Thar Desert

• 1. Introduction

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  The Thar Desert covers 264091 square kilometres of the north-western Indian subcontinent, and an international border runs straight through it. About two-thirds of the desert lies in India, and most of that is in the state of Rajasthan. The rest belongs to Pakistan. People also call it the Great Indian Desert. Most deserts are close to empty, but this one is among the most populated on Earth. Villages, herds and small fields are scattered across its sand. How did a land once fed by rivers and rain turn dry? Where does a person find water there today? What lives in the thorn scrub, and which empires crossed this ground? The answers begin with ice.

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• 2. Ice and Lost Monsoons

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  Long before any dune formed, the ground beneath the Thar was a low plain lying under shallow water. That was in the Mesozoic era, between 252 and 66 million years ago. Erosion later carved three layers of flattened land surfaces, called planation surfaces, across the following periods. Then the Himalayas rose during the mid-Miocene, between 23.4 and 5.3 million years ago, and their rise gave birth to the monsoon.

  The decisive change came during the Last Glacial Maximum, 26,000-20,000 years ago. An ice sheet estimated at 2400000 square kilometres covered the Tibetan Plateau. Because it sat at a low latitude, it threw back at least four times more sunlight per unit area than ice at higher latitudes. The air above it cooled. Without the heated, low-pressure air that pulls rain inland, no monsoon formed over the subcontinent.

  The same shift brought heavy rainfall to the Sahara region, while more dust settled toward the Arabian Sea. Animals responded too. Javan rusa deer were among the species that migrated into India as its life zones changed. Yet ice alone did not finish the job. A nearer mountain range, the Aravallis, was still rising.

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• 3. The River That Never Reached the Sea

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  Between 10,000 and 8,000 years ago, a channel of the Ghaggar-Hakra River met the Sutlej and flowed on into the Nara River, a delta channel of the Indus. Then it changed course. This channel is identified with the paleo Sarasvati River.

  The Aravalli Range had formed rapidly and reached significant height in the early Holocene, about 11,700 years ago. Its rise redirected the water. More flowed through the Yamuna River, while the headwaters of the Ghaggar-Hakra were starved. What remained was a set of monsoon-fed rivers that no longer reached the sea. They ended in the Thar.

  Starting around 4,500-5,000 years ago, the monsoons weakened further, because the Aravallis blocked the monsoon winds arriving from the east. The land grew steadily drier. The Indus Valley Civilisation had prospered here, with settlements strung along the river system. As the rains faded, the Hakra shrank into an intermittent river. The urban Harappan civilisation declined, and its people withdrew into smaller agricultural communities.

  Wind meanwhile carried sediment from the alluvial plains and the coast, and sand piled up over the old river country. Beneath that sand, the rock tells its own story.

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• 4. Stone Beneath the Dunes

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  Near the Aravallis, the eastern Thar rises to about 325 metres, and the land slopes down to 150 metres at the India-Pakistan border. Between those marks lie sandy plains broken by low, eroded hills. Dunes cover much of the ground. They are built from wind-blown sand laid over alluvial sediment. Each year, strong winds rise before the monsoon arrives, and the sand moves easily. Most of the bedrock beneath is igneous and metamorphic.

  The oldest rocks sit in the Barmer region in the south. They are volcanic and made of felsite. Around Pokhran, shales appear in many colours and degrees of hardness. South of Jodhpur, pale sandstones made mostly of quartz come to the surface.

  Farther west, the stone carries fossils. Sandstones from the Jurassic period, 201.4-143.1 million years ago, lie east of Barmer and to the east and north of Jaisalmer. Around Jaisalmer, sandstone beds are capped by sandstone and limestone layers full of fossils. Builders use this rock extensively. To the west and north-west, dark sandstone holding calcium lies under a cap of red sandstone, with yellow ammonite rocks scattered through it.

  Those same Jurassic layers near Jaisalmer would later hold a far larger surprise.

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• 5. Rationing Water

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  In the peak of summer, temperatures in the Thar often climb above 50 C. In winter, the minimum can fall to -2 C. Rain arrives mostly with the southwest monsoon from June to September, and the average is less than 500 millimetres a year. The total swings widely from one year to the next, and long droughts are common. The semi-arid east has fewer dunes and slightly more rain.

  Underground water is a poor bargain. The water table lies at varying depths, and the water is mostly brackish. On the surface, the Luni River system is the only major river system, and the Luni itself is the longest river in the desert. Its tributaries include the Bandi, Ghaggar, Guhiya, Jawai, Jojari, Liladi and Sukri.

  The desert also holds salt lakes with no outlet to the sea, among them Sambhar, Kharaghoda, Didwana, Pachpadra and Phalodi. They fill during the monsoon and slowly evaporate in the dry months. Their salt comes from the weathering of surrounding rock.

  Villagers store rain in reservoirs called tobas, johads and taankas. The largest lifeline is the 649 km Indira Gandhi Canal, which carries water from the Indus river system for irrigation and drinking.

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• 6. Empires at the Edge

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  Stone tools of the Aterian culture, a Middle Paleolithic people of the Maghreb, have turned up in the Thar. That is a long way from home. Around 1900 BCE, after the Indus Valley Civilisation collapsed, Indo-Aryan peoples migrated into north-western India. During the Vedic period, 1500-500 BCE, the Kuru kingdom emerged as the earliest Vedic state. A super-tribe had joined several tribes into one unit. Earlier, small settlements of the Painted Grey Ware culture had appeared in the Ghaggar-Hakra valley.

  By the third century BCE, the Mauryan Empire held much of the subcontinent, including parts of the desert. The Kushan Empire pushed in from what is now Afghanistan in the middle of the 1st century CE. The Gupta Empire flourished between the 2nd and 6th centuries CE. At its peak in the 5th century, it took in the whole Thar region.

  The east passed through many hands. A Brahmin dynasty ruled in the 7th and 8th centuries before being annexed to the Umayyad Caliphate in the early 8th century, and later to the Abbasid Caliphate. The Pratihara dynasty held the east from the 8th to the 11th century. Then Mahmud of Ghazni brought the region into the Ghaznavid Empire.

  Rajput states began forming in the west from the late 7th century and rose to prominence later. The Soomras and the Sammas ruled the east from the later 11th to the early 16th century. Then came the Timurid king Babur, whose invasion was resisted by the Rajput states under Rana Sanga. The conflict with the Mughal Empire lasted more than 200 years. The Rajputs retook control once the Mughal empire began to collapse in the late 16th century.

  The Marathas took most of the region in the 18th century. In the 19th century, it fell under the suzerainty of the British Raj. It was a patchwork of princely states, with power shared between local rulers and the British.

  The partition of India split the desert between two new countries and brought large-scale conflict and mass migration. Most of the eastern desert became part of Rajasthan, with smaller portions in Haryana, Punjab and Gujarat. The western third went to the provinces of Sindh and Punjab in Pakistan. More population exchanges followed in 1965 and 1971. About 3,500 people, mostly Muslims, moved from India to Pakistan. Thousands of Hindu families crossed the other way.

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• 7. Life in the Thorn Scrub

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  Botanists count 168 plant species from 48 families in the Thar. The natural cover is northwestern thorn scrub forest, made of small, loosely scattered patches of green. The patches grow denser and larger from west to east, following the rainfall. Native species include Calligonum polygonoides, Acacia nilotica, Tamarix aphylla and Cenchrus biflorus. Shrubs and perennial herbs fill the spaces between trees in low-lying ground.

  Dry soil is the desert's weakness. High winds lift it, drop some on neighbouring fertile land, and keep the dunes moving. To hold the sand, workers first build tiny windbreak barriers from scrub. They then plant the treated dunes. Shrubs include Cassia auriculata and Ricinus communis. Trees include Acacia senegal, Prosopis juliflora and Albizzia lebbeck.

  The animal life mixes desert and damper habitats. About 60 mammal species, 51 reptile species and eight amphibian species have been reported. Roughly 69 percent of the reptiles and amphibians and 54 percent of the mammals are affiliated with the Sahara region. Mammals include the chinkara, desert fox, Indian fox, desert cat, hairy-footed gerbil, desert hare and long-eared hedgehog.

  The reptiles include 14 lizards and seven snakes. The Rajasthan toad-headed lizard and the Sindh awl-headed snake are found only here. The desert monitor and the saw-scaled viper live here too. In 2023, fossils of a new sauropod dinosaur, Tharosaurus indicus, were found in the Jaisalmer Formation. It dates to the Bathonian age of the Middle Jurassic.

  More than 100 bird species, resident and migratory, use the desert. The Oriental white-backed vulture and the Indian vulture are endangered, and the Houbara bustard visits. The Great Indian Bustard is critically endangered and is one of the world's heaviest flying birds. The Indian peafowl breeds here and has adapted to the desert.

  Several protected areas shelter this life. In India, Desert National Park in Rajasthan covers 3162 square kilometres and includes the Akal Wood Fossil Park. Tal Chhapar Sanctuary in Churu district covers just 7 square kilometres and is an Important Bird Area. Sundha Mata conservation reserve, in Jalore district, covers 117.49 square kilometres. In Pakistan, Nara Desert Wildlife Sanctuary covers 6300 square kilometres in Mirpurkhas District. Lal Suhanra Biosphere Reserve and National Park in Cholistan is a UNESCO biosphere reserve covering 65,791 hectares.

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• 8. People of the Thar

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  The Thar holds 83 people per square kilometre, a density that places it among the most populated deserts in the world. The Thar people are its natives, and they include Hindus, Muslims and many ethnic groups. Marwari is the most widely spoken language in the central and eastern parts. Sindhi is heard in the southwest and Lahnda in the northwest.

  Most people live in rural communities, many of them nomadic. Their huts are shaped like cylindrical beehives under conical thatched roofs. The huts stand in small, irregular clusters, yet the layout is careful about privacy. The entrances of neighbouring huts never face each other. Middle-class families in permanent settlements live in single-storey homes with large rectangular courtyards and wide verandahs. Local timber supports them, and clay plasters the upper side.

  One tree does much of the work. The khejri, Prosopis cineraria, gives high-quality fuel wood and building material. Its roots also fix nitrogen, which raises crop yields.

  Scarcity still shapes daily life. Villages often have only a few water sources, such as temporary wells and storage ponds. People spend a great deal of time fetching water for themselves and their animals. The harsh environment and distance from the outside world have held back development.

  Oil exploration by the Government of India began in 1955 and 1956. Natural gas was discovered in the Jaisalmer basin in 1988. Tourists now come for camel safaris across the dunes, which has built an ecotourism industry. The newest harvest comes from the sun. Bhadla Solar Park has a generation capacity of over 2 gigawatts.

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