BharatNotes 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
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 (launched 2007) to restore an 8,000 km-long belt of land across the southern Sahara (Sahel zone) from Senegal to Djibouti; 11 core countries
- Aim: Restore 100 million hectares by 2030; create 10 million jobs; sequester 250 million tonnes of carbon
- Progress (2025): Only ~20 million hectares (~20%) restored so far; significantly behind target; Senegal leads but even there many plantings have failed; political instability in Sahel (Mali, Burkina Faso, Niger coups) has disrupted implementation
- Funding: Of $14.3 billion pledged at COP26 (2021), only $2.5 billion disbursed by 2023
The Thar Desert — India's Great Desert
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; Bhadla Solar Park (Jodhpur district) = 2,245 MW capacity; world's largest single-location solar park (though China's Talatan Solar Park at 15,600 MW surpasses it in total capacity); 56 sq km area; 10 million solar panels
- 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 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
[Additional] 9a. India's Desertification Crisis — ISRO Data, UNCCD, LDN Targets, and NAPCD
The chapter covers the Thar Desert's ecology but lacks India's desertification and land degradation data — the ISRO SAC atlas findings, India's LDN commitment to the UNCCD, the NAPCD, and India's 26 million hectare restoration target — all of which are heavily tested in UPSC GS3.
Key Terms — Desertification and Land Restoration:
| Term | Meaning |
|---|---|
| Desertification | Degradation of land in arid, semi-arid, and dry sub-humid areas resulting from various factors including climatic variations and human activities; defined by the UNCCD |
| UNCCD | United Nations Convention to Combat Desertification — one of the three Rio Conventions (with UNFCCC and CBD); adopted June 17, 1994; entered into force December 26, 1996; 197 parties; Secretariat = Bonn, Germany |
| LDN | Land Degradation Neutrality — UNCCD target: a state where the amount and quality of land resources remains stable or increases within specified ecosystems and time periods; countries set voluntary LDN targets |
| NAPCD | National Action Programme to Combat Desertification — India's plan submitted to UNCCD outlining status of desertification and government response measures; first submitted 2001; revised 2023 |
| ISRO SAC Atlas | Desertification and Land Degradation Atlas of India — published June 2021 by Space Applications Centre (SAC), ISRO; uses remote sensing data for 2018-19 base year; the authoritative source for India's land degradation statistics |
| Bonn Challenge | Global effort to restore 150 million hectares of degraded land by 2020 and 350 million hectares by 2030; India pledged 13 mha by 2020 + additional 8 mha by 2030 when it joined in 2015 |
[Additional] India's Desertification — ISRO Data, UNCCD/LDN Commitments (GS3 — Environment):
India's land degradation — ISRO SAC data (trend over three periods):
| Period | Land Degraded (mha) | % of India's Total Land |
|---|---|---|
| 2003–05 | 94.53 mha | 28.76% |
| 2011–13 | 96.40 mha | 29.32% |
| 2018–19 | 97.85 mha | 29.7% |
India's total geographical area (TGA) = 328.72 mha.
Of the 97.85 mha degraded in 2018-19, specifically 83.69 mha underwent desertification (up from 81.48 mha in 2003-05 — consistently worsening).
Nine most-affected states/UTs (ISRO SAC 2021): Rajasthan, Maharashtra, Gujarat, Karnataka, Ladakh, Jharkhand, Odisha, Madhya Pradesh, and Telangana — together accounting for 23.79% of India's total land area undergoing degradation. Rajasthan alone accounts for approximately 22% of India's total degraded land.
Key causes of land degradation in India (ISRO SAC):
- Water erosion (most widespread — 83% of degraded area)
- Wind erosion (Thar Desert + coastal areas)
- Vegetation degradation/deforestation
- Salinity/alkalinity (waterlogged/irrigated areas in Punjab, Haryana)
- Mining (Jharkhand, Odisha, Chhattisgarh)
UNCCD — India's framework:
| Parameter | Detail |
|---|---|
| India ratified UNCCD | 1996 |
| NAPCD first submitted | 2001 (MoEF&CC, Desertification Cell = UNCCD focal point) |
| NAPCD revised | 2023 (includes 26 mha restoration target + 2.5–3 billion t CO2 carbon sink by 2030) |
| LDN target (India) | Land Degradation Neutrality by 2030 under UNCCD |
| Restoration target | 26 million hectares by 2030 — announced by PM Modi at COP14 of UNCCD (New Delhi, September 2019); increased from earlier target of 21 mha |
| Area restored so far | ~18.94 mha restored as of last reported figures |
| Bonn Challenge pledge | 13 mha by 2020 + 8 mha by 2030 (India joined 2015) |
UNCCD COP14 (New Delhi, 2019) — significance:
- India hosted UNCCD COP14 in Greater Noida, September 2–13, 2019 — first time India hosted a UNCCD COP
- PM Modi announced increase of India's land restoration target from 21 mha to 26 mha by 2030
- Theme: "Restoring Land, Sustaining Life"
- Delhi Declaration adopted — called for enhanced international support for land restoration
UNCCD COP15 (Abidjan, Côte d'Ivoire, May 2022):
- Theme: "Land. Life. Legacy: From scarcity to prosperity"
- India reiterated commitment to restore 26 mha by 2030
- COP15 collectively committed parties to restore 1 billion hectares globally by 2030
- India's Minister Bhupender Yadav represented India
India's land restoration pledge — GS3 UPSC connect: India's 26 mha restoration target by 2030 is also linked to India's NDC (Nationally Determined Contribution) under the Paris Agreement — creating an additional carbon sink of 2.5–3 billion tonnes of CO2 equivalent by 2030 through additional forest and tree cover.
UPSC synthesis: Desertification = GS3 Environment + GS2 International Conventions. Key exam facts: UNCCD = adopted June 17, 1994 = entered into force December 26, 1996 = 197 parties = Secretariat Bonn, Germany (same city as IPBES); India's land degradation = 97.85 mha = 29.7% of total land (ISRO SAC, 2018-19 data, published 2021); desertification specifically = 83.69 mha; India's LDN/restoration target = 26 mha by 2030 = announced at COP14 UNCCD, Greater Noida, September 2019; NAPCD first = 2001 = revised 2023; most affected state = Rajasthan (~22% of India's degraded land); Bonn Challenge = India joined 2015 = 13 mha by 2020. Prelims trap: UNCCD = Bonn, Germany Secretariat (NOT Geneva — IPBES is also in Bonn; UNFCCC Secretariat is also in Bonn; CBD Secretariat is in Montreal — three Rio Conventions have different HQs); India's restoration target = 26 mha (NOT 21 mha — was updated from 21 to 26 mha at COP14 in 2019; both figures appear in old sources, so always use 26 mha); UNCCD COP14 = India (Greater Noida) = 2019; UNCCD COP15 = Abidjan, Côte d'Ivoire = 2022; land degradation = 29.7% of India's land (NOT 30% — this is the 2018-19 figure; 30% is an approximation that appears in some sources).
[Additional] 9b. Ladakh's Strategic Geography — LAC Sectors, Pangong Tso, Key Routes, and BRO Projects
The chapter briefly mentions Ladakh's strategic importance (LAC, Galwan) but lacks the geographic framework — the three LAC sectors and their lengths, Pangong Tso's India-China division, key passes, DSDBO Road, Atal Tunnel details, and the 2024 disengagement — that are essential for UPSC GS3 (Security) and GS2 (International Relations).
Key Terms — Ladakh's Strategic Geography:
| Term | Meaning |
|---|---|
| LAC | Line of Actual Control — de facto boundary between India and China; NOT a demarcated/surveyed line; both sides have different perceptions of where it runs; India claims total length ~3,488 km; China claims only ~2,000 km |
| Western Sector | LAC sector covering Ladakh — ~1,597 km; the most disputed sector; friction points include Depsang, Galwan, Pangong Tso, Gogra, Demchok |
| Middle Sector | LAC covering Himachal Pradesh + Uttarakhand — ~545 km; relatively peaceful |
| Eastern Sector | LAC covering Arunachal Pradesh + Sikkim — ~1,129 km; contentious; McMahon Line is India's claimed boundary |
| Aksai Chin | ~38,000 sq km high-altitude plateau; India claims as part of Ladakh UT (India's claim based on Johnson Line, 1865); China administers as part of Xinjiang/Tibet; China built a 1,200 km road through it in the 1950s = trigger for 1962 war |
| DSDBO Road | Darbuk–Shyok–Daulat Beg Oldie Road — strategic BRO-built road in Ladakh running parallel to LAC, enabling year-round access to Daulat Beg Oldie (DBO) — India's northernmost outpost near the Karakoram Pass |
| Atal Tunnel | 9.02 km all-weather tunnel through Rohtang at 3,100 m altitude; inaugurated October 3, 2020; provides year-round Leh connectivity |
[Additional] Ladakh Strategic Geography — LAC, Pangong Tso, DSDBO, Atal Tunnel (GS3 — Security / GS2 — International Relations):
LAC — three sectors:
| Sector | States Covered | Approximate Length | Dispute Level |
|---|---|---|---|
| Western | Ladakh (UT) | ~1,597 km | Highest — multiple active friction points |
| Middle | Himachal Pradesh + Uttarakhand | ~545 km | Low — relatively stable |
| Eastern | Arunachal Pradesh + Sikkim | ~1,129 km | Moderate — Arunachal claimed by China |
| Total | — | ~3,488 km (India's claim) | — |
Pangong Tso — key facts:
| Parameter | Detail |
|---|---|
| Total length | 134 km |
| India's share | ~1/3 (~45 km on India's side, Ladakh) |
| China's share | ~2/3 (~90 km on China's side, Tibet) |
| Altitude | ~4,350 m (14,270 ft) |
| Salinity | Brackish (not freshwater); salinity too high to freeze easily but edges freeze in winter |
| LAC position | The LAC passes through the lake; the Finger Area (numbered spurs = "Fingers") on the northern bank was the 2020 friction point |
| Strategic significance | Lies on the Chushul approach — key route for potential Chinese advance toward Leh; Chushul airstrip was critical in 1962 war |
Key passes in Ladakh (strategic):
| Pass | Altitude | Significance |
|---|---|---|
| Karakoram Pass | ~5,540 m | Gateway to Xinjiang; historic Leh-Yarkand trade route; near DBO and end of DSDBO Road |
| Khardung La | 5,359 m | Route to Siachen sector; BRO-built (1976); claimed as one of highest motorable roads |
| Chang La | 5,360 m | On route from Leh to Pangong Tso |
| Zoji La | 3,528 m | Gateway to Ladakh from Kashmir; currently being tunneled (14.2 km Zoji La Tunnel) |
DSDBO Road (Darbuk–Shyok–Daulat Beg Oldie):
| Parameter | Detail |
|---|---|
| Route | Leh → Darbuk → Shyok river valley → Daulat Beg Oldie (DBO) |
| Length | ~255 km (Darbuk–Shyok–DBO section; total from Leh = ~322 km) |
| Elevation | 4,000–5,000 m (13,000–16,000 ft) throughout |
| Strategic purpose | Runs parallel to LAC; enables rapid troop/logistics movement to DBO; supports DBO airstrip (world's highest airstrip, ~5,000 m) near Karakoram Pass |
| Key feature | 500 m Bailey Bridge (world's highest Bailey Bridge) over Shyok river, inaugurated 2019; 37 bridges total |
| Significance | Near Depsang Plains — area where China blocked Indian patrolling 2020–2024 |
BRO projects in Ladakh:
| Project | Specification | Significance |
|---|---|---|
| Atal Tunnel (Rohtang) | 9.02 km; altitude 3,100 m; inaugurated October 3, 2020 | World's longest highway tunnel above 10,000 feet; provides year-round Leh connectivity, bypassing snowbound Rohtang Pass |
| Zoji La Tunnel | 14.2 km; under construction; revised completion February 2028 | Will become longest tunnel in Asia; connects Sonamarg (J&K) to Dras (Ladakh) under Zoji La pass; ~64% complete (early 2025) |
Post-Galwan disengagement timeline:
| Friction Point | Disengagement Status |
|---|---|
| Galwan Valley | June 2020 (deadly clash; 20 Indian + ~4 Chinese soldiers killed) |
| Gogra-Hot Springs (PP-17A) | September 2022 |
| Depsang Plains | Patrolling agreement: October 21, 2024; implemented December 2024 |
| Demchok | Patrolling agreement: October 21, 2024; implemented December 2024 |
The October 21, 2024 agreement on Depsang and Demchok resolved the last two unresolved friction points from the 2020 standoff. India's key demand was restoration of patrolling rights to pre-April 2020 status at all patrol points (PPs 10–13 in Depsang).
Aksai Chin — strategic significance:
| Parameter | Detail |
|---|---|
| Area | ~38,000 sq km |
| India claims | Part of Leh district, Ladakh UT (based on Johnson Line, 1865) |
| China administers | Part of Hotan Prefecture, Xinjiang + Ngari Prefecture, Tibet |
| Why China cannot concede | Aksai Chin contains the only land route connecting Xinjiang to Tibet — the G219 highway (built 1950s); losing it would sever China's Tibet logistics |
| 1962 connection | China's secret road-building through Aksai Chin (discovered 1957) was a direct trigger for the 1962 Sino-Indian War |
UPSC synthesis: Ladakh strategic geography = GS3 Security + GS2 International Relations. Key exam facts: LAC total India claim = ~3,488 km = three sectors: Western ~1,597 km (Ladakh, most disputed), Middle ~545 km (HP+UK), Eastern ~1,129 km (Arunachal+Sikkim); Pangong Tso = 134 km long = 1/3 India (~45 km) + 2/3 China (~90 km) = altitude ~4,350 m = brackish; Aksai Chin = ~38,000 sq km = India claims as Ladakh = China administers = G219 highway runs through it = 1962 war trigger; DSDBO Road = Leh to Daulat Beg Oldie = ~255 km (or 322 km from Leh total) = parallel to LAC = DBO = world's highest airstrip; Atal Tunnel = 9.02 km = 3,100 m altitude = inaugurated October 3, 2020 = world's longest highway tunnel above 10,000 ft; Zoji La Tunnel = 14.2 km = under construction = deadline February 2028 = will be longest tunnel in Asia; Depsang + Demchok disengagement = October 21, 2024. Prelims trap: Atal Tunnel = 9.02 km (NOT 8.8 km — the 8.8 km figure is commonly misquoted; BRO official site says 9.02 km); Atal Tunnel altitude = 3,100 m (NOT 3,978 m — 3,978 m is the height of Rohtang Pass itself; the tunnel cuts through lower than the pass); Pangong Tso India share = ~1/3 (NOT 1/2 — 2/3 is in China); Aksai Chin = ~38,000 sq km (NOT 5,000 sq km — that is a common error; it is larger than many Indian states); LAC Western Sector = Ladakh (NOT Arunachal — the Eastern Sector covers Arunachal; Western = Ladakh); Depsang-Demchok disengagement = October 2024 (NOT 2022 — Gogra-Hot Springs was the 2022 disengagement; Depsang+Demchok were resolved in October 2024).
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 (Rajasthan) = world's largest single-location solar park (2,245 MW); NOT the world's largest overall (China's Talatan is larger at 15,600 MW); 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
Practice Questions
Prelims:
The world's largest desert (by area) is:
(a) Sahara Desert
(b) Arabian Desert
(c) Antarctic Desert
(d) Gobi DesertThe 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 desertificationThe "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 ManaliSonam 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
