What is a Desert?
A desert is any area that receives less than 10 inches (25 cm) of precipitation per year. That's the defining feature — not necessarily heat. Deserts cover about one-third of Earth's land surface and come in two main types: hot deserts and cold deserts.
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Hot Deserts
Scorching & Dry
- The Sahara (Africa) is the world's largest hot desert — nearly the size of the United States
- The Arabian Desert covers most of the Middle East
- The Sonoran Desert (USA/Mexico) is one of the most biologically diverse deserts on Earth
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Cold Deserts
Frozen & Dry
- Antarctica is actually the world's largest desert — it receives almost no precipitation
- The Gobi Desert (China/Mongolia) has extreme temperature swings between seasons
- Cold deserts have freezing winters but can be very hot in summer
Desert Animal Adaptations
Desert animals have evolved remarkable strategies to survive extreme heat, cold nights, and almost no water.
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Camel
Desert Traveler
- Humps store fat (not water) — which can be converted to energy during long journeys
- Wide, flat feet spread their weight on sand like natural snowshoes
- Long eyelashes and closeable nostrils protect against blowing sand
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Fennec Fox
Heat Dissipator
- Enormous ears act like radiators — blood vessels release heat into the air
- Get almost all their water from the food they eat — rarely need to drink
- Dig deep burrows to escape the midday heat and sleep through the hottest hours
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Sidewinder Snake
Sand Mover
- Moves in a distinctive S-shaped sideways motion to minimize contact with hot sand
- Nocturnal — hunts at night when temperatures are cooler
- Can detect the body heat of prey using heat-sensing pits on its face
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Scorpion
Nocturnal Hunter
- Fluoresce under ultraviolet light — glow bright blue-green in the dark
- Can slow their metabolism to survive on a single insect meal per year if needed
- Thick exoskeleton prevents moisture loss in the driest desert conditions
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Desert Lizard
Sun Regulator
- Cold-blooded — use the sun to warm up and shade to cool down
- Many have light-colored scales that reflect sunlight and reduce heat absorption
- Can run bipedally (on two legs) to move quickly across hot sand
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Roadrunner
Fast Runner
- Prefers running over flying — can reach speeds of 20 mph on foot
- Eats venomous rattlesnakes and scorpions — immune to their venom
- Absorbs morning sun through dark patches on its back to warm up quickly
Desert Plant Adaptations
Desert plants have evolved extraordinary ways to find, store, and conserve water in one of Earth's most challenging environments.
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Cactus
Water Storer
- Stores water inside its thick, fleshy stem — a large saguaro can hold 200 gallons
- Spines are actually modified leaves that reduce water loss and deter animals
- Shallow but wide root system quickly absorbs any rainfall across a large area
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Sagebrush
Drought Resistant
- Small, gray-green leaves with a waxy coating to prevent water loss
- Produces aromatic oils that give the desert its distinctive smell after rain
- Deep taproot reaches groundwater far below the surface
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Joshua Tree
Desert Icon
- Actually a type of yucca — found only in the Mojave Desert of California
- Spiky leaves minimize water loss while still conducting photosynthesis
- Can live for hundreds of years and grow very slowly — about 3 inches per year
🏜️ The Sahara Desert
The Sahara is the world's largest hot desert — covering about 3.5 million square miles across North Africa. It's larger than the contiguous United States! Temperatures can reach 136°F (58°C) during the day and drop below freezing at night. Despite its harshness, over 500 plant species, 70 mammal species, and 90 bird species live there.
Desert Facts
#1
Largest desert on Earth is Antarctica — not the Sahara! Antarctica receives almost no rain or snow
3.5M mi²
Size of the Sahara Desert — the world's largest hot desert, spanning 11 African countries
136°F
Hottest temperature ever recorded on Earth — in the Sahara Desert in Libya in 1922
33%
of Earth's land surface is desert — more than any other land biome type
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