PACIFIC DESERT: CHARACTERISTICS, CLIMATE, FLORA AND FAUNA - ENVIRONMENT - 2024

The Pacific desert or Atacama-Sechura desert is a coastal desert that extends along the south-western coast of South America, in territory belonging to Chile and Peru. This desert forms a narrow strip 30 to 100 km wide and has elevations of 600 to 1000 meters above sea level in the north and above 2000 meters above sea level in the south. Two large coastal deserts make up the Pacific desert: the Atacama Desert in Chile and the Sechura Desert in Peru.

Deserts are regions that have evaporation rates greater than precipitation rates; In other words, more water evaporates than falls due to the rain. Desert regions are classified into semi-deserts (with annual rainfall between 150 to 400 mm) and extreme deserts (with annual rainfall less than 70 mm).

Figure 1. Geographic location of the Pacific desert. Source: Hookery, from Wikimedia

In general, the subtropical zones located between 15 ° and 35 ° latitude in the northern and southern hemispheres of the planet are desert regions.

Location

The Pacific desert is located on the western coast of South America and extends from the Pacific Ocean to the Andes mountain range, between 6 ^° and 27 ° south latitude.

characteristics

Aridity and temperature

The Pacific desert is a region of extreme aridity; in it is the driest and most arid region of planet Earth, which is the Atacama desert, in Chile.

This desert has low temperatures in the Chilean Atacama desert and relatively high temperatures in the Sechura desert of Peru.

Biodiversity

The Pacific desert has few ecosystems and these are fragile. The diversity of organisms is very low.

Weather

The prevailing climate is of the arid, dry, subtropical type. It is an extremely dry climate, with average annual rainfall below 150 mm and average annual temperatures between 17 ° C and 19 ° C. The exception is the Sechura desert, in Piura, where maximum temperatures can reach 40 ° C.

The air of the Pacific desert is humid in general, so the relative humidity presents high values, greater than 60%.

Why are the rains so rare in the Pacific desert?

In the sea of ​​Peru there is an underwater current of very cold waters, which rises to the surface of the sea, called the Humboldt current.

The almost absolute absence of rains is due to the fact that when the moisture-laden trade winds pass over the cold Humboldt marine current (in Peru), they cool down and fog and clouds are produced in the form of strata between 800 to 1000 meters above sea level., without originating rain.

Above this layer of haze and clouds, the temperature rises to 24 ° C. This relatively hot air absorbs moisture preventing rain from falling.

When the relative humidity reaches very high values, a very fine drizzle called garúa originates. In the summer season (from December to March), the fog layer disappears and rainy precipitations occur in the mountains, which load the small rivers with water.

In the city of Lima (capital of Peru), rainfall is extremely low, with an annual average of 7 mm. Only in exceptional years, when the El Niño phenomenon occurs, precipitation can show a significant increase. In Iquique and Antofagasta (Chile), it only rains when powerful winds come from the south.

Temperatures in the southern part of the Pacific desert, that is, in the Chilean Atacama desert, are relatively low when compared to other similar latitudes on the planet. The average summer temperature in Iquique is 19 ^° C and Antofagasta is 1 ^or C, both cities located in the Atacama.

To the north of the Pacific desert, that is to say in the Sechura desert, in the summer temperatures are relatively high, above 35 ^° C during the day and on average higher than 24 ^° C.

In this northern part of the Pacific desert, during winter the weather is cold and cloudy, with temperatures that vary between 16 ° C at night and 30 ° C during the day.

Figure 2. Atacama Desert. Source: Jowyto, from Wikimedia Commons

Relief

The relief or topography of the Pacific desert is made up of plains of sedimentary origin and hills whose low altitude increases as they approach the Andes mountain range.

Towards the south, in the territory of Chile, the Pacific desert presents an intermediate depression between the coastal mountain range and the Andean mountain range.

Hydrology

In the Pacific desert there are about 40 low-flow rivers, which originate in the Andes and many of them do not even reach the sea. There are many absolutely dry river beds, which only have water when it rains heavily in the upper springs or on the coast.

There are lagoons and swamps close to the seashore; Several of these lagoons are of brackish water and have abundant aquatic vegetation.

Floors

The soils of the Pacific desert are mostly sandy, with very fine grains or sand mixed with rocks, stones and remains of shells of marine animals. This desert presents some areas with high salinity and stony.

There are also some areas with soils of alluvial origin on the banks of the small rivers that are in the valleys of the Pacific desert. These small areas are used in agricultural activities with irrigation systems.

Ecology

All deserts on planet Earth present forms of life that have managed to adapt to the rigorous existing environmental conditions. However, plants and animals are very rare.

Humans have also managed to adapt to life in the desert, efficiently taking advantage of the little available water, living near springs, in oases or by digging wells in dry river beds.

The most common plants in deserts are succulents, which store water in their tissues. Among these we can mention cacti with fleshy stems and roots, which have the ability to accumulate water.

The loss of the leaves, which turn into thorns, guarantees these desert plants a minimal rate of water loss through transpiration. The stems are provided with a waxy cuticle that also reduces water loss.

Animals also have different survival strategies under conditions of low water availability. They have a very low consumption of water, as they obtain it from the metabolism of foods such as starches.

Animals, in general, are exposed to the environment only in the hours of lower temperatures, such as sunset and sunrise. The rest of the time they are kept in their burrows to protect themselves from high daytime temperatures and low nighttime temperatures.

Flora

In the Pacific desert there are four well-differentiated vegetation zones:

1. The deserts.
2. The river valleys or oases that present gallery forests.
3. The few aquatic environments with the presence of reed beds, totorales and grasslands.
4. The coastal hills, with varied vegetation, which develops with the winter fogs (called camanchacas).

To the north, in the Sechura desert, there is a predominant presence of carob (Prossopis pallida), sapote (Capparis sacbrida) and vichayo (Capparis crotonoides).

To the south, in the Atacama desert, on the coastal hills, the annual herbaceous species Viola sp., Solanum remyanum, Oxalis breana, Palana dissecta and the shrubs Euphorbia lactiflua and Oxalis gigantea are present.

In turn, there are the cacti Copiapoa haseltoniana, Eulychnia iquiquensis and Trichocereus coquimbanus, and the bromeliads Thillandsia geissei and Puya boliviensis.

Shrubs such as Parastrephia lucida and Parastrephia quadrangularis can be found. Species of the so-called salty grass (Distichlis spicata) and foxtail (Cortadeira atacamensis) are also reported on the riverbanks.

Fauna

North Pacific desert

In the northern part of the Pacific desert, in the Sechura desert, 34 species of birds, 7 species of reptiles (Iguanidae and Teiidae), and 2 species of mammals (Canidae and Mustelidae) have been reported. Goats and donkeys are also found in the wild.

As predominant and emblematic species the Sechura fox (Pseudalopex sechurae) and the skunk (Conepatus chinga) are reported.

Birds

Among the birds we can mention the cuclú (Zenaida meloda), the tortolita (Columbina cruziana), the sleeper (Muscigralla brevicauda), the pepite (Tyrannus melancholicus), the soña (Mimus longicaudatus) and the chuchuy (Crotophaga sulcirostris).

Reptiles

Among the reptiles that inhabit the Sechura desert are the cane (Dicrodon guttulatum), the lizard (Microlophus peruvianus) and the geko (Phyllodactylus sp.)

South Pacific desert

In the southern part of the Pacific desert, in the Atacama desert, the representative fauna is constituted by small rodents and marsupials such as the chinchilla (Abrocoma cinerea), the degu (Octodon degus), the vizcacha (Lagidium viscacia), the little mouse of the puna (Eligmodontia puerulus) and the southern long-eared walleye (Phyllotis xanthopygus).

Birds

There are also birds such as the chickadee (Sittiparus olivaceus) and the imperial cormorant (Phalacrocorax atriceps), and reptiles such as the puna lizard (Lioelamus puna).

References

1. Marquet, PA (1994). Diversity of Small Mammals in the Pacific Coastal Desert of Peru and Chile and in the Adjacent Andean Area - Biogeography and Community Structure. Australian Journal of Zoology 42 (4): 527-54
2. Reyers, M. and Shao, Y. (2018). Cutoff Lows over the Southeast Pacific off the Coast of the Atacama Desert under Present Day Conditions and in the Last Glacial Maximum. 20th EGU General Assembly, EGU2018, Proceedings from the Conference held 4-13 April, 2018 in Vienna, Austria, p.5457.
3. Alan T. Bull, AT, Asenjo, JA, Goodfellow, M. and Gómez-Silva, B. (2016). The Atacama Desert: Technical Resources and the Growing Importance of Novel Microbial Diversity. Annual Review of Microbiology. 70: 215-234. doi: 1146 / annurev-micro-102215-095236
4. Wierzchos, J., Casero, MC, Artieda, O. and Ascaro, C. (2018). Endolithic microbial habitats as refuges for life in polyextreme environment of the Atacama Desert. Current Opinion in Microbiology. 43: 124-131. doi: 10.1016 / j.mib.2018.01.003
5. Guerrero, PC, Rosas, M., Arroyo, MT and Wien, JJ (2013). Evolutionary lag times and recent origin of the biota of an ancient desert (Atacama – Sechura). Proceedings of the National Academy of Sciences of the United States of America. 110 (28): 11,469-11,474. doi: 10.1073 / pnas.1308721110