TOPIC: The Living World: DesertsSlide 1: The distribution of hot deserts

Describe the distribution of hot deserts. (2marks)

Most deserts are found on or close to 30° north or south of the equator.

Deserts are commonly found on the western side of continents such as the deserts found in the west of North and South America.

Large areas of desert are also fond inland including the Gobi desert in Asia, large areas of desert in Australia and the Sahara desert in northern Africa.

TOPIC: The Living WorldSlide 2: The characteristics of hot deserts

What is a desert?

An area that receives less than 250mm rainfall per year.

Climate:

• Less than 250mm rainfall per year.

• Extremely hot daytime temperatures (can reach up to 50°𝐶)

• High daily temperature range. At night temperatures can drop down towards 0°C. There can be a difference of 35 degrees between day and night in a desert. This is called the diurnal temperature range.

Soils:

• Sandy or stony.

• Little organic matter – infertile.

• Dry but can soak up water quickly after heavy rain.

• Evaporation because of high temperatures draws salts to the surface leaving a white crust on the ground.

TOPIC: The Living WorldSlide 3: Hot deserts - Plant adaptations

Explain how plants have adapted to the difficult conditions found in hot deserts. (6marks)

Plants have adapted to the following difficult conditions:

Lack of water:

• Succulent plants can store water in their roots, stems, leaves or fruits. Cacti are an example.

• Seeds or desert flowers can stay dormant for years and germinate quickly when it rains. They can complete their whole life cycle (produce more seeds) within a month.

• Small leaves, spines, waxy leaves all help to reduce water loss.

• Some plants have long tap roots to reach water (7-10m deep)

• Some plants have a large horizontal root system that covers a large area.

• Acacia trees have developed short, fat trunks to store water.

High temperatures:

Some plants have the bulk of their biomass below the ground where it is cooler.

TOPIC: The Living WorldSlide 4: Hot deserts – animal adaptations:

Explain how animals have adapted to the difficult conditions in hot deserts. (6marks)

Animals have adapted to the following difficult conditions:

• High temperatures:

• Many rodents are nocturnal and therefore only come above ground in the cooler night time temperatures.

• Desert foxes have thick fur on the soles of their feet to stop them burning their feet. They also have light coloured fur to reflect sunlight and keep them cooler.

• Camels can tolerate body temperatures of up to 40 degrees C.

Lack of water:

• Snakes and lizards have waterproof skin to retain water and only produce tiny amounts of urine.

• Kangaroo rats do not need to drink water – they get it from food.

Sand/sand storms:

• Camels have large flat feet to cope with the sandy surface. They also have long eyelashes to keep the sand out of their eyes during sand storms.

Lack of food:

• The camel stores fat in its hump to access during times where there is little food.

TOPIC: The Living WorldSlide 5: Hot deserts - The interdependence of climate, water, soils, plants, animals and people.

Outline one way in which biotic and abiotic parts of a hot desert ecosystem are interdependent. (2marks)

The abiotic (climate and soils) and biotic (animals, plants and people) components of the ecosystem are interdependent (rely on one another)

Some examples are…

• Plants get nutrients from the soil, animals eat the plants, animals and plants die returning nutrients to the soil.

• Plant roots stabilise the sandy soil stopping it from blowing away. Plants get food and water from the soil.

• People rely on the desert to sustain them ( see Thar desert case study) but must learn to use it in a sustainable way so to not destroy the natural ecosystem e.g. through desertification.

Issues to do with biodiversity:

• Desert biodiversity is far lower than other ecosystems.

• Biodiversity is threatened by dry conditions, high temperatures, short periods of rainfall.

• Specific adaptations have allowed certain species to survive in the deserts.

• Hot deserts are fragile environments. What does this mean?

Once damaged they will find it very difficult to recover. This threatens biodiversity.

An example is over grazing, over cultivation by people which dries out the land so plants and animals cannot survive (desertification)

Biodiversity: The number of variety of species living in a place.

TOPIC: The Living WorldSlide 6: Thar Desert Case study – opportunities and challenges.

Where is the Thar Desert?

North-west India and Pakistan. It is the most densely populated desert in the world – why? What opportunities are there?

1. Mineral Extraction:

• There are valuable reserves of minerals which are used by India and exported. E.g.:• Gypsum – used in making cement.

• Feldspar used to make ceramics

• Kaolin used to whiten paper.

• Also valuable reserves of stone e.g. limestone and marble used in the construction industry.

2. Tourism:

• The beautiful desert landscape is popular with tourists. 10s of 000s visit every year, mainly from Pakistan.• Desert safaris and camel rides based at Jaisalmer.

• Annual desert festival held each winter.

• Tourists provide opportunities for local people to make money by providing food or accommodation or as paid guides.

• Jaisalmer is a desert city which attracts many tourists who come to see the large fort and use it as a base to explore the desert.

• Tourism is causing problems for the city as it struggles to keep up with the demand for water.

TOPIC: The Living WorldSlide 1: Thar desert case study – opportunities.

3. Energy:

• Coal deposits. Thermal energy plant at Giral.

• Large oil field has been discovered at Barmer which could transform the local economy.

• Wind Power – India’s largest wind farm, the Jaisalmer Wind Park was constructed in 2001.

• Deserts are ideal for solar power. At Bhaleri, solar power is used to treat water.

4. Farming:

• Subsistence farming is the most common type – what is this?

Farming to feed your family.

• People graze animals such as goats and cultivate vegetables and fruit trees. People live in small dark homes to keep cool during the day and have to collect water twice a day. They live in small settlements such as Pithorai.

• Commercial farming (where goods are sold for a profit) is growing in the Thar Desert because of irrigation (adding water to crops artificially). The construction of the Indhira Ghandi Canal in 1950 revolutionised farming. Crops such as wheat, cotton, pulses and sesame can thrive.

• As farming becomes more and more intensive more and more pressure is being put on water supplies.

TOPIC: The Living WorldSlide 8: Thar Desert Case study – opportunities and challenges.

“It s impossible for people to survive in desert environments.” To what extent do you agree with this statement? (9marks)

Challenges for development in the Thar Desert:

1. Extreme temperatures – sometimes up to 50 degrees C.

• Working outside e.g. farming is very difficult.

• High rates of evaporation lead to water shortages so farming is tough and it is hard for people to survive.

• Livestock such as cattle and goats need shade to protect them from the sun.

2. Water supply challenges:

• Population growth, increased farming and industry have put huge pressure on the water supply.

• Annual rainfall is low. High temperatures and high winds lead to high levels of evaporation.

• Rivers such as the Luni are intermittent. This means that they only flow after rainfall. Most settlements are located beside these rivers.

• Some water can be got from underground but it tends to be salty and poor quality.

• Irrigation schemes such as the Indhira Ghandi Canal have allowed farming to expand and have lessened the problem of water supply in some areas.

TOPIC: The Living WorldSlide 8: Thar Desert Case study – opportunities and challenges.

To what extent s a hot desert environment you have studied facing opportunities and challenges. (9marks)Discuss the opportunities provided in a hot desert environment you have studied. (9marks)

Challenges for development in the Thar Desert:

3. Accessibility:

Very limited road network due to high temperatures causing tarmac to melt and wind blowing sand across the roads.

Many places only accessible by camel and the only public transport is overloaded buses.

To what extent are there opportunities and challenges in the Thar desert.

• There are huge challenges to be faced as extreme heat, lack of water and inaccessibility make life extremely hard for the people who live there.

• However, there must also be huge opportunities as the Thar Desert is the most populated in the world and there are a variety of ways people can survive from subsistence farming, working in tourism as well as economic opportunities from mineral resources and energy creation.

• The problem of water shortages has been eased by irrigation projects such as the Indhira Ghandi Canal.

• However, the challenges are only likely to get worse in the future as population growth and a growing demand for resources especially water puts increasing pressure on this fragile environment.

TOPIC: The Living WorldSlide 10: Hot deserts - desertification

Outline two human causes of desertification. (4marks)Explain how population growth can lead to desertification. (4marks)

Key idea: Area on the fringe of hot deserts are at risk from desertification.

What is desertification?

The process by which land becomes drier and degraded, as a result of climate change or human activities, or both.

What are the causes of desertification?

1. Climate change. This makes temperatures warmer and rainfall less reliable in some desert areas although the impacts of global warming on these areas are currently debatable.

2. Population growth. This put pressure on the vegetation and land in 3 ways:

1. Overgrazing – what is this?

Grazing too many animals for too long on the land, so it is unable to recover its vegetation.

This is being done as there are more people to feed.

2. Over cultivation – what is this?

Exhausting the soil by over-cropping the land. (growing too many crops) This is being done because there are more people to feed.

3. Removal of fuel wood – trees and vegetation are cut down to provide fuel for the growing population.

TOPIC: The Living WorldSlide 11: Causes of desertification

All these activities remove vegetation which protects the soil in the following ways.

• Roots bind the soil together.

• Vegetation add nutrients to the soil when it dies.

• Trees intercept rainfall, slowing it down which means the water is more likely to soak into the ground rather than running off over the surface and leading to soil erosion.

• Trees shade the ground and stop the sun baking the ground hard.

Without vegetation, soil erosion will occur and this leads to desertification.

Therefore any activity that removes vegetation (overgrazing, over cultivation or removal of fuelwood) will contribute to desertification.

How big is the problem?

1 billion people are threatened around the world. It affects every continent except Antarctica.

The Sahel (southern Sahara) is an example of an area threatened. 50million poor and vulnerable people live there with littlemoney or technology available in their countries.

TOPIC: The Living WorldSlide 12: Strategies used to reduce the risk of desertification:

Explain how appropriate technology can be used to tackle desertification. (4marks)

There is a need for soil and water management to reduce the risk of desertification. There is also a need for the use of appropriate technology. What is this?

(Also called Intermediate technology) Technology that is suited to the needs, skills, knowledge and wealth of local people inthe environment in which they live. It usually combines simple ideas with cheap and readily available materials, especially for use in poorer countries, and is environmentally friendly.

There is no point in using expensive machinery and methods to tackle this problem if people and countries cannot afford to maintain it.

2 examples:

1. Acacia Tree Planting in Senegal in the Sahel:

2. Building stone lines in Burkina Faso.

TOPIC: The Living WorldSlide 13: Hot deserts – Examples of soil and water management as strategies to reduce desertification.

Assess how soil and water management techniques can contribute to tackling desertification. (9marks)

1. Acacia tree planting in Senegal:

Locals were taught how to sow and plant the trees ad the UN provided a nursery to grow seedlings.

They were given a tractor to help them plant the trees to reduce the labour.

How does this manage water?

• Trees intercept water, slow it down and allow it time to soak into the ground rather than runoff over the surface and erode the soil.

• Trees provide shade to reduce evaporation.

How does this manage the soil?

• Roots bind the soil together.

• Shade stops the sun baking the soil hard.

• Trees intercept rainfall and stop it washing soil away.

• Trees return nutrients to the soil

The trees also provide an income as gum can be harvested and sold.

TOPIC: The Living WorldSlide 14: Hot deserts – Examples of soil and water management as strategies to reduce desertification.

Outline one way in which we can tackle desertification (2marks)

2. Stone lines in Burkino Faso in the Sahel

Line of stones are laid out along contour lines on slopes. Behind them trees such as Acacia trees are planted.

How does this manage water?

• The stones stop water running down the slope and it collects behind the lines of stones and soaks into the ground. This provides ideal conditions for trees and other crops to be grown.

How does this manage the soil?

• Instead of water eroding the soil and washing it away down the slope, soil collects behind the stone lines providing ideal conditions for planting trees and crops. Soil erosion is prevented.

This technique is an excellent example of appropriate technology.

The stones are found lying around in the local area, all that is required is education about the use of the technique.

Both projects have been hugely successful at tackling and reversing the process of desertification where they have been implemented.

TOPIC: The Living WorldSlide 15: Hot deserts – To what extent can the problem of desertification be managed?

To what extent can the problem of desertification be managed? (9marks)

To what extent can the problem of desertification be managed?

• There are a variety of strategies that can tackle the problem of desertification such as planting trees and building stone lines. These have been hugely successful in the areas they have been implemented.

• These projects use appropriate technology and can therefore can be implemented over a large scale with minimal resources.

• However, the scale of the problem is huge (1billion affected across 6 continents) therefore there is a long way to go before we have solved it. In addition population growth continually increases pressure on resources which may worsen the threat of desertification in the future.

• There is also the problem of climate change which will currently have an unknown effect

• Overall, in many areas the problem of desertification has been tackled successfully, however, the scale of the problem means that many more are at risk than have been helped and this number is sure to increase in the future.

TOPIC: Living WorldCase Study: Hot DesertsFacts Quiz

How far north and south of the equator are hot deserts normally found?

30° north and south of the equator.

How much rainfall do deserts receive?

Less than 250mm.

How hot can temperatures get in deserts?

Up to 50 degrees C

What can the temperatures range be between day and night?

35 degrees C.

Name an example of a succulent plant (one that can store water)

Cactus.

What body temperature can camels cope with?

40 degrees C

Name an example of a mineral available in the Thar Desert.

Kaolin or Feldspar

TOPIC: Living WorldCase Study: Hot DesertsFacts Quiz

Name a city in the Thar Desert that attracts tourists.

Jaisalmer

Name a location in the Thar Desert with coal deposits.

Giral

Name a type of animal grazed in the Thar Desert.

Goat

Name the canal in the Thar Desert that was built in 1950 that allowed more commercial farming

Indhira Ghandi Canal

Name an intermittent river in the Thar Desert. (a river that only flows after rainfall)

The River Luni

Give three causes of desertification

Over grazing (too many animals), over cultivation (too many crops) and cutting down trees for fuel wood

How many people around the world are threatened by desertification?

1 billion

TOPIC: Living WorldCase Study: Hot DesertsFacts Quiz

How many continents are affected by desertification?

6 (all except Antarctica)

Name two strategies to cope with desertification.

Planting Acacia trees and building stone lines

Name a country where acacia trees have been planted

Senegal

Name a country where stone lines have been used.

Burkina Faso.

Where is the Sahel

The southern border of the Sahara Desert which is threatened by desertification.