The physical characteristics and adaptations of hot deserts, the opportunities and challenges of developing a hot desert, the causes of desertification, and strategies to reduce the risk.

What this dot point is asking

This is AQA GCSE Geography (8035) Paper 1, Section B (3.1.2 The living world). Hot deserts is the optional ecosystem you study if your school does not study cold environments. AQA expects you to describe the climate, soils and biodiversity of hot deserts, explain how plants and animals are adapted, use a case study (the Thar Desert) to assess the opportunities and challenges of developing a hot desert, explain the causes of desertification, and evaluate strategies to reduce the risk.

Physical characteristics and adaptations

Hot deserts lie in two belts around 30 degrees north and south of the Equator, where the dry, sinking air of the Hadley cell prevents cloud and rain from forming. The climate is very hot by day (often over 40 degrees Celsius) but cold at night (sometimes near freezing) because the clear, dry skies that let intense heat in by day let it escape rapidly after sunset. Rainfall is very low and unreliable, less than 250 mm a year. Soils are thin, sandy, salty and low in nutrients because there is little vegetation to add organic matter and little rain to weather the rock. Biodiversity is low because the lack of water is such a powerful limiting factor, but the species that survive are highly specialised.

Developing a hot desert: the Thar Desert

The challenges of development are: extreme heat that limits the hours people can work and increases water demand; an unreliable, scarce water supply that limits farming and can cause the canal water to evaporate or salinise the soil; and poor accessibility, because building and maintaining roads and railways across shifting sand and dunes is difficult and expensive, isolating communities.

Desertification

Strategies to reduce desertification include water management (drip irrigation that delivers water straight to roots, and small earth bunds or stone lines that trap water and let it soak in), tree planting to bind the soil and provide shade (the Great Green Wall initiative across the Sahel), soil management such as adding manure to restore fertility, and appropriate (intermediate) technology such as solar cookers and efficient stoves that cut the demand for fuel wood.

Try this

Q1. State two ways a cactus is adapted to the desert. [2 marks]

• Cue. A thick stem to store water and spines to reduce water loss and deter grazers.

Q2. Explain two causes of desertification. [4 marks]

• Cue. Over-grazing removes vegetation that protects soil; climate change brings less rain and higher temperatures, drying out the land.