326 CHAPTER 13 Land Resources
countries (see Chapter 18). Highly developed countries
consume more than three-fourths of the remaining 50
percent of harvested wood for paper and wood products.
Loggers harvest trees in several ways—selective cut-
ting, shelterwood cutting, seed tree cutting, and clear-
cutting (see What a Scientist Sees). Selective cutting, in
which mature trees are cut individually or in small clus-
ters while the rest of the forest remains intact, allows
the forest to regenerate naturally. Selective cutting has
fewer negative effects on the forest environment than
other methods of tree harvest, but it is not as profit-
able in the short term because timber is not removed
in great enough quantities.
The removal of all mature trees in an area over an
extended period is shelterwood cutting. In the first
year of harvest, undesirable tree species and dead or
diseased trees are removed. Subsequent harvests occur
at intervals of several years, allowing time for remain-
ing trees to grow. Little soil erosion occurs with this
method of tree removal, even though more trees are
removed than in selective cutting.
In seed tree cutting, almost all trees are harvested
from an area; a scattering of desirable trees is left behind
to provide seeds for the regeneration of the forest.
Clear-cutting is harvesting timber by removing all
trees from an area and then either allowing the area to
reseed and regenerate itself nat-
urally or planting the area with
one or more specific varieties of
trees. Timber companies prefer
clear-cutting because it is the most
cost-effective way to harvest trees.
Clear-cutting in small patches
actually benefits some wildlife species, such as deer and
certain songbirds. These species thrive in the regrowth of
trees and shrubs that follows removal of the overhead can-
opy. However, clear-cutting over wide areas is ecologically
unsound. It destroys biological habitats and increases soil
erosion, particularly on sloping land, sometimes degrad-
ing land so much that reforestation doesn’t take place.
Mudslides on steep hillsides that were clear-cut can follow
heavy rains, damaging properties and roads and killing
people. Sometimes the land is so degraded from clear-
cutting that reforestation does not take place. Clear-cut
areas at lower elevations are usually regenerated success-
fully, whereas those at high elevations are often difficult
to regenerate. Obviously, most recreational benefits of
forests are lost when clear-cutting occurs.long-term commercial harvest of timber and nontim-
ber forest products. Sustainable forestry also at tempts to
sustain biological diversity by providing improved habi-
tats for a variety of species, to prevent soil erosion and
improve soil conditions, and to preserve watersheds that
produce clean water. Effective sustainable forest manage-
ment involves cooperation among environmentalists,
loggers, farmers, indigenous peoples, and local, state,
and federal governments.
When logging adheres to sustainable forestry princi-
ples, unlogged areas and habitat corridors are set aside
as sanctuaries for organisms. The
purpose of habitat corridors is
to provide animals with escape
routes, should they be needed,
and to allow them to migrate so
they can interbreed. (Small, iso-
lated, inbred populations may have an increased risk
of extinction.) Habitat corridors may also allow large
animals such as the Florida panther to maintain large
territories. Some scientists question the effectiveness
of habitat corridors, although recent research in frag-
mented landscapes suggests that habitat corridors help
certain wildlife populations persist. Additional research
is needed to determine the effectiveness of habitat cor-
ridors for all endangered species.
The actual methods for ecologically sustainable for-
est management that distinguish it from traditional for-
est management are under development. Such practices
vary from one forest ecosystem to another, in response
to different environmental, cultural, and economic con-
ditions. In Mexico, many sustainable forestry projects
involve communities that are economically dependent
on forests. Because trees have such long life spans, sci-
entists and forest managers of the future will judge the
results of today’s efforts.
Harvesting Trees According to the U.N. Food and
Agriculture Organization (FAO), about 3.4 million m^3
(120 million ft^3 ) of wood are harvested annually (for fuel-
wood, timber, and other products). The five countries with
the greatest tree harvests are the United States, Canada,
Russia, Brazil, and China; these countries currently pro-
duce more than half the world’s timber. About 50 percent
of harvested wood is burned directly as fuelwood or used
to make charcoal. (Partially burning wood in a large kiln
from which air is excluded converts the wood into char-
coal.) Most fuelwood and charcoal are used in developing
habitat corridor
A protected zone
that connects
isolated unlogged or
undeveloped areas.clear-cutting A
logging practice in
which all the trees in
a stand of forest are
cut, leaving just the
stumps.