Pistachios are Iran's biggest export after crude oil, with 250,000 tonnes of the nut produced last year—a figure only recently topped by the United States. In Kerman province in southern Iran, cities have grown rich from pistachios, but time is running out for the industry as unconstrained farming and climate change take a devastating toll.
Near the city of Sirjan, a long line of enormous sinkholes like bomb craters mark the points where an underground aquifer was pumped completely dry, and the ground simply collapsed.
"Farming is being destroyed," says Hassan Ali Firouzabadi, who has lived in the nearby village of Izadabad for half a century.
His business is barely clinging on. Some of his pistachio trees are old enough to remember the golden age of Shah Abbas in the 17th century, but the leaves have turned yellow-green from the salty water he now dredges up.
'A long-held illusion'
Iran faces two key challenges—dealing with a years-long nationwide drought that shows little sign of abating, and trying to convince farmers to stop the uncontrolled pumping of water.
Some 300,000 of Iran's 750,000 water pumps are illegal—a big reason why the United Nations says Iran is officially transitioning from a state of "water stress" to "water scarcity".
In 2013, Iran's chamber of commerce carried out a survey showing that Kerman province was losing about 20,000 hectares (49,400 acres) of pistachio farms every year to desertification.
For centuries, Iran relied on one of the world's most sophisticated irrigation systems—a web of underground canals known as "qanats" that carried water from under the mountains to the arid plains.
But then came the electric pumps and the chaotic politics of the last century. The need to preserve water was little understood and became secondary to self-sufficiency in food production—an attitude that persisted into the sanctions era.
"We are slowly moving past the long-held illusion that we have endless resources," says Mohsen Nasseri at the National Climate Change Office in Tehran.
He says the government is finally looking at financial incentives to encourage water conservation. One scheme offers funding for farmers to buy modern irrigation equipment, but changing ingrained attitudes will take time.