Geoscience Reference
In-Depth Information
Plate 27.3
Subsistence agriculture on the banks of the Amazon near Iquitos, Peru. Cattle are grazing near by.
Photo: Peter Smithson
of land may drive people to move into forested areas with
or without government permission. Equally, pressure to
raise money for government can permit and encourage
commercial exploitation for timber or for subsequent
agricultural development, as in ranching schemes in parts
of Brazil. It is estimated that 60-70 per cent of deforesta-
tion is the result of cattle ranching schemes. Some agree-
ments are with multinational corporations that provide
money for investment in the hope of greater returns.
A major area experiencing rapid deforestation is
Borneo and Indonesian Kalimantan. Over the last three
decades it has provided a major source of tropical timber
imported into western Europe, Japan and China. As well
as wood, the cleared areas are now planted with oil palms.
They are very productive; a hectare of oil palms can yield
about 500 kg of oil. As a result, the area given over to this
crop is expected to rise to about 10 M ha by 2010 in
Indonesian Kalimantan alone. There is some good news
for the forests here in that the Malaysian and Indonesian
governments are proposing a core area to protect the
vegetation, but enforcement is often a major problem.
Impacts of deforestation
When rain forests are cleared we are losing more than a
collection of trees because of the implications which total
clearance would have on the world environment. Here we
will concentrate on the main impacts, which can be
summarized as (1) loss of species diversity; (2) loss of
natural resources; (3) environmental consequences; (4)
possible changes of climate on a local, regional and global
scale.
Loss of biodiversity
As we have seen, rain forests are incredibly diverse in terms
of the number of species which grow there and of those
which are dependent upon the forest for their survival. As
habitats are removed through clearance, so the number
