Thar desert
Cholistan Desert, Pakistan (Photograph by Mauri Rautkari)
The arid Thar Desert is the world's seventh largest desert and is without doubt the most inhospitable ecoregion in the Indo-Pacific region.
However, 4000 to 5000 years ago this area supported what is considered to be one of the world's oldest civilizations, the Mohenjo Daro and Harappa.
Location and General Description
This large ecoregion lies to the west of the Aravalli Mountain Range in northwestern India and includes the deserts that cover portions of the Indian states of Gujarat, Rajasthan, and Punjab, as well as the Punjab and Sind in Pakistan. At the west margin of the Thar Desert lies the Indus River.
Source: WWF
The climate is extreme: annual temperatures can range from near-freezing in the winter to more than 50oC during the summer. All rainfall is associated with the short July-September southwest monsoon that brings a mere 100-500 millimeters of precipitation. About 10 percent of this ecoregion is composed of sand dunes, and the other 90 percent of craggy rock forms, compacted salt-lake bottoms, and interdunal and fixed dune areas.
The habitat is greatly influenced by the extreme climate. The sparse vegetation consists of xerophilious grasslands of Eragrostis spp. Aristida adscensionis, Cenchrus biflorus, Cympogon spp., Cyperus spp., Eleusine spp., Panicum spp., Lasiurus scindicus, Aeluropus lagopoides, and Sporobolus spp. Scrub vegetation consists of low trees such as Acacia nilotica, Prosopis cineraria, P. juliflora, Tamrix aphylla, Zizyphus mauritiana, Capparis decidua, and shrubs such as Calligonum polygonoides, Calotropis spp., Aerva spp., Crotalaria spp., and Haloxylon salicornicum. Haloxylon recurvum is also present.
Biodiversity Features
Despite the climate, several species have evolved to survive the extreme conditions here. Among the mammal fauna, the blackbuck (Antilope cervicapra), chinkara (Gazella bennettii), caracal (Felis caracal), and desert fox (Vulpes bengalensis) inhabit the open plains, grasslands, and saline depressions known as chappar or rann in the core area of the desert. The overall mammal fauna consists of forty-one species. None are endemic to the ecoregion, but the blackbuck is a threatened species whose populations take refuge in this harsh environment.
Among the 141 birds known in this ecoregion, the great Indian bustard (Chirotis nigricaps) is a globally threatened species whose populations in this ecoregion have rebounded in recent years. A migration flyway used by cranes (Grus grus, Anthropoides virgo) and flamingos (Phoenicopterus spp.) on their way to the Rann of Kutch further south crosses this ecoregion.
Chaudhry et al. reported eleven reptile species from ten genera from the Cholistan desert in the western Thar.
Current Status
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Table 1. WCMC (1997) Protected Areas That Overlap with the Ecoregion. Protected Area Area (km2) IUCN Category Nara Desert 7,290 IV Desert 2,710 II Tando Mitha Khan 220 UA Rann of Kutch 10,540 IV Nara 600 UA Cholistan 21,830 UA Rahri Bungalow 50 UA Abbasia 100 UA Ramgarh Bundi 300 IV Lal Suhanra 70 V Tal Chapar 80 IV Total 43,790 There are eleven protected areas that cover almost 44,000 kilometers2, representing about 18 percent of the ecoregion's (Thar desert) area (Table 1). These include several reserves that are quite large, with one (Cholistan) exceeding 20,000 km2, and two (Nara Desert, Rann of Kutch) being over 5,000 km2. Types and Severity of ThreatsThe Thar probably is the world's most densely populated desert. Grazing of livestock, mostly sheep and goats, is intensive, affecting soil fertility and destroying native vegetation. Many palatable perennial species are being replaced with inedible annual species, thus changing the vegetation composition and the ecosystem dynamics. Availability of water since the completion of the Indira Gandhi Canal Scheme has provided irrigation water to the once nonarable desert, thus attracting farmers to the area. Salt pans for commercial salt production will have serious impacts on Sambhar Lake in Rajasthan. Together with recent climatic changes, these pressures combine to degrade and destroy the fragile desert [[ecosystem]s]. Justification of Ecoregion DelineationIn a previous assessment of conservation units, MacKinnon (1997) assigned the deserts in northwestern India and Pakistan into four subunits (I3a-d). We used MacKinnon's (1997) digital map of original habitat to reclassify these biounits into eight [[ecoregion]s] based on the extent of distinctive habitat of [[region]al] spatial scales. Under this schema, we assigned the Thar deserts into its own ecoregion, the Thar Desert . This ecoregion falls within Udvardy's Thar Desert biogeographic province. Additional Information on this Ecoregion
Further Reading
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