Argentine Monte

• Category: Grassland, Tundra, and Human Biomes.
• Geographic Location: South America.
• Summary: Temperate-arid band of scrub-dotted steppe, home to many unique plant and animal species, many under threat from human activities and climate change.

The Argentine Monte corresponds to the most arid region of Argentina. It has a landscape of extensive plains and plateaus. The climate is temperate-arid, with rainfall of four to eight inches (10 to 20 centimeters) per year and marked annual temperature ranges. The vegetation is less diverse toward the south, with disappearing cactus and mesquite. The fauna is similar to that of the Patagonian steppe.

The Monte biogeographical province occupies a vast territory of more than 114 million acres (46 million hectares) that runs east of the Andes and toward the south. It is shaped like a sweeping band that starts in the northwest, in the province of Salta in the eastern foothills of the Andes, and becomes wider as it passes through the Patagonian steppe, going as far south as the province of Chubut, where it extends outward to the Atlantic Ocean. Despite its large extension, physiognomy, and floristic composition, the climatic conditions are fairly homogeneous.

The Monte goes from an elevation of 9,186 feet (2,800 meters) in the Andes foothills to sea level on the Atlantic coast. The westernmost part of the Monte transitions into the southern Andean steppe as elevation increases. To the east of the Rio Colorado, the Monte gradually becomes pampas. The fauna and flora in the Monte area are closely related to those of the Chaco biogeograhic province, with those in the central and southwestern areas showing similarities to the fauna and flora of Patagonia.

The climate is temperate-arid; the general area receives very little rainfall, although there is a marked and highly variable rainfall gradient from east to west, ranging from only three inches (7.6 centimeters) per year in the east to 10 inches (25.4 centimeters) of annual rainfall in the west. It rains primarily during the summer in the northern and central regions of the Monte, but in the colder south, the rainfall is distributed throughout the year, particularly south of the Rio Diamante. Another notable feature of the Monte is its fairly uniform temperature (isothermal), with average temperatures varying only from 55 degrees F to 64 degrees F (13 degrees C to 18 degrees C).

Scrublands

The shrub steppe occupies most of the Monte. The province is characterized by the presence of thorn scrub and dry grasslands; of shrub steppes of the Zygophyllaceae family; and with sparse gallery forests scattered throughout those areas; all are fed by a continuous if scant supply of water from the river systems that wind through this area or wherever underground water is available. The Argentine Monte is ,therefore, considered to be a warm scrub desert.

The most widespread and characteristic type of steppe is the jarillal or larrea (creosote bush) steppe. The jarillal tends to grow in pockets on sandy or rocky-sandy soil. The scrubs are 5 to 8 feet (1.5 to 2.5 meters) in height, not exceeding 10 feet (three meters). There also are cactus (in northern parts) and low trees and shrubs of medium size, such as Bulnesia spp., Monthea aphylla, Bougainvillea spinosa, Cassia aphylla, Cercidium praecox, Chuquiraga erinacea, Prosopis alpataco, and Zuccagnia punctata. The herbaceous cover is spatially variable, depending on rainfall and the effect of livestock.

In the Piedmont area, thorny steppes can be found, mainly featuring Plectrocarpa species. Other local types of shrubs are jumeales (Suaeda divaricata) and zampales (Atriplex spp.), which are associated with saline conditions; cardonales, which are giant cactus found on the northern rocky slopes; and the chilcales (Baccharis salicifolia), which are associated with wet soils. Other plant communities are made up of Prosopis scrubs, of Baccharis salicifolia (chilca), and Tessaria dodonaefolia (pájaro bobo) in humid places; Atriplex scrubs in clayish soils; and Suaeda divaricata and Allenrolfea vaginata in salty soils.

These scrublands are, for the most part, wide and open tracts of land. The hotter and drier areas are colonized by Larrea cuneifolia; near the rivers, the L. divaricata can be found. L. nitida grows in the cold areas of the Monte as well as on the slopes of the Andes.

Endemic Plants and Animals

Since the Oligocene, the Monte area has played an important role in the evolution of temperate biota on the continent and has led to a great level of endemism in the area. This region has several endemic species of flora and fauna. Among the endemic (unique to the area) plants are Romorinoa girolae (chica); Gomprhena colosacana var. andersonii from Sierra de las Quijadas National Park; and species with limited distribution in Argentina, such as verdolaga (Halophytum ameghinoi), a fleshy grass that grows in bogs.

One characteristic mammal fauna is the screaming hairy armadillo (Chaetophractus vellerosus). Others include the pink fairy armadillo (Chlamyphorus truncatus); carnivores such as puma (Felis concolor), South American gray fox (Pseudalopex griseus), patagonian weasel (Lyncodon patagonicus); the ungulate guanaco (Lama guanicoe); and the southern mountain cavy (Microcavia australis) and mara (Dolichotis spp.).

The red viscacha rat (Tympanoctomys barrerae) and the pink fairy armadillo (Chlamyphorus truncatus) are endemic to this biome; they are also listed as vulnerable according to the International Union for Conservation of Nature (IUCN) categories. The critically endangered rodent Ctenomys validus (tuco-tuco de Guaymallén) makes the Monte its home; vulnerable rodent species such as Octomys mimax, Andalgalomys roigi, and Salinomys delicatus also abound here, along with the mara (Dolichotis patagonum); and in some parts of the region the guanaco (Lama guanicoe) can be found.

The avian fauna of the Monte include the copetona or elegant crested tinamou(Eudromia elegans), cinnamon warbling finch (Poospiza ornata), inambú pálido or Darwin's nothura (Nothrura darwinii), burrowing parrot (Cyanoliseus patagonus), and others. Among the threatened birds are the pereguine falcon (halcón peregrino) and the chaco eagle (Harpyhaliaetus coronatus). There are also threatened reptiles species that inhabit the Monte such as the terrestrial turtle (Chelonoidis chilensis) and boa constrictor (Boa constrictor). Various species of reptiles can be found here like the red tegu (Tupinambis rufescens), the smooth fronted caiman (Pseusotomodon trigonatus), Patagonian pit viper (Bothrops ammodytoides), lampalagua (Boa constrictor occidentalis) and ringed hognose Snake (Lystrophis semininctus). There is less variety of amphibians found in the Monte, but one of importance is the Pleurodema nebulosa which is endemic to Argentina.

Protected Areas and Damage

There are many national and provincial protected areas within the central and southern parts of the Argentina Monte region. These include Los Cardones National Park (Salta province), Sierra de las Quijadas National Park (San Luis province), Talampaya National Park (La Rioja province), Valle Fértil Provincial Reserve (partially within the ecoregion), San Guillermo Provincial Reserve, Ichigualasto Provincial Park (San Juan province), Telteca Provincial Reserve, Nacuñán Provincial and Biosphere Reserve, Laguna de Llancanelo Provincial Reserve, Divisadero Largo Provincial Reserve (Mendoza province), Lihué Calel Provincial and National Park, La Humada Provincial Reserve, La Reforma Provincial Reserve, Salitral Levalle Provincial Reserve (La Pampa province), Cinco Chañares Provincial Reserve, Complejo Islote Lobos Provincial Reserve, Caleta de los Loros Provincial Reserve (Rio Negro province), El Mangrullo Provincial Reserve (Neuquén province), and Península de Valdés provincial Reserve (Chubut province). Despite the list being extensive, none of these protected areas are in the northern parts of the Monte biome and the total area of protection represents less than 2 percent of the Monte's surface area. This means that the large tracts of land needed by many species are not available for them to be able to complete their life cycles.

Serious damage is occurring and has occurred in the Monte, as well as the Chaco and Patagonia lowland, due to human (anthropogenic) activities—in particular, overgrazing by goats, sheep, and cattle; clear-cutting for fuel; and land clearing for agriculture, mining, and oil exploration. Human populations are found mainly in the oases in valleys and other locations close to rivers that make irrigation possible. This is why some sections of the Monte have been intensively altered while others are fairly untouched.

The forest also underwent significant depredation as man occupied patches and used wood for vineyards, mining, furniture making, construction, and fuel. Overgrazing and deforestation have caused erosion that has affected millions of hectares of the Monte. The deforestation and selective extraction of hardwood and clear-cutting of mesquite forests began in the late 19th and early 20th centuries and continues in the 21st century. These activities have caused pronounced desertification, disruption of habitats, and changes in the biodiversity and geographic ranges of many species. The effects of global warming, too, must be added to the list. A region of delicate moisture balance, the Argentine Monte harbors many species that depend on pockets of land and water where seasonal conditions are now moving toward climate extremes on a long-term basis.

Bibliography

Ezcurra, E., et al. "Architecture, Light Interception, and Distribution of Larrea Species in the Monte Desert, Argentina." Ecology, vol. 72, no. 1, 1991, pp. 23-34.

Ojeda, R. A., et al. "The MaB Reserve of Ñacuñán, Argentina: Its Role in Understanding the Monte Desert Biome." Journal of Arid Environments, vol. 39, no. 2, 1998, pp. 297-313.

Roig, V. G. "Desertification and Distribution of Mammals in the Southern Cone in South America." Latin American Mammalogy: History, Biodiversity, and Conservation, edited by M. A. Mares and D. Schmidly, University of Oklahoma Press, 1991, pp. 239-79.

Roig-Juñent, S., et al. "Monte Desert (Argentina): Insect Biodiversity and Natural Areas." Journal of Arid Environments, vol. 47, no. 1, 2001, pp. 77-94.

Salariato, Diego L., et al. "Threat Patterns for Endemic Plants of Argentina Reveal Disparity of Vulnerability and Protection among Spatially Associated Species Groups." Journal for Nature Conservation, vol. 74, Aug. 2023, doi.org/10.1016/j.jnc.2023.126422. Accessed 4 Nov. 2024.

Zampini, Iris Catiana, et al. "Propolis from the Monte Region in Argentina: A Potential Phytotherapic and Food Function Ingredient." Metabolites, vol. 11, Feb. 2021, p. 76, doi.org/10.3390/metabo11020076. Accessed 4 Nov. 2024.