Parched ground during drought in Namibia
Case study: drought in the Sahel
Map showing location of Sahel
Food for distribution Yabelo area, Southwest Ethiopia
The
Sahel region of Africa has been suffering from drought on a regular
basis since the early 1980s. The area naturally experiences alternating
wet and dry seasons. If the rains fail it can cause drought.
In
addition to natural factors, the land is marginal. Human activities such
as overgrazing, overcultivation and the collection of firewood can lead
to
desertification, particularly when combined with drought conditions.
The result is crop failure,
soil erosion,
famine and hunger: people are then less able to work when their need is
greatest. It becomes a vicious circle and can result in many deaths,
especially among infants and the elderly. In Niger in 2004, the
situation was made worse when a plague of locusts consumed any remaining
crops. In these cases, people rely on food aid from the international
community.
On its own, food aid is unsustainable in the long term.
What is really needed is development aid, which involves educating the
local community in farming practices.
DESERTIFICATION
Desertification of the arid lands of the world has been
proceeding--sometimes rapidly, sometimes slowly--for more than a
thousand years. It has caused untold misery among those most directly
affected, yet environmental destruction continues. Until recently, few
if any lessons seemed to have been learned from the past. It was not until
the 20th century--when easy land expansion came to an end--that
governments and people finally realized that continued careless
degradation of natural resources threatened their future.
INTERNATIONAL DIRECTIONS
The decade of the 1950's witnessed the first worldwide effort to call
attention to the problems and potentials of arid regions. It started
when the United Nations Educational, Scientific, and Cultural
Organization (UNESCO) launched its Major Project on Scientific Research
on Arid Lands in 1951.
The impetus generated by the UNESCO project led to expanded interest in,
and support of, arid lands studies throughout the world. By 1970,
knowledgeable scientists were well aware of the magnitude of the land
destruction that had taken place in the past, and that was becoming even
more serious as population pressures increased.
At about the same time, one event served to focus world attention on
desertification: the 1969 to 1973 drought in the African Sahel.
Recognition of the severity of the drought affecting six countries on
the southern border of the Sahara (Mauritania, Senegal, Mali, Upper
Volta, Niger, and Chad) was slow to develop.
Desertification Characteristics in Spain
During the past several centuries, heavy grazing by sheep and goats has
led to the destruction of much of the herbaceous and woody vegetation on
the noncultivated land (Albareda, 1955). Water erosion has been severe
on the overgrazed slopes as a result of the loss of vegetative cover and
the torrential character of the rains. Cutting of wood for fuel and
construction and the extension of dryland farming into the pasture lands
has accompanied overgrazing. Plant cover has changed to a more xeric
type and surface runoff has increased.
A monoculture of grain in the cultivated regions has depleted the native
fertility of the soil and has been responsible for increasing the
susceptibility of the land to wind and water erosion. Extended droughts
from time to time have served to accelerate desertification. Water
erosion is severe nearly everywhere on sloping land.
Salinization and waterlogging do not affect a high percentage of the
total cultivated land in Spain but important and large areas of affected
soils do occur in irrigated valleys. The major salt-affected areas in
the northeast are in the Ebro River watershed in the vicinity of
Zaragosa and Herida. Seepage water from irrigation on the higher land
has caused waterlogging and salinization of lower-lying areas (Martinez,
1978). Gypsum is a common constituent of the soils.
The other major salt-affected areas are in southwest Spain near the
coast. The soils are composed of fine-textured sediments that were
subjected regularly to flooding by seawater in the past. Surface and
internal drainage of the irrigated land is poor and water tables
generally are close to the surface. Pumping is required to lower the
water tables (Ayers et al., 1960).
Magnitude of Desertification
Approximately 50 percent of Spain is arid. In the arid regions about 70
percent is moderately desertified and 30 percent is severely desertified
Virtually all of the rangeland has suffered severe land degradation.
Range productivity is probably stabilized at a low level now, with
little improvement anywhere. Erosion continues on the extensive dryfarm
lands except in a few places where soil and water conservation measures
have been instituted. Soil fertility remains low.
Salinization and waterlogging affect about 240,000 hectares of irrigated
land to various degrees (Ayers et al., 1960). Reclamation has been
undertaken in several areas. Because of the need for more agricultural
production and the gradual worsening of the salt problem, irrigation has
received special attention in recent decades. Much remains to be done.
Soil and water conservation techniques for dryland farming are known but
their application to the field is limited. Range management is not a
well-supported science in Spain. Considerable progress has been made in
the reclamation of saline soils and procedures for doing so are quite
well-known (Martinez, 1978).
Salinization of aquifers:
