The starchy tuber domesticated in the Andes and carried to the Old World after 1492 — the potato's extraordinary caloric yield per acre helped fuel Europe's population explosion and, historians argue, contributed to the labor surpluses that powered industrialization; yet the same crop's monoculture vulnerability turned a fungal blight into the catastrophic Irish Famine of the 1840s, making the potato the clearest single case of how an imported plant can remake a continent's demography and then, through fragility and policy failure, help produce one of the nineteenth century's defining demographic catastrophes.
An acre of potatoes feeds roughly twice as many people as an acre of grain. That single fact changed Europe. Between 1700 and 1900, the continent's population doubled — and then doubled again — partly because a New World tuber could grow on marginal land, survive harsh winters, and pack more calories per plot than almost anything else. The same tuber, planted as a monoculture in Ireland, met a water mold called Phytophthora infestans in 1845. Within seven years, somewhere between half a million and a million people were dead and a million or more had fled. Abundance and catastrophe, from the same plant.