Climate impact of meat, vegetarian and vegan diets

The greenhouse gas emissions of food, and particularly meat products, is a big deal. Food accounts for roughly a quarter of all human greenhouse gas emissions. Of this, livestock constitutes about 56%, while only providing 37% of our protein and 18% of our calories. 

But not all livestock is equal – it is ruminants (animals that chew the cud – mostly cows and sheep) that weigh the heaviest on the climate – they are responsible for about 80% of the livestock figures, although they only produce about 40% of all animal protein.

Exactly how bad meat is for the climate depends on what it is, how it is produced, and also how you divide up responsibility for things like deforestation.

Meat is inherently inefficient

As a rule of thumb, the production of meat from plants is inherently inefficient. Each time you go up a level in the food chain you lose energy. 

A comparison of the emissions and land use associated with various animal products and substitutes are shown below. The reason that land matters is talked about below.

The figures in the infographic are presented in the table below.

The overall picture that emerges, unsurprisingly, is that vegetarian options are generally better, and red meat is the super villain.

Land use and inefficient use of resources

The two biggest reasons animal products are bad for the environment are:

• Land use 
• Methane 

Livestock uses huge amounts of land, both for grazing and for growing feed. One estimate is that if we all went vegan, we could reduce the land used by agriculture by 75%. 

There are worries specifically about how much deforestation is being driven by soya cultivation in South America, most of which is used to feed animals. 

There is a moratorium on growing soya on recently deforested land in the Amazon, which has had a significant effect, and while deforestation rates have risen over the last decade, they are still vastly lower than the horrendous rates that were being seen in the early years of the century.

But some people argue that soya is still playing a role, it is just being disguised (see our guide to meat substitutes). 

The methane issue affects ruminants, which burp large amounts of methane during the torturous process of digesting grass. Methane is a very powerful greenhouse gas. 

The overall emissions of diets

Below is one academic estimate of the average carbon footprint of UK diets, calculated from food diaries.

According to this, going from a medium meat to a vegan diet saves about a tonne of CO2eq a year.

There are some comparisons with other carbon footprint calculations below for context:

[1] Calculated from total UK footprint of 784 million tonnes CO2e From “Defra – UK’s carbon footprint”, and population of 65.65 million; [2] Calculated from Ofgem's Typical Domestic Consumption Values; [3] Calculated from the Defra's greenhouse gas reporting: conversion factors 2019

There is, however, a very important caveat to these figures. And that is that, like nearly all calculations of the impact of animal products, they do not include land ‘opportunity costs’ – what else you could theoretically do with the land in a best-case scenario for the climate.

Land can absorb carbon if you let it turn back into forest or use it to grow biomass which you can then preserve in some form (such as charcoal). In other words, it can be ‘carbon negative’.

If you do include these land ‘opportunity costs’, the impact of animal products can double (or more) because of the amount of land that livestock uses.

How does Ethical Consumer rate companies on these issues?

Our ratings system addresses these issues in the following ways:

• Vegan companies are awarded a positive Company Ethos mark.
• Marks can be lost under the Animal Rights and Factory Farming categories for using meat, eggs, dairy or other animal products.
• For our Carbon Management rating, we require companies to talk about meaningful ways in which they are reducing their carbon emissions, which can include reducing the use of animal ingredients.

To find more information about how companies are rated on other connected issues, such as Animal Rights, Factory Farming and Animal Testing, you can visit our ratings page.

Myth Busting: Has meat been given an unduly bad reputation?

Climate arguments against meat consumption have been disputed by some who claim that animal products have been given an unduly bad rap. Several arguments have been made by people in the farming industry.

Argument one: soil carbon and the saviour cow

One of the principle arguments concerns soil carbon. Soil carbon is below-ground ex-plant matter from things like roots and litter from above. It’s a big deal – there is more carbon stored in this form than in the plants above the ground. 

The quantity varies depending on things like the vegetation on the land and on temperature (heat increases the rate of decomposition), and you can build it up by restoring degraded land, but eventually, like the above-ground carbon in a forest, it reaches a plateau level.

The claim is that grazing livestock can play a huge part in building it up. 

The most extreme and high-profile proponent of this claim is a man called Allan Savory. Savory was born in Zimbabwe to British colonial parents, and he doesn’t have a glowing ecological past: as a young man he argued that elephants were causing desertification, and approximately 40,000 were slaughtered on his advice, to no benefit. However, now wracked with remorse about this, he is pushing a different idea for how to solve the problem: cows.

In 2013, Savory gave a TED talk claiming that grazing cattle can reverse desertification, sequestering so much soil carbon that they could reverse climate change and bring carbon dioxide levels back to pre-industrial levels. The talk went viral – it has now been viewed nearly seven million times.

The cow turns out to not be the saviour

Plenty of scientific analyses have been done of the issues in Savory’s talk. And the summary is: there is a grain of truth in it, but nothing remotely on the scale being claimed.

It is true that grasslands, which have huge underground root systems, can store a lot of carbon under the ground – in some areas even more than would be stored on the land, in total, if it were a forest. Grassland does not necessarily need to be grazed (in some places it is just the natural ‘climax vegetation’), but it does seem that in some situations cows can help to regenerate degraded grassland – nibbling can encourage root growth for example. However, it can also go the other way – cows can trash the land, and often do.

One huge research project looked into the issue and concluded:

“In some specific contexts, where the climate, soil, land use history, and grazing management are just right, additional carbon [through grazing] can be removed from the atmosphere and sequestered in soils. But realistic rates for this are far below those claimed outside of the scientific literature. And only rarely can sequestration outweigh the greenhouse gas emissions from the grazing animals.”

They further concluded that at a global level, the absolute largest possible sequestration potential from grazing management “offsets only 20-60% of annual average emissions from the grazing ruminant sector and makes a negligible dent on overall livestock emissions.”

Argument two: animals, ships and packaging

A second argument often used to claim that eating food from animals isn’t really bad for the climate is that it is less important than other things, particularly how far the food has travelled.

However, again, the science doesn’t really support this. Pretty much all of the research done in the 40 years since the ‘food miles’ concept was first proposed has shown that transport is generally a small part of a food’s climate impact, compared with what the food actually is. On average, it only constitutes around 11%.

The reason is that most of it travels in huge, slow freight ocean liners, whose energy use is very low – up to 250 times less per tonne-km than trucks. In fact, even when food has come from the other side of the world, the last bit of transport, within the UK, can contribute more of the transport emissions.

The same is true of packaging – it’s not a huge contributor on the climate front. Milk cartons contribute about 5% of the carbon footprint of milk, for example, and plastic packaging contributes about 4% of the carbon footprint of pork.

That doesn’t mean that packaging doesn’t matter (for one thing, there are other environmental issues as well as climate change). But it does mean the overwhelmingly important factor in the carbon footprint of your diet is what you actually eat.

Argument three: ‘default meat’ or ‘ecological left overs’

A third argument sometimes used is that it is possible to get some animal products without using dedicated resources. This is sometimes called ‘default meat’ or ‘ecological left overs'.

For example, you can feed pigs on food waste, although it is currently illegal to do so in the UK. There is also a ‘sustainable yield’ that you can take of wild game that doesn’t use extra resources, because you’re just acting like a normal predator in the system, and if you weren’t taking it, the animals would be expending more energy competing for resources.

The problem is that the amounts we are talking about here are small.

UK post-farm food waste would be enough to make about 6 kg of pork per person per year. (Calculated from WRAP’s figure of 150 kg per person for 2018 UK post farm food waste, and a 24:1 conversion ratio of swill into pork, reported by Simon Fairlie in Meat: A benign extravagance.) In the UK we consume about 24 kg of pork per person per year.