Theme 3 Chapter 4 - Desertification Flashcards
What does ‘desertification’ mean?
When a dry place with a dry climate - like the semi-arid - becomes even drier - into a desert.
Which other parts of the world, aside from the Sahel, are suffering with the risk of desertification?
Australia, Middle East
What physical processes is allowing desertification to take place (i.e Hadley Cell and less rainfall)?
HADLEY CELL:
1) At the equator, warm air is constantly rising leaving low pressure conditions at the Equators - rainy, cloudy, windy.
2) When the warm air rises into altitude it cools into cold air and splits.
3) The cold air is heavier so it falls on 30N and 30S - resulting in high pressure in these places (no rain, no wind, no clouds)
UNRELIABLE RAINFALL:
Precipitation can be unreliable, no rainfall, soil dries out and turns to sand
What human activities allow desertification to take place?
1) Farmers allow cattle to over graze, less vegetation for evapotranspiration or soil erosion occurs more
2) Trees and shrubs burnt to make space for crops and homes
3) Trees cut for firewood
4) Commercial farms use land intensively so soil quickly worn out
How might climate change increase the threat of desertification?
Climate change -> less rainfall and increased drought-> Vegetation dies -> soil exposed to wind and rain-> soil erosion -> Lack of vegetation -> desertification
How might population growth increase the threat of desertification?
Population growth -> more animals reared-> overgrazing -> vegetation cover removed -> soil exposed to wind and rain-> soil erosion -> Lack of vegetation -> desertification
What strategies could people at a local scale do to manage desertification?
1) Drip irrigation: Crops and planted where water drips from holes in hose pipes - the drip effect reduces water wastage
2) Stone Bunds:
- Slow surface flow of rainwater giving more time for infiltration and irrigate farmer’s soil
- Any pre-eroded soil is trapped and deposited by bunds
3) Drought tolerant crops: Millet is a very drought tolerant crop that provides food, fuel and construction materials
Bottom-up development meaning?
Changes agreed and developed at a local scale involving local people
Top-down development meaning?
Changes imposed on local people from national governments
At an international scale describe what the Great Green wall is?
15KM wide strip of trees and shrubs 9000 miles long through 11 countries to prevent the southwards spread of the Sahara Desert
What benefits will the Great Green Wall do for desertification?
- Prevents soil erosion in rainy season
- Leaves and other materials decompose in soil returning nutrients
- Encourages farmers to grow fruit trees
- Provides shade for crops
- Once established, relatively cheap to maintain
- Encourages cooperation between countries
How successful has the Great Green Wall been so far?
- Progress clearly been made in Senegal and Niger, however not a great deal has happened in the other 9 countries
- probably because locals are often suspicious of changes being imposed on them by other governments
