Hot Desert Ecosystem (AQA GCSE Geography)
Revision Note
Written by: Bridgette Barrett
Reviewed by: Jenna Quinn
Characteristics of Hot Desert
Hot desert biomes are mostly found in a band around the Tropic of Cancer and Tropic of Capricorn
Approximately 20% of the Earth's surface is covered by hot desert ecosystems including in the following areas:
North America: The Mojave and Sonoran Deserts of the USA and Mexico
South America: The Sechura Desert in Peru and the Atacama Desert in Chile
Africa: The Sahara, Kalahari, Namib and Somali Deserts
Middle East: The Arabian Desert
Asia: The Dasht-e Lut in Iran, the Gobi, Turkestan, Thar and Taklamakan Deserts
Oceania: The Australian Deserts such as the Simpson and Great Victorian deserts
Hot desert characteristics
Characteristics of Hot Desert Regions
Characteristics | Hot Desert |
|---|---|
Location |
|
Annual Precipitation |
|
Temperature Range |
|
Seasons |
|
Humidity |
|
Soils |
|
Biodiversity |
|
Factors influencing the hot desert climate
High pressure all year which means the air is descending and warming so precipitation does not occur because the air is not rising
Prevailing winds are often from over land masses which means they contain little moisture
Some deserts are in a rain shadow so there is little rainfall
Cold ocean currents on the west side of continents may reduce summer temperatures due to the cooling effect of the ocean
Influence of pressure systems
Hot deserts form between 15°- 30° north and south of the equator as a result of the atmospheric pressure systems
Air rises at the equator and when it reaches the upper atmosphere it moves north and south
The air cools and starts to sink
This creates a zone of high pressure at about 30° north and south of the equator
Due to the sinking air, warm air cannot rise, condense and form clouds, resulting in high aridity
Humans
The edges of the desert are used for livestock herding
Communities such as the Bedouin are nomadic
Live in large open tents made from fabric woven from camel hair and vegetable fibres
Food sources are mainly from the animals that the Bedouin herd - goats and cattle
Headwear is worn to protect against the heat of the sun and sand
Restrictions on movements due to international borders have affected the Bedouin lifestyle
Many Bedouin are no longer nomadic and live in permanent settlements
Interdependence in a Hot Desert
All parts of the hot desert ecosystem are interdependent
A change in one part affects the others
Nutrient cycle
The growth of plants is limited due to the extremes of temperature and lack of water
The nutrient cycle is very slow
Most nutrients are stored in the soil
Due to a lack of organic matter the soils are coarse, sandy and low in nutrients
Plant & Animal Adaptations
Adaptations
To be able to survive the extreme temperatures and lack of rainfall the plants and animals are extremely well adapted
Adaptations of Plants and Animals in Hot Desert Ecosystems
Plants | Animals |
|---|---|
Low growing - this helps to avoid water loss due to strong winds | Camels have a range of adaptations including two sets of eyelashes and nostrils which close to keep sand out of their ears and noses. They also store fat in their humps so they can survive for long periods without food or water |
Thick stems - used to store water | Fennec Fox - have large ears which help them to lose heat |
Shallow roots - these spread out near the surface to catch whatever rain falls | Burrowing - many animals burrow to avoid the intense day time heat |
Long roots - some plants have long tap roots instead of shallow roots to reach water deep underground | Insects and reptiles have waterproof skin to reduce water loss |
Small leaves or needles - the smaller surface area reduces water loss | Nocturnal - some animals hunt at night to avoid the daytime heat |
Worked Example
Study Figure 1,
Plants and animals adapt in order to survive in a hostile environment.’
Explain this statement. Use either Figure 1 and your own understanding.
[6 marks]
The command word “explain” is used, which means to provide an account of the ways that animals and plants adapt to a hot desert
You need to give examples for both plants and animals and then explain them
It is not enough to say 'spines instead of leaves' you need to explain how this helps the plant survive
In a level 2 and 3 answer you are expected to use geographical terms and include both examples of plant and animal adaptations
You should include examples from your own understanding as well as from figure 1.
An example of an answer for each level can be seen below
These are just examples and there are many others which can be found in the mark scheme - see topic question 2
Level | Marks | Exemplar Answer |
|---|---|---|
1 (Basic) | 1-2 | Cacti have spines instead of leaves and have thick stems. Camels have two sets of eyelashes and a hump to store fat. |
2 (Clear) | 3-4 | The hot desert has low rainfall and high temperatures. Cacti are adapted to this by having spines instead of leaves which reduce water loss. Camels are adapted by having two sets of eyelashes which keep out the sand. |
3 (Detailed) | 5-6 | The hot desert has less than 250mm of rainfall a year, daytime temperatures can reach 50oC and night time temperatures fall as low as 0oC. To survive cacti have spines instead of leaves and a thick waxy coating which helps to reduce water loss. Other plants grow very slowly which requires less energy such as the welwitschia . Camels are adapted in a variety of ways including two sets of eyelashes and nostrils they can close to help keep out sand. Other animals are adapted by having large ears which give off heat such as the Fennec Fox. |
Biodiversity Issues
Low levels of precipitation and high temperatures in many areas of hot deserts lead to low biodiversity
Where water is available there are higher levels of biodiversity
When rainfall does occur in desert areas a desert bloom may follow
Seeds and bulbs which have laid dormant germinate
In the Atacama Desert desert blooms may occur between September and November when rainfall is unusually high
This can lead to over 200 species of flowers blooming, attracting insects and lizards
Threats to hot desert biodiversity are mainly human activities including:
Mining
Climate Change
Fuelwood gathering
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