DesertificationDesertificationNamib Desert

What is desertification?

Desertification occurs where land is turned into desert. Desertification is the intensification or spread of arid conditions.

It occurs mainly in semi-arid lands which border the world’s major deserts.

Rate of Desertification

Since the 1970’s there has been a growing body of evidence to show that deserts are increasing in size. Semi-arid areas on the edges of deserts such as the Sahel south of the Sahara have been getting drier and changing into full deserts.

http://www.poodwaddle.com/earthclock.swf Rate of desertification

HOW WIDESPREAD IS DESERTIFICATION? About one third of the world's land surface is

arid or semi-arid. Worldwide, desertification is making approximately 12 million hectares useless for cultivation every year.

http://www.green.tv/unep_global_desertification_outlook# Desertification Video 8 mins

Which areas are vulnerable?

Vulnerability: Red = very high Orange = high Yellow = moderate

The area of greatest risk: The Sahel

South of the Sahara desert / North of the savanna grasslands

The Sahel region lies just to the south of the Sahara Desert in Africa.

What is The Sahel like?

• Semi-arid area.

• Periods of rainfall and drought.

• Supports small bushes.

• Windbattered trees.

Physical reasons for desertification in The Sahel

1950/60’s - above average rainfall, causing nomadic herders to settle and farmers to intensify agriculture.

1970’s - below average rainfall leading to extreme drought. Crops and animals die. Desert advances.

Why does the Sahel suffer from desertification?Why does the Sahel suffer from desertification?

DESERTIFICATION

Increase in population Increase in cattle

Deforestation for fire wood Grassland grazed more intensively

Roots no longer hold soil together Roots may be eaten as well as grass

Leaves no longer protect soil from weatherLess vegetation means less protection from weather

Loose top soil blown away by wind

(Soil Erosion)

=

Loose top soil blown away by wind

(Soil Erosion)

=DESERTIFICATION

Causes of desertification

Vegetation roots bind soil.

Vegetation dies.

Soil is left exposed.

Sun bakes the soil and it cracks.

Wind blows away soil.

No leaves to intercept rain. Soil is washed away.

The soil is degraded, losing

fertility and structure.

How have each of these factors contributed to desertification?

desertification

climate humans animals

Climate Drought: low rainfall since 1968.

Soils become dry and there is no water left in wells.

Trees die, grass withers and is replaced by poor desert scrub.

Crops fail and cattle feed on poor pasture.

Less roots to protect the topsoil, less humus; soils become more sandy and dry.

Wind erosion removes the soil, causing dust storms, leaving bare rock.

http://news.nationalgeographic.com/news/2008/02/080221-nomad-video-vin.html

Human reasons for land degradation

Traditional nomadic tribes settle in one place. Vegetation no longer protects the soil.

Trees provided protection for the soil, from wind and rain.

The growing of cash crops, depletes the soil fertility of the area. The soil structure breaks down.

Overgrazing. Deforestation. Over cultivation (Intensive agriculture).

‘Desertification’ - caused by climate change. ‘Land degradation’ - caused by human activity

Human activity Population is high and increasing

fast.

To increase food supplies more crops are grown and more cattle kept leading to over-cultivation and over-grazing.

Yields decline and cattle are undernourished and die.

Demand increases for water as population grows.

Trees are cut down for fuel supplies.

Less vegetation; more dry, bare soil; more wind erosion.

Put the following statements into the correct order as a flow diagram.

Vegetation roots bind the soil.

Vegetation dies.Soil is left exposed.

Sun bakes the soil and it cracks.

Wind will blow away the soil.

Leaves are no longer present to

intercept rain. The soil is washed

away. The soil is degraded, over

time losing fertility and structure.

Animals/insects

Locusts destroy the crops.

Overgrazing means all vegetation is eaten.

Animals trample the ground reducing it to dust.

Animals die and can’t breed.

Physical impacts of desertification

• Soil erosion.

• Sun baked, cracked soil.

• Loss of plants and animals.

• Gullying.

• Dry rivers.

• Growth of desert.

• Increase in sand storms.

• Flash floods.

Human impacts of desertification

• Crops and cattle die, resulting in famine.

• Death.

• Migrants move to cities, resulting in the growth of informal settlements, shanties, in already massively overpopulated urban areas.

http://www.abc.net.au/science/photos/desertification/blank.htm Effects slideshow

The UN currently estimates that desertification directly affects 46% of land in Africa, and around 250 million people. In Kenya, where desertification and drought has threatened over 11 million with famine.

Starvation

Food and water shortages lead to malnutrition, famine, disease and high death rates.

Problems? Civil wars, as in

Ethiopia and Sudan prevent aid reaching stricken areas and cause mass migration to refugee camps.

Population growth continues to outstrip food supplies.

Aid Programmes

Large numbers of people become dependent on food aid programmes.

Migration

From rural to urban areas causing over-population in towns.

To refugee camps.

Solutions?

How can we solve the problems of desertification?

Tackling desertification

Plant Trees.

• Roots bind the soil together. Leaves provide shade, and intercept water.

• Cheap, long term.

• Provide fuel wood and building materials.

Tackling desertification

Terracing.

• Prevent rainfall from washing away topsoil and nutrients.

• Cheap to build, only man power needed.

Tackling desertificationMagic Stones.

• Similar to terracing, stones are placed along contours.

• Topsoil can not be washed past the stones. Water infiltrates, instead of running over the surface.

• Cheap to build, only man power needed.

• Effective, shown to increase yields by 50%.

Magic stones Animation!

http://www.sln.org.uk/geography/magicstones/MagicStonesExcercise.swf

http://www.sln.org.uk/geography/magicstones/Default.htm Part 2

Possible Solutions to Desertification

Deforestation - Afforestation, that is re-planting trees. Planting trees can help stabilise the soil and cut down on erosion by wind and rain.

http://www.tree-nation.com/index.php Using good farming practices such as proper crop rotation. Overgrazing - It is important that the young trees are fenced

off to prevent grazing by animals Terracing the land to slow down the water running off will

make better use of the rain that does fall Most of all desertification can be controlled by human activity.

Solutions In the short-term, provide food aid and water supplies to prevent

suffering.

Improve water supplies by building large reservoirs and drilling deeper wells.

Conserve water in local small-scale schemes eg ‘magic stones’ in Burkino Faso.

Encourage sustainable farming practices (using locally-made tools, not tractors).

Provide drought-resistant seed such as millet (northern Nigeria). GM crops.

Tree planting schemes to reduce soil erosion (Mauritania).

International action to reduce the causes of global warming.

Your tasks:Desertification in the Sahel

Explain what desertification means. Draw a sketch map of Africa to show the Sahel. Name 6 Sahel countries on your map. Make notes about the causes of desertification - physical

and human factors (see pgs 252-253 Geog Text). Make notes about ways of managing the land

sustainably in the Sahel. Use sub-headings or bullets.