The Patagonian steppe is a cold, semiarid South American biome lying between 40° and 52°S. It covers a large area of low mountains, plateaus, and plains between the Andes and the Atlantic Ocean. Climate and vegetation vary according to distance from these two major geographic features as well as latitude. Much of the Patagonian region of Argentina and southwest Chile has steppe conditions. The Valdés Peninsula of central eastern Argentina is a warmer outlier to the north, and the Falkland Islands are considered an insular variant in some biome schemes.
Strong westerly winds affect the steppe throughout so Pacific air masses dominate the climate. Temperatures are generally higher near the Atlantic than inland with cool and even cold summers characteristic almost everywhere. On the Valdes Peninsula summer daily maxima may reach into the 90s F, however. The steppe lies in the rainshadow of the Andes; annual precipitation is generally less than 20 in (500 mm) and often less than 8 in (200 mm); slightly less than half is received in winter. Central Patagonia is the driest part. Heavy snowfalls occur in winter; frost may occur any time during the year.
Vegetation reflects the regional climate, varying from semi-desert to shrub-steppe to grass-steppe. Short tussocks of feathergrasses (Stipa spp.) and meadowgrasses (Poa spp.) prevail in most areas. Shrub-steppes are widespread and feature cushion plants such as the deciduous Mulinum spinosum (neneo) and globular shrubs such as deciduous Ademisia volkmanni and evergreen Senecio filaginoides as a second stratum in the grassland. Endemism is high within dominant plant families. Sixty percent of Leguminosae and 33 percent of Compositae are reportedly unique to the region. Endemic species of mesquite (Prosopis), creosotebush (Larrea), wolfberry (Lycium) and peppertree (Schinus) also occur.
Patagonian Steppe: grass-steppe vegetation showing dominance of tussock grasses
Courtesy Jason Hollinger, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons
The fairly rich fauna includes endemic species of mammals, birds, and amphibians. The Patagonian steppe is home to such animals as Patagonian opossum, mara (Patagonian hare), Wolffsohn’s viscacha, Patagonian weasel, Patagonian “false” fox (zorro gris), guanaco, Lesser or Darwin rhea (nandu), Patagonian tinamou, and Patagonian mockingbird.
Mara or Patagonian Hare is a Neotropical caviomorph rodent related to capybaras.
Patagonian “false” fox or Zorro Gris or in southern Brazil, Graxaim (Lycalopex griseus) is endemic to southern South America.
Courtesy Antonio Carlos de Barros Corrêa, UFPE, Brazil.
Guanacos in the shrub-steppe of the Valdes Peninsula.
Darwin’s or Lesser Rhea, also known as nandu or choique, is the smaller of two species of this ratite in South America.
Courtesy Deensel, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons
Patagonian Mockingbird is one of at least ten birds endemic to the Patagonian steppe.
The steppe is sparsely populated by humans but overgrazing by sheep threatens desertification in many areas. Poaching and trade, especially in rhea feathers and young guanaco skins, has diminished several animal populations.
Merino sheep graze on the Valdes Peninsula. Sheep raising plays a major role in the economy of Patagonia and requires careful management to prevent overgrazing and desertification.
A number of natural reserves have been established throughout this vast area in efforts to conserve natural landscapes, flora, and fauna. The Valdes Peninsula in Chubat Province, Argentina, became a UNESCO World Heritage site in 1999 in recognition of the diverse marine life that comes to its shores and bays to breed, calve, and nurse. Of particular significance are the congregations of Southern Right Whale, but also important are the gatherings of Southern Elephant Seal, Southern Sea Lion and Orca. Resting areas and large breeding colonies of migratory shorebirds and Magellanic Penguin as well as the nearly intact example of Patagonian steppe on the peninsula itself add to the site’s scientific and conservation value.
Southern Right Whales come in large numbers to the bays surrounding the Valdes Peninsula to calve and nurse their young.
Courtesy Dave Mutter.
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Magellanic Penguins nest in large colonies along the coasts of Argentina and Chile.
Elegant crested tinamous are abundant on the Valdes Peninsula, where the Patagonian steppe is still relatively intact.
Courtesy Dave Mutter.
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Sources: “Patagonian Steppe.” One Earth. https://www.oneearth.org “Península Valdés.” UNESCO World Heritage. https://whc.unesco.org/en/list/937/ “Patagonian Steppe.” World Wildlife. https://www.worldwildlife.org/ecoregions/nt0805