Food and climate change

Professor Sarah Bridle was originally an astrophysicist, but when she started to think about climate change, her curiosity led her to pivot her research in a new direction – food and climate change.  She shared her knowledge on the podcast; here are some highlights.

How does food relate to climate change?

pizza, different foods have varying carbon emissions

Food and climate change interlink in two ways:

  1. Food causes a third of climate change; it is bigger than the transport or heating sectors.  The production of greenhouse-gas emissions occurs across the food system, from growing to packaging to transporting and cooking.
  2. Food production is impacted by climate change, from the increasing global temperatures and the resulting extreme weather events, such as droughts, heat waves, hurricanes and floods.

Which foods have the most impact on climate change?

Not all foods are equal when it comes to climate change.  In general, plants produce less greenhouse-gas emissions.  So, a vegetarian or vegan diet tends to fare better than an omnivore diet.  Amongst the commonly consumed foods, beef and lamb cause the most climate impact.  For illustration, 1g of prime beef contributes 46g of emissions, whereas 1g of beans leads to 0.63g of emissions. Emissions from cows and sheep (ruminants) are mainly through burping methane.  Their poo also emits methane and nitrous oxide.

Sarah’s fabulous book provides loads more accessible information on the climate impact of commonly eaten foods in a western diet.

Land use

Food can seem widely available, but resources across the world are limited.  Producing food for an increasing global population needs reflection – are we using our land wisely?  According to the FAO, the global agricultural land area approximates 5 billion hectares, 38% of the global land surface.  About 80% of agricultural land is devoted to growing animal products (beef, lamb etc.).  Animal products require about 16 times more land per calorie than plant products, so growing plants is a more resource-efficient way to feed people.  Switching to a more plant-based diet could lessen deforestation and free up more land for other uses, which could be more amenable to capturing carbon and promoting biodiversity. 

Food miles

You might think that the further away a food is produced, the higher the impact; this isn’t necessarily the case.  Bananas, for example, are transported across continents, but as this is by boat, the transport impact is actually less than those associated with growing the bananas.  For those foodstuffs that are sufficiently hardy to travel in this way, such as mangoes and pineapples, food miles are less of an issue.  However, travelling by air is a different story altogether, as it causes one hundred times more climate impact when compared to a boat.  Transport by air for perishable items, such as berries and sugar snap peas, is routine.  The emissions of 100g of green beans by air are similar to chicken, a low-impact animal product.

It is not always easy to determine the method of transport, but a rule of thumb is their perishability.  If foods only last a few days in the fridge, they will probably travel by air if produced in another country.

And what about those foods that are grown locally but in heated greenhouses, such as cherry tomatoes.  These may have fewer food miles, but their growing conditions up their impact.

It is perhaps important to note though eating local can provide benefits of fresh food, generate community and a vibrant economy for local people.

Seasonal food and freezing

frozen berries, a better option for climate change in winter

Eating local fruits and vegetables means eating in-season.  Although supermarket shopping would lead us to believe food can be grown all year round, this is not necessarily the case.  Bananas are grown all year in Latin American countries, whereas apples grown in the UK are only available from late summer through to late autumn.

If you are keen to have out of season produce, buying frozen is a good alternative to getting them flown in.  The energy used for freezing is not particularly substantial.  The additional benefit of freezing is it can cut down on food waste.  When shoppers seek out fresh food with later dates, there is inevitable waste; this is not the case with frozen.

Food waste

One-third of food is lost or wasted globally (yes, an eye-watering third!), contributing to 10% of climate change.  This waste occurs across the food system.  A whopping 70% (post-farm gate waste) arises in the home (UK figures).


Environmental issues are complex, and packaging demonstrates this nicely.  Plastic pollution is a complete nightmare; it has infiltrated every part of our existence.  So ideally, we want to purchase stuff without plastic.  As mentioned, food waste is not an insignificant contributor to climate change.  Plastic packaging protects food from spoiling, as can be seen with the cucumber – it will last 2-3 days without plastic packaging but possibly 2 weeks with packaging.  This fact perhaps supports the argument for buying locally grown food – where the perishability risk is less problematic as there are fewer food miles.

Packaging, in terms of its greenhouse-gas emissions, is way less important than the contents, whether it’s plastic or metal, e.g. plastic contributes 5% emissions to a milk bottle.


So, I guess the upshot is, eat less meat and more plants, be mindful of season and steer clear of food flown in, avoid wasting food, frozen food can be a good option, and although packaging is problematic, it isn’t of climate concern.