land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including climate variation and human activities" (UNCCD 1995).

Almost half of the land surface, about 6.45 billion hectors is dry lands, One billion of these hectors are real deserts such as the Sahara.

Desertification is worse in places like Africa and Asia

Introduction

World desertification map

Causes ofDesertification

Causes of Desertification

• There are 4 main factors in desertification

• Drought • Over grazing • Over cultivation • Trees used for fuel and shelter

Causes : Climate variation

Drought

Climatic fluctuations

How have each of these factors contributed to desertification

Causes of DesertificationDrought A long period without rainfallcauses crops to die

lack of foodmay have to move to find food

Deserts and Desertification

Causes of DesertificationOvergrazing–

◦ too many animals grazing on the land

◦ animals eat all the vegetation

◦ vegetation fails to grow

◦soil is exposed to rain and wind

◦ soil is washed or blown away.

CAUSES OF DesertificationOvergrazing

too many animals grazing on the land

animals eat all the vegetation

vegetation fails to grow

soil is exposed to rain and wind

soil is washed or blown away.

Causes of Desertification

Overcultivation –

◦ many crops being grown on the land year after year,

◦ no rotation of crops,

◦ crops take all the nutrients from the soil,

◦ the soil becomes infertile and nothing can grow.

◦ Because there are no crops to protect the soil the soil is again easily eroded by the wind and rain .

Causes of Desertification

Removal of trees for fuel and shelter–

There are few trees in the desert and their roots hold the soil together.

When the trees are removed for firewood or to build shelter the roots die and the soil becomes loose .

Yet again this means the soil can be easily blown or washed away .

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.

Human activityPopulation 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. Called deforation.

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

SolutionsShort Term Solutions Refugee Camps Medical Aid Food and Clothing AidLong Term Solutions Fence off areas to prevent animals grazing

there Introduce drought resistant crops e.g. millet Plant trees and bushes to provide cover for

soil and stop it being blown or washed away Rotate crops and water them using

irrigation techniques Build stone walls to collect moisture

Causes of desertificationAny factor that leads to the following is considered a desertification factor:

“Removal of vegetation”“Removal of top fertile soil and reduction in biological productivity of soil” ‘Depletion of surface and ground water resources”

Estimates of percentage of human actions causing:

desertification are: overgrazing (35%), deforestation,(30%), other agricultural activities (28%), overexploitation

of fuel wood (7%), and bioindustrial activities (1%) (Cullet).Human impacts can exacerbate but not initiate desertification.

Human Actions

Eeffects of desertification?

Starvation

Food and water shortages lead

to malnutrition, famine, disease and high death

rates.

Environmental impacts

Loss of ecological stability.Loss of biodiversity.Reduction in carbon sink capability and their

effects on climate.Floods, drought and related losses. Damages to watershed Soil erosion.Silting up of reservoirs. Desertification and Drought. Changes in hydrological regime.

Multifactorial, multiscale and multidisciplinary nature of desertification

Desertification

Drought

Land degradatio

n

Biodiversity

Change in land

use

Crop productio

n

Poverty

MigrationsAbandonme

nt

Unsustainability

The soil becomes unusable Nutrients in the soil can be removed by wind or water. Vegetation is lacked or damaged

Loosened soil may bury plants or leave their roots exposed and overgrazing might make different plats extinct.

Lack of sales for some countriesCountries that rely on crops being sold cannot make anything off of them if the soil isn’t fertile enough to produce them.

Food loss/ famineThe soil cannot produce food so people cannot eat. Poor countries that rely on this food source may result in a famine. People near affected areasDesertification can cause flooding, poor water quality, dust storms, and pollution. All of these effects can hurt people living near an affected region

Environmental/Social/Economic effects

SolutionsIn 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.

Solving the Problems: the results

Nov 1992

Nov 1998

Before and after animals have

overgrazed and trampled the

savanna.