Atacama Desert ecosystem
The Atacama Desert ecosystem, located in northwest South America, is one of the driest regions on Earth, characterized by its extreme aridity and unique environmental conditions. Stretching from southwestern Peru to northwestern Chile, the desert features a coastal strip known as the "Atacama hyperdesert," where annual precipitation is typically less than 0.2 inches (5 mm). This dryness is largely influenced by the cold Humboldt Current and the rain-shadow effect of the Andes mountains, which block moist air from the Atlantic.
Despite its harsh conditions, the Atacama supports specialized biological communities, particularly in areas where coastal fogs penetrate inland. The "Atacama lomas formation" is a notable ecosystem here, hosting unique flora such as airplants and endemic cacti. The desert is home to diverse wildlife, including mammals like llamas and vicuñas, as well as various bird species. Salt flats and mineral deposits, such as nitrates and lithium, add to the region's economic significance, leading to historical disputes over resource control.
In the higher altitudes of the Andes, the Puna de Atacama features a distinct landscape of stony plateaus and sparse vegetation, where seasonal rains provide a brief moment of moisture amidst the extreme conditions. Although human habitation in this challenging environment is limited, the valleys support agriculture facilitated by river systems and have historically been significant to indigenous cultures. Overall, the Atacama Desert ecosystem represents a remarkable intersection of extreme natural conditions and diverse ecological adaptations.
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Atacama Desert ecosystem
- Category: Desert Biomes.
- Geographic Location: Northwest region of South America.
- Summary: This extremely arid coastal and mountain desert is located in western South America, in the main area of the cold Humboldt Current influence.
The Atacama Desert stretches along the western Pacific margin of South America from southwestern Peru to northwestern Chile. The desert includes not only the basal coastal strip below 6,560 feet (2,000 meters), called the “Atacama hyperdesert,” but also the adjacent cold and very arid western mountain slopes of the Andes, rising to more than 13,125 feet (4,000 meters), an area called Puna de Atacama.
The coastal zone of the Atacama Desert, located at 6,500 to 9,840 feet (2,000 to 3,000 meters) altitude depending on latitude, is considered to be among the driest deserts on Earth. In fact, it has been described as an absolute desert or hyperdesert, with 0 to 0.2 inch (0 to 5 millimeters) of average annual precipitation. The extreme drought is due mainly to the strong influence in this area of the cold Humboldt coastal marine current, which flows south to north, and to the rain-shadow effect caused by the high Andes, which intercept the arrival of the moist trade winds from the Atlantic Ocean to the coastal Pacific. The Humboldt Current creates a temperature inversion in the atmosphere due to the cooling of the layers of air in contact with the ocean. Cold air cannot ascend enough to cause cloudiness and rainfall, so it originates dense, almost-permanent coastal fogs. These fogs are the main sources of moisture in the coastal Atacama Desert, supporting a specialized ecosystem called the “Atacama lomas formation” that develops inland on west-exposed hillsides, mainly from 2,300 to 3,930 feet (700 to 1,200 meters).
Flora and Fauna
The Atacama lomas formation is dominated largely by several species of terrestrial Tillandsia (Bromeliaceae), called “airplants” because they depend exclusively on atmospheric moisture for their nourishment. Another type of lomas is dominated by arborescent and shrubby cacti, mainly endemic species of Haageocereus and Eulychnia, which form rather small, isolated populations on steep slopes exposed to the west. Tillandsia and the cacti lomas ecosystem have a patchy and fragmentary geographic natural distribution related to the presence of the main areas of coastal fog's inland penetration. These are highly specialized biological communities, threatened by impacts such as the construction of coastal roads and power lines. They are also vulnerable to the effects of climate variability associated with the El Niño Southern Oscillation (ENSO) that periodically causes changes in the normal regime and intensity of the Humboldt Current, which can produce anomalies in the distribution and duration of the coastal fogs.
Outside lomas, the vegetation is almost totally absent; the barren landscape consists of large rocky low mountainous areas (the Pacific Coastal Ranges), often with an aeolian (wind-driven) sandy coverage, interspersed with rocky plateaus and some salt flats. Due to the relative proximity of the Andes, there are several seasonal or temporal allochthonous (from elsewhere) rivers (locally called quebradas or arroyos) that originate in the eastern high mountains and reach the coast by crossing the desert. It is in these arid valleys that human populations have concentrated, both the present settlements and historically the diverse indigenous cultural groups that historically inhabited the Atacama Desert, including the Nazca, Atacameño, and Inca cultures. In the valleys some agriculture can be practiced, due to moisture and fertility periodically provided by the muddy sediments deposited by rivers in flood times. Along with agriculture, fishing in the sea provides the main traditional source of livelihood for Atacama coastal human populations.
The original natural vegetation of the Atacama Desert valleys are low and open forests and shrublands, which are dominated mostly by several species of Prosopis (mesquite tree) specially adapted to live by exploiting the groundwater levels in the valleys. This natural vegetation has been largely replaced by crops and pastures, but there remain several managed populations of mesquite because of its traditional use as firewood, timber, and for support of livestock.
Despite the harsh conditions, the Atacama desert supports an array of wildlife. Most of the animals of the region dwell near the shoreline and coastal river valleys of the area. Mammals of the ecosystem includes llamas, vicunas, alpacas, huemul, deer, mice, foxes and viscacha. Along with mammals, many birds reside in the desert, including three species of flamingos, giant hummingbirds, and Andean swallows. Coastal birds include terns, gulls, boobies, and pelicans. Surprisingly, few reptiles inhabit this area.
Salt Lakes and Plateaus
Salt deposits are very characteristic of the Atacama Desert, where they are widespread and represent a key mineral resource of great economic value. In Atacama there are two main types of salt deposits: those in which precipitate a remarkable diversity of evaporite salts, mainly chlorides, iodides, carbonates, and sulphates of sodium, potassium, boron, and lithium (salares); and the salt flats characterized by nitrate deposits and locally called salitreras.Salares are distributed both in coastal areas as well in the high Andean plateaus of the Puna de Atacama, while salitreras are restricted to basal and pre-Andean regions of the Atacama Desert in Chile. The dispute over the possession of the valuable nitrate deposits was a contributing factor in a five-year war between Bolivia, Peru, and Chile in 1879, as a result of which Chile took possession of the salitreras and the desert region where they are located, which previously belonged to Bolivia and Peru.
On the western slopes of the Andes, above 6,560 to 9,840 feet (2,000 to 3,000 meters) altitude, the dense fog layers typical of the basal Atacama Desert disappear, and some rains occur seasonally across the high mountains from the east during the warmest time of year (December to March), creating a tropical rainfall regime. These scarce rains bring only small amounts of rainfall, less than 3 inches (80 millimeters) annually, and characterize the cold, high-Andean Atacama Desert or Puna de Atacama. These rains are distributed in northeastern Chile (Antofagasta and Atacama regions), the northwest corner of Argentina (Jujuy), and adjacent areas in far southwestern Bolivia (Lípez).
The topography of the Puna de Atacama is characterized by high and large stony desert plateaus (altiplano) and mountain slopes of volcanic origin, with the presence of numerous volcanoes both dormant and semi-active, many of them reaching altitudes above 16,400 feet (5,000 meters). At the foot of volcanoes and plateaus, diverse salt flats, salt lakes, and ponds occur, mostly located above 13,125 feet (4,000 meters). Natural vegetation is sparse, consisting mainly of open bunch-grassland (pajonal) and widely scattered low shrubby vegetation adapted to the strong diurnal alternation of ice and thawing which is typical of the high tropical mountains. Moreover, in small humid valleys and in the margins of saline lakes and ponds, a peat-swamp Andean vegetation (bofedal) locally develops, mainly conditioned by the presence of underground geothermal water springs related to the regional volcanism.
The human resident population in the Puna de Atacama is extremely scarce, mainly due to the harsh climatic conditions and high altitudes. However, the region has a great scenic value, with extraordinarily luminous and unique landscapes, annually attracting a significant flow of tourists from around the world to visit the protected areas.
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