Read the following article about the way in which deserts are expanding across the world. On the opposite page write a summary of the causes of the expansion of deserts.
Your summary should be about 100 words (and no more than 120 words). You should
use your own words as far as possible.
You will receive up to 8 marks for the content of your summary, and up to 8 marks for the style
and accuracy of your language.
Deserts cover a third of the world's surface and thirteen
per cent of the world's population live in deserts. Today,
one of the major problems that the planet faces is the
expansion of deserts. This is a serious problem that
affects not only those countries in the direct path of the
expanding deserts, but also the rest of the world. To give
some idea of the scale of the problem, the last 50 years
have seen the Sahara desert spread southwards to cover
an extra 65 million hectares. Across the whole world, the area of useful land lost each year is more
than 6 million hectares.
The increase in desert land is caused by our planet's changing climate. The world is becoming
warmer and drier, and this means there is less water to support plants and animals. However, the
natural rate of desert growth has been greatly increased as a result of the exploitation of the land
by humans. The causes of this increase are similar in many ways to those that bring about
deforestation, and once again the chief offenders are people working in agriculture.
People have been farming the land for thousands of years, cultivating the soil to grow crops and
rearing animals for food and transport. Traditionally, the land is rotated": in some years plants are
grown and in other years the soil is left to rest. However, to meet the demands for food of an
ever-growing population, it has been necessary to reduce the amount of time during which land is
left unplanted. As a result, the soil has become poorer, and, in some cases, unable to support plant
life.
Continual growing of crops in soil which has lost its nutrients is often combined with the need to
allow animals such as goats, cattle, sheep and camels to feed on plants. This increases the
problem by further weakening the soil and, in addition, the few remaining trees and shrubs are cut
down for fuel. This can have disastrous effects on the fragile desert ecosystem, removing all the
natural vegetation which covers the ground, and exposing what little soil is left to the wind, rain and
sun. Soil and plants have a two-way relationship in which neither can survive without the other.
Most plants need soil in which to root. This anchors them to the ground and stops them being
blown away, whilst also providing them with essential water and nutrients. Soil is dependent upon
plants for two main reasons. Firstly, plants provide most of the material from which new soil is
made, and secondly, plant roots help to hold the soil together and prevent it from being eroded by
the wind and rain. Without this covering of soil the land quickly becomes a further area of desert.
The bad effects of agriculture on the desert are not only found on its edges. The growing of crops
requires large amounts of water, something which is in short supply in dry lands. To try to overcome
this problem, farmers have developed irrigation systems to bring water from springs, oases and
underground sources elsewhere in the desert. In many cases this does not present a threat to the
environment, and centuries of experience have taught farmers how to extract water without causing
much damage to the environment. However, farmers are under increased pressure to produce
more and more food to feed the growing world population. As a result, in a very short space of time,
farmers have drained the water sources which took thousands of years to fill up naturally