226 CHAPTER 10 Sustaining Terrestrial Biodiversity: The Ecosystem Approach
and establishing vast plantations of crops such as soy-
beans and oil palm.
The degradation of a tropical forest usually begins
when a road is cut deep into the forest interior for log-
ging and settlement (Figure 10-5). Loggers then use
selective cutting (Figure 10-6, top) to remove the best
timber. When these big trees fall, many other trees fall
with them because of their shallow roots and the net-
work of vines connecting the trees in the forest’s can-
opy. Thus, removing the largest and best trees by selec-
tive cutting can cause considerable ecological damage
in tropical forests, although the damage is much less
than that from burning or clear-cutting areas of such
forests. Most of this timber is used locally and much of
it is exported, but a great deal is also left to rot.
Foreign corporations operating under government
concession contracts do much of the logging in tropi-
cal countries. Once a country’s forests are gone, the
companies move on to another country, leaving eco-
logical devastation behind. For example, the Philippines
and Nigeria have lost most of their once-abundant
tropical hardwood forests and now are net importers
of forest products. Several other tropical countries are
following this ecologically and economically unsustain-
able path.
After the best timber has been removed, timber
companies or the government often sell the land to
ranchers. Within a few years, the cattle typically over-
graze the land and the ranchers move their operations
to another forest area. Then they sell the degraded land
to settlers who have migrated to tropical forests hoping
to grow enough food to survive. After a few years ofFigure 10-16Natural capital
degradation: large areas of tropical
forest in Brazil’s Amazon basin are
burned each year to make way for
cattle ranches, small-scale farms, and
plantation crops such as soybeans.
Questions: What are three ways in
which your lifestyle probably contrib-
utes to this process? How, in turn,
might this process affect your life?
crop growing and erosion from rain, the nutrient-poor
tropical soil is depleted of nutrients. Then the settlers
move on to newly cleared land to repeat this environ-
mentally destructive process.
The secondary causes of deforestation vary in dif-
ferent tropical areas. Tropical forests in the Amazon
and other South American countries are being cleared
or burned (Figure 10-16) mostly for cattle grazing and
large soybean plantations. In Indonesia, Malaysia, and
other areas of Southeast Asia, tropical forests are be-
ing cut or burned and replaced with vast plantations of
oil palm, whose oil is used in cooking, cosmetics, and
biodiesel fuel for motor vehicles (especially in Europe).
In Africa, tropical deforestation and degradation are
caused primarily by individuals struggling to survive by
clearing plots for small-scale farming and by harvesting
wood for fuel.
Burning is widely used to clear forest areas for ag-
riculture, settlement, and other purposes. Healthy rain
forests do not burn naturally. But roads, settlements,
and farming, grazing, and logging operations fragment
them (Science Focus, p. 195). The resulting patches of
forest dry out and readily ignite.
The burning of tropical forests is a major compo-
nent of human-enhanced global warming, which is
projected to change the global climate at an increas-
ing rate. Scientists estimate that globally, these fires
account for at least 20% of all human-created green-
house gas emissions. They also produce twice as much
CO 2 , annually, as all of the world’s cars and trucks emit
(Concept 10-1C). The large-scale burning of the Amazon
(Figure 10-16) accounts for three-fourths of Brazil’sHerbert Giradet/Peter Arnold, Inc.