YEMEN is on the brink of famine, say aid agencies, which often blame the civil war, Saudi Arabia’s blockade of northern seaports and its bombing of vital infrastructure. The government’s refusal to pay salaries to employees in rebel-held areas and the depreciation of Yemen’s riyal mean many cannot afford the food that is available. But one of the biggest causes of hunger often goes unmentioned: a leafy plant called qat.

The weed is Yemen’s most popular drug: 90% of men and over a third of women habitually chew its leaves, storing the masticated greenery in their cheek until the narcotic seeps into their bloodstream. In the past Yemenis might indulge once a week and the practice was largely confined to the north-west mountains, where qat grows. But following unification in 1990 it spread south. Now qat markets bustle all over the country.

Men spend far more feeding their addiction than their families: sometimes $800 a month. Rather than searching for weapons and other contraband, soldiers extort bribes at checkpoints to pay for their habit, jacking up transport costs. And while the country runs out of basics, such as wheat, its best farmland is devoted to producing the crop, which is more lucrative. Cultivation of qat is said to be increasing by 12% a year.

Officials refer to it as Yemen’s Viagra and encourage its use. Taher Ali al-Auqaili, the army’s chief of staff, says it is “our whisky” and claims it gives his men strength to fight (see article). Both sides feed it to their child soldiers.

When local governors in Hadramawt, the largest province, tried to revive an old ban on consumption in their offices, they were summoned to Riyadh to join Yemen’s president, Abd Rabbo Mansour Hadi, for a communal chew. Only al-Qaeda in the Arabian Peninsula has had any success in banning it.

Northern Yemen is the region most under threat of famine, but the Houthi rebels who control it value their monopoly on qat as much as Mr Hadi does his hold on the country’s oil- and gasfields. It keeps roads open across enemy lines. Dozens of trucks full of the harvest cross into Marib each day. Taxes on qat also earn both sides in the war big revenues. Recent data are scarce, but back in 2000 the World Bank estimated that qat accounted for 30% of Yemen’s economy. Even the hungry cite an advantage: the drug suppresses their appetite. But the absurdity is not lost on all. In the words of a southern official, “We’re fighting Houthis with our arms and funding them with our mouths.”