Studies warn climate change will bring faster warming to subtropical dry areas, making crops like wheat and potatoes unviable

As subtropical drylands expand, trees and food crops will struggle (Pic: Ollivier Girard/Center for International Forestry Research)

In what may be good news only for cactus, termites and drought-resistant grasses, subtropical dry areas are going to expand over large parts of the Earth as the climate warms.

This will seriously reduce the amount of land that can be used to grow crops for human consumption and prevent many deeper-rooted shrubs and trees from growing at all.

This latest finding in Nature Communications overturns received wisdom that deep-rooted woody plants would survive better in subtropical dry areas because they would be able to extract moisture from far below ground.

Scientists discovered that these deep soils dried out and stayed dry for longer periods because the moisture from the rains evaporated or was used by shallow-rooted plants before it could percolate down to the subsoil.

Groups of scientists studied vast areas of land in North and South America, Asia, Southern Africa and the Western Mediterranean basin. They found that temperate drylands reduced in size by about one-third but only because they morphed into subtropical drylands as temperature rose. Absence of frost from temperate drylands enabled subtropical plants and insects to invade them.

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The paper says these impacts “could have large consequences for human wellbeing: aggressive human diseases, including dengue and schistosomiasis, as well as mound-building termites, occur in subtropical climates and could expand as temperate drylands warm, whereas cool season crops such as wheat and potato would no longer be economically viable”.

All areas, except for some parts of East Asia and North…