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Cambridge University Science Magazine
Climate change probably isn’t news to you. Perhaps you have also heard that plant-based food is better for the environment than animal products in some way. But does that make sense? Surely local meat is better for the environment than some vegan meat made of soya beans grown halfway around the world. Here, we’re going to look at these concerns and see why plant-based does indeed just make sense. Understanding the impact of animal products on the environment is key to tackling the climate crisis. This is the motivation behind the Plant-Based Universities campaign; it urges universities to be leaders in making this transition. We will learn more about this campaign later.

Firstly, we should address what exactly we mean by ‘plant-based’. Plant-based simply means derived completely from plants, i.e., contains no ingredients sourced from animals. When it comes to food, ‘plant-based’ is more or less synonymous with the older term ‘vegan’. Neither terms have a definitive definition but the main difference, if there is one, is that plant-based refers to only food, whereas vegan describes someone’s beliefs about how animals should be treated.

So why are plant-based diets better for the environment? Human activities often have a negative environmental impact. The most common is greenhouse gas emissions — the main drivers of climate change. However, there are other ways that human activities negatively impact the environment, such as land use, water use, and chemical pollution derived from the use of pesticides and fertilisers. Plant-based foods tend to perform better in all of these categories.

All life on Earth gets energy from the sun. Plants do this directly by photosynthesis; animals consume plants or other animals to obtain energy. When an organism consumes energy, most of it is used by the organism itself for it to live, meaning that only a small amount can be obtained by consuming the organism. It is therefore most efficient to consume plants, rather than consuming animals that have consumed plants. This means that growing plants to feed to animals to then eat is a grossly inefficient way of feeding the world that results in higher use of land, water, fertilisers, and pesticides and leads to higher emissions.

So now that we understand this conceptually, what does this mean in the real world? Currently, 50% of all habitable land is used for agriculture. Of course we need this to live off, but could we use it more efficiently? Of that agricultural land, 77% is used for animal agriculture, but this only provides 18% of the calories and 37% of protein supplied globally. This makes plant-based agriculture 15 times more efficient in terms of calories and 6 times more efficient in terms of protein than animal agriculture.

Land use for agriculture is a primary driver of habitat loss around the world, causing mass biodiversity loss and the Earth's sixth mass extinction, meaning we need to reduce the land we use, while also feeding the world. The most effective way to do this is by switching to a plant-based food system. Beef, for example, accounts for 41% of deforestation worldwide. Additionally, 24,000 endangered species are threatened by agriculture, that is 85% of all endangered species.

By switching to an entirely plant-based food system, the vast majority of the land currently used for animal agriculture would be freed up and could be rewilded into its natural state, reducing the threat to endangered species. Doing this would also allow this land to act as natural carbon sinks, offsetting the equivalent of 16 years’ worth of fossil fuel emissions.

Animal agriculture is also a much larger source of emissions than plant-based agriculture. Cows and sheep are ruminants, meaning they produce lots of methane during digestion. Methane is a much more potent greenhouse gas than CO2, its warming potential is 84 times greater over 20 years. This is why beef, lamb, and mutton and cheese have the highest emissions of any food. The larger amounts of land required for any animal products also means that more fertiliser is required, resulting in more emissions in its production.

A common misconception about plant-based diets is that they must have worse emissions due to the greater distances that foods like chickpeas and soybeans have to travel. This is understandable as food miles are a much more tangible form of emissions than many of the other types of emissions associated with our diets. However, a study in the US found that eating plant-based just one day a week can reduce your dietary emissions more than by sourcing all your food locally. This is because for most food, especially animal products, farming practices make up a much larger proportion of emissions than transport. It’s often the case that even animals raised locally in the UK are fed crops grown outside the UK, such as soya beans from Brazil. In fact, 77% of all soy produced globally is fed to livestock and only 20% is consumed directly by humans, mostly as oil.

There are many things that we need to do in order to prevent catastrophic climate change. We need to completely phase out fossil fuels, reduce our dependence on aviation and develop some form of carbon capture technology. Switching to a plant-based food system is also an essential step in ensuring the future of our planet. It also has major advantages over other methods: it doesn’t require the invention or scaling up of any new technologies nor does it require any large-scale changes in infrastructure. Arguably, its greatest advantage is that anyone can play a role in this change every time they decide what food to buy.

Another way is through showing support for campaigns such as Plant-Based Universities, which was started at UCL in 2021. This is an international campaign to make universities switch to 100% plant-based catering (PBU). Its aim is to hold universities to account in the role they should play in educating on and tackling the climate crisis. It is universities that produce the research that show how important a step this is in tackling climate change. This year the campaign was launched in Cambridge and has already received a large amount of support. The next steps are to hold a vote at the Students’ Union on whether to make it an official campaign of the SU. The more support the campaign receives from students the more likely this is to pass. Then the aim is to make all catering run by the University 100% plant-based. So make sure you vote!

William Smith is a second year PhD student at Downing College, studying climate science. He has an MSci in Natural Sciences and an MSc at the University of Exeter in Mathematical Modelling in Climate Science. Artwork by Barbara Neto-Bradley.