The bananapocalypse is coming. That’s the likelihood that sometime in the next decade bananas may disappear, victims of a fungal pathogen known as Panama Disease. The disease is on the march throughout the world, threatening the future of the world’s most popular fruit.

Panama Disease may be the cause of this disaster, but it’s also a symptom of a bigger problem afflicting global agriculture: a failure to diversify. For the past couple of centuries, the tendency has been to adopt a single reputable cultivar and — literally — bet the farm on it.

The most devastating case study in the dangers of monoculture comes from Ireland in the 1840s. After the discovery of potatoes in the New World, the Irish began cultivating them en masse. But while the Incas and other peoples had cultivated thousands of varieties of potatoes, the Irish only grew three kinds, mostly a homely variety known as the “Lumper.”

This particular potato proved remarkably productive. But it was vulnerable to a fungal pathogen known as Phytophthora infestans, better known as potato blight. In 1845, the organism destroyed that year’s crop of Lumpers, and then raged across the rest of Europe. It’s estimated that a million people died of starvation in Ireland alone, with another two million people emigrating out of desperation.

Despite this object lesson in the dangers of monoculture, farmers planting crops often favoured a handful of trusted varieties. This was a rational choice, particularly for growers of crops destined for global markets, where economies of scale tended to privilege homogeneity over diversity. But this choice can end badly.