How will extreme heatwaves affect our food?

Those heatwaves were caused by a phenomenon called ‘heat domes’ – an area of high pressure that gets stuck in the same place for several weeks, trapping hot air underneath and pushing temperatures higher and higher.

Heat domes do occur in normal weather systems, but Bill McGuire, professor emeritus of geophysical and climate hazards at University College London and author of Hothouse Earth: An Inhabitants Guide (£9.99, Icon Books), says they will become more intense and more common.

He says, ‘Heat domes are held in place by the Jet Stream, the system of high-altitude winds that travel from West to East around the globe. Normally, the Jet Stream travels quite directly but global heating may be causing it to meander more.’ This new extra-twisty route means heat domes are more likely to get ‘locked in’, leading to more extreme heatwaves, more often.

‘Intense heatwaves will become more common; it’s unlikely that a year will go by now without heatwave conditions developing in many parts of the world,’ says Prof Maguire. ‘Simply put, heatwaves will get hotter because the Earth is getting hotter.’

How will that affect our food supply?

Last year’s heatwaves had an immediate impact on some foods. Olive crops in Spain, the world’s largest producer of olive oil, were decimated by drought for the second year in a row – you may have noticed olive oil prices are now much higher. In Italy, tomato plants were hit by flooding earlier in 2023, drought during June and July, then extreme heat scorching and ruining the fruit, leading to smaller harvests.

Cereal crops may have been the hardest hit: Copa & Cogeca, the European farming organisation, estimated that 2023 cereal harvests in southern Europe were down 60 per cent compared with 2022. This was partly due to the heatwaves, but heavy rainfall and flooding earlier in the year also meant planting had to be delayed.

It looks like we’re in a similar situation this year – wetter weather in the winter months has made it tough for farmers to successfully plant crops, while some countries are still struggling to recover drought-damaged crops from last summer. And, experts believe we’re on track for another season of blistering heatwaves.

Not only will this lead to an increased shortage of the cereals we eat, such as maize, wheat and barley, it impacts the livestock industry, too – if there’s not enough feed for animals like cows and pigs, this has a knock-on effect on farmers.

Professor Tim Benton, director of the Environment and Society Centre at Chatham House, says, "The majority of what we eat comes from a small number of crops, or livestock fed on those crops. Globally, we grow far more grains than anything else, so if supplies go down, this puts an upward pressure on food prices worldwide."

The end result may be more gaps on supermarket shelves and fewer supplies of steak, sausages and bacon, for example, while the cost of ingredients for bread, pasta sauces, ketchup and pizzas climbs even higher.

What else could happen?

If extreme heatwaves are here to stay, this could trigger the disappearance of some of our favourite foods. Professor Maguire says, "It’s not so much the heat that’s the problem – although it doesn’t help – but extended drought conditions. This puts all cereal crops at risk, plus cocoa, coffee, avocado, olives, cashew nuts, grapes… Nothing is immune."

Rising temperatures can also change the type of animals and insects that live in certain areas. "We call this the 'habitat envelope'," says Professor Benton. "As temperatures increase, the habitat envelope moves north. The original species move out, then new climate-adapting species move in. But, some species move much slower than others – compare a snail to a bird – so they could die out."

This changes the ecosystem in that area; insects like bees or wasps that pollinate certain plants may no longer be around to do their job, leading to lower crop yields. Migrating species could then move in, forcing farmers to use different or stronger pesticides and insecticides on their crops. This, in turn, can also lead to lower yields.

Professor Benton says, "Global warming will change what it is possible to grow and change the stability of crop yields from year to year."

Climate change is also pushing up the temperatures in our seas – the North Atlantic experienced several severe "marine heatwaves" last summer.

Higher sea temperatures can kill off marine animals, including billions of fish, but they also force those that prefer colder waters to move north. This reduces the food available for any remaining species, and limits the amount of seafood that can be caught in established fisheries. The result? Lower fish stocks and higher prices.

Can we produce more food in the UK?

In 2021, the government produced a report showing how climate change poses a risk to our food security, particularly because we import 46 per cent of the food we eat. This makes us really vulnerable to "unpredictable weather events overseas" like heatwaves in Europe or hurricanes in the tropics.

One answer is to grow more of our own produce at home, but not everyone has the space (or green fingers) to be able to do so. "Failing that, try to eat as much locally grown UK produce as possible," says Professor Maguire. "This also cuts down on the emissions that cause global heating."

However, higher temperatures are becoming more common for us too – in 2018, extreme heat and drought conditions hit our carrot, onion and potato harvests, leading to much lower than average yields. In fact, the lack of water and intense heat that year reportedly cut more than an inch off the size of the average chip!

So, the crops we grow will need to change, while the prices we pay for food will go up. "The era of cheap food is over," says Professor Benton. "For the past 50 or 60 years, food prices kept reducing. But now, year on year, food will become more expensive."

What can we do right now?

The report from Defra says the government is "building the UK’s resilience to overseas climate impacts on food", which includes working with trade partners and other organisations to help strengthen our food supply chain. But, it’s not clear yet exactly what this means or what it will look like in practice.

While we wait to find out, is there anything we can do, as consumers, to help stop extreme weather affecting our food?

We can change our diet to reduce its environmental impact, such as cutting down on meat and dairy, or choosing more sustainable foods. But Professor Benton says it may be more effective to increase pressure on the government.

He says, "If the government sees tackling climate change as a vote winner, they’re more likely to bring in policies that do make a difference to the future of our food security. Instead of changing the market as a consumer, do it as a citizen – we need to raise the temperature on politicians, not on the planet."