Note: This chapter was removed from the NCERT curriculum in the 2022 rationalization. Retained here as desert ecosystems, the Thar Desert, and Ladakh (cold desert) are directly relevant to UPSC GS1 (Physical Geography) and GS3 (Environment, security — Ladakh is strategically important).

PART 1 — Quick Reference Tables

Hot Desert vs Cold Desert

Feature Hot Desert (Sahara / Thar) Cold Desert (Ladakh / Atacama highland)
Temperature Extreme — 45–55°C in day; −10 to 0°C at night Cold — summers 15–25°C; winters −20 to −40°C
Rainfall <250 mm/year; often <100 mm <100 mm/year (precipitation mostly as snow)
Cause Subtropical high pressure (30° lat.) Rain shadow of mountains (Himalayas block monsoon from Ladakh)
Vegetation Sparse — cacti, thorny scrub, oases Alpine steppe — sparse grasses, cushion plants
Key examples Sahara (Africa), Thar (India/Pakistan), Arabian, Australian Ladakh (India), Atacama highlands, Patagonian desert

World's Major Deserts

Desert Location Size Type
Antarctic Desert Antarctica ~14.2 million km² Cold polar
Arctic Desert Arctic ~13.9 million km² Cold polar
Sahara North Africa ~9.2 million km² Hot
Arabian Desert Arabian Peninsula ~2.3 million km² Hot
Gobi Central Asia (Mongolia/China) ~1.3 million km² Cold
Patagonian South America (Argentina) ~670,000 km² Cold
Great Victoria Australia ~647,000 km² Hot
Thar India/Pakistan (Rajasthan/Sindh) ~200,000 km² Hot

PART 2 — Detailed Notes

The Sahara — World's Largest Hot Desert

Explainer

Sahara Desert:

  • Largest hot desert: ~9.2 million km² — covers ~31% of Africa
  • Stretches across 11 countries: Morocco, Algeria, Tunisia, Libya, Egypt, Mauritania, Mali, Niger, Chad, Sudan, Eritrea
  • Not all sand: Only ~25% is sandy (erg — sand sea); 75% is rocky (hamada — stony plateau) or gravel (reg)
  • Temperature extremes: Day: 50°C+; Night: can drop below 0°C; sand has extremely low heat capacity

How people live in the Sahara:

  • Nomadic herders (Tuareg, Bedouin, Berber): Move with their animals (camels, goats) following water and pasture; traditional lifestyle under pressure from modern borders and drought
  • Oasis settlements: Permanent settlements around underground water sources (artesian wells, springs); date palm cultivation; caravan trading posts
  • Modern cities: Algiers, Tripoli, Khartoum — on the Sahara's edges; dependent on deep aquifers and oil revenues

Great Green Wall Initiative:

  • African Union project to grow an 8,000 km-wide belt of trees across the southern Sahara (Sahel zone) to halt desertification
  • 20 countries participating; aim to restore 100 million hectares by 2030
  • Progress: ~15–18% complete as of 2025; mixed results

The Thar Desert — India's Great Desert

UPSC Connect

UPSC GS1 — Thar Desert:

Basic facts:

  • Location: Rajasthan (India) and Sindh/Punjab (Pakistan) — extends ~200,000 km² total; India's portion ~170,000 km²
  • Only large hot desert in South Asia
  • Bounded: Aravalli Hills on the east (prevent monsoon rains from reaching deeper into Rajasthan), Sindh Plain to the west, Rann of Kutch to the south
  • Annual rainfall: <100 mm in the west; 300–400 mm on the eastern edge (relatively "wetter")

Why the Thar exists — the Aravalli controversy: The Aravallis run from SW to NE (roughly parallel to moisture-bearing winds) rather than perpendicular, so they do NOT block the southwest monsoon effectively. The desert's aridity is more due to: distance from moisture source + subtropical high pressure + dry continental winds from west.

Flora and fauna:

  • State tree of Rajasthan: Khejri (Prosopis cineraria) — can survive extreme drought; nitrogen-fixing; edible pods; the Bishnoi community died protecting it (Chipko-like movement in 1730 CE — Amrita Devi and 363 Bishnois killed protecting khejri trees)
  • State animal of Rajasthan: Chinkara (Indian Gazelle) — adapted to arid conditions; can survive on dew
  • Great Indian Bustard (GIB): Critically endangered; ~150 individuals (2025 estimate); last stronghold in Rajasthan (Jaisalmer, Pokhran); threatened by power lines, hunting, habitat loss; Supreme Court ordered power line undergrounding in GIB areas
  • Wildlife: Desert fox, desert monitor lizard, spiny-tailed lizard, Indian eagle-owl

Resources:

  • Oil and natural gas: Barmer-Sanchore basin (Rajasthan) — significant oil production (Mangala, Bhagyam, Aishwarya fields); operated by Cairn India/Vedanta
  • Solar energy: Thar has India's highest solar radiation; Rajasthan is India's top solar energy producing state (~52 GW installed capacity as of 2025); Bhadla Solar Park (Jodhpur) = world's largest solar park (~2,200 MW+)
  • Wind energy: Strong winds especially in Jaisalmer district
  • Minerals: Gypsum (construction), feldspar, limestone (cement)

Water in the Thar:

  • Indira Gandhi Canal (Rajasthan Canal): Longest irrigation canal in India (~650 km); diverts water from Harike Barrage (Punjab) → transforms western Rajasthan; enables agriculture in previously desert areas
  • Traditional water harvesting: Tanka (underground tank), Johad (village pond), Kund (catchment cistern), Bawdi (stepwell) — traditional methods reviving under water conservation movements (like Tarun Bharat Sangh by Rajendra Singh — "Waterman of India")

Ladakh — India's Cold Desert

UPSC Connect

UPSC GS1/GS3 — Ladakh:

Geography:

  • Union Territory (since October 2019, carved out of J&K under J&K Reorganisation Act 2019)
  • Bordered: Tibet (China) to the east, Pakistan (PoK) to the north, Himachal Pradesh to the south, Kashmir Valley to the west
  • Altitude: Most of Ladakh is above 3,000 m; Leh is at 3,500 m; many passes above 5,000 m
  • Cold desert: Rain shadow of Himalayas and Karakoram blocks all moisture; annual rainfall <50–100 mm

Why cold desert? (Rain shadow effect):

  • Southwest monsoon is blocked by the Greater Himalayas before reaching Ladakh
  • Western disturbances bring some snowfall in winter
  • Result: Desert conditions despite being surrounded by the world's highest mountains

Ecology:

  • Sparse vegetation: alpine steppe grasses, cushion plants, willow/poplar along stream banks
  • Snow leopard: Apex predator of the Himalayas; endangered; Ladakh is one of the best places to see them; estimated 200–300 individuals in India
  • Black-necked crane: Migratory; breeds in Ladakh; India's only crane species; state bird of Sikkim; listed as Vulnerable
  • Kiang: Tibetan wild ass; found in Changthang plateau (Ladakh); largest wild equid in the world
  • Hangul (Kashmir stag): Critically endangered; restricted to Kashmir Valley + Dachigam National Park; ~300 individuals

Strategic importance of Ladakh:

  • Line of Actual Control (LAC): Dispute with China; Aksai Chin administered by China (claimed by India)
  • Siachen Glacier: World's highest battlefield; India controls it since 1984
  • Galwan Valley standoff (June 2020): Violent clash between Indian and Chinese troops; 20 Indian soldiers and ~4 Chinese killed; triggered largest India-China military standoff in decades; subsequent diplomatic and military measures (BRO roads, forward posts)
  • Border Roads Organisation (BRO): Constructs strategic roads in Ladakh; Atal Tunnel (Rohtang, 8.8 km) provides all-weather connectivity to Leh

Traditional life and water:

  • Zingchen/Nomadic herders (Changpa): Breed Pashmina goats (wool for world-famous Pashmina/Cashmere shawls)
  • Zanskar Valley: Extremely remote; the famous Chadar Trek — walking on frozen Zanskar River in winter (only winter route before road built)
  • Glacial meltwater: Primary water source for Ladakh; climate change is accelerating glacier retreat
  • Artificial glaciers (Icestupa): Invented by Sonam Wangchuk (inspiration for 3 Idiots' Phunsukh Wangdu); cones of ice formed in winter → melt slowly in spring when crops need water; innovative water conservation solution

Exam Strategy

Prelims traps:

  • World's largest desert = Antarctic Desert (cold polar, ~14 million km²) — NOT Sahara (largest HOT desert, ~9 million km²); common trick question
  • Thar = hot desert in Rajasthan (NOT cold); Ladakh = cold desert — distinguish clearly
  • Great Indian Bustard (GIB) = critically endangered, ~150 remaining (2025) — Rajasthan; Supreme Court case about power lines
  • Ladakh = UT since 2019 (without legislature — unlike J&K which became UT with legislature); Leh and Kargil are two districts
  • Bhadla Solar Park = world's largest solar park (Rajasthan); Rajasthan = India's #1 solar energy state
  • Indira Gandhi Canal (Rajasthan Canal) = longest canal in India (~650 km main canal + distributaries)
  • Pashmina wool = Changpa nomads' Pashmina goats (Ladakh) — NOT regular wool; cannot be called Pashmina unless from this species in this region

Previous Year Questions

Prelims:

  1. The world's largest desert (by area) is:
    (a) Sahara Desert
    (b) Arabian Desert
    (c) Antarctic Desert
    (d) Gobi Desert

  2. The Great Indian Bustard, which is critically endangered and found mainly in Rajasthan, is threatened primarily by:
    (a) Poaching for its feathers
    (b) Habitat loss and collision with overhead power lines
    (c) Competition from invasive species
    (d) Drought and desertification

  3. The "Chadar Trek" in Ladakh involves walking on:
    (a) A glacier in the Karakoram mountains
    (b) The frozen Zanskar River in winter
    (c) A dried river bed during summer
    (d) A mountain ridge connecting Leh to Manali

  4. Sonam Wangchuk's concept of "Ice Stupa" (artificial glacier) was developed to address which problem in Ladakh?
    (a) Prevent avalanches near villages
    (b) Provide irrigation water in spring when crops need water but natural snow has not yet melted
    (c) Create tourist attractions for winter sports
    (d) Cool down Ladakh's rising summer temperatures