Peru is traditionally divided into three distinct longitudinal regions defined by massive changes in elevation. These natural divisions run parallel to the Pacific coastline. The three primary zones are known by their Spanish names: La Costa (the narrow coastal strip), La Sierra (the towering Andean mountain range), and La Selva (the vast Amazon basin).
The Coastal Strip (La Costa)
La Costa is a long, narrow strip along the Pacific Ocean, representing about 11% of the national territory. It is predominantly a desert landscape characterized by extreme aridity and minimal rainfall. The climate is controlled by the cold, north-flowing Humboldt Current, which chills the air above the ocean and suppresses the evaporation needed for rain clouds.
This atmospheric cooling often results in dense, persistent fog known as garúa, which provides moisture for coastal ecosystems during the winter months. Despite its desert nature, the Costa is home to over 44% of Peru’s population, including the capital city of Lima, making it the country’s economic heart. Agriculture is concentrated in the fifty-two river valleys that cut through the desert, where irrigation allows for the cultivation of commercial crops like sugar cane, cotton, and asparagus. The nutrient-rich upwelling driven by the Humboldt Current supports one of the world’s most productive marine ecosystems, fueling a substantial fishing industry focused on species like anchovy and sardine.
The Andean Highlands (La Sierra)
East of the coastal deserts, the landscape ascends into La Sierra, defined by the spine of the Andes Mountains. This mountain zone covers approximately 32% of Peru’s land area and features an average elevation of around 3,000 meters above sea level, though peaks frequently exceed 6,000 meters. The topography consists of rugged cordilleras, deep river canyons, and high-altitude plateaus.
The climate is generally cold and dry, experiencing a distinct seasonal cycle with a dry, sunny winter (May to October) and a rainy summer season. Temperatures show significant diurnal variation, with warm sunlight during the day and freezing conditions common at night in higher elevations. The Altiplano, a broad intermontane plateau averaging over 3,600 meters, is a prominent feature of the southern Sierra. This region is the historical heartland of the Inca civilization and remains the center of indigenous Andean culture. Traditional economic activities include high-altitude agriculture, cultivating native tubers (like the potato) and grains (such as quinoa), alongside raising livestock like llamas and alpacas.
The Amazon Basin (La Selva)
Moving eastward from the Andes, the land drops into La Selva, the vast Peruvian Amazon rainforest. This region is the largest of the three, covering about 57% of the country’s surface area. It is characterized by a hot, humid, tropical climate with high annual rainfall, and is drained by the headwaters of the Amazon River and its tributaries, forming a dense network of waterways.
The Selva is divided into two sub-regions based on elevation.
Selva Alta (High Jungle)
The Selva Alta, or High Jungle, occupies the eastern slopes of the Andes, generally between 400 and 1,000 meters. This area is noted for its steep relief and is characterized by cloud forests, receiving some of the highest precipitation in the country.
Selva Baja (Low Jungle)
Below 800 meters lies the Selva Baja, or Low Jungle, a flat, expansive plain of tropical rainforest. This lowland is home to extraordinary biodiversity and supports a local economy centered on resource extraction, including logging and petroleum, as well as developing ecotourism.
The Role of Altitudinal Zonation
The contrast between Peru’s three primary zones results from the Andes Mountains rising abruptly parallel to the Pacific coast. This geological feature creates a rapid change in elevation over a short horizontal distance, which dictates localized climate and ecological conditions. The concept of altitudinal zonation explains this vertical stratification of environments.
As elevation increases, temperature decreases by approximately 1°C for every 180 meters of ascent, a phenomenon known as the lapse rate. This rapid change in altitude results in distinct ecological layers that determine what crops can be grown and where populations can thrive. The zones transition from the hot, humid tierra caliente (Selva) to the temperate tierra templada (lower Sierra valleys), and finally to the cold tierra fría and tierra helada (highest peaks). This vertical ecology, rather than just latitude, generates Peru’s unique and highly varied geographical divisions.