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.
The climate is extreme: annual temperatures can range from near-freezing in the winter to more than 50(C during the summer. All rainfall is associated with the short July-September southwest monsoon that brings a mere 100-500 mm of precipitation (Hawkins 1986). 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 (Grewal 1992).
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. (Mares 1999). 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 (Puri et al. 1989; Mares 1999).
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 (Grewal 1992; Rodgers and Panwar 1988). The overall mammal fauna consists of forty-one species. None are endemic to the ecoregion, but the blackbuck is a threatened species (IUCN 2000) 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 (IUCN 2000) 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 (Grewal 1992) further south crosses this ecoregion.
Chaudhry et al. (1997) reported eleven reptile species from ten genera from the Cholistan desert in the western Thar.
There are eleven protected areas that cover almost 44,000 km2, representing about 18 percent of the ecoregion's 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.
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
Ecoregion numbers of protected areas that overlap with additional ecoregions are listed in brackets.
Types and Severity of Threats
The 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 (Hawkins 1986), 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 (Allan and Warren 1993). 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 ecosystems.
Justification of Ecoregion Delineation
In 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 ecoregions based on the extent of distinctive habitat of regional spatial scales. Under this schema, we assigned the Thar deserts into its own ecoregion, the Thar Desert [IM1304]. This ecoregion falls within Udvardy's Thar Desert biogeographic province.
References for this ecoregion are currently consolidated in one document for the entire Indo-Pacific realm.
Indo-Pacific Reference List
Prepared by: Gopal S. Rawat and Eric D. Wikramanayake