Hot deserts

Learn about hot deserts including characteristics of deserts, plant and animal adaptations and desertification.

This lesson includes:

  • one video exploring the characteristics of hot deserts

  • one video exploring how people, plants and animals adapt to live in the Arabian desert

  • a case study of the Thar Desert, Rajasthan, India

  • three activities to build on the knowledge

Learn

Characteristics of hot desert ecosystems

Hot deserts are found near the tropics of Cancer and Capricorn. The largest hot desert is the Sahara in Africa which spans the whole width of the continent.

Watch this short film exploring the characteristics of hot desert biomes and how hot deserts are growing as a result of desertification.

Hot deserts have an extreme climate and challenging environment. There is very little biodiversity in hot deserts because of the harsh climate. Few species are specialised enough to survive there. Plants and animals which do survive there have adapted to difficult conditions.

The biotic (living elements of an ecosystem, such as plants and animals) or living components and the abiotic (non-living elements of an ecosystem, such as climate, temperature, water, and soil type) or non-living components of the hot desert rely on one another - a change in one will lead to a change in the other.

The Sahara desert

Climate

  • The climate is very hot. Summer day time temperatures can exceed 40 °C. However, at night the temperature can drop below 0 °C.
  • The climate is very dry with less than 250 mm of rainfall a year.
  • Hot deserts have two distinct seasons: summer, when the temperature ranges between 35 - 40 °C, and winter, when the temperature ranges between 20 - 30 °C.

Soil

  • Desert soils are thin, sandy, rocky and generally grey in colour.
  • Desert soils are very dry. When it does rain they soak up the water very quickly.
  • The surface of the soil may appear crusty. This is due to the lack of rainfall. As it is so hot water is drawn up to the surface of the soil by evaporation (the process in which a liquid changes state and turns into a gas). As the water evaporates, salts are left behind on the surface of the soil.

Plants and animals

Hot deserts have distinct characteristics that allow certain species (a type of organism that is the basic unit of classification. Individuals of different species are not able to interbreed successfully) to thrive in such an extreme environment. Plants and animals have developed adaptations (a feature of an organism's body which helps it to survive) which allow them to survive in hot and dry conditions.

Plant adaptations - xerophytic

Plants with adaptations which allow them to live in hot and dry conditions are called xerophytic (a type of plant that has adapted to living in a dry habitat such as a desert).

The following adaptations allow plants to survive in the hot desert environment:

  • Small leaves - these ensure that less water is lost from the plant by transpiration (the loss of water from leaves by evaporation through the stomata) because the leaf has a smaller surface area.
  • Tap roots - these are long roots (7-10 metres long) that reach deep under the ground to access water supplies. The tap roots are much longer and bigger than the plant which is visible at the surface.
  • Spines - some plants have spines instead of leaves, eg cactuses. Spines lose less water than leaves so are very efficient in a hot climate. Spines also prevent animals from eating the plant.
  • Waxy skin - some leaves have a thick, waxy skin on their surface. This reduces water loss by transpiration.
  • Water storage - some plants, known as succulents, store water in their stems, leaves, roots or even fruits. Plants which store water in their leaves and stems also have a thick waxy skin so that they lose less water by transpiration.
Cactuses have spines to reduce water loss.

Cactuses

Cactuses have spines to reduce water loss.

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Case study - the Thar Desert, Rajasthan, India

The Thar Desert is located in northwest India. It is one of the major hot deserts of the world with the highest population density (the average number of people in a certain area).

Many people living in this desert are subsistence farmers (only grow enough food to feed themselves and their family) but with increasing development opportunities, the human population is also growing.

Due to population pressures this environment is increasingly under threat.

Development opportunities

Despite having an extreme climate, the Thar Desert can provide development opportunities. These include:

  • Mining - the desert has valuable reserves of minerals such as feldspar, phosphorite, gypsum and kaolin. These minerals are used to produce a range of things from cement to fertilisers and are therefore valuable. Limestone and marble are also quarried in the area. Limestone is used for building and producing cement, and marble is used in construction.
  • Energy generation - energy is produced in the Thar Desert using solar panels. This energy is used to clean water supplies contaminated with salt (desalination). Wind energy is also used to generate electricity. A wind farm consisting of 75 wind turbines has the capacity to produce 60 megawatts (MW) of electricity.
  • Farming - irrigation (the channelling of water from rivers and streams to fields in order to help crops grow) in the Thar Desert has made commercial arable farming (growing crops on a large scale for sale) viable. Producing crops such as wheat and cotton has created many jobs and generated income for the local economy.
  • Tourism - the Thar Desert National Park attracts many visitors who want to see some of the 120 species found there. Tourists explore the desert with local guides on camels. Tourism is an important source of income and creates many jobs for local people. The multiplier effect (this occurs when a positive change happens, which then has a knock-on effect on other businesses e.g. a new office may open, which leads to an increase in lunchtime sandwich sales at the local cafe and more bus passengers) of tourism creates many development opportunities.
Camels and their riders cross the Thar Desert

Challenges of development

Development in the Thar Desert includes many challenges such as:

  • Extreme temperatures - temperatures in the Thar Desert can exceed 50°C in the summer months. It is hard for people to farm, work in mines or as tourist guides during these months as it is simply too hot. This makes development difficult.
  • Water supply - the supply of water to the Thar Desert is precious and limited. With only 120-240 mm of rain falling per year in the desert, water must be used sensibly and sustainably (which does not consume or destroy resources or the environment). Without water the development of mining, farming and tourism and therefore the economy would not be possible. Some parts of the desert have experienced over-irrigation, which has caused waterlogging (water that submerges land and makes it marshy) of the ground. Here the excess water has evaporated, leaving a layer of salt on the surface making it difficult to grow crops.
  • Inaccessibility - the desert covers a huge area of 200,000 sq km. Most of the desert is inaccessible due to the extreme environmental conditions and poor infrastructure. Beyond the city of Jaisalmer, development is limited. This has created a honeypot site(a popular visitor attraction or area, where large numbers of people visit) for tourists in Jaisalmer but not beyond. Inaccessibility to many parts of the desert has led to greater differences between rich and poor.

Desertification

Causes and prevention strategies

Desertification is the process of land turning into desert as the quality of the soil declines over time. The main causes of desertification include:

  • Population growth - the population in some desert areas is increasing. In places where there are developments in mining and tourism, people are attracted by jobs. An increased population is putting greater pressure on the environment for resources such as wood and water.
  • Removal of wood - in developing countries, people use wood for cooking. As the population in desert areas increases, there is a greater need for fuel, in this case wood. When the land is cleared of trees, the roots of the trees no longer hold the soil together so it is more vulnerable to soil erosion (when earth is washed or blown away)
  • Overgrazing - an increasing population results in larger desert areas being farmed. Sheep, cattle and goats are overgrazing the vegetation. This leaves the soil exposed to erosion.
  • Soil erosion - this is made worse by overgrazing and the removal of wood. Population growth is the primary cause of soil erosion.
  • Climate change (the long term alteration of weather patterns) - the global climate is getting warmer. In desert regions conditions are not only getting warmer but drier too. On average there is less rain now in desert regions than there was 50 years ago.

Strategies to reduce desertification

Desertification can be reduced by adopting the following strategies:

  • Planting more trees - the roots of trees hold the soil together and help to reduce soil erosion from wind and rain.

  • Improving the quality of the soil - this can be managed by encouraging people to reduce the number of grazing animals they have and grow crops instead. The animal manure can be used to fertilise the crops grown. Growing crops in this way can improve the quality of the soil as it is held together by the roots of plants and protected from erosion. This type of farming is more sustainable.

  • Water management - water can be stored in earth dams (earth is used to create a circular hollow to store rain water) in the wet season and used to irrigate crops during the dry season. This is an example of using appropriate technology (simple equipment and technology that the local people are able to use easily and without much cost) to manage water supplies in the desert environment.

The great green wall

This short film from BBC News looks at how eleven countries in Africa are planting trees across the edge of the Sahara desert to bring dry lands back to life.

Trees are being planted across 8,000 km

Activity 1

Quiz

Test your knowledge of hot deserts with this 10 question multiple choice quiz.

Take the test

Activity 2

Plants and animals of the Arabian desert

Watch this short film to explore how people, plants and animals adapt to live in the Arabian desert.

Download the activity sheet below.

Have a go at the questions to see how much you have learnt.

This resource is from Teachit

Arabian desert activity sheet

Activity 3

Desert adaptations exam skills practice

Download the work sheet below and have a go at answering this exam style question on desert adaptations.

The work sheet also includes a sample answer.

This resource is from Teachit

Desert adaptations work sheet

Where next?

BBC News: The people whose land is turning to dust.

How land is turning to desert in Senegal

There's more to learn

Have a look at these other resources around the BBC and the web.

Bitesize Daily lessons
KS4 Geography
Race Across the World
video
14 - 16 Geography
Hot deserts - resource pack
Sub-Sahara Africa projects