The weather conditions prevailing in an area in general or over a long period
The Sahara
Largest and hottest desert in the world
Covers roughly the same area as the USA
About one-quarter is covered by sand desert (ergs)
The rest consists of gravel-strewn plains (reg) and areas of barren rocks (hamada)
Used to be wetter 1000 years ago
Growing even larger, spreading to the south due to more overgrazing and deforestation
Sahel
A semi-arid belt of poor, dry soil 300-500 km wide from north to south, stretching from west to east across north Africa between the Sahara Desert and the savanna grasslands
In the Sahel, average rainfall ranges from 300 to 600 mm per year, and up to 90 per cent of the moisture evaporates
Drought is natural to the Sahel
Desertification and land degradation by people have moved the limit for growing crops and grazing animals further south each year
Countries like Mali now have even less inhabitable land to survive on
Desertification caused by climate change
1. Less rainfall
2. Land degradation
3. Overgrazing
4. Overcultivation
5. Deforestation
6. More bare ground exposed
7. More wind erosion
8. Less topsoil
Desertification caused by human activity
1. Population pressure
2. Migration or starvation
3. Less nutrients for decomposers to return to soil
