According to a study led by scientists at the London School of Hygiene and Tropical Medicine (LSHTM), climate change could make it harder to eat healthily, with yields of vegetables falling by more than a third as temperatures rise and water becomes scarce.

It is the first study to systematically investigate the extent to which climate change could affect the production and nutritional quality of common crops such as vegetables and pulses.

Fresh water scarcity, loss of biodiversity, more frequent extreme weather and rising sea levels are already affecting food security in some parts of the world. As global temperatures continue to rise, food security is likely to become a more serious and widespread problem.

There have previously been studies investigating the impact of climate change on staples such as rice and wheat, although the impact on vegetables and legumes – key to all healthy diets – has not been studied in such detail.

The LSHTM researchers began by reviewing all available evidence from experimental studies since 1975 looking into the impact of environmental changes on the quantity and nutritional quality of vegetables and legumes across 40 different countries. Next, they estimated the damage that could be caused by predicted increases in greenhouse gases, reduced availability of water and rising temperatures.

While previously it had been suggested that rising levels of carbon dioxide could have an unexpected silver lining - increased crop yields - the latest study found that any increase to yield caused by increased atmospheric carbon would likely be cancelled out by other environmental changes. The scientists found that average yields of vegetables could fall by 35 per cent, while those of legumes could fall nine per cent. These falls in yield, the researchers say, could lead to healthy foods becoming far more expensive, with a knock-on effect on public health.

“Our study shows that environmental changes such as increased temperature and water scarcity may pose a real threat to global agricultural production, with likely further impacts on food security and population health,” said lead author Dr Pauline Scheelbeek.

“Vegetables and legumes are vital components of a healthy, balanced and sustainable diet and nutritional guidelines consistently advise people to incorporate more vegetables and legumes into their diet. Our new analysis suggests, however, that this advice conflicts with the potential impacts of environmental changes that will decrease the availability of these important crops unless action is taken.”

Taking a “business as usual” approach will lead to vegetables and legumes becoming scarce, they warned.

“Urgent action needs to be taken, including working to support the agriculture sector to increase its resilience to environmental changes, and this must be a priority for governments across the world,” said senior author, Professor Alan Dangour.

“Vegetables and legumes are essential constituents of healthy diets and so efforts to ensure that their global availability is not threatened by predicted environmental changes must also be high on the global public health agenda.”