Llamas and alpacas, which were tamed in prehistoric times, graze in the Central Andes in the high grasslands called puna or paramos. Below the grasslands, farmers have removed many forests. They have created large terraces and irrigation systems, and they grow such crops as potatoes, corn, and coffee. The passes of the Andes Mountains are narrow, steep, and winding. The mountains are so high and rise so sharply from low plains that they divide the continent into Pacific South America and Atlantic South America.
Engineers find railroads much harder to build in the Andes Mountains than in the Rocky Mountains.
Four railroads run up the west slope to the rich mineral beds on the plateaus of Peru and Bolivia. It is the highest standard gauge railroad in the world. From here, an all-weather road continues down a deep canyon in the eastern Andes to a branch of the Amazon River. Other highways lead over the Andes into the eastern lowlands. Trucks, buses, and automobiles travel over these roads.