The variety of plants and animals living in a particular ecosystem.
What is a hot desert?
A hot desert is an area that is very dry (usually receiving less than 250mm of rainfall per year). They also experience very high temperatures of 45°c.
Where are hot deserts located?
Generally found 30°N and 30°S of the equator in areas of land away from large expanses of coast.
What is the climate (temperature and precipitation) like in a hot desert?
Temperature: highs of 45°c in the day, lows of 5°c at night.
Precipitation: less than 250mm per year
Why is it hot and dry in hot deserts?
Hot: Close to the equator where suns rays are more concentrated
Dry: in areas of high pressure where air is sinking.
What is the soil like in a hot desert?
- Shallow and dry
- Coarse texture
- Infertile due to lack of leaf litter
What wildlife (plants and animals) would you find in a hot desert
- Animals that are well adapted to the hot, dry climate, limited vegetation. e.g snakes, lizards
- The animals are generally very small in size and tend to sleep through the day time when temeperatures are high.
- Limited plants. Those that do grow are short in height and don't live a long time.
How have animals adapted to hot deserts?
- Nocturnal - hunt in the cool evenings
- Big ears to allow temperature regulation
- Can store fat that breaks down into water e.g. camels
- Long eyelashes, flat wide feet to cope with sand
How have plants adapted to hot deserts?
- Long plant roots to reach water deep in soil
- Small leaves to reduce moisture lost
- Succulent plants (fleshy skin to retain moisture)
- Sharp needles on surface to deter predators
What is the biodiversity like of hot deserts?
- Limited due to extreme climate
- This means any changes can have drastic consequences
- Global warming is the biggest threat to hot deserts biodiversity.
Why are hot deserts are interdependent ecosystem?
- Plants gain nutrients from soil, animals require energy and nutrients from plants
- The climate causes the soils to be infertile and unable to support large amounts of vegetation.
- Changes to one part of the ecosystem can have huge knock-on impacts on another part e.g. removing vegetation can cause soil erosion.
What are the opportunities in the Thar Desert?
Tourism: tens of thousands of tourists visit each year. Lots of desert safaris at Jaisalmer and desert festival.
Mining: gypsum (for cement), feldspar (for ceramics), phosperite (fertiliser)
Energy exploitation: rich in coal and oil. Opportunities for wind (Jaisalmer Wind Park) and solar power (Bhaleri solar plant)
Farming: mostly subsistence farming. Irrigation has made commerical farming possible e.g. cotton, wheat.
What are the challenges facing the Thar desert?
Extreme temperatures: highs of 50°c makes it difficult to work outside and plants and animals need large amounts of shade to survive.
Inaccessibility: limited roads to the area due to low population density. Tarmac roads don't cope well in high temperatures.
Water supply: farming and population increase has put pressure on water use. Low temperatures and high evaporation rates makes water scarce.
What is desertification?
When land becomes degraded to the point it turns to desert. This tends to happen on the edges of existing deserts.
The accumulation of salts in the soil that occur as a result of rapid evaporation of water.
What are the phyiscal causes of desertification?
1. Less rainfall - less rainfall in areas that are already dry. This means less plants (plants hold soil together) which leads to soil erosion
2. Higher temperatures - increasing tempratures which causes water to evaporate from ground, in turn, killing plants which hold they soil together.
What are the human causes of desertification?
1. Over grazing - cattle eat too much vegetation which holds the plants together. Soil becomes easily eroded if there is less vegetation.
2. Over cultivation - repeated farming exhausts the soil
3. Population pressures - more deforestation to make space leads to soil exhaustion
4. Demand for fuel wood - removing branches for fuel exposes soil to erosion
List the four strategies used to reduce desertification
- Water management
- Soil management
- Tree planting
- Use of appropriate technology
How can water and soil management reduce desertification
- Switching to growing crops that don't require as much water to grow e.g. olives, millet.
- Drip irrigation means drip feeding the soil with water rather than over-irrigating the soil at once. This prevents soil degradation.
- Contour traps - building embankments along contours of a hill side so that soil doesn't slow down hillsides during rainfall.
- Rotating crop yields and giving a rest period between crop rotations allows soils to recuperate.
How can tree planting reduce desertification
Trees are important in soil health. They can be planted to act as a wind break to prevent the top soil blowing away. They also provide shade for crops to be grown underneath, reducing moisture loss.
How can appropriate technology reduce desertification?
'Appropriate technology' means using technology that is cheap and sustainable for the chosen location. Examples include:
1. Sand fences that trap windblown sand
2. Solar panel cookers reduces need for fuelwood
3. Magic stones - lines of stones along contours to prevent water loss from soil. The stones catch the water and retain it.