Distribution
Deserts, both tropical and mid-latitude, are mostly found on the western margins of continents between 15° and 45° latitude in both hemispheres. These are areas where high-pressure belts and dry trade winds dominate, leading to very low rainfall.
Key desert regions include:
- Tropical deserts: Sahara (Africa), Arabian Desert, Thar (India-Pakistan), Kalahari, Namib, Australian desert, Sonoran (USA/Mexico), Atacama (Chile)
- Mid-latitude deserts: Gobi (Mongolia-China), Patagonian Desert (Argentina), Turkestan Desert (Central Asia)
Tropical deserts are often hot and dry, while mid-latitude deserts tend to have more temperature extremes.
Climate: Rainfall and Temperature Ranges
Desert climates are defined by their aridity and extreme temperature variations.
Rainfall
- Rainfall is scarce and highly unreliable, usually less than 250 mm annually
- When it does rain, it often comes in the form of short, intense showers, leading to flash floods.
- Some deserts like the Atacama can go years without measurable rainfall
Temperature Ranges
- Tropical deserts: Very high day temperatures (often above 45°C) and low night temperatures due to lack of cloud cover
- Mid-latitude deserts: Greater annual and diurnal ranges – hot in summer and cold in winter, with frosts at night
Deserts show huge temperature contrasts – both daily and seasonally.
Climatic Conditions in Mid-Latitude Deserts
Mid-latitude deserts like the Gobi and Patagonian are not as intensely hot as tropical deserts, but their dryness is equally harsh.
Key features:
- Aridity: Caused by being far from oceans (continental interiors) or behind mountain ranges (rain-shadow effect)
- Depressions: Occasionally, temperate cyclones may bring brief showers or snow during winters
- Convectional Storms: In summer, intense surface heating may cause short-lived convectional thunderstorms, often accompanied by dust storms
Despite seasonal differences, the overall moisture remains low, and the air is dry and crisp.
Desert Vegetation
Vegetation in deserts is sparse and specialized, designed to survive with minimal water.
Key characteristics:
- Xerophytic vegetation: Plants adapted to dry conditions – like cacti, thorny bushes, and succulents
- Features include deep roots, thick waxy leaves, and the ability to store water
- Most plants grow widely spaced to avoid competition for moisture
- Soil is sandy and deficient in humus, due to low organic matter from plants or animals
- Vegetation blooms rapidly after rain but dries out quickly
In some deserts like the Kalahari, patches of grass and shrubs appear during wetter periods.
Life in Deserts
Despite the harsh environment, people have adapted to desert life in creative and resilient ways.
Primitive Hunters and Collectors
- Found in isolated, resource-poor deserts like the Australian Outback
- Survive on wild berries, roots, and small game
- Highly nomadic, depending entirely on natural availability
The Nomadic Herdsmen
- Found in deserts like the Sahara and Gobi
- Depend on camels, goats, or yaks that can survive harsh terrain
- Move in search of water and pasture; known for tribal lifestyles and traditional dress
- Examples: Tuaregs in Sahara, Bedouins in Arabian desert, Mongols in Gobi
The Caravan Traders
- Trade has historically flourished through desert caravans, using camels as the “ships of the desert”
- Caravans linked remote oasis towns with larger trade hubs
- The trans-Saharan trade was one of the most significant desert-based commerce systems
The Settled Cultivators
- Found near oases, rivers, or where irrigation is possible (e.g., Nile Valley)
- Grow date palms, wheat, barley, and vegetables using canals, wells, or qanats
- Settlements are compact and closely knit, often built with mud or clay for insulation
The Mining Settlers
- Deserts are often rich in minerals and fossil fuels – e.g., oil in Arabia, uranium in the Sahara, copper in Atacama
- Mining towns have sprung up around resource zones, attracting workers and development
- However, these are often isolated, with challenges related to water supply and transportation
