Introduction

The Northwestern Thorn Scrub Forests ecoregion represents a large expanse of degraded dry forest surrounding the Thar Desert. Neither exceptionally species-rich nor high in endemism, the ecoregion nevertheless harbors viable populations of chinkara (Gazella bennettii), chousingha (Tetracerus quadricornis), and blackbuck (Antilope cervicapra)

Location and General Description

Pushkar, Rajastan, India. (Photograph by Boschidar Ganev)

The ecoregion represents the thorn scrub forests in northwestern region of theIndian subcontinent. Many ecologists consider this thorn scrub to represent a degraded state of tropical dry forests. The ecoregion stretches across the border between India and Pakistan and covers parts of Gujarat, Rajasthan, Haryana, and Punjab states of India and the lower parts of Jammu and Kashmir. The average annual rainfall in this arid ecoregion is less than 750 millimeters (mm). The temperature can exceed 45 degrees Celsius (^oC) during the hottest months, and in winter temperatures can drop to below freezing.

The flat alluvial lowlands extend into the low hills. Local variations in soil salinity affect the distribution of vegetation; patches of highly saline soil usually are bare of vegetation. The vegetation is stunted and open, dominated by Acacia species such as A. senegal and A. leucophloea that rarely exceed 6 meters (m) in height. Other characteristic species that make up the vegetation are Prosopis spicigera, Capparis zeylanica, Salvadora spp., Carissa spp., Gymnosporia spp., Grewia spp., and Gardenia spp. and xerophytic climbers such as species of Tragia, Rivea, Tinospora, Vitis, and Peristrophe. In drier areas, the thorn forest transitions into xerophytic shrubland and semiarid vegetation, usually dominated by Euphorbia species. Intermingled with the Euphorbia scrub is a Zizyphus scrub that is characterized by Zizyphus nummularia with Acacia leucocephala, Acacia senegal, Anogeissus pendula, and Dicrostachys cinerea. The poor soils along rocky tracts promote a Cassia-Butea community. Closer to the coast, where the soils are more saline, the community includes Salvadora and Tamarix. The southwestern part of the Aravalli Range supports a distinct deciduous forest characterized by Anogeissus pendula, Aegle marmelos, Boswellia serreta, Cassia fistula, Mitragyna parviflora, Diospyros melanxylon, and Wrightia tinctoria.

Biodiversity Features

The ecoregion is not exceptionally rich or high in endemism but does harbor several large mammals of conservation importance, including the leopard (Panthera pardus), caracal (Felis caracal), chinkara (Gazella bennettii), chousingha (Tetracerus quadricornis), and blackbuck (Antilope cervicapra). Overall, the mammal fauna consists of about ninety species, including two bats that are endemic to the ecoregion (Table 1).

Both of these bats are strict endemics, their known range being limited to this ecoregion. The chousingha and blackbuck are threatened species and should be focal species for conservation actions.

The Aravalli Hill Ranges and the surrounding flat areas support two very distinct rodent communities that are influenced by the geology, soil, and vegetation conditions. Detailed studies are under way to determine the species composition of these communities.

The bird fauna consists of an impressive list of more than 400 species, among the highest for ecoregions in this bioregion. The list includes two endemic species (Table 2).

The rufous-vented prinia is a strict endemic limited to this ecoregion, and the white-winged tit is a near endemic shared with the adjacent Khathiarbar-Gir Dry Deciduous Forests. The ecoregion also harbors the globally threatened Indian bustard (Ardeotis nigriceps) and lesser florican (Eupodotis indica).

Current Status

More than 90 percent of this ecoregion's natural habitat has been converted, and only small, scattered fragments remain. There are an astounding sixty protected areas in the ecoregion (Table 3), but they cover only about 11,000 square kilometers (km²⁾, or just over 2 percent of the ecoregion area. Many of the protected areas are small, at an average size of just over 175 km².

The local people, especially the Bishnoi communities, have a cultural reverence for wild animals, particularly blackbuck and the tree Prosopis cinerea. For this reason, the wildlife and habitat have been protected over the years.

Types and Severity of Threats

Blackbuck (Antilope cervicapra), Pakistan. (Photograph by WWF / Mauri Rautkari

This ecoregion is subject to intensive degradation threats from livestock grazing. Associated human impacts such as lopping and cutting of vegetation for fuelwood, setting fires to create grazing lands, and settlements also contribute to habitat degradation. The marble beds of the ancient Aravalli Range are being heavily mined. Rodgers and Panwar present an analysis of conservation gaps and needs for the Indian part of the ecoregion.

Justification of Ecoregion Delineation

In a previous analysis of conservation units, MacKinnon placed these desert and thorn scrub forests of northwestern India and Pakistan in Biounit (13) along with other habitat types that included dry deciduous forests and deserts. In keeping with our rules for representing distinct habitat types of regional extent in separate ecoregions, we used MacKinnon's digital map of the original vegetation to delineate and separate the thorn scrub forests from the desert and dry deciduous forests. The thorn scrub around the Thar Desert therefore was placed in the Northwestern Thorn Scrub Forests. The Northwestern Thorn Scrub Forests lie in both the Indus-Ganges monsoon forest and Thar Desert biogeographic provinces.

Additional information on this ecoregion

• For a shorter summary of this entry, see the WWF WildWorld profile of this ecoregion.
• To see the species that live in this ecoregion, including images and threat levels, see the WWF Wildfinder description of this ecoregion.
• World Wildlife Fund Homepage