Can eating less meat really tackle climate change?

With the food system accounting for up to a third of global greenhouse gas emissions, anything that reduces its impact will make a big difference to the climate.

It is a system riddled with inefficiencies and waste. Humans don’t simply eat food straight out of the ground, of course. It’s harvested, stored, processed – or fed to animals who are in turn slaughtered and processed – and finally packaged and delivered. Each of these stages uses energy, which means emissions.

In very rough terms, the world grows about 6,000 calories per person a day in edible crop harvest. That is about three times the 2,000 calories a day that end up getting to be eaten by humans. This would be enough to feed everyone if we shared it round perfectly, which we don’t, so some people go hungry while others eat more than is good for them.

So what happens to the massive 4,000 calories per day gap between field and fork and what has this got to do with going vegetarian or even vegan?

Here, again in rough numbers, is how the missing calories can be accounted for:

About 900 are agricultural waste, much of which is simply left in the ground. Supply exceeds demand or the crop is deemed not able meet customer standards.

About 500 go to biofuels. This is not necessarily a bad thing, but it is something we need to keep a very close eye on if we are ever to achieve a low-carbon world. If free market forces were allowed to do their thing we could see a huge shift from food crops to more profitable fuels, at the expense of nutrition in poorer countries.

Around 600 calories are then lost in post-harvest waste. This is mainly an issue in developing countries and is inherently solvable, at face value, through the provision of such things as sealed containers to keep food dry.

Where do the calories go? A simple map of the food system. Adapted from ‘The Burning Question’p163, Mike Berners-Lee & Duncan Clark (2013), Author provided

So far in the story from field to plate there is still a plentiful 4,000 calories per day left for feeding people. Around 1,700 of these are fed to animals. The animal diet is further supplemented with a substantial amount of grass, some but not all of which is grown on land that could alternatively be used to grow yet more human food.

Animals – some more than others – add an intrinsic inefficiency into the food chain, using up energy for such things as walking around and keeping warm (per kilo of meat, poultry do a lot less of less of this through their lives than cows, making chicken a significantly more efficient energy source than beef). A mere 500 calories per person per day come back out of the animal food system as meat and dairy foods. So the inefficiency of our meat and dairy diet leads to a loss of 1,200 calories per person per day, excluding any grassland that could be used for edible plant crops. And meat consumption is rising fast in developing countries.

Better than beef – at least for the environment. Danish Siddiqui / Reuters

To finish off the story, around 800 calories are lost to processing, distribution and household waste, of which the biggest element is household waste in developed countries – the homes of most of the people reading this are included here. Inadequate sharing of the remaining 2,000 that humans actually eat means that some people end up obese while others are hungry.

Seen in this way, the world food system looks to be brimming with opportunities for improvement. If we can get organised – which of course is not at all easy – we ought to be able to use new technologies and deploy best practices to increase yields, as well as cutting out most of the 2,300 calories that are wasted. Even with a rising population – and even with climate change adversely affecting land fertility in some areas – we ought to be able to feed everyone while improving biodiversity and increasing the biofuel output somewhat.

A carbon footprint hierarchy of meats at UK check-outs: deforestation costs Brazilian beef, all cows and sheep ruminate, whereas chickens make relatively efficient food converters. ‘The Burning Question’, Mike Berners-Lee & Duncan Clark (2013), Author provided

Our animal intake puts a huge and growing pressure on the food and land system. If the world went vegan overnight we might be able to feed several billion more people and double biofuel production, even without tackling waste or improving yields.

We need to be asking how plants can become more aspirational foods than cows. But if we are still going to eat meat, stick to chicken which has only about one-tenth of the carbon footprint per kilo of Brazilian beef. This is partly because a chicken is a more energy-efficient meat producer, partly because chickens don’t ruminate, or chew the cud (which emits methane, roughly doubling the footprint of a cow) and partly because chicken farms are less strongly associated with deforestation.

Our studies of the footprint of UK dietary choice have shown that going vegetarian might cut the greenhouse gas footprint by 25%. However the same reduction can also be made through modest actions split across what for most UK people are the three most important things you can do to cut your food carbon: reduce meat, switch type of meat and, of course, cut waste.

US-China deal shows all that effort to tackle climate change might actually be worth it

By Mike Berners-Lee, Lancaster University

Smokes billow out of chimneys of a sweetcorn processor in northeast China

Some great news at last, as China and the US announce a secretly negotiated deal to reduce their carbon emissions.

After years of seeming to get nowhere at all it looks like we have the beginnings of meaningful commitments. If the rest of the world can fall in line with the combined targets of China, the US and EU, and if between us all we can enforce them, we would actually have progress. Not success, but for the first time we would have better-than-nothing global progress on climate change.

But just before we all relax, lets get things into perspective. Global emissions have been on a mathematically predictable exponential trajectory for at least 160 years. Cumulative CO2 emissions (broadly speaking that’s what determines the temperature change) continue to double every 39 years. Nothing that anyone has done to date has succeeded in making even the faintest detectable change in that.

To be blunt, our species has so far not demonstrated any ability whatsoever to influence global emissions growth through deliberate action on climate change. Savings in one place have simply popped up elsewhere. And if we stay on our age-old trajectory we will shoot through the likely threshold of two degrees in the mid-2040s.

The maths we’re up against.
Clark & Berners-Lee, Author provided

By that I mean that by about 2045 we will pass the point at which we will probably experience more than a 2°C rise even if no-one anywhere in the world ever again set fire to any coal, oil or gas. And, roughly speaking, 39 years after that we will crash through the 4°C threshold which humans would be very likely to find extremely unpleasant.

Of course we don’t really know all that much about what level of temperature change will cause us what level of suffering and death. We don’t understand the climate discontinuities that we might trigger, and we don’t know how good we will be at adapting to change and we don’t know how good we will be at preserving world order if things get tough.

The mainstream consensus is that 2°C entails significant risk of something nasty happening while 4°C is probably very nasty indeed. No one knows for sure.

What we need is a global constraint on greenhouse gases. And it needs to be rapid enough to keep temperatures as close to 2°C rise as possible. This much, thankfully, seems to be uncontested these days among people who talk any sense on climate change.

Coming off the curve

So how far do the latest US and China pledges take us? If (and it’s still a big “if”) the world falls quickly in line with the US (27% cuts by 2025), China (peak by 2030 – by which time their emissions could be enormous) and EU (40% cut by 2030) announcements we will come off the exponential curve but still fly through the 2℃ threshold and well beyond. Coming off the curve would be a huge achievement but not nearly enough.

So when I say we might actually stand a chance of getting somewhere, I don’t mean that things are looking rosy. But I do mean this gives me real hope, as big players are talking the right language at last.

Emissions cuts can’t come soon enough for some Chinese.

All we need now is more of the same – and to make sure the words turn into enforced action. That will be enormously challenging but it is radically more hopeful position than the situation we have been in in which sticky plasters have been proposed, no amount of which could help.

What we need from here

  1. We need the rest of the world to come into the fold with similar commitments, so we get a leak-proof deal on leaving fuel in the ground. Any countries that don’t participate will probably end up growing their emissions to undo efforts made elsewhere, because that is how the system dynamics work to negate piecemeal actions.
  2. Binding targets need tightening up for everyone, beyond what is currently on the table, to take us a lot closer to topping out at 2°C.
  3. The deal needs enforcing. This is going to be tough, remember that the exponential global emissions curve has proved incredibly resilient to date.
  4. All the greenhouse gases need to be properly included in the plan.
  5. We need to head off a global dash for biofuels which will undoubtedly be at the expense of feeding the world’s poorest if left to market forces. Some smart and robust agreements are going to be needed on land use for biofuels.

While all this is being put in place we can start investing in the technologies we will urgently need – redirecting the money we have been channelling into fossil fuel research and development.

To sum up, the announcement is very encouraging. There may still be a long way to go yet and we all need to push hard for next year’s Paris talks to put it all in place – but it is starting to look as if it might actually be worth the effort.

The Conversation

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