South Deccan Plateau Dry Deciduous Forests

The South Deccan Plateau Dry Deciduous Forests lie to the east of the Western Ghats. They lie in the range’s rains shadow. That is, in an area leeward to the mountains, where the annual precipitation is very low on account of the Western Ghats acting as a barrier to the movement of rain-bearing clouds and capturing all the moisture. Hence, the region’s flora and fauna have to make do with far less water than is available to the inhabitants of the montane rain forests and moist deciduous forests of the Ghats. They give way to an even more arid zone, the Deccan Thorn Scrub Forests to the north and east. The regions of Male Nadu in western Karnataka and Kongu Nadu in western Tamil Nadu harbour most of the South Deccan Plateau Dry Deciduous Forests. Given below is a description of the ecoregion by the World Wildlife Fund for Nature (WWF):

Although not exceptionally outstanding for biological richness or endemism by itself, the South Deccan Plateau Dry Deciduous Forests ecoregion is contiguous with the moist deciduous forests that lie along the foothills of the southern extent of the Western Ghats Mountains. Two of India’s most important elephant conservation areas, the Nilgiris-Eastern Ghats and the Anamalais-Nelliampathis, and two of the most important TCUs extend across three ecoregions: the South Western Ghats Montane Rain Forests, South Western Ghats Moist Deciduous Forests, and South Deccan Plateau Dry Deciduous Forests. Together, these three ecoregions provide an important, contiguous habitat landscape for conservation of Asia’s largest terrestrial herbivore and predator.

The ecoregion represents a large area of tall, tropical dry forests in the southern Deccan Plateau, on the leeward side of the Western Ghats Mountain Range. It extends across the southern Indian states of Karnataka and Tamil Nadu. The ecoregion’s links to the ancient, southern circumpolar continent, Gondwanaland, are evident in the biotic links to Africa and Madagascar. The ecoregion’s vegetation is highly influenced by climate. The tall Western Ghats Mountain Range intercepts the moisture from the southwest monsoon; therefore, the eastern slopes and the Deccan Plateau receive very little rainfall; annual rainfall ranges from 900 to 1,500 mm. The undulating hillsides have very shallow soils. The dry deciduous forests of this ecoregion are flanked by the moist deciduous forests along the lower elevations and foothills of the Western Ghats to the west and by thorn scrub to the east. Therefore, this ecoregion probably represents a transition zone between the moister western vegetation and the drier vegetation to the east.

Champion and Seth classified these forests as Southern Dry Mixed Deciduous Forests, where Teak (Tectona grandis) is not conspicuous. Thorny plants become more common in areas where grazing pressure is high. Structurally, these dry forests have a three-storied forest, with an upper canopy at 15-25 m, an understory at 10-15 m, and undergrowth at 3-5 m. Lianas drape the trees in denser, mature forests. The vegetation is characterized by Boswellia serrata, Anogeissus latifolia, Acacia catechu, Terminalia tomentosa, Terminalia paniculata, Terminalia belirica, Chloroxylon swietenia, Albizzia amara, Cassia fistula, Hardwickia binata, Dalbergia latifolia, Sterospermum personatum, Pterocarpus marsupium, Diospyros montana, and Shorea talura, among others. One of the important species of this forest, Sandalwood (Santalum album), has been selectively removed from most of the forests in this ecoregion.

Although not high in endemism or diversity, the ecoregion harbors several important populations of India’s large threatened vertebrates whose populations are fast declining throughout their ranges because of habitat loss and hunting pressure. For instance, the elephant population that ranges from the Nilgiri Hills to the Eastern Ghats, estimated at more than 6,000 animals, is considered to be the largest single elephant population in India. A second important population ranges along the Anaimalai and Nelliampathi Hills. Two high-priority TCUs (Periyar-Kalakad and Dandeli-Bandipur) overlap with parts of this ecoregion. The ecoregion’s mammal fauna includes seventy-five species. One, the critically endangered Salim Ali Fruit Bat (IUCN 2000), is a near-endemic species. Other threatened mammals include the Asian Elephant (Elephas maximus), Wild Dog (Cuon alpinus), Sloth Bear (Melursus ursinus), Chousingha (Tetracerus quadricornis), Gaur (Bos gaurus), and Grizzled Giant Squirrel (Ratufa macruora). The bird fauna consists of about 260 species, of which two are near-endemic species.

Endemic and Near-Endemic Mammal Species (an asterisk signifies that the species’ range is limited to this ecoregion)

  • Pteropodidae Latidens salimalii

Endemic and Near-Endemic Bird Species (an asterisk signifies that the species’ range is limited to this ecoregion)

  • Timaliidae Turdoides subrufus
  • Pycnonotidae Pycnonotus xantholaemus

Two species in this ecoregion, the Indian Bustard (Ardeotis nigriceps) and Lesser Florican (Eupodotis indica), are globally threatened and warrant conservation attention. More than 80 percent of the ecoregion’s forests have been cleared, but two large blocks of contiguous habitat remain in the north. There are seven protected areas that cover about 1,100 sq km, or a little more than 1 percent of the ecoregion. But none of these exceed 500 sq km; therefore, the ecoregion’s protected area system is woefully inadequate to conserve the several large vertebrates in this ecoregion.

Protected Areas That Overlap with the Ecoregion

  • Bilgiri Ranga Swamy
  • Bannerghatta
  • Melkote
  • Ranganthittu
  • Arabithittu
  • Cauvery
  • Vedanthangal

Most of the dry deciduous forests represented by this ecoregion have already been degraded to thorn scrub. The remaining forests are highly threatened with conversion to cash crop plantations, excessive fuel-wood collection, and overgrazing by large herds of cattle. The habitat contiguity with the moist deciduous forests along the foothill of the Western Ghats, in particular, has been severed in several areas by conversion to agricultural lands. Large areas of forested land are lost to development projects such as dams, mining, and resettlement of displaced people. Many of the habitat areas that will be lost to large-scale hydroelectric projects now serve as refuges for the ecoregion’s biodiversity. The conservation status of the ecoregion was changed from endangered to critical because of the threats from human population to the remaining forest blocks.

Poaching is a major threat in this ecoregion. The capacity to protect and manage the ecoregion’s biodiversity is lacking, especially because these habitats are perceived as being unimportant for biodiversity conservation. Where conservation efforts have been made, poor planning has resulted in the introduction of exotic species and conversion of grassland and open scrub habitat that are important for many focal species such as bustards and floricans. A major threat in the future will be the development of these areas for mining and industrialization. Licenses have been granted to exploit several areas in the ecoregion, and there is an urgent need to counter these initiatives by setting aside key areas for conservation of the ecoregion’s representative biodiversity. In a previous analysis of conservation units, Rodgers and Panwar (1988), and subsequently MacKinnon (1997), divided the Deccan Peninsula into five biotic provinces. This ecoregion lies within Rodgers and Panwar’s Deccan Plateau South biotic province. But this biotic province contains several vegetation types.

Image Attribution: The image above, sourced from Wikimedia Commons, shows a Grizzled Giant Squirrel (Ratufa macroura). The photograph was uploaded by Firos AK, and taken in Chinnar Wildlife Sanctuary, Kerala. The species is found in South India and Sri Lanka.