These are documents with detailed information about the ongoing process of desertification. These are catered to A-Level Students who are studying AQA Geography but can be applicable to other exam boards. These can be helpful for the Physical Paper and desertification essays.
Desertification In The Sahel
What is Desertification?
Desertification as a process has generally been viewed as series of incremental changes in
biological productivity in arid and semi-arid ecosystems. It can encompass changes such as
decline in yield of a crop, or a decrease in density of existing vegetation. Essentially
desertification is the creation of desert-like conditions (where perhaps none had existed in
the past) as the end result of a process of change.
Figures:
More than half of the worlds productive capacity is now being appropriated by humans
for food and raw materials as well as 85% of the worlds water
20 million km ^2 of land is degraded every year
Desertification affects over 280 million people
After 1970s Sahel Drought, there has been 40 years of below average rainfall in the
region
By 2050, Niger Projects to increase population size by 175% bringing its population size
over 60 million
Rate of desertification is 30 to 35% higher than the historical rates
Vegetation around a borehole in Niger, it was shown that dry-matter biomass declined
from 100kg ha-1 to 8 kg ha-1 in 8 years
Natural Causes:
High Temperatures - high rate of evapotranspiration and therefore high rate of moisture
loss from soils
High Rainfall Variability - Infrequent and often intense periods of rainfall which compacts
soils, increasing their erodibility
Occurrence of Droughts - 1970s Drought in the Sahel
Socio-Economic
Overgrazing
Over-Cultivation
Deforestation and excessive fuelwood cutting
Inappropriate Irrigation Practices (Salinisation and Water-logging)
, High Temperatures - High temperatures can cause a high rate of evapotranspiration causing
increased moisture loss from plants and soil
When soil moisture content is high, it provides the necessary conditions for soil aggregation
to occur. Water acts as a binding agent, allowing soil particles to stick together and form
aggregates. This process helps to create stable soil structure, which is important for
maintaining soil health and reducing erosion.
However, when evaporation rates are high, soil moisture content can decrease rapidly,
reducing the amount of water available for soil aggregation. As a result, soil particles can
become more loose and unconsolidated, making them more susceptible to erosion.
Microbes in the soil act as decomposers, microbes break apart organic material and recycle
the nutrients back into the atmosphere. If it gets too hot, the microbes become less active
and die. Therefore soil formation is slow, causing further depletion of soil.
Raising the temperature will increase soil respiration. Soil Respiration is considered to be the
second largest Carbon effluvia in terrestrial ecosystems. It emits 10 times more carbon to the
atmosphere than fossil fuel combustion. Higher temperatures provide more energy to living
organisms increasing their chemical and biological activity in metabolising detritus. This
results in greater rates respiration, and thus an increase in carbon dioxide emissions from the
soil. Extreme hot temperatures decrease soil respiration, but areas subject to a period of
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