Impact Assessment of the Indira Gandhi Canal on the Avifauna of the Thar Desert

Abstract

The Thar Desert is one of the smallest deserts in the world. The origin of the Thar is a controversial subject—some scientists consider it to be 2,000–4,000 years old, while others are of the opinion that it is more than 10,000 years old. Avian diversity in the Thar is quite spectacular, and 364 species of birds have been reported from the region. The significance of this rich diversity of birdlife becomes clear by considering that, of 88 families of birds found on the Indian subcontinent, 63 are reported from the Thar. The Indira Gandhi (IG) Canal was constructed to rejuvenate the Thar region, and it has had many positive socioeconomic impacts. However, the ecological impacts of this new canal water supply have mainly been negative. The xeric biodiversity of the region is under threat, to the point of extinction of some species. As many as 153 species of plants have disappeared from the irrigated region of the Thar Desert. About 21% of the flora has changed in the Sriganganagar District, where irrigation is being practiced for the past seven decades. This change has been of lesser magnitude (about 12%) in Bikaner, where irrigation is being practiced for the past two decades. This clearly indicates that, with time, the floral composition of the region will change and, hence, also the faunal composition. As many as 22 bird species reported in the 19th century by two English naturalists have vanished from the region. Many desert-adapted species, such as the great Indian bustard, houbra, Stoliczka’s bushchat and white-bellied sand grouse, are under threat of extinction. Many mesic and water-loving bird species are invading the region from Haryana, Punjab and Pakistan. Many mesic species found in the Aravalli hills have extended their range into the Thar Desert because of environmental changes brought about by the IG Canal. All these water-loving and mesic species of birds are increasing at the cost of desert-dwelling species. To conserve xeric avifauna in the Thar, continuous ecological monitoring of the desert is absolutely necessary so that these ecological impacts are assessed and remedial measures taken.