Environmental Engineering Reference
In-Depth Information
converted into pasture land. Additionally, the income derived from the timber can
be very high. Some types of wood—such as mahogany—have high export mar-
ket values. Forest plantations are increasing, but only account for 3.8% of the total
world forest areas, or 140 million hectares. About 22% of the planted forests are
used for water and soil conservation and 78% for productive ends, including en-
ergy.
The harvesting of fuel wood is not the major cause of deforestation or of the
consequent desertification in developing countries. The exception occurs in sens-
itive areas, such as islands and elevated regions, where the vegetal cover is not
enough to supply the energy needs of growing and needy populations.
Even though the use of fuel wood is not the main cause of deforestation, there
are “hotspot” areas in the world in which its contribution to deforestation is of
major importance. As previously discussed, this occurs mainly in Africa, where a
large part of the population depends on fuel wood for cooking. Charcoal produc-
tion can also cause the degradation of vast forest areas. This is the case in northern
Thailand, which produces charcoal for Bangladesh. It is also the case in the states
of northern Brazil, which produce charcoal to supply the steel industry. Many times
the industry consumes “biomass waste” from sawmills, therefore being indirectly
responsible for deforestation, a fact that still occurs in several charcoal works and
metallurgy industries. Other industries that frequently use fuel wood without con-
sidering its origin are ceramics, gypsum, and food industries.
Besides desertification, deforestation significantly contributes to global warm-
ing due to CO
2
emission. Each hectare of tropical forest contains about 500 tons of
stored CO
2
, which goes into the atmosphere when the land is cleared.
The ecological footprint is a measure of human demand on the Earth's ecosystems;
it measures the amount of biologically productive land (measured in hectares) and
sea area required to produce the resources consumed by human activity and absorb
and render harmless the waste it generates.
Biologically productive land and sea include areas that (1) support human de-
mand for food, fiber, timber, energy, and space for infrastructure and (2) absorb the
waste products from the human economy (mainly CO
2
). Biologically productive
areas include cropland, forest, and fishing grounds but do not include deserts, gla-
ciers, or the open ocean.
