Download H2 Geography

H2 Geography
Tutorial 9: Droughts essay
Q1. Explain the causes of droughts. With reference to an example or
examples, discuss the problems of managing an inhabited environment
prone to droughts [16]
Droughts are one of the adverse weather conditions that occur at specific locations around
the world due to certain global climatic patterns. The nature of droughts however is very
different from other environmental hazards such as earthquakes and volcanic eruptions. It is
defined as a ‘creeping’ hazard as it tends to develop very slowly and have a prolonged
existence. We are unable to properly state the time at which it starts and ends, for there is
no obvious signs that can be observed to marks its start and end. Furthermore, it is also not
confined to particular topographic settings as it can extend to regions sub-continental in
scale, affecting several countries, for instance the Sahel region in Africa where drought
conditions can affect many sub-Saharan countries. Due to its nature, it will cause many
difficulties in the prediction, and management of the hazard.
Many different definitions of droughts exist, however in simple terms; a drought implies a
lack of moisture for an extended period of time which in turns causes a deficit of moisture in
the soil. However as different areas around the world experience varying amounts of
rainfall, the definitions of what constitutes a drought would vary. In an area which receives
high amounts of precipitation in the form of rain or snow, the condition of drought can
develop more rapidly than in an area which doesn't. For instance in the semi arid region of
central Australia, a drought occurs when the level of precipitation is much lower than in sub
tropical Indonesia, where the normal conditions in Australia would be a drought condition in
Indonesia. Hence, drought should be considered relative to some long-term average
condition of balance between precipitation and evapotranspiration in a particular area, a
condition perceived as “normal”.
The causes of drought are mainly natural; however human activities can have the effect of
exacerbating the impact of the drought such as increasing the chances of desertification.
The main reason that droughts occur is when there is not enough moisture in the air and
soil, thus preventing the processes that form rain in the atmosphere from happening.
Therefore, an area where there is no moisture available or no condensation will be at high
risk of drought. There are a few main reasons on why some areas have droughts.
Firstly, there are latitudes and longitudes along the earth where the air is generally sinking.
For instance, at the latitude of around 20-30 degrees north and south of the equator, it is
the zone of sub-tropical high pressure where air is subsiding, also known as the sinking limb
of the Hadley cell. The descending air makes it very difficult for any moist air to rise;
condensation will not occur and rain clouds will not be able to form as the air is warming
due to compression. It is also important to note that the inter-tropical convergence zone
can also shift in position depending on the movement of the overhead sun. The high
pressure areas are the main causes of deserts such as the Sahara and in northern Australia.
The size of the areas will vary from year to year as the air can sink over a larger area, this
will cause droughts to occur, especially at the edges of deserts. It must be noted that should
the area be confined to the desert areas, it will not be defined as a drought. This is because
the amount of rainfall in the deserts are already extremely low and thus there will be hardly
any change in the level of precipitation from normal conditions to be able to define it as a
drought. At the edges however, there can be a delaying of the rainy season for a period of
time, causing a substantial change in the precipitation level below normal levels and hence a
drought would occur there.
Secondly, the periodic atmospheric El Nino event can also cause droughts to occur in South
East Asia which has normal conditions of very high amounts of precipitation. El Nino is the
event where there is an extensive warming of the upper ocean in the tropical eastern Pacific
for periods lasting for a year or more. The event is linked with a change in atmospheric
pressure known as the Southern Oscillation. Under normal atmospheric conditions, pressure
rises over the eastern Pacific Ocean and falls over the western Pacific Ocean. There will be
warm, moist ascending air over the Western Pacific which gives the South East Asia region
its heavy convectional rainfall. During an El Nino event there will be a reversal in pressure,
precipitation, and often winds and ocean currents, in the Equatorial Pacific region, where
there will be a rise in pressure over the western Pacific and falls over the Eastern Pacific.
This will cause the inter- tropical convergence zone to migrate southwards and cause the
trade winds to weaken in strength, and in certain cases even a reversal of direction. The
descending air which is now over the South East Asian region causes much drier conditions
there than normal conditions and in extreme cases causing drought when there is a very
pronounced fall in the amount of rainfall.
As droughts occur due to the lack of rainfall, factors that impede the movement or
formation of rainclouds are also a cause of droughts. First and foremost, certain areas will
face droughts should the winds that normally bring the rainclouds either blow very weakly
or not blow at all. For instance the droughts that occurred in the Indian states of West
Rajasthan and East Rajasthan in 2000 could have happened as the winds from the Indian
Ocean were much weaker and could not blow the clouds far inland. Secondly, the
fundamental air movements that make moist air rise do not happen. An example would be
the droughts over most of Europe from 1988 to 1992, where an anomalous circulation
pattern caused rainfall deficits over a large area. This can be due to the lack of low pressure
systems moving across Europe and causing less frontal rain to form.
There are anthropogenic causes of droughts as well. The main anthropogenic cause of
drought would be a rise in the absolute population and population densities. For example in
the Sahel region, rural population densities have increased due to high birth rates. This
means that the population doubles every 20- 30 years. The rapid increase in population has
led to food production being outstripped by the population. With an increase in population,
there will be a rise in demand for food and leads to the progressive conversion of natural
ecosystems into farmland. In the Sahel region, most of the land is only marginally arable and
is unable to support the increased number of people living on it. The carrying capacity of the
land bordering the southern Sahara region was only 0.3 people per square km while the
number of people living on it was 2 per square km. Hence there will be increased pressure
on the land and can lead to desertification and degradation of the land which ultimately
leads to a drought. Desertification occurs due to over- cultivation of croplands, Overgrazing
of rangelands, mismanagement of irrigated cropland and finally deforestation. All of these
are caused indirectly or directly by an increase in population.
First of all, over cultivation occurs when rising populations force farmers into cropping more
marginal areas on the fringes of deserts, in order to feed the extra mouths. They are forced
to increase yields from their land and fallow periods are being ignored which causes the soil
to quickly lose its fertility. The farmers also tend to keep livestock as another means of
livelihood. The herds of livestock would concentrate in certain areas, stripping the
vegetation and exposing the soil to erosion. The trampling of the ground also leads to
ground compaction and destroys the structure of the soil. As the population increases, so
does their demand for fuel. In these areas which are less developed, the main source of fuel
is firewood from the forests. This causes wide tracts of forests to be cleared as the people
use the wood as fuel sources, the removal of trees exposes the soil to erosion from wind
and rain leading to desertification. Desertification can be a cause of droughts. Deserts have
higher albedo levels then soils and thus reflects more sunlight away, thus reduces the
possibility of cloud formation and decreases the level of precipitation, and should the fall in
level of precipitation be substantial from the normal levels, a drought will occur.
The impact of droughts varies greatly according to the national wealth of the individual
countries, and thus the management of the drought in each country will differ. The impacts
of droughts are the most serious in the developing nations in Africa which depend primarily
on agriculture. Generally the economic and mortality impacts are more pronounced in the
LDCs. As the impacts of droughts in LDCs and DCs differ, the methods of management will
be different although there is an overlapping of certain strategies in the management of the
droughts in the different groups of countries.
Both the governments of LDCs and DCs face the same problem in the prediction of droughts.
This is mainly because droughts are difficult to identify due to its creeping nature. Hence it
would hinder the ability of the governments to recognise the true impacts of the drought
and also adversely affects their capability to set in motion a timely and comprehensive
response.
The less developed nations especially those in the Sahel region in Africa suffer the greatest
impact from droughts mainly because the economies of the countries involved are not yet
developed and are still reliant on the agricultural sector for a large proportion of their GDP.
At the micro level, the farmers themselves are also suffering as they are mainly subsistence
farmers who farm to feed themselves and earn a livelihood. When a drought hits, their
entire livelihood can be wiped out and they can suffer from starvation. Hence, these families
have to figure out methods to mitigate the effects the drought has on them. For instance,
during a drought, the families can promptly sell their livestock in order to earn some money
to get them through the period of drought. Moreover, they can also move to towns and
cities to find jobs and earn wages to support their family. However, should there be a
oversupply of labour in the market, it can lead to a collapse of the precarious labour market.
At the political level, the government can also take steps to mitigate the effects of the
drought. During bumper harvests, the government would have to carefully conserve food
stocks to prepare for a period of drought, although as the food is perishable, it can be
difficult to store it for extended periods of time. Hence, the government would have to rely
on international relief agencies to supply supplementary food supplies to the people.
Furthermore, the government can subsidise or directly provide farmers with drought
resistant crops such as millet so that the farmers can continue to farm even in drought
conditions and thus be self reliant.
Although it is possible to develop strategies to deal with droughts in the Sahel, there are
obstacles that impede progress. This can include high rates of population growth where
population growth constantly outstrips food production, civil wars which can result in the
disruption and theft of food relief and also difficulties in establishing social and economic
stability. These problems would thus hamper the steps taken to managing the droughts in
the Sahel region and also in other LDC countries.
The developed countries suffer less serious economic and mortality impacts due to greater
national wealth and hence ability to cope with the impact of the drought. The economic
impact is smaller as the economy is much more diversified and complex and able to absorb
the impacts of a drought. Mortality rates are also low as farmers do not rely on their farms
for a living as they are commercial farmers. They are able to import food stocks from
overseas as they tend to be more affluent as well. An excellent example of a DC which
suffers from droughts would be Australia. The national drought policy has a core principle of
self reliance. This is because the farmers are in the best position to develop agronomic
systems, practices and business strategies to manage agriculture drought. Hence with this in
mind the government plays a role of providing farmers with the skills and tools to manage in
a self- reliant fashion. Examples of such support would be research into climate variability
and predictions, training and education, and tax incentives for them. These components
would thus increase the resiliency to drought through proactive, mitigation measures.
However, the government would step in should the drought event be very severe or affect a
significant portion of businesses in the region. This policy works on the basis of the market
mechanism where the commercial farmers will act to mitigate the effects of droughts in
order to keep up their profits and hence will work without much government intervention.
The principle of self reliance will only apply for farmers in the DCs as they have the
resources and education to make the right decisions.
In conclusion, in order for drought management to be successful, there must firstly be the
political will from governments to change the drought management paradigm as lessons are
learnt from past events. Nations can also learn from one another, adapting monitoring risk
and impact assessment tools and planning methodologies to each individual nation’s needs.
Most importantly drought plans and policies must be dynamic, incorporating lessons
learned and changing societal vulnerability because drought risk is a product of both
exposure to the hazard and the vulnerability of society to the hazard.