The Andes Mountains

  • Range / Length: 7,000 km approx.
  • Range / width: 200 to 700 km approx.

The Cordillera de los Andes is the result of the colossal collision between two tectonic plates: Nazca and Sudamericana. One of the major consequences of its emergence is the collection and distribution of water in the region. Its current descends from the snowy peaks, at more than 6.000 meters high, towards the Pacific and Atlantic Oceans.

The Andes stretch from north to south through 7 countries: Venezuela, Colombia, Ecuador, Peru, Bolivia, Argentina, Chile. The Andes Mountains are the longest in the world. They form a continuous plateau along the western edge of South America. This range is approximately 7,000 km (4,300 mi) long, 200 to 700 km (120 to 430 mi) wide (widest between 18 ° South and 20 ° South latitude), and an average height of approximately 4,000 m (13,000 ft).

The Andes are the highest mountain range in the world outside of Asia. The Andean arboreal subregions (north, center, and south) differ in their genesis and the way they interact with atmospheric circulation, resulting in a wide range of environmental conditions.

Andean forests are very diverse ecosystems with endemic species in each one of them. These forests play a key role in the provision of ecosystem goods and services: they regulate the climate and water supply, mitigate floods and droughts, mitigate GHG emissions and maintain habitats that allow the long-term permanence of biodiversity. .

  • Area: 3 370 794 km² approx.
  • Average altitude: 4000 meters above sea level.


  • Mountains on all continents represent about 1/10 of the Earth's surface.
  • They are home to about 1/4 of all terrestrial species.
  • In mountains, environmental heterogeneity is related and interacts with geology, climate and species richness.
  • Everest (8848 masl) is the highest mountain on the planet, it is located on the border between China and Nepal, constituting the highest natural border in the world. In South America, the highest mountain is Aconcagua, in Argentina (6962 meters above sea level).


The Andes presenta wide variety of climates

Andean ecosystems vary according to elevation. In the northern and central Andes there are 133 different ecosystems. Each thermal floor, with its unique atmospheric conditions, shapes a type of forest.

The climate of South America changed completely with the rise of the Andes. The great mountain range created temperate and cold climates in the tropics. If it weren't for the mountains, the climate in this region would be uniformly hot.

The mountains of the tropical zone of South America, depending on their location and height, can dampen or exaggerate the effect of winds and, therefore, the path of clouds and rains. This generates very cold and dry, very cold and humid places as well as very hot and dry or very hot and humid valleys. In the tropical Andes, more than in any other region, all the climates of the world are present.


Being located in the tropical zone, Peru receives intense solar radiation throughout the year. This effect is dampened by the presence of the Andes.


In the northern Andes, humidity comes from both sides. The central Andes, on the other side of the coastal desert, can only trap Amazonian moisture by forming a green strip known as Yungas.


The height produces steps or floors that represent more or less stable temperature bands throughout the year. The higher, the colder.


The Peruvian-Chilean deserts and the humid forests in the coastal strip of Colombia and Ecuador are due to the influence of the sea: the sun cannot heat the cold water of the Humboldt current to form clouds and rain. On the other hand, on the warm equatorial current it generates abundant humidity.


The Earth revolves around the Sun at an inclination of 23.5 degrees. This makes the sun hotter the northern hemisphere in June and the southern hemisphere in December. In the tropics this difference in temperature is not felt, but its effect on the rains, which move north and south following the path of the sun, can be felt.

The Andes hosthundreds of endemic species

High reservoir of Biodiversity

Andean ecosystems have unique characteristics that provided opportunities for important biological adaptation and speciation processes. The tropical Andes (north and center) are considered the region that harbors the greatest biological wealth and diversity on Earth: hundreds of birds, trees, mammals, flowers, amphibians and insects that do not live anywhere else in the world.

Genetic wealth

It is estimated that around 25% of the world's plant diversity is found in the tropical Andean region. In the forests of the tropical Andes, several native species, especially plants, were domesticated by pre-Hispanic cultures. The meticulous genetic selection carried out by these settlers contributed significantly to the appearance of hundreds of varieties that are now cultivated around the world, such as corn and potatoes.

Water fountain

The Andes offer basic ecosystem services, such as water supply or carbon sequestration, to more than 50 million people who live in or near the longest mountain range on the planet. More than 60% of the water available in the Amazon basin originates in the Andes.

Biodiversity map (Antonelli et al. 2018.)

It is important to highlight the richness of the species of the tropical Andes indicated here in red on the map.

Broad ecosystems

The Andean forests cover a total of 31 million hectares, connecting 7 countries: Colombia, Venezuela, Ecuador, Peru, Bolivia, Chile and Argentina.

The Andes reservewater in its cloud forests


In the tropical Andes, clouds form between 2 and 3 meters above sea level, which is known as the “condensation strip”, right where the treetops act as water dams. This ecosystem of trees that trap and distill mist is called the Cloud Forest, and it is one of the largest producers of fresh water in the country. Many of the rivers that run in the Amazon are born from the humidity of the cloud forests.

In Peru, the humid forests are limited to the eastern flank of the mountain range, where a multitude of valleys make up the region known as the Yungas. Peru is the largest of the countries in the tropical Andes and the one with the most varieties of Andean forests.

Water: the most important harvest

The ability to collect water from clouds and produce abundant fresh water is one of the most important characteristics of páramos and cloud forests.

The difference between a cloud forest in the mountains and one in the lowlands is that the water does not come only from above: it also arrives horizontally when the clouds, carried by the wind, hit the mountains and form something similar to a light drizzle. This "horizontal rain" represents an extra income of up to 30% of water in these forests.

Aquatic condos

Bromeliads, abundant in cloud forests, act as natural cisterns. The largest can store up to 10 liters of water, creating microenvironments where an infinity of organisms inhabit: insect larvae, snails, small and colorful poison frogs and other small vertebrates. Lichens, orchids, ferns and mosses also abound.

The Andes mitigateclimate change

Andean forests can store millions of tons of carbon dioxide in their vegetation. Deforesting those forests is equivalent to releasing all that toxic dirt into the atmosphere. As forests disappear, the planet loses its ability to maintain clean air. Forest land is turned into farm plots, cattle pastures, or mining operations, all activities that emit carbon dioxide.

Andean forests can mitigate the effects of climate change by reducing greenhouse gas emissions. Forests are carbon reservoirs and their potential for capturing greenhouse effects is unmatched: they significantly cooperate in the goal of keeping the increase in temperature below 2 ° C.

Andean forests also contribute to reducing the vulnerability of ecosystems and increasing resilience, the ability to successfully adapt to climate change. These benefits apply to the daily life of the inhabitants. The presence of trees in agricultural fields regulates the water, the soil and the microclimate for a more resilient production.