How will extreme heatwaves affect our food?

This year’s 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, 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 meandering, 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.’

What's happening to our food right now?

The heatwaves of summer 2023 had an immediate impact on some foods. Olive crops in Spain, the world’s largest producer of olive oil, have been decimated by drought for the second year in a row, while tomato harvests in Italy were hit by flooding earlier in the year, drought during June and July, then extreme heat scorching the fruit. But the biggest impact may be on cereal harvests.

Copa Cogeca, the European farming organisation, says cereal harvests in Southern Europe could fall by 60% compared with last year. This is partly due to the heatwaves but heavy rainfall and flooding earlier in the year also meant planting had to be delayed, leading to smaller harvests. Not only will this affect the cereals we eat, such as maize, wheat and soybeans, it impacts the livestock industry too – if there’s not enough feed for the animals, like cows and pigs, what can farmers do?

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. On a global basis, we grow far more grains than we do anything else, so if supplies go down, this puts an upward pressure on food prices worldwide.’

Which all means there could be more gaps on supermarket shelves, lower supplies of steak and sausages, for example, and the cost of ingredients for pasta sauces, ketchup, pizza and more will be higher.

And in the future?

With extreme heatwaves here to stay, this will have significant, long-term effects on our food. Prof Maguire says, ‘It’s not so much the heat that’s the problem – although that 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.’

In addition to a lack of water, rising temperatures can change the type of animals and insects that live in certain areas. ‘We call this the “habitat envelope”,’ says Professor Benton. ‘As temperatures rise, 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 bird to a snail – 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 of bugs could then move into an area, forcing farmers to use different, or stronger, pesticides and insecticides on their crops. This, in turn, can lead to lower yields.

Prof Benton says, ‘Climate change 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 has had several severe ‘marine heatwaves’ already this summer.

Higher sea temperatures can kill off marine animals, including billions of fish, but also forces those that prefer colder temperatures to move North, reducing the amount of seafood that can be caught in established fisheries. The result? Lower fish stocks and higher prices.

Can we produce more in the UK?

The government recently released a report showing how climate change poses a risk to our food security, particularly as we import 42% of the food we eat. This makes us particularly vulnerable to ‘unpredictable weather events overseas’ such as heatwaves in Europe or hurricanes in the tropics.

One answer is to grow more of our own produce in gardens or window boxes – you can find out how here – 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 Prof Maguire. ‘This also cuts down on the emissions that are causing global heating.’

However, rising temperatures will also affect what we can grow in the UK. Heatwaves are becoming more common for us too – in 2018, extreme heat and drought conditions hit 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!

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 Prof 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?

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 exactly what this means or what that looks 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 diets so they have less of an environmental impact, such as reducing or giving up meat and dairy or choosing foods that have a smaller water footprint. But Prof 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 should raise the temperature on politicians, not on the planet.’