Geography Reference
In-Depth Information
NORTH AMERICA
Total: 18.4%
6
0
°
40°
Tropic of Cancer
20°
20
20
Equator
0°
SOUTH AMERICA
Total: 20.1%
20°
AREAS THREATENED
BY DESERTIFICATION
Tropic of Capricorn
Extreme desert
already
Very high risk
of desertification
High risk
of desertification
Moderate risk
of desertification
40°
40°
40°
40°
160°
140°
120°
80°
60°
40°
60°
60°
60°
60°
0
1000
2000
3000 Kilometers
0
1000
2000 Miles
Figure 10.13
Areas Threatened by Desertifi cation.
Deserts expand and contract cyclically, but nature's
cycles can be distorted by human intervention. This map shows areas threatened or affected by
desertifi cation.
Data from
several sources, including J. Turk et al.,
Environmental Science
, Philadelphia: Saunders,
1984, p. 305.
Desertifi cation has hit Africa harder than any of the
other continents (Fig. 10.13). More than half of Africa is
arid or semiarid, and many people farm the marginal, dry
lands of the continent. Land ownership patterns, the need
for crops and protein sources (both for local consumption
and for export), and power differences among groups of
people lead some farmers and ranchers to turn marginal,
semiarid lands into farm and ranch lands. Lands that are
available for farming or ranching may be used more inten-
sively in order to increase agricultural production (see
Chapter 13). In semiarid regions, the decision to farm
more intensively and increase agricultural production has
the unintended consequence of eroding the land, encour-
aging out-migration, and creating confl ict.
In Subsaharan Africa over the last 50 years, more
than 270,000 square miles (700,000 square kilometers)
of farming and grazing land have become desert, extend-
ing the Sahara Desert to the south. Some of the African
