Geoscience Reference
In-Depth Information
support to protect the environment and this is not always
forthcoming.
There is considerable scientific debate about the area
of reserved land which is needed to sustain suitable
habitats for animals as well as plants. A few very large areas
are seen as more appropriate than many smaller sites.
Unfortunately, even those sites which have been agreed are
not unaffected by exploitation. Many reserves exist on
paper only, with no policing or support, through lack of
financial resources. It is not unknown for logging to
continue even in areas designated as parks. On the
Indonesian island of Siberut, off Sumatra, plans were
advanced to log 1,500 km
2
of virgin forest in a reserve and
replace it with an oil palm plantation.
Ideally what is needed for the rain forest is the
maintenance of as much as possible of the present variety
of species and habitats and the restoration of damaged
areas. At the same time, the forests must be used to
generate revenue at a greater rate than could be obtained
by clearance and replacement by some other use (
Figure
otherwise, in a world where economic pressures dominate,
the forests will disappear. Is this approach possible?
Estimates have been made of the economic returns of
different types of land use in a forested area of eastern Peru
(
Table 27.2
).
Low-intensity exploitation of nuts, fruit,
rubber and other products together with minor logging
could generate greater income than that from conven-
tional methods of forest clearance and ranching. Even
then, care must be taken over transport and marketing.
The products need to have some international value to
compensate for the loss of hard currency obtained from
the sale of tropical hardwood. Ironically the decrease in
the sale of such timber could increase its value unless
demand declined, placing even greater pressure on the
forests. See additional case study 'Paraguay, capital of
conservation and development' on the support website at
Efforts have been made to develop the idea of eco-
tourism to provide additional income for forested areas.
Tourists are encouraged to visit an area to view the beauty
of virgin tropical rain forest (
Plate 27.4
).
Although still
on a small scale in countries such as Costa Rica, Belize
and Ecuador, and not without its own problems, it
does represent an additional source of hard currency
if correctly operated. The benefit here is that income is
generated at the local level through guides, transport and
accommodation, with no major disturbance of the forest
as long as the development does not get too extensive.
CONCLUSION
The humid tropics are a sensitive environment. They
occupy the hotter parts of the world where solar energy
is absorbed and transferred towards deficit parts of the
(
a)
Bulk density
(
b)
Phosphorus
12
1.4
10
1.2
1.0
8
0.8
6
0.6
0.4
4
2
0
0.2
0 2 4 6 81012141618
Age of pasture (years)
0 2 4 6 81012141618
Age of pasture (years)
(
d)
pH
7.0
6.5
(
c)
Calcium and magnesium
6.0
8
6
5.5
4
2
5.0
4.5
Figure 27.10
Changes in soil properties
after conversion of tropical
forest to pasture.
Source: After Park (1992)
0
4.0
0 2 4 6 81012141618
Age of pasture (years)
0 2 4 6 81012141618
Age of pasture (years)
