Fjölrit RALA - 05.12.1999, Blaðsíða 57

OsvaldoA. Fernández et al.
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species is representing a definitive loss of genetic materials. On the whole this is a
subject poorly studied from a scientifíc point of view. Parodi (1934) has cited many
woody species of our arid and semi-arid rangelands as omamentals for parks, gardens
and streets.
One of our most serious concems about rangeland desertification is the extensive
damage caused to the soil. There exist good records of vegetation deterioration but
only a few of soil degradation. Excessive reduction of plant growth deprives the soil
of its protective plant cover thereby exposing it to soil erosion. This process is intensi-
fíed by the inherent fragility of the natural system. Dominant forms of degradation are
associated to wind and water-sheet erosion of a soil which is no longer sheltered by a
plant canopy and therefore lost by raindrop impacts and animal trampling. Intensive
and continuous trampling can reduce plant renewal by affecting seed germination sites
and seedling and adult plant growth. A clear evidence of wind or sheet soil erosion is
shown by the abundance of plants growing in a kind of pedestal with increasing root
exposure. The end result is a depleted fertility and in some cases physical degradation
of the top soil laver due to a decline in soil stmcture. Unabated soil erosion is consid-
ered to be one of the most serious environmental problems of our country’s range-
lands.
With a depleted plant cover and incipient or accentuated soil erosion, one of the
most precious and limiting factors of dry areas is affected: the water cycle. Water will
run away from the primary productive system. The geochemical and energy cycles
will also be altered. Recovery may take many years where there has been a change in
plant structure or a loss of species. The ecosystem may undergo irreversible desertifi-
cation where the top soil has also been lost since many of the biotic and abiotic stmc-
tural constituents are no longer present there.
A side effect of the grazing livestock industry has been its impact on the native
fauna. Several species of animals are disappearing in extensive areas, some of them
with exploitable potential. With depleted vegetation, many animals have less shelter
and food. and fewer places to reproduce in, and this applies to small animals such as
insects as well as to large mammals. Twenty to forty years ago, guanacos and os-
triches were common representatives of the fauna in extensive regions. Today, how-
ever, they have completely disappeared from the landscape and are recluded in more
inaccessible areas or are under the protection of national parks, and occasionally in
private ranches. Many animals in the native fauna have been considered predators or
grazing competitors and thereby undesirable for the rangeland livestock industry. As
such, they have been the target of an indiscriminate battle and “control programs” in-
cluding foxes, pumas (American lion), guanacos, American ostriches (lesser rhea),
deers, etc. Indiscriminate control methods like poisons or traps have also seriously
damaged non target species (e.g., birds, rodents, armadillos, etc.). Some predators
have been efficient in keeping under control serious pests of today such as comadrejas
and some rodents. Fortunately, human awareness of the importance of preserving the
very rich native fauna of the country is rapidly increasing, leading to some research
projects on its biology and utilization.
Desertification has recently become one of the most serious environmental prob-
lems of the country. The degradation process has to stop now. If not, it could be too