Thoughts on diet and global warming

Everyday in the media I hear about global warming and how it’s connected to the way we live our lives. Whilst it’s easy for me to believe that there is a link between what we consume (food, technology, leisure, etc) and the decreasing health of the planet, I have realised that I’m not very educated on the subject.

I think one of the reasons I find it tricky to understand what influences what when it comes to global warming and human behaviour is simply that…it’s not a simple problem to study. Why? Well, human behaviour is studied at many different levels already, e.g. neuroscience, psychology, sociology etc. Also, the health of the planet is studied in many different ways e.g. by measuring greenhouse gas emissions, melting ice, temperature…

With so many variables it seems almost impossible to try and understand this huge question of how human behaviour influences the state of the planet. But people are trying. By combining multiple fields of research such as psychology, anthropology, and physics (to name a few) and finding ways of modelling how different factors interact with each other, researchers are able to make predictions on where the planet is heading.

One of the most discussed ways of decreasing our impact on the planet is through being mindful about what we eat. I am in the privileged position of being able to decide what I eat, and so, my diet is linked to my behaviour and choices. I’m interested in trying to understand how I can decrease my impact on the planet through food choices. This prompted me to spend some time researching into this subject.

What are the facts?

To get started, I refreshed myself on some statistics on the current state of the planet compared to past years. NASA offers some great information on global warming which I highly recommend checking out if you’re interested.

Now for a quick overview.

Greenhouse gasses, such as CO2, trap heat close to the surface of the earth. We need these gasses in our atmosphere for the earth to stay at a warm enough temperature for life to be happy.

Reconstruction of CO2 levels from ice cores up until today, NOAA

But if the levels of these gasses increase, then more heat gets trapped and the Earth’s temperature rises.

When the planet warms, more ice melts and the sea levels rise.

Arctic ice levels over time, NASA
Change in sea levels over time, NASA

Next, I wanted to find out more specifically about how our diet is linked to global warming, and so it was time to go through some research papers…

How is our diet linked to global warming?

Many factors influence what we chose to eat – society and social media, income, moral reasoning, and so on. Researchers are considering how these factors will influence global food choices and how this will influence global warming. One way of predicting how our diet choice will affect the planet is by combining psychological theories on human behaviour with pre-existing models that take into account multiple factors that are implicated in the social, economic, and environmental state of the Earth. These factors are all combined into a model that predicts different outcomes for the planet depending on the scenarios you give it.

For example, in this study, they feed a bunch of different scenarios relating to the how much people reduce their meat intake into a model to see how this would affect greenhouse gas emissions.

Predicted emissions for different levels of meat consumption

Scenario 0 (Sc0) reflects a situation where the vegetarian population increases, but meat eaters still eat the same levels of meat, and subsequent scenarios correspond to progressively less meat/animal product consumption overall (meat eaters consuming meat less often, vegetarians becoming vegan). The fewer meat and animal products consumed, the fewer greenhouse gasses are emitted.

This paper lead me to this website, run by the United Nations, which has loads of data on how different countries across the world produce food, utilise their land, and how this is linked to their CO2 emissions.

For example, here’s a chart showing the CO2 emissions produced by different agricultural sectors in the UK.

Chart showing fraction of greenhouse emissions for different agricultural sectors in the UK

The big purple chunk, ‘Enteric Fermentation’, which is (as defined by wikipedia) ‘a digestive process by which carbohydrates are broken down by microorganisms into simple molecules for absorption into the bloodstream of an animal’, basically relates to the gasses produced by (mostly) sheep and cattle that are farmed for their meat and dairy products. Considering that some of the manure-dependent emissions shown on this plot are also a byproduct of animal farming, this data collected by the FAO (an agency of the United Nations) shows that in the UK, more than half of the greenhouse emissions produced by the agricultural industry are linked to the farming of animals.

Another study, published in 2018 also predicted that decreasing the amount of meat consumed globally would decrease greenhouse gas emissions, with a potential 56% decrease in emissions if enough people adopted a more plant-based diet.

Does decreasing your meat intake really have a positive effect on the planet?

Yes! There are many many other factors that I haven’t mentioned in this post, but from the time I have spent reading up on the research investigating how diet and the health of the planet are linked, it’s clear that eating less meat and shifting to a more plant based diet is a good idea. In particular, this research highlights the importance of reducing meat intake even if you are not vegetarian, as this is predicted to make a huge difference when it comes to decreasing greenhouse emissions.

I’m hoping to follow up this post with some of my favourite vegetarian recipes, which show that reducing your meat intake doesn’t mean reducing the tastiness of your meals!

I realise that the articles I have linked are not open access – so here are some other references that are: