Fjölrit RALA - 05.12.1999, Blaðsíða 56

54
Arid and semi-arid rangelands of Argentina
gional scale. Ignorance of subtle changes in ecosystem quality has been widespread
throughout the arid and semi-arid non cultivable territories of the country. It is possi-
ble for ranchers and land managers to remain ignorant of the slow deterioration of de-
sirable vegetation and the time lag for the disappearance of good forage plants with
subsequent consequences on field carrying capacity. Thus, ranch owners of today tend
to think that the present stage of the land is the natural situation and not the result of
more than one hundred years of mismanagement.
Proper identification of the progressive rangeland degradation in the country is im-
portant. Beyond a threshold level of accumulated loss, the natural system will fall into
a degree of deterioration were reversibility will be impossible, at least in terms of hu-
man life-span. A succession of good years can delay the perception of the degradation
process which is usually associated with intensification of land use. This optimistic
ignorance facilitates the way towards irreversible desertification.
As in many other parts of the world, ecological degradation of arid and semi-arid
regions in Argentina is associated with overgrazing, timber extraction, fuelwood har-
vesting, soil erosion and poor management. Livestock will graze not only grasslands
but also brushlands, forests, and almost any accessible place with some kind of forage
or browse. They will eat almost everything in dry years.
Trying to explain the adverse impact of livestock grazing upon the vegetation and
the ecosystem as a whole is a difficult task. It will require the use of adequate meth-
odologies under the supervision of rangeland specialists. Not many of the primitive
natural plant associations remain today.
Floristic impoverishment of natural pastures has led to changes in the kind of live-
stock in many areas of the Argentinean rangelands. Areas initially capable of sup-
porting cattle raising have been changed to caprine livestock production. Goats are
able to survive with the remnant rustic food, a consequence of previous misuse of
pasture resources. Successive stages for vegetation replacement in the Monte have
been as follows: (a) Non-regulated overgrazing has been mostly the routine manage-
ment, (b) the primitive climax vegetation disappears as a result, (c) cattle will browse
on shrubs and tree seedlings after the herbaceous layer has been degraded, (d) cattle is
replaced by goats in the most affected areas which are able to eat on any kind of plant
growth, (e) this sequence ends with presence of a new ecosystem where much of the
natural vegetation has been replaced by a poorly productive, thomy chaparral, (f) a
fmal situation may be characterized by soil erosion by water and wind. Plant species
or livestock can be different in different regions but the fmal result may be equivalent.
Sheep replace cattle in most of Patagonia; the end result is similar: it includes deserti-
fication and bare soil covered by a pavement of boulders as the upper soil layer is be-
ing taken off by the strong winds.
Loss of plant diversity in the native flora may affect the potential use of many spe-
cies producing resins, gums, wax, chemical and pharmaceutical products. There are
several plants in the Puna with therapeutic value like Pellaea nivea, Chenopodium
graveolens, Artemisia copa, Ephedra americana, E. breana, Azorella compacta and
Haplopappus rigidus (Cabrera 1957, Ruthsaz 1974). We could include many other
examples of desert plants which may represent valuable materials for human use in
the country according to circumstantial and historical evidence. Disappearance of wild