Fjölrit RALA - 05.12.1999, Blaðsíða 43

RALA Reportno. 200
Arid and semi-arid rangelands: two thirds of Argentina
Osvaldo A. Fernández and Carlos A. Busso
CERZOS and Departamento de Agronomia, Universidad Nacional del Sur, 8000 Bahía Blanca, Argentina
Tel: 54 91 86112717: Fax: 54 91 883933: E-mail: ofernanQcriba.edu.ar
ABSTRACT
Argentina is 3 million km2, with altitudes ranging from 7000 m in the Andes in the west to sea level in
the east. Therefore, the diversity in vertical and horizontal biogeographical regions is of extraordinary
magnitude. About two thirds of this vast territory is associated with arid and semi-arid rangeland eco-
systems. This work provides a comprehensive assessment showing the distribution of the main
rangeland phytogeographical regions ranging from the hot deserts and semi-deserts in the north to the
cold subantartic arid zones in Patagonia. The intensive use of these lands was initiated with the arrival
of Europeans in the region about 120-150 years ago. Although population density always remained
very low, they introduced their new domestic animals which contributed to vegetation degradation
and soil erosion because of overgrazing and poor management. Deforestation, fuelwood harvesting,
and occasionally plowing of non-arable lands were contributing factors to the present situation in
these regions where progressive signs of the various forms of land degradation are clearly evident.
Desertification has become one of the most serious environmental problems for the rangeland territo-
ries of Argentina. Fortunately the present devastation has not reached an irreversible stage. We can
foresee improvements in land use which may ensure its sustainability.
Kev words: Argentina, degradation, desertification, rangelands, Patagonia.
IMTRODUCTION
Argentina extends ffom latitude 22 to 55°S with a surface of 3 million km2, and is
3300 km in length and about 1200 km wide at its widest point. Altitude ranges from
7000 m in the Andes at the west to sea level in the east. The diversity in vertical and
horizontal biogeographical regions is of extraordinary magnitude over such a vast
territory, including subtropical rain forests; central temperate, fertile mollisol soils in
the Humid Pampas; extensive westem arid and semi-arid regions bordering the Andes
and cold subantartic zones at the south of the country. About two thirds of continental
Argentina are associated with arid and semi-arid rangeland ecosystems: the arid zone
is 170xl06 ha (60%) and the semi-arid zone is 48xl06 ha (15%).
Environmental conditions of the major phytogeographical rangeland regions of Ar-
gentina (Figure 1) allow for the development of a more or less continuous plant cover
where the vegetation is usually a combination of grass, herbaceous and woody spe-
cies. Femández et al. (1989a) have described the general characteristics and composi-
tion of shrublands in South America. There is naturally a broad ecological variation in
environmental factors within the territories shown in Figure 1, making each of them
unique in several ways. Some of these regions such as the Monte have shrubs as the
dominant plant strata, whereas others like the Caldenal constitute a very rich grass sa-
vanna with isolated trees and shrubs. The cold Patagonian desert is characterized by a
low shrubby steppe intermingled with tussock grasses. As expected, the boundaries
among these phytogeographical formations are characterized by the development of
wide ecotones.