UN report: Climate change has permanently ruined farmland the size of France

There may be those who feel the apocalyptic plot of the new Hollywood film Interstellar seems a bit far-fetched, with humans forced to look for an alternative planet because this world can no longer feed them.

But it has been given credence by a new United Nations report that has found that the destruction of the environment has left an area of farmland the size of France useless for growing crops.

Batman director Christopher Nolan’s latest film may ultimately prove implausible – Matthew McConaughey leads an interstellar mission to find another world for the human race to inhabit – but the reasoning for his expedition appears to be sound, if a little extreme.

McConaughey’s character, known only as Cooper, is a farmer in a world that has become desperately short of food. Human activity has degraded the soil so badly that they're forced to live in a giant dustbowl and crops are all but impossible to grow.

Although soil degradation is nothing new, Interstellar is proving strangely prescient, as its release coincides with a new UN report showing the trend has reached alarming levels, with 7.7 square miles of agricultural land being lost every day because it has become too salty. Climate change is making the situation worse because warmer temperatures require more irrigation and increase the speed at which the water evaporates, the report warns.

The report, written by the United Nations University, highlights large areas of farmland in arid and semi-arid parts of the world, such as the south west of the US and Australia, which are suffering from a combination of heavy irrigation and poor to non-existent drainage systems. As a result, a thick crust of salt is forming across much of the world, which is costing £17bn a year in lost crop production in regions including China, India and Pakistan.

Water used for irrigation contains varying quantities of salt, which, in the absence of a good drainage system, is left behind when the water evaporates.

The effect can be intensified by groundwater – which also contains salts – and which rises to the surface as the water table rises following irrigation without drainage. In other words, drainage systems serve to flush the salt out of the ground by carrying it away from soil.

A total of 240,000 square miles of farmland worldwide has now been contaminated. The Indus Valley in Pakistan is one of the worst hit areas, with salinization cutting rice production by 48 per cent in recent years, while wheat is down 32 per cent. Salty soils also cause losses of around £469m annually in the Colorado River basin, an arid region in the south west of the US. In Turkmenistan, more than half of the irrigated land is damaged by salt.

Manzoor Qadir, lead author of the research, told The Independent that the growth of salty land has huge implications for feeding the world in the coming decades, at a time when population growth is already putting huge pressure on resources.

“To feed the world’s anticipated nine billion people by 2050, and with little new productive land available in irrigated zones, it is important we promote and invest in sustainable land management practices,” said Dr Qadir, of the United Nations University Institute for Water, Environment and Heather.

“Basically, with every irrigation we tend to add salts to the soil. If we do not remove them or decrease them from the roots, they tend to accumulate there. It can be cost-effective to invest in sustainable land management in countries confronting salt-induced land degradation,” he added.

Salt damage can also be reversed through measures such as tree planting and crop rotation using salt-tolerant plants, but these measures are extremely expensive and can take years.

The report has been published in the journal Natural Resources Forum.

Interstellar is part of a growing movement in the arts, in which creative people such as poets, playwrights and filmmakers are incorporating climate change and other environmental themes into their work, increasingly with input from scientists.

Chris Rapley, professor of climate science at University College London, has teamed up with Duncan Macmillan, the playwright who recently adapted George Orwell’s 1984, on a new climate change “performance” called 2071, which opens at the Royal Court Theatre in London next week.

This follows the debut of In a Vulnerable Place in Norwich in October, a new play in which University of East Anglia creative writing lecturer Steve Waters performs a personalised monologue about the risk climate change is posing to the Norfolk Broads, which was influenced by conversations with science colleagues.

Other examples of the arts tackling environmental issues include In Promised Land, a 2012 film starring Matt Damon that focuses on the dangers of fracking and Climate Dress – a collaboration this year between Exeter University, the Met Office, the London College of Fashion and the Victoria and Albert Museum looking at how clothing can be used to communicate ideas about climate change. The London School of Economics’ Grantham Institute on Climate Change held a slam poetry competition on the subject of climate change in March.