Peru’s foreboding terrain belies its extraordinary fertility. The country’s arid coastal climate is caused by the frigid Humboldt Current, which sucks moisture away from the land. But these Antarctic waters also cause a rich upwelling of plankton, which in turn nourishes one of the world’s richest fishing grounds. Peru’s earliest cultures took root near the ocean and depended on mollusks and fish for their survival.
The snow-covered mountains and high passes of the Cordillera de los Andes would appear to be an impediment to the spread of advanced cultures. But the slow melting of the snowpack provides the desert coast with a vital source of year-round water. Once ancient Peruvians developed irrigation technologies, Peru’s early cultures converting Peru’s desert valleys and into rich farming areas. The ingenious aqueducts at Nasca, which carry mountain water for miles underneath the desert floor, are still in use today.
In the more moderate topography of North America and Europe, temperature differences and climate zones are largely a question of latitude. Florida, for example, produces oranges, while Kansas produces wheat. But in Peru, climate zones are caused not by latitude, but by altitude. In places Peru’s coast can rise from sea level to over 4,000 meters in less than 100 kilometers, creating a variety of climates apt for fruits, vegetables, grains, and potatoes. The same phenomenon occurs to an even greater extent where the Andes plunge into the Amazon , a dizzying range of ecosystems that nourish a huge variety of fruits and medicinal plants such as the coca leaf.
Peru’s cultural diversity has always been determined by its geography. Trade routes from the Amazon  over the Andes to the desert coast were key to the flourishing of Peru’s ancient cultures. The Chavín culture, based in the Andes south of the Cordillera Blanca , deified jaguars, snakes, caimans, and other Amazon animals in their enigmatic carvings. They traded their high-altitude grains and potatoes for fruits from the Amazon, dried fish and vegetables from the coast, and the highly valued spodylus seashells brought from Ecuador.