paper was useful work – groundbreaking research – exploring the complexities of mitigation. And Poore's soundbite is right in some respects, of course – there are huge problems with livestock production globally. The fatal flaw is to ignore farming. And to ignore soil.
HEARING THAT THE best thing you can do for the climate is to avoid eating meat set the anti-­livestock movement in motion. Finally, their cause wasn't about just the exploitation of animals or selflessly giving up a nutrient-­dense and historic dietary staple. It was about saving the world.
Eating for the climate has become a buzz topic of the times. And as with all things, it's starting to become tribal. Depending on your bent, you can find studies to back up just about any diet you'd like to espouse. Vegan, vegetarian, paleo, low carb and high fat. There's no doubt that what we eat has an impact on the world, but just what that is, and how to fix it, tends to get caught up in slogans, simplicity and slanging matches.
I'd like to reframe the debate. As a farmer, cook, consumer advocate and campaigner for more ethical food, I'm interested in how we can feed the world. But first, we need to consider what the aim of the debate is, and how we can perceive diet within the bigger constructs of community, society and nationhood, as well as the environment.
First, we need to recognise that all animals, humans included, have to eat something that has already lived. Our goal as eaters is to ingest something between its death and its complete rot, be that something a carrot or a cow. In doing so, we will always have an impact on the world. The question isn't whether growing food (or foraging or hunting or fishing) damages the world. The question needs to be if we can repair the damage we do when we grow (or find) food. We need to ask, 'Is what we consume sustainable in the true sense of the word? Can we keep doing what we do now forever?'
This doesn't just come down to the food we eat, but to the ecosystems that nourish us and the population we want to sustain. The global population, now 7.8 billion, is forecast to hit about 9.6 billion by mid-­century. So let's take feeding 10 billion people as the medium-­term goal. We already produce enough food for about 11 billion. We waste about 40 per cent of it. If we stopped wasting food and kept our yields stable and our farming land in good repair, we'd already have hit the mark.
The difficulty is that we will continue to waste food. And we also don't seem to have the political will to get the food we do produce to all the people who need it – not just in quantity, but in nutrient density. (Up to three billion people suffer some kind of micronutrient deficiency, most notably in iron and vitamin A.) Tragically, barring some unforeseen political upheaval on a global scale, problems with both waste and distribution are unlikely to magically resolve. So we need to grow more, and grow it better.
Most food, about 70 per cent globally, is grown on small farms. These farms are often mixed, which means they grow crops and raise livestock. Most food is grown by women. And a lot of farming, small and large scale, has had a bad impact on the land that feeds us. We're losing topsoil, the bit that does all the world's growing, at a remarkable rate. Some estimates suggest that for every breakfast, lunch and dinner every one of us eats, nine kilograms of topsoil are lost. That's often because we haven't concentrated on feeding soil, which is the thing that feeds us. And soil won't thank us for the slight.
If we're losing topsoil, what are we doing wrong? Well, bare earth is obviously the worst thing you can do for soil, and that bare earth includes land that's overgrazed by livestock. Every time you plough the ground – turn it over to grow vegetables or grain or pulses – you actually leave it even more open to erosion than grazing. Raindrops hit the ground at up to thirty kilometres an hour. It's estimated that the energy of annual rainfall on a hectare of land is equivalent to the explosive force of fifty tonnes of TNT. And bare earth isn't just washed away – it's also easily blown away. If you plough, you lose topsoil one hundred times faster than it's made, according to the Intergovernmental Panel on Climate Change (IPCC). If you grow crops using a no-­till method, which means directly drilling seeds into the ground instead of ploughing, you can still lose topsoil ten to twenty times faster than it's made. Growing annual crops is, by definition, unsustainable the way we're currently doing it.
Another, perhaps worse, issue is the loss of carbon from soil. Soil holds more carbon than all the plants, animals and atmosphere combined. There's three times more carbon in soil than in atmosphere, and four-­and-­a-­half times more than in all living things. And that's after about half the carbon in soil has been lost from agricultural land since we started ploughing. Carbon, the same stuff that's in carbon dioxide, is the same carbon in carbohydrate (sugars), protein and fat. It's the same carbon that cycles from the ocean to the air, to plants, to animals, to soil and around again. But more carbon in the soil, unlike more in the air, is usually a good thing.
The origin of all energy on earth is the sun, and plants capture that energy and convert it into a form we can use, sugars, through photosynthesis. Plants make sugar out of thin air, using carbon from carbon dioxide and hydrogen and oxygen from water. They give some of that sugar to things in the ground. Carbon in soil can take the form of humus, the magical dark part of topsoil that holds moisture in the land. It can take the form of fungal threads, with their soil superglue, glomalin, that gives soil structure. There can be ten kilometres of these fungal hyphae in a single teaspoon of healthy soil. Carbon in soil is trapped in the bodies of microbes. It not only becomes food for that soil life as the microbes eat each other, but also creates a better home for the trillions of bacteria, protists, nematodes and algae that inhabit every square metre of the earth. Carbon in soil is good for soil health, good for soil fertility and good for soil resilience.
If you look at pretty much any research on how to restore at least some of the carbon that has been lost from arable land, the sort you grow crops on, then the first suggestion is to turn it into pasture. Pasture helps feed soil, as grasses convert carbon dioxide into sugar. And grasslands need grazing to trigger growth, which in turn can store more carbon. So land that has been used for crops (vegetables, grain, pulses) is improved if it's turned into pasture.
We can't digest the cellulose in grass. But ruminants can. They ferment the cellulose and can thus turn grass into energy for themselves. This energy means they can become meat and milk for us. They become a conduit for nutrition. They can also convert plants such as barley and wheat stalks into human-­grade, nutrient-­dense food.
One of the downsides of ruminants is that this very wonderful conversion of cellulose into food we can digest comes at a cost. Much of the energy stored in the cellulose is converted to methane, not meat. And methane, as we're all learning as we become more climate conscious, is a powerful greenhouse gas. By some estimates, it's about twenty-­eight times more warming than carbon dioxide. But a group from the Oxford Martin School in the UK now estimates – by looking less at theoretical results and more at its actual effect – that methane is about eight times more warming. Which just means it's less bad, in theory.
But methane only lasts in the environment for about a decade, as opposed to carbon dioxide's hundreds, if not thousands, of years. And the carbon in the methane from the grass a cow ate, which was breathed out, was previously in the air, not locked away in the form of fossil fuels. It's carbon that is in a constant state of flux in the soil/ocean/plant/animal/atmosphere cycle.
Methane's short life means that if we don't increase our herd, then we won't cause an atmospheric rise in methane, and there will be a negligible effect on warming. While ruminant numbers have stagnated in recent decades, atmospheric methane has kept climbing. So if cows and sheep and goats aren't to blame, where's the increase coming from?
The answer, as is often the case, is fossil fuels.
WHEN YOU DIG coal, when you extract gas and when you frack, you release methane. This is new carbon in the modern world, carbon that hasn't been in the atmosphere since long before the emergence of humans. Much of it has been stashed away underground for 300 million years, from a time when dragonflies were a metre in wingspan and mammals didn't exist. A time when atmospheric carbon dioxide was multiple times what it is today. This was the appropriately named 'carboniferous' period, when rampant plant and algae growth meant that dead plants piled up – they couldn't rot quickly enough and a whole heap got trapped underground, compressed and turned into energy-­dense fuel. Oil and coal and gas are made from fossilised plants, essentially. Hence the name fossil fuels.
Even the gas industry's own figures support the contribution of fossil fuels to atmospheric methane levels. In 2015 it was estimated that the gas industry released seventy-­six million tonnes of methane. By comparison, it's estimated that the world's 1.5 billion cattle produced between 105 and 180 million tonnes in the same period. One is new carbon going into the atmosphere, the other is (potentially) cyclical carbon. When I say potentially, that maths only works if you don't feed cows something grown using fossil fuels, like grain or artificially fertilised pasture.
You can point the finger of blame at ruminants all you like, but they've been around a long time, and fracking hasn't. If methane levels are rising, fossil-­fuel extraction is the cause. Even so, we could kill all the ruminants and keep fracking. This would cause a one-­off cooling event, but after ten years (the lifespan of all the methane that would be emitted from the ruminants alive today) we'd be back to square one. Except without ruminants to turn cellulose into human-­grade food.
Ruminants can do something else fracking can't, and something grains and vegetables really struggle to do: store carbon in soil. Soil carbon could well be a huge aid in slowing climate change. According to an initiative spearheaded by the former French Minister for Agriculture, Stéphane Le Foll, if all the world's human-­managed soils absorbed just 0.4 per cent more carbon, we could offset a year's worth of fossil-­fuel emissions, buying ourselves some time to transition away from their use. Far from hurting the climate, livestock has the potential to store carbon far more easily than crops. Growing rice, for instance, emits as much methane as the equivalent carbon dioxide from 1,200 coal-­fired power stations. And rice doesn't usually store carbon in the soil when it's grown.
We also need to take account of the only way we know how to get rid of atmospheric methane. Most is broken down by sunlight, which we have no control over. But about 20 per cent is broken down by methanotrophs, microbes that live in soil and consume methane. They do better under soil where methane is emitted (grazing land), and they do very badly in ploughed land. The best way to increase methanotrophs is to have healthy soil. We could cover all our land with forests, which might help, but we'd not grow a lot of food in the process.
The problem with many simplistic arguments around climate solutions, such as adopting a one-­size-­fits-­all diet, is that they ignore topsoil. They ignore communities. And they ignore the complexity of the food system.
For instance, because many of us don't want to eat animal fat anymore, much of the 540,000 tonnes of beef fat (tallow) Australia produces annually is used for industrial purposes instead. But at the same time, about 95 per cent of the oil from the soybeans grown around the world (including those in the Amazon) is fed to humans. The soy pulp, in a strange dichotomy, is considered food waste and fed to livestock.
Then there's our dependence on palm oil. Clearing for palm plantations is devastating ecosystems in high-­rainfall areas throughout South-­East Asia. In 2015, Indonesia cleared more than six million acres of rainforest and upended its carbon-­rich peat land mostly to plant palm. Emissions from clearing Indonesian rainforest have at times exceeded all the emissions from the US economy. So replacing beef fat in biscuits, frying oil or pastry with 'vegetable' oil (almost invariably soy or palm) is an unseen ecological disaster.
DIETS NEED TO reflect place. Farms are ecosystems, reliant on soil. All terrestrial ecosystems need animals, either wild or domesticated, to function, from the soil up. Where you live, it may make environmental sense to avoid all meat, because that role of cycling nutrients in the ecosystem can be filled by birds or lizards or insects. In other places, that won't be the case. But the concept of veganism as somehow above reproach has no basis in science.
Diet options and their effect on the climate are more nuanced than simply avoiding a whole food group. Of course processed, transported food has its own costs. It's been noted by some researchers that the vegan diet might not have the lowest environmental footprint. That's because, as a 2019 review of vegan, vegetarian and omnivorous diets by the University of Copenhagen puts it, 'vegans tend to replace animal-­based products in their diet by industrially, highly processed plant-­based meats and dairy substitutes.'
Most of the world's food, as we saw, is grown on small farms. Many of those use animals to upcycle waste – the things we humans don't, can't or won't eat. Originally, pigs and chickens were recyclers, turning garden waste or leftover milk into meat or eggs. Nowadays we grow grain specifically for them to eat. But to say going vegan is best for everybody, for every farming system, for every community, is an oversimplification.
Research out of the US shows that a vegan diet, or a diet very low in meat products, could indeed reduce greenhouse gas emissions. But modelling also shows that a completely animal-­free diet could only reduce America's total emissions by about 2.6 per cent, while at the same time leading to more micronutrient deficiencies (calcium, fatty acids, vitamins A and B12). Already in the US, which is usually a decade or two in front of Australia, over half the calories consumed come from hyper-­processed foods. Junk food. And much of that is plant based, from the three grains that provide half the world's calories: wheat, rice and corn. The growing of these grains is generally extractive, and releases soil carbon. Research suggests a diet that excludes animal products will focus even more on these grains, meaning an oversupply of calories compared with micronutrients. That's bad news in the diet stakes, when rates of type 2 diabetes and other non-­communicable diseases that can be caused by what we eat are skyrocketing.
I think it's up to the individual to frame their diet the way they think is best. For some that means abstaining from all animal products. For some that means being an omnivore. But making those decisions should be based on sound science, not on soundbites. Poore and Nemecek's paper hit the headlines and is frequently used as evidence to support removing all animals from farming systems. Those who work in the field of growing food, especially in vulnerable, poorer nations, know it's more complicated than a single review. They know that animals are part of the solution, but only if they're managed right.
There are lots of ways to eat for the climate. Buying local may well be one. Every time something has been trucked, it adds to the environmental cost. Air-­freighted food is worse still, having about one hundred times more greenhouse gas emissions than things sent by boat or land. Eating less meat, for many of us in affluent nations, may be another way to reduce our impact. So could eating meat, as the IPCC recommends, that comes from sustainable, low greenhouse gas emitting farms. What that looks like might vary from place to place. For instance, research shows that organic meat is less damaging than many greenhouse-­grown vegetables.
Ruminants that eat grass, grown on land that can't be used for crops, that doesn't have fossil fuel-­derived fertiliser put on it, is probably about as low impact as possible. Pigs and chickens raised on a mixed diet, including waste from the human food chain, would be considered low emission. And it should be noted that many of the world's nutrient deficiencies, such as anaemia and vitamin A deficiency, are tied to low protein consumption and are more readily fixed with the intake of meat.
Some of us eat so much meat that our impact on the globe is actually unsustainable. Australia, for instance, eats a diet with a high environmental cost, both in terms of unsustainable meat and processed foods. In fact, if the whole world chose to eat like us, it would take 1.6 worlds to feed it. And we don't have 1.6 worlds to farm.
We do have both animal-­ and plant-­based farming systems that are bad for the Earth. But neither growing grains nor growing livestock is good or evil by definition. Eating industrially produced meat probably is bad for the climate, but eating no meat isn't a guarantee of sainthood, to stay with the language of belief systems. All farming, all humans, all plants and animals rely on the thin veneer of topsoil that does the entirety of the world's growing. Caring for that, while marrying community concerns, environmental imperatives and dietary necessity, should be the goal, not focusing on arbitrary lifestyle choices.
If you want to eat for the climate, buy from a farmer who puts the land first. Who cares for the soil. Who feeds the earth that feeds us. Buy from those who are trying to regenerate landscapes, to heal some of the harm caused by farming before we knew better. There are wonderful growers out there producing nutrient-­dense food without ruining the world.
Fresh, seasonal and local food is better than processed, whether or not you eat something that came from an animal. It's as boring as the advice your mother gave you when she suggested you eat your greens, but just as valid. Eat a balanced diet. Buy produce at its peak. It isn't as catchy as 'give up meat to save the world', but it does have more evidence to back it up.
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