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ENVIRONMENTAL IMPACTS
Impacts on Species Composition
The original vegetation that covered most of the valley floor
and lower slopes was likely tropical dry forest (pre-montane
and low montane). The dry tropical forest existed in Vilcabamba
because of the overall aridity of the valley, and the marked
dry season. In this type of forest, many species lose some
or all of their leaves in the dry season. At higher elevations,
the forest gave way to shrubs, and above this, to natural
grassland.
It is widely believed that the huilco tree was a dominant
species prior to deforestation, although there is some dispute
about whether it was native to the area, or introduced by
the Inca. While there is no undisturbed primary forest left
in the valley, there are small wooded areas that include the
huilco. (For more information on the huilco tree, see Section
3 under Gullies.)
Land-clearing for wood, agriculture and pasture has of course
led to extinction of some, perhaps many, endemic species.
(An endemic species is one not found outside a relatively
limited area.) It also led to the introduction of exotic species
(those not original to the area), and to changes in species
composition. Exotic species are not limited to those that
were purposefully brought in for agriculture. Many species
were introduced as a by-product of human activity. The acacia,
for example, soon became widespread with the introduction
of livestock. The seeds are dispersed by the animals, which
graze on the plant, and release the seed back to the soil
when they defecate. The digestive process helps prepare the
seed for easier sprouting, and the manure also acts as a fertilizer,
giving the seed a vigorous start. (There is more information
on the acacia under the Arid
Uplands heading in Section 3.)
Impacts
on Sloping Lands
While the valley of Vilcabamba has a relatively broad,
fertile base, a high proportion of the land is still
steeply sloping. Soils are already thin on steep lands,
and the risk of erosion is high. Erosive forces include
both the heavy rains in the wet season, and the hot
dry winds in the dry season. According to most studies,
and to land classification systems, an undisturbed cover
of vegetation is generally best for such areas. But
given population pressures and poverty, even steeply
sloping lands in the valley are farmed or cleared for
pasture. Practices to minimize erosion (e.g., terracing
or the planting of windbreaks) are not in general use.
These issues are by no means unique to Vilcabamba. Most
of the Ecuadorian Andes have been deforested, and have
experienced massive erosion.
Impacts on the Hydrological Cycle
Rainwater runoff is generally slower where the soil
is deeper, and where there is more vegetative cover
and an associated root system. Thus human activity in
the valley has probably resulted not only in more intensive
occasional surges and flash floods (see the Rivers and
Hydrology heading in Section 1), but also in reduced
soil moisture, and possibly in lower flow in streams
and rivers between surges. Though data for scientific
analysis are lacking, there is anecdotal evidence that
recent forest destruction in rain catchment areas throughout
Loja province has seriously reduced both the quantity
and quality of water supplies.
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This
water feeds low-erosion micro-sprinklers in coffee/fruit
huertos. The orchards were established where there was
previously overgrazed pasture. The fruit trees and other
plantings in the huertos have not only improved living
standards, but have also created richer habitat and
forage for birds and other species. The farm families
are strongly committed to protecting the forests of
the watershed from which their irrigation water comes.