UN warns of an impending 'existential crisis' that destroys crops

More than three-quarters of all land on Earth has become permanently drier over the last 30 years .

Since 1990 , arid regions have expanded by an area a third larger than India and now cover 40 per cent of the Earth 's land excluding Antarctica .

Experts warn that this has 'dire implications for agriculture' as an increasingly hot climate turns the world's former 'breadbaskets' lush grain-growing regions into drylands.

By 2040 , the spread of arid areas will cost the world 20 million tonnes of maize, 21 million .

tonnes of wheat, and 19 million tonnes .

of rice.

The researchers conclude with certainty that human-caused climate change is the principal reason.

Warmer air holds more water and energy so when rain does fall it is more likely to do so in violent storms, hurricanes and flash floods.

A quarter of the world has actually become wetter over the last 30 years .

Hot, dry soils have less vegetation and can't absorb as much water so even areas that are becoming drier on average can still be hit by flash flooding.