ThePampas (from theQuechua:pampa, meaning "plain"), also known as thePampas Plain, are fertileSouth American lowgrasslands that cover more than 1,200,000 square kilometres (460,000 sq mi) and include theArgentineprovinces ofBuenos Aires,La Pampa,Santa Fe,Entre Ríos, andCórdoba; all ofUruguay; andBrazil's southernmoststate,Rio Grande do Sul. The vast plains are anatural region, interrupted only by the low Ventana and Tandil hills, nearBahía Blanca andTandil (Argentina), with a height of 1,300 m (4,265 ft) and 500 m (1,640 ft), respectively. This ecoregion has been changed by humans, especially since the release of animals like cattle, pigs, and especially sheep onto these plains.[1]
The climate is temperate, withprecipitation of 600 to 1,200 mm (23.6 to 47.2 in) that is more or less evenly distributed throughout the year, making the soils appropriate foragriculture. The area is also one of the distinct physiography provinces of the largerParaná–Paraguay plain division.
This region has generally low elevations, whose highest levels generally do not exceed 600 metres (2,000 ft) in altitude. The coastal areas and most of the Buenos Aires Province are predominantly plain (with somewetlands) and the interior areas (mainly in the southern part of the Brazilian state of Rio Grande do Sul and Uruguay) have low ranges of hills (likeSerras de Sudeste in Brazil andCuchilla Grande in Uruguay). Low hills covered by grasslands are calledcoxilhas (Portuguese pronunciation:[koˈʃiʎɐs]) in Portuguese andcuchillas (Spanish pronunciation:[kuˈtʃiʝas]) in Spanish, and it is the most typical landscape of the countryside areas in the northern parts of the Pampas. The highest elevations of the Pampas region are found in theSierra de la Ventana mountains, in the southern part of Buenos Aires Province, with 1,239 metres (4,065 ft) at the summit ofCerro Tres Picos.
TheVentana mountains ranges are the most important system in the Pampas Plain.
The climate of the Pampas is generally temperate, gradually giving way to a morehumid subtropical climate in the north (Cfa, according to theKöppen climate classification, with aCwa tendency (drier winters) in the northwestern edge); a coldsemi-arid climate (BSk) on the southern and western fringes (likeSan Luis Province, western La Pampa Province and southern Buenos Aires Province); and anoceanic climate (Cfb) in the southeastern part (in the localities ofMar del Plata,Necochea, Tandil and the Sierra de la Ventana mountains, Argentina). Summer temperatures are more uniform than winter temperatures, generally ranging from 28 to 33 °C (82 to 91 °F) during the day. However, most cities in the Pampas occasionally have high temperatures that push 38 °C (100 °F), as occurs when warm, dry, northerly winds blow from southern Brazil, northern Argentina orParaguay. Autumn arrives gradually in March and peaks in April and May. In April, highs range from 20 to 25 °C (68 to 77 °F) and lows from 9 to 13 °C (48 to 55 °F). The first frosts arrive in mid-April in the south and late May or early June in the north.
Coxilhas (low hills covered by grasslands) inMorro Redondo, Rio Grande do Sul, Brazil
Winters are generally mild, but cold waves often occur. Typical temperatures range from 12 to 19 °C (54 to 66 °F) during the day, and from 1 to 6 °C (34 to 43 °F) at night. With strong northerly winds, days of over 25 °C (77 °F) can be recorded almost everywhere, and during cold waves, high temperatures can be only 6 °C (43 °F). Frost occurs everywhere in the Pampas, but it is much more frequent in the southwest than around the Parana and Uruguay Rivers. Temperatures under −5 °C (23 °F) can occur everywhere, but values of −10 °C (14 °F) or lower are confined to the south and west. Snow almost never falls in the northernmost third and is rare and light elsewhere, except for exceptional events in which depths have reached 30 cm (12 in). Springs are very variable; it is warmer than fall in most areas (especially in the west) but significantly colder along the Atlantic. Violent storms are more common as well as wide temperature variations: days of 35 °C (95 °F) can give way to nights of under 5 °C (41 °F) or even frost, all within only a few days.
Precipitation ranges from 1,400 millimetres (55 in) in the northeast to about 400 millimetres (16 in) or less in the southern and western edges. It is highly seasonal in the West, with some places recording averages of 120 millimetres (4.7 in) monthly in the summer, and only 20 millimetres (0.79 in) monthly in the winter. The eastern areas have small peaks in the fall and the spring, with relatively rainy summers and winters that are only slightly drier. However, where summer rain falls as short, heavy storms, winter rain falls mostly as cold drizzle, and so the amount of rainy days is fairly constant. Very intensethunderstorms are common in the spring and summer, and it has among the most frequent lightning and highestconvective cloud tops in the world.[2][3] The severe thunderstorms produce intensehailstorms, bothfloods andflash floods, and the most consistently activetornado region outside the central and southeastern US.[4]
The dominantvegetation types are grassyprairie and grasssteppe, in which numerous species of the grass genusStipa are particularly conspicuous. "Pampas grass" (Cortaderia selloana) is an iconic species of the Pampas. Vegetation typically includes perennialgrasses andherbs. Different strata of grasses occur because of gradients of water availability.
Why the pristine pampas were treeless regions has been much debated. Perhaps the most commonly cited explanation is seasonal drought. A related hypothesis is that grass roots compete for water and exclude tree seedlings. The effect might be increased by heavy, clayed soils which limit tap root penetration. Other causes that have been proposed are fires set by indigenous peoples for land clearance; the existence of heavy-bodied herbivores; and that the pampas are relicts of drier past climates. These explanations have been criticised as mono-causal. "Overall, we expect that low propagule pressure, abiotic stresses, biotic resistance, and a paucity of specific symbionts might have exerted a synergistic influence in slowing tree invasion rates ".[12]
TheWorld Wildlife Fund divides the Pampas into three distinctecoregions. TheUruguayan Savanna lies east of theParaná River, and includes all of Uruguay, most of Entre Ríos andCorrientes provinces in Argentina, and the southern portion of Brazil's state of Rio Grande do Sul. TheHumid Pampas include eastern Buenos Aires Province, and southern Entre Ríos Province. TheSemiarid Pampas includes western Buenos Aires Province and adjacent portions of Santa Fe, Córdoba, and La Pampa provinces. The Pampas are bounded by the drierArgentine Espinal grasslands, which form a semicircle around the north, west, and south of the Humid Pampas.
Winters are cold to mild, and summers are hot and humid. Rainfall is fairly uniform throughout the year but is a little heavier during the summer. Annual rainfall is heaviest near the coast and decreases gradually further inland. Rain during the late spring and summer usually arrives in the form of brief heavy showers and thunderstorms. More general rainfall occurs the remainder of the year ascold fronts and storm systems move through. Although cold spells during the winter often send nighttime temperatures below freezing,snow is quite rare. In most winters, a few light snowfalls occur over inland areas.
Central Argentina boasts a successful agricultural business, with crops grown on the Pampas south and west ofBuenos Aires. Much of the area is also used forcattle, and more recently, to cultivate vineyards in theBuenos Aires wine region. The area is also used for farming honey using Europeanhoneybees. These farming regions are particularly susceptible toflooding during thunderstorms. The weather averages out to be 16 °C (60 °F) year-round in the Pampas.
Starting in the 1840s but intensifying after the 1880s, European immigrants began to migrate to the Pampas, first as part of government-sponsored colonization schemes to settle the land and later as tenant farmers "working as either a sharecropper or as paid laborers for absentee landowners"[13] in an attempt to make a living for themselves.
However, many immigrants eventually moved to more permanent employment in cities as industrialization picked up after the 1930s. As a result, Argentina's immigration history in Buenos Aires Province is typically associated with cities and urban life, unlike in Entre Ríos Province and Santa Fe Province, where European immigration took on a more rural profile.
^Chaneton, Enrique J.; Mazía, Noemí; Batista, William B.; Rolhauser, Andrés G.; Ghersa, Claudio M. (2012). "Woody Plant Invasions in Pampa Grasslands: A Biogeographical and Community Assembly Perspective". In Myster, Randall W. (ed.).Ecotones Between Forest and Grassland. Springer.doi:10.1007/978-1-4614-3797-0_5.ISBN978-1-4614-3797-0. Retrieved7 May 2024., pp. 122-7.
^Meade, Teresa A. (2016).History of Modern Latin America: 1800 to the Present. Wiley Blackwell Concise History of the Modern World. Wiley.ISBN978-1-118-77248-5.
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