Areas at Risk of Desertification
- Distribution of hot arid and semi-arid lands has changed over time
- Changing climates have changed the extent and distribution of hot deserts
- A large percentage of the world was wetter after the last ice age and this reduced the amount of land covered in desert
- Until about 5000 years ago, there were only narrow strips of hot deserts to be found on the west coasts of South America and Africa
- Gradually, these areas of desert increased in size, but new hot deserts began to form
- The Sahara region was not always a desert
- Between 11000 and 5000 years ago, the area was known as the Green Sahara with lakes, lush vegetation and animals of the savanna biome such as elephants and lions
- These are natural climatic variations forming hot deserts, however, human activity has influenced the extent and distribution of these drylands
Distribution of drylands have changed over time, increased by human activity. Note that the most at risk areas already fringe the driest areas.
- Drylands are found on all continents and cover about 40% of Earth's land surface
- Home to more than 38% of the total global population of approximately 2.7 billion people
- They are areas of water scarcity, where rainfall is limited (arid areas) or seasonal (semi-arid)
- Temperatures are high, leading to high rates of evaporation and transpiration
- These areas have high levels of climatic uncertainty, and many areas can experience drought for several years
Worked example
The figure below shows desertification risk levels by landscape type in an area of Tunisia, north Africa.
Analyse the relationship between landscape type and risk of desertification shown in the figure.
[6 marks]
Figure – desertification risk levels by landscape type in an area of Tunisia, north Africa
Answer:
- The whole region is at risk of some degree of desertification.
- There is a link between different land use and a tendency for desertification, though the relationship is by no means predictable.
- The northern region has a large area of territory, which is at a very high risk of desertification. In the area where crops and grasslands dominate, 71% of the land is at very high risk. This is over 65% higher than the Type 4 region to the south, of the grassland plains.
- The Type 7 region in the southwest is also experiencing a very high risk of desertification. Looking at the coverage on the map, it appears higher than the 57% suggested by the data.
- There is a band of territory across the centre of the region in Type 5 and 6 regions where cropland expansion and urban expansion have occurred.
- Areas affected by human activity (settlement, road, cropland) are more likely to experience a very high risk of desertification. However Type 1 and 7 areas both appear to be more natural environments but, are severely affected by the risk of desertification.
