Geoscience Reference
In-Depth Information
Deforestation in Brazil
HUMAN IMPACT
Brazil provides a good example of the way in which government policy has a major impact on forest clearance.
Deforestation rates are strongly correlated with the economic health of the country. Much of Brazil's population is
concentrated on the east coast. It has been rising faster than employment opportunities and many landless peasants
flocked to the cities, where sprawling suburbs and favellas or shanty towns were constructed. Drought frequently
affected the agricultural north-east, causing further problems. The aim of the government became that of exploiting
the vast area of forest in Amazonia as well as reducing pressure on the eastern cities. It was believed to be an empty
land, rich in mineral, agricultural and water resources (
Figure 27.9
).
New roads were constructed to provide access to the forest lands of Rondonia and Pará. Government subsidies
were provided to encourage cattle ranching and resettlement of peasants displaced by changes in agricultural systems
in the south-east of the country. Satellite monitoring of forest burning during the drier season indicated losses of
about 3.5 M ha per year of primary forest in Brazilian Amazon. The rate of clearance does appear to have declined
since then for a variety of reasons. It has been realized that the fertility of the land is low unless it is carefully tended:
productivity of crops declined rapidly once the initial nutrient content was exhausted. Artificial fertilizers are expensive
because of high transport costs in such locations, so peasant farmers could not afford them and hence the soil fertility
declined. Even unsuitable crops were supplied to the settlers which did not grow well. Mining, especially of gold,
presents an added problem in some areas as toxic chemicals are used in ore concentration. The Brazilian currency
has become more stable after years of inflation. Land is therefore no longer such an important speculative asset, so
the capital cost of purchase has to be recouped by means of production on the land through timber sales or agriculture.
Figures for 2005/6 indicate the lowest levels of clearance since 1991. Increased enforcement and government
conservation initiatives have been proposed as important factors behind this decrease but, perhaps most relevant
of all, commodity prices were falling in this period. The Brazilian government is attempting to control the amount of
deforestation yet at the same time provide an adequate economy for those living in the area. It seems inevitable
that further demands will be made on this valuable resource.
For a variety of reasons we find that there is great pressure on the tropical rain forests of the world. Their area is
declining rapidly. Many ecologists believe that early in the twenty-first century only two significant areas of tropical
rain forest will remain - in western Amazonia and in central Zaire.
of individuals will decline. There will be greater pressure
on the surviving habitats and the remaining species will
be forced to live in a smaller area. As we have no clear idea
of the number of species in the rain forest it is hard to be
precise about the rate of species loss. Estimates range
from one species becoming extinct every half-hour as a
result of the destruction of rain forest to between one and
fifty species per day worldwide. Whatever the true
number, we are definitely increasing the rate of extinctions
which would occur naturally.
have yet to be discovered. How many species living in
the rain forest might be commercially exploited? There
may be much genetic diversity which is needed for
improved plant breeding to sustain our increasing
population. An example of this followed the blight which
developed on the US maize crop in 1970 and halved
production in an area which acts as the main cereal
surplus area of the world. Other varieties of maize which
were immune to that form of blight were sought and
suitable stock was found in Mexico. Later a new species
of maize was found in the Mexican rain forest which
was immune to at least seven major diseases and which
could be grown in cooler, damper environments. World
maize production should increase in areas previously
unsuitable. Ironically the maize was found in an area
undergoing clearance and only a few thousand stalks
remained.
Loss of natural resources
The rain forests act as a reservoir of natural resources
in the form of fruits, food, timber, raw materials and
medicines. Species extinction through clearance would
lead to the loss of any of these products. Greater concern
has been expressed about the loss of resources which
