Drought essay
A drought is defined as a continuous period of dry weather. It is usually found in semiarid regions where there is a low mean annual rainfall and high rainfall variability.
Causes of droughts can be classified under natural factors and anthropogenic factors.
Under natural causes, the shifting of rain belts is one reason. As the Inter-Tropical
Convergence Zone (ITCZ) shifts in position depending on the movement of the overhead
sun, locations that lie within the fluctuating zone will experience distinct wet and dry
seasons. The dry seasons, especially, tend to coincide with periods where the
subtropical high pressure belts lie across the area. Since the area experiences
descending air, formation of clouds is inhibited since air would be warmed due to
compression in the high pressure zone, called anticyclones. Dry seasons, combined with
anticyclones, affect precipitation amounts and lead to droughts as a result.
The El Nino effect is another natural cause that describes an extensive warming of the
upper ocean in the tropical eastern Pacific lasting up to a year or even more. It has a
close link with the change in atmospheric pressure, known as the Southern Oscillation
(SO). Thus, they are often known collectively as the EL Nino Southern Oscillation, or
ENSO. This system oscillates between warm to neutral conditions every three to four
years. During an El Nino event, a reversal in pressure, precipitation, winds and ocean
currents, in contrast to normal conditions, occurs in the Equatorial Pacific region.
Pressure rises over the western Pacific (high pressure area) and falls over the eastern
Pacific (low pressure area). This enables the ITCZ to migrate southwards, causing the
trade winds near the surface level to weaken in strength, or even be reversed in its
direction (moving from west to east instead). The descending air now falls over at the
western side of Pacific (Indonesia), giving South-east Asia much drier conditions than it
usually experiences under normal atmospheric conditions. On extreme occasions,
droughts may result as well. In particular, severe droughts were experienced in the
Sahel desert, southern Africa and the India sub-continent.
The rise in population densities is one anthropogenic factor. In areas where high
population densities exist, shortage of food production may occur. The increasing
demand for food to feed the entire population may result in progressive conversion of
natural ecosystems into farmland. This gave rise to desertification when there is overcultivation of croplands, shortening of fallow seasons, overgrazing of rangelands,
mismanagement of irrigated cropland and deforestation. Desertification occurs when
human activities permanently transform a land surface to resemble a desert. Eventually,
land becomes fallow and so dry that it further accentuates the effects of drought on
food supply for the population. This is especially seen in the Sahel. The Sahel, which
experiences droughts previously (with a low rainfall or 100-200mm annually), suffers a
worsened drought condition due to land degradation by human activities.
Global warming is another cause of drought that results from both natural and human
factors. The greenhouse effect is a naturally occurring phenomenon in which the
purpose of the greenhouse gases in the atmosphere is to keep the earth warm and
enable life existence by absorbing energy (long wave radiation). However, with human
activities, there is an increase in the amount of carbon dioxide in the air. This raises
concern for an enhanced greenhouse effect, which may lead to rising global
temperatures when too much air is being trapped in the atmosphere. Linking back to
drought, global warming may cause climate boundaries to shift their positions, thus
making some regions drier than the other, according to the air circulation of the Hadley
cell.
Since droughts have adverse effects, there is a need for drought management in that
area to reduce these impacts. However, there were management problems to
implement prediction and mitigation strategies on the drought situation in Sahel.
Firstly, in terms of strategies for prediction, the high rainfall variability in the Sahel
makes prediction of drought difficult. As fluctuations in rainfall are often abrupt and
extreme, the change from wet conditions to persistent drought periods cannot be
forecast. One method of prediction is to use weather records. By making observations
from precipitation and temperature, and understanding the historical occurrence of
drought, it allows planners to better determine the likelihood and potential severity of
future droughts. To do this, instrumental records are often used. These instrumental
records detect the onsets of droughts by providing information on current and
developing droughts. The Tropical Ocean Global Atmosphere (TOGA) project is one
example. For those areas whose climate is affected by ENSO, TOGA project helps to
make reliable forecasts that can reduce the drought effects on the economies. However,
the fact that scientists cannot predict longer, multi-year droughts is one limitation.
Furthermore, two global warning systems put in place to anticipate crop failure and food
shortage are part of the prediction strategies used. The UN-sponsored Global
Information and Early Warning System (GIEWS) and the USA-sponsored Famine Early
Warning System (FEWS NET) are initiatives that aim to predict severe famine
emergencies. However, it these large-scale surveillance systems may not be effective in
predicting famine droughts at the sub-national or local levels, when the prompt
detection of failing supplies is necessary to prompt swift reactions from donors.
In terms of mitigation strategies, countries in the Sahel region tend to lose out to the
other developed countries where they can spend on advanced farming methods to
ensure permanent vegetation cover. This can be achieved through crop rotation, which
helps to minimize erosion. The use of xeriscaping is also becoming popular in the dry
western United States. However, these technologies do not come cheap and are often
too costly for the less developed countries in the Sahel to afford.
Another mitigation strategy would be the use of population control. This is done so as to
lessen the increased pressure on the land, especially for food. Since Sahel has a high
population density that doubles every 20 to 30 years, this strategy may seem useful for
Sahel. However, moving a large number of people from a country to another may
require a large manpower and a lot of time, which offsets the benefits of reducing
negative effects of droughts since alternate solutions to droughts may be used (ie.
animal population control).
All in all, problems in managing an inhabited environment prone to droughts, such as
the case of Sahel, may be eliminated depending on the response. This may be in the
form of resettlement to even out population densities and providing food aids as a form
of famine drought relief. However, high rainfall variability experienced in the Sahel may
hinder management strategies as it is difficult to forecast future droughts. Furthermore,
since droughts are often known as a ‘creeping hazard’, the onset and end of a drought
becomes undefined, making prediction strategies more difficult to implement. Thus, the
only way to manage droughts effectively is for the many countries in the Sahel region to
cooperate together. As Sahel consists of many countries, this means that a lack of
common beliefs may affect how Sahel copes with the effects of droughts. It is only with
a common understanding among all countries would Sahel then be able to overcome
any obstacle and reduce the effects of droughts to its minimum.