Patagonian grasslands

Category: Grassland, Tundra, and Human Biomes.

• Geographic Location: South America.
• Summary: The Patagonian grasslands are experiencing land degradation because of a variety of stresses, mainly from overgrazing and climate change.

Patagonia is a mostly cold, semi-desert region in Argentina and Chile that covers a variety of settings, mostly shrub-covered steppes, with sub-Andean grasslands in the southern portions. Almost all of Patagonia’s grazing lands are on the cool, semiarid steppes of the extra-Andean territory of southern Argentina, and extending into Chile around the Straits of Magellan. These mainly grass-covered steppes comprise approximately 289,577 square miles (750,000 square kilometers).

A description of Patagonia’s climate is hampered by the low density and uneven distribution of weather stations, one station for every 15,444 square miles (40,000 square kilometers). However, it is known that the climate is influenced mostly by warmer-than-land Pacific Ocean air masses that are forced inland by prevailing westerly winds. The Andes Mountains range stands between this moist air and the Patagonian steppes, creating an extensive rain shadow that controls regional climatic patterns. There is a very steep gradient of mean annual precipitation, decreasing toward the east from 157 inches (4,000 millimeters) in the eastern foothills of the Andes to 6 inches (150 millimeters) on the central plateau, some 112 miles (180 kilometers) east of the mountains.

Annual precipitation in different areas of the Patagonian grasslands reaches variations greater than 45 percent from the more moist to the drier end of the gradient. The eastern coastal strip is influenced by moist air from the Atlantic, leading to somewhat higher annual precipitation rates of 8–9 inches (200–220 millimeters) that is evenly distributed seasonally, as opposed to the generally heavier winter rainfall in most of Patagonia.

Some of the variation found in the precipitation rates can be associated with the El Niño-La Niña cycles of temperature and humidity influence, but scientists report a longer-term cycle for southern Patagonia: a significant decrease in precipitation during 1930 to 1960, followed by a reversal of this trend, with significant increases over the subsequent 30 years.

Mean annual temperatures range from 61 degrees F (16 degrees C) in the north to 41 degrees F (5 degrees C) in the far south of Tierra del Fuego. Mean temperatures of the coldest month, July, are above the frost mark, although absolute minimum temperatures can be below minus 4 degrees F (minus 20 degrees C). Scientists reported a significant increase in mean annual temperatures over the last sixty years of the twentieth century for Río Gallegos, a provincial capital located on the steppes surrounding the Straits of Magellan, which has one of the longest regimes of weather record-keeping. Many also believe the area is in the midst of a drying and warming trend, which will continue throughout the twenty-first century, and thus temperatures are expected to continue to rise as rainfall decreases. This trend is also seen as consistent with predictions of climate change from global circulation models that simulate enhanced atmospheric carbon-dioxide concentration.

Another issue impacting temperature rises has been more frequent fires throughout the region that demolish trees, which keep the ground cooler. Storms and lightening have increased over the twentieth and twenty-first centuries in the area due to circulation of the subtropical air masses, which has led to more lightening-ignited fires.

Strong, persistent westerly winds are an outstanding characteristic of Patagonia’s climate. Because there is relatively little land in the Southern Hemisphere to act as a barrier, westerlies can gain impressive momentum, with annual intensities of 9–14 miles per hour (15–22 kilometers per hour) and frequent gusts of more than 62 miles per hour (100 kilometers per hour), mostly in spring and fall. Strong winds increase evaporation, and can have a considerable influence on the productivity of sheep husbandry, through the chill effect.

Soils and Biota

Soil textures can explain a large portion of the variation in dominant plant life form, such as grasses versus shrubs, across the region. Small-scale, uneven distribution of various of soils tends to increase with aridity, and important differences in leaching and salinity occur over short distances, possibly causing soils within a taxonomic group to function differently. More than 90 percent of Patagonian soils are degraded to some degree, mostly because of improper land use. More than 70 percent of the topsoil is coarse-textured, ranging from sand to sandy-loam. The sandy loam is composed of sand, silt, and clay.

In addition, severe desertification affects 19–30 percent of the region. Some of the most dramatic erosion processes occur in the form of sand accumulations that, in the early 1970s, covered approximately 32,819 square miles (85,000 square kilometers). Both aerial photography and satellite imagery indicate that many of these accumulations are about 100 years old, suggesting that the rate of wind-driven erosion has been accelerated by the introduction of domestic livestock, due to the fact that the livestock trample the fragile vegetation of the grasslands, resulting in native plant die-offs. Fewer plants means that fewer roots hold the Earth together, and nothing retains moisture in the ground, which results in the desertification of the grasslands. The Patagonian grasslands, by capturing and storing carbon, are essential to helping manage climate change effects in the area; their degradation undermines this vital ecoservice.

Although the Patagonian Grasslands biome was generally considered to have evolved under light grazing pressure, pre-European numbers of guanacos (Lama guanicoe), the only native ungulates, may have been higher than previously thought, with the highest estimates being around fifty million. In the late twentieth and early twenty-first centuries, guanaco populations fell to around two million for all of Patagonia due largely to sheep grazing and overhunting.

Throughout the beginning of the twenty-first century, sheep farmers began to recognize the dangers of overgrazing on the land and native flora and fauna, such as greenhouse gas emissions, land degradation, and water pollution. Therefore, in an effort to address their environmental impacts, farmers, often working with fashion designers, developed alternative methods of grazing and raising their animals. Restorative wool, for example, is an attempt at creating a more natural grazing process for sheep. Some farmers have opted to receive a grassland certification (Grassland Regeneration and Sustainable Standard, also known as GRASS) for instituting regenerative grazing practices. These efforts are meant to curb the environmental effects of livestock on the area.

The lesser rhea (Pterocnemia pennata pennata) and the upland goose (Cloephaga picta) are the most conspicuous birds. The Patagonian hare (Dolichotis patagonum), skunk (Conepatus humboldtii), and the small armadillo (Zaedyus pichyi), together with the lesser rheas, are important zoogeographical indicators. There are significant numbers of predators, such as red fox (Dusicyon culpaeus), gray fox (Ducisyon griseus), and puma (Felis concolor). Red foxes and pumas are responsible for most predation; lamb losses due to red-fox predation can be as high as 75–80 percent.

Bibliography

Bellotto, Maria. “Eileen Fisher's Regenerative Wool: Restoring Patagonia's Grasslands with Sheep.” Lampoon Magazine, 23 July 2021, lampoonmagazine.com/article/2021/07/23/regenerative-wool-patagonia-eileen-fisher/. Accessed 24 Oct. 2024.

Elbers, Joerg and Javier Beltran. Patagonian Steppe—Developing a Transboundary Strategy for Conservation and Sustainable Management. Temperate Grasslands Conservation Initiative, 2010.

Gold, Raphi. “Plans to ‘Rewild’ Guanacos in Argentina Trigger Scientific Debate and Legal Threats.” State of the Planet, Columbia Climate School, 22 Oct. 2024, news.climate.columbia.edu/2024/10/22/plans-to-rewild-guanacos-in-argentina-trigger-scientific-debate-and-legal-threats/. Accessed 24 Oct. 2024.

Gonzalez, Sofia Laura and Luciana Ghermandi. "Overgrazing Causes a Reduction in the Vegetation Cover and Seed Bank of Patagonia Grasslands." Plant and Soil, vol. 464, pp. 75-87, 10 Apr. 2021, doi.org/10.1007/s11104-021-04931-y. Accessed 14 Oct. 2024.

Herzog, Sebastian K., Rodney Martinez, Peter M. Jorgensen, and Holm Tiessen, eds. Climate Change and Biodiversity in the Tropical Andes. Inter-American Institute for Global Change Research (IAI), and Scientific Committee on Problems of the Environment (SCOPE), 2011.

“The Patagonian Grasslands: Guardians of the Windswept Plains.” LAC Geo, 7 Feb. 2024, lacgeo.com/patagonian-grasslands-argentina. Accessed 24 Oct. 2024.

Suttie, J. M., S. G. Reynolds, and C. Batello. Grasslands of the World. Plant Production and Protection Series No. 34. Rome, Italy: Food and Agriculture Organization (FAO) of the United Nations, 2005.

Wernick, Adam. "Fire and Climate Change Are Altering Patagonia's Ecosystems." The World from PRX, 10 Feb. 2022, theworld.org/stories/2022/02/10/fire-changing-patagonia-s-ecosystems. Accessed 24 Oct. 2024.