Hot deserts

Question 1

Describe the hot desert climate.

Answer 1

Very dry – <250mm rainfall per year. Very extreme temps – up to 45˚C in the day; below freezing at night.

Question 2

Explain the hot desert climate.

Answer 2

At 30˚N and 30˚S of the equator, air that has risen at the equator descends to form high pressure = lack of cloud formation = lack of precipitation.

Question 3

Describe hot desert soils.

Answer 3

Sandy/stony, dry & shallow. Soak water up quickly. Little organic matter due to lack of leafy vegetation. Not very fertile due to salinisation.

Question 4

How are hot deserts interdependent?

Answer 4

Animals spread seeds through dung = plants reproduce. Sparse vegetation keeps animal population sizes in check. Extremely dry so adaptation by people & animals is necessary.

Question 5

How have plants adapted to hot desert conditions?

Answer 5

Long plant roots to reach deep water supplies. Cacti – large stems for storing water & thick waxy skin to reduce transpiration. Low surface area to reduce transpiration.

Question 6

How have animals adapted to hot desert conditions?

Answer 6

Some are nocturnal to avoid searing daytime temps. Camels – store fat in hump; break down into water. Long eyelashes to bat sand away. Large, flat feet to spread weight over sand to prevent sinking.

Question 7

How are cactus mice adapted to hot desert conditions?

Answer 7

Get all the water they need from cactus fruits & insects.

Question 8

What is biodiversity like in hot deserts?

Answer 8

Fairly low. Highest on temporary ponds on edges of deserts.

Question 9

How do humans affect biodiversity in hot deserts?

Answer 9

Building roads divides habitats & affects migration patterns of animals like desert bighorn sheep.

Question 10

Define ‘transpiration’.

Answer 10

The evaporation of water from plant leaves, stems or flowers.

Question 11

How do mineral resources provide opportunities for economic development in the Sahara?

Answer 11

Increase export income and GNI. Create jobs. Morocco – world’s largest exporter of phosphate. Holds 75% of world’s phosphate reserves.

Question 12

What can phosphate be used in?

Answer 12

Fertilisers, cleaning products & batteries.

Question 13

How do oil & gas provide opportunities for economic development in the Sahara?

Answer 13

Increase export income and GNI. Create jobs. Algeria – 60% of income comes from oil & gas industry; employs 40,000 people.

Question 14

How does solar energy provide opportunities for economic development in the Sahara?

Answer 14

Increase export income. Create jobs. Help meet targets. Tunisia – 400 hectare power plant in Gafsa will produce 30% of Tunisia’s renewable energy by 2030.

Question 15

How does tourism provide opportunities for economic development in the Sahara?

Answer 15

Create jobs. Marrakech – desert treks & sandboarding are popular activities.

Question 16

How does farming provide opportunities for economic development in the Sahara?

Answer 16

Increase export income and GNI. Increase food security. Egypt – Aswan Dam provides year-round water supply; important for irrigating crops.

Question 17

Challenges of economic development in the Sahara: Population

Answer 17

Harsh weather = only 2 million people live in Sahara, many nomadic. Lack of workforce to develop industries.

Question 18

Challenges of economic development in the Sahara: Extreme temperatures

Answer 18

Exposure to big temp. range = illness & death. Tourism can only be seasonal; many months too hot for tourists.

Question 19

Challenges of economic development in the Sahara: Inaccessibility

Answer 19

Sahara is huge. Expensive pipelines built to transport oil, gas & mineral resources from remote parts of desert. 5 days needed to transport salt from mines in Mali.

Question 20

Challenges of economic development in the Sahara: Water supply

Answer 20

Rainfall is unpredictable = difficult to provide enough water for workers, irrigation & industry.

Question 21

Define ‘desertification’.

Answer 21

The degradation of land so that it becomes more desert-like.

Question 22

What proportion of the world’s land is at risk of desertification?

Answer 22

A third.

Question 23

How many people live in areas at risk of desertification?

Answer 23

Approximately 1 billion.

Question 24

Natural causes of desertification: Climate change

Answer 24

Climate will become drier in already-dry places = less rain for plant growth = less roots to stabilise soil = loose top-soil = easily blown away by wind.

Question 25

Natural causes of desertification: Climate change

Answer 25

Climate will become hotter = quicker evaporation of water from soil = salinisation = salt leaves soil infertile = less plant growth to stabilise soil.

Question 26

Human causes of desertification: Deforestation

Answer 26

Wood needed for cooking & fuel = deforestation = less nutrients returned to soil by leaf decomposition = infertility = soil becomes sandy & dusty.

Question 27

Human causes of desertification: Overgrazing

Answer 27

Too many cattle/sheep eating plants faster than they can re-grow = soil erosion as no plants to bind soil together.

Question 28

Human causes of desertification: Over-cultivation

Answer 28

Growing the same crops continually exhausts nutrients in soil = nutrients unable to recover = infertility = plants unable to grow = soil erosion.

Question 29

Human causes of desertification: Trampling

Answer 29

Too many cattle/sheep heavily walking over plants = die = less soil stability due to lack of roots.

Question 30

Human causes of desertification: Population growth

Answer 30

Pressure on land on margins of deserts as a result of growing populations. Exacerbates other human causes of desertification.

Question 31

How can water management be used to reduce desertification?

Answer 31

Drip irrigation – only delivering water to plant roots reduces salinisation = reduces soil infertility. Growing crops that don’t need much water e.g. millet or olives.

Question 32

How can tree planting be used to reduce desertification?

Answer 32

Protect soil from wind erosion. Stabilise soil; prevent desert encroaching on farmland. Provide shade to crops = reduces temp. & evaporation rates.

Question 33

How does Prosopis cineraria (Thar Desert) help reduce risk of desertification?

Answer 33

Produces good quality firewood. Provides shade & moist growing conditions for plants. Roots stabilise sand dunes.

Question 34

How can soil management be used to reduce desertification?

Answer 34

Allow areas to rest in between grazing and planting so nutrients can be recovered. Rotate crops so same nutrients not always removed. Add compost to add extra nutrients to soil.

Question 35

How can appropriate technology be used to reduce desertification?

Answer 35

Construct sand fences & terraces to stabilise soil & reduce erosion. Use solar cookers (which use sun’s energy to heat food) to reduce need for deforestation.