Geographical location and climate
Patagonia lies in Chile and Argentina, between latitude 39°S and 55°S, and covers an area of more than 900,000 km2. Politically, the boundary in the Southern Patagonian ice field remains to be settled. It has five distinctive habitats: ice fields, high Andes, forest, scrub and steppe. The steppe of Argentina is one of the largest single habitats in the world and its environment is shaped by low humidity, relent-less winds and impoverished soil.
In the west and south the Andes shadow the steppe from the rain, resulting in a desiccated plateau that gives way towards the Atlantic Ocean to low, flat or gently undulating plains. The annual precipita-tion of 4m at the eastern foothills of the Andes (at about 42°S) drops over a distance of 180 km to the east to 15 cm. The moist At-lantic air increases the annual rainfall on the east coast to 24cm, al-lowing for lusher vegetation.
Although the average annual wind intensity varies between 15 and 22 km/h, in spring and summer dry, dust laden, gusts of over 100 km/h are frequent. It takes the breath away of those who experi-ence it.
Over 70% of the topsoil is coarse-textured sand or sandy-loam, poor in minerals and organic matter. In the hollows of the plains are freshwater lakes, ponds with brackish water or saltpans, intersected by the streams and rivers flowing into the Atlantic Ocean.
In pre-Columbian Argentina the Puelche and Tehuelche nomadic hunters lived off guanacos, foxes and rheas. Today only about 100 Tehuelche remain. Patagonia is still one of the most sparsely popu-lated areas on Earth (1 person/square km). Over 95% of Argentin-ian Patagonia are under private ownership and only about 1% of the steppe and scrub habitats enjoy strict protection. Monte León National Park (Spanish: Parque Nacional Monte León), established in 2004 on a former 165,000 acre (~ 67,000 ha) sheep ranch in the east of Santa Cruz Province, is the latest and most significant at-tempt to preserve the region’s unique flora and fauna. It is arid grassland is beautified by 40 km of Atlantic coast with breeding colonies of 60,000 pairs of Magellanic penguins Spheniscus magel-lanicus and numerous marine rock cormorants Phalacrocorax ma-gellanicus. With the declining sheep industry and increase in tour-ism two further ranches (estancias) have been purchased and their habitat protected by the provincial administration: Estancia la Es-peranza (Ranch of Hope) located on the buffer zone of the Valdes Peninsula with a total size of over 15,000 acres (6,000 ha) and supported by the World Land Trust; and the Esperanza Reserve covering 17,000 acre (7,000 ha) with more than 12 km of coastline.
Biodiversity of the steppe flora
The whole of Argentina has an estimated 10,000 species of vascular plants (Zuloaga & Morrone, 1994-1999), while Argentinian Patago-nia has about 2,400 (Correa, 1998), about half of which ~1000 species are from the Patagonian steppe (verbal communication from biologist Claudia Guerrido). Asteraceae (daisies) and Poaceae (grasses) families are the most numerous. There is a high number of endemic genera (~15) and species (~300). Endemism reaches 60% in the Leguminosae genus and 33% in Compositae. Other en-demic species are in the genera Benthamiella, Duseniella, Eria-chaenium, Larrea, Llepidophylum, Lycium, Neobaclea, Pantacantha, Philipiella, Prosopis, Saccardophyton, Schinus and Xerodraba.
Summer droughts, sandy soil and persistent winds, result in grass-land plains too dry to support a forest but not parched enough to be classified as a desert. The plants are xeromorphic, morphologically adapted to cope with severe water deficits. Shrubs, like Junellia tridens and Nassauvia glomerulosa, have very small sclerophyllous leaves. Other plants are adapted to these adverse climatic condi-tions with a covering of glandular hairs or a waxy layer over the surface of their leaves. The dwarf cushion growth habit of the Acantholippia, Benthamiella, Nassauvia and Verbena genera, Mulinum spinosum, and Brachyclados caespitosus is another useful adaptation. The tuft grasses of Poa and Stipa have leaves with a thick cuticle, convoluted laminae and bunch growth habits. Anarthrophyllum, Berberis and Schinus represent shrubs growing up to 3m high. Valleys and lowlands with higher water levels provide habitats suitable for sedges Eleocharis, rushes Juncus and grasses Agrostis, Hordeum, Polypogon, while halophytic plants Distichlis, Ni-trophila, Puccinellin, Sarcocornia inhabit the saline areas.
Many steppe plants are armed with spines to protect them from grazing herbivores. Their flowers are conspicuous to attract pollina-tors and in spring draw the eye of the observant visitor.
Krystyna Szulecka 30.09.1012