Climate change threatens to poison the food supply of some of the world’s poorest people as crops respond to rising temperatures by pumping out dangerous chemicals.

Experts are already concerned about the devastating impact extreme weather can inflict on vital crops, but these conditions also pose subtler hazards.

When drought strikes, plants like maize, beans and cassava response by flooding themselves with nitrates and hydrogen cyanide – substances that can be fatal to livestock and humans alike.

Further problems arise from the spread of toxin-producing fungal infections under warmer conditions, which are already responsible for thousands of liver cancer cases in Africa every year.

While these issues are a particular concern in developing nations with hotter climates, if temperatures rise as scientists predict, they will probably begin to take their toll further north as well.

Climate strike: See the best signs from the protest here Show all 29 1 /29 Climate strike: See the best signs from the protest here Climate strike: See the best signs from the protest here The protest in Parliament Square, London on February 15 AFP/Getty Climate strike: See the best signs from the protest here The protest in Parliament Square, London on February 15 Getty Climate strike: See the best signs from the protest here The protest in Parliament Square, London on February 15 EPA Climate strike: See the best signs from the protest here The protest in Manchester on February 15 Getty Climate strike: See the best signs from the protest here The protest in Manchester on February 15 Getty Climate strike: See the best signs from the protest here The protest in Parliament Square, London on February 15 Getty Climate strike: See the best signs from the protest here The protest in Brighton on February 15 Getty Climate strike: See the best signs from the protest here The protest in Parliament Square, London on February 15 AFP/Getty Climate strike: See the best signs from the protest here The protest in Parliament Square, London on February 15 AFP/Getty Climate strike: See the best signs from the protest here The protest in Parliament Square, London on February 15 Reuters Climate strike: See the best signs from the protest here The protest in Parliament Square, London on February 15 PA Climate strike: See the best signs from the protest here The protest in Parliament Square, London on February 15 PA Climate strike: See the best signs from the protest here The protest in Parliament Square, London on February 15 PA Climate strike: See the best signs from the protest here The protest in Parliament Square, London on February 15 PA Climate strike: See the best signs from the protest here The protest in Parliament Square, London on February 15 PA Climate strike: See the best signs from the protest here The march in Brussels, February 14 Reuters Climate strike: See the best signs from the protest here The march in Brussels, February 14 Reuters Climate strike: See the best signs from the protest here The march in Brussels, February 14 AP Climate strike: See the best signs from the protest here The march in Brussels, February 14 AP Climate strike: See the best signs from the protest here The march in Brussels, February 14 Reuters Climate strike: See the best signs from the protest here The march in Brussels, February 14 AP Climate strike: See the best signs from the protest here The march in Brussels, February 14 AP Climate strike: See the best signs from the protest here The march in Brussels, February 14 Reuters Climate strike: See the best signs from the protest here The march in Brussels, February 14 Reuters Climate strike: See the best signs from the protest here The march in Brussels, February 14 Reuters Climate strike: See the best signs from the protest here The march in Brussels, February 14 Reuters Climate strike: See the best signs from the protest here The march in Brussels, February 14 Reuters Climate strike: See the best signs from the protest here The march in Brussels, February 14 Reuters Climate strike: See the best signs from the protest here The march in Brussels, February 14 AP

The alarm was raised by Professor Jacqueline McGlade, a former chief scientist at the United Nations Environment Programme, at a Gresham College lecture in London.

Her interest in the problem was first roused when reports emerged from Ethiopia of impoverished farmers and their animals dying in mysterious circumstances.

The country was in the grip of a drought, but this did not explain the neurological problems that were afflicting these people, including blindness, difficult movements and ultimately death.

Researchers working in the area realised the drought had damaged the farmers’ crops, forcing people to consume wild plants they found by the roadside.

Unfortunately, the stress of drought had also triggered a defence mechanism inside these plants, flooding them with hydrogen cyanide.

Professor McGlade collected all the available information on this topic into a report for the UN back in 2016, in which she and a team of scientists attempted to identify emerging environmental problems.

“What I was trying to do was raise issues long before they become embedded as problems – raising the red flag,” she said.

“Fast-forward to today and we are talking about climate change – here is something that is really going to challenge food safety, because the very plants we are relying on are themselves adapting to climate change.

Support free-thinking journalism and attend Independent events

“One of the ways they adapt is dangerous to livestock and humans – clearly we need to pay attention.”

Since her report, the most recent findings from the UN’s Intergovernmental Panel on Climate Change have laid out the impact of global warming on extreme weather and food systems worldwide.

Scientists think these effects are already being felt, with the extreme heatwaves and droughts that struck last year from California to Sweden bringing an associated panic about crops. In the UK, farmers said some vegetable yields had been cut by as much as half.

These problems could be exacerbated as aflatoxin, a substance produced by fungi growing on maize and other crops during drought conditions, spreads beyond its normal range.

The European Food Standards Agency has warned the toxin, which is linked to cancer, immune problems and stunted foetal growth, is likely to become a food safety concern in Europe even if the global temperature rise is limited to 2C.

Though the outcomes look bleak, Professor McGlade said hope for the future could come from locally grown and wild crop species that have higher tolerance for heat and disease.

Dr Carlo Fadda, a researcher at Bioversity International, said he had been working on varieties of barley and durum wheat that has been cultivated in Ethiopia for 4,000 years.

“These varieties are much more tolerant to drought conditions, they maintain relatively good productivity even in bad years and are rarely susceptible to diseases,” he said.