Fertilizer was one of Peru's largest exports until the El Niño of 1877-78. Huge colonies of seabirds gather on Peru's coastal islands. At one time guano, the birds' droppings, supplied most of the world's fertilizer. But when an El Niño struck, massive numbers of seabirds died, and torrential rains partially dissolved the guano deposits. The guano industry totally collapsed after the severe El Niño in 1877-1878.