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Southern Asia: Southern India

The South Western Ghats Montane Rain Forests [IM0151] are the most species-rich ecoregion in the Deccan Peninsula. They also harbor the highest levels of endemics. Consider the numbers: 35 percent of the plants, 42 percent of the fishes, 48 percent of the reptiles, and 75 percent of the amphibians that live in these rain forests are endemic species (GOI 1997). Ten mammals and thirteen birds are endemic or near endemic to the ecoregion. More than 80 percent of the flowering plants characteristic of this mountain range are in the species-rich forests of the south. Large, charismatic mammals such as the tiger (Panthera tigris), Asian elephant (Elephas maximus), sloth bear (Melursus ursinus), gaur (Bos gaurus), and raucous hornbill inhabit the forests. These species evoke images of wild jungles of the Indian subcontinent. Large expanses of high-elevation, undulating grasslands interspersed with patches of stunted shola forests harbor the endemic Nilgiri tahr and India's largest elephant population. Every twelve years, the blue flowers of Neelakurunji (Phlebophyllum kunthianum) impart a blue hue to these grassland-shola mountains.

  • Scientific Code
    (IM0151)
  • Ecoregion Category
    Indo-Malayan
  • Size
    8,700 square miles
  • Status
    Critical/Endangered
  • Habitats

Description
Location and General Description
This ecoregion represents the montane rain forests above 1,000 m along the southern half of the Western Ghats. It extends as a long and narrow unit through the Indian states of Kerala and Tamil Nadu. The northern boundary of this ecoregion is the Wyanad, where the habitat makes a transition from the drier forest in the north to the more moist forest in the south. From here the ecoregion runs parallel to the Western Ghats Mountain Range, about 35 km inland, all the way to the southern end of the range.

The Deccan Plateau itself was once part of Gondwanaland, evident in relicts of the ancient southern flora and fauna. After becoming detached from this southern continent during the Cretaceous, it drifted northward to finally crash into the northern Laurasian continent. After this initial collision, a series of geological uplifts created the Western Ghats Mountain Range, with several peaks higher than 2,000 m. The highest of these is Anaimudi, which rises to 2,695 m.

As the moisture-laden southwest monsoon winds sweep in from the Malabar Coast and rise above the mountain range, they release more than 2,500 mm of rainfall. The northeast monsoon from October to November supplements the June to September southwest monsoon rainfall, for an average annual precipitation that exceeds 2,800 mm. But because of the deeply dissected topography, some areas can receive more than 8,000 mm of rainfall throughout the year (Mishra and Johnsingh 1998). This produces local variations in habitat types and localized centers of endemism (Rodgers and Panwar 1988; Kendrick 1989). The Periyar River, which originates from Periyar Tiger Reserve, is one of the larger rivers that carry the monsoon rains east across the peninsula.

The habitat types include the wet montane evergreen forests and shola-grassland complexes in the higher elevations. The montane evergreen forests are diverse, multistoried, and rich in epiphytes, with a low canopy at 15 to 20 m (Puri et al. 1989; WWF and IUCN 1995; Ganesh et al. 1996). The forest communities are characterized by Cullenia exarillata, Mesua ferrea, Palaquium ellipticum, Gluta travancorica, and Podocarpus wallichiana (Ramesh et al. 1999). Podocarpus represents a Gondwanaland relict carried across during the long northward journey. Other evergreen species in these montane forests include Calophyllum austroindicum, Garcinia rubro-echinata, Garcinia travancorica, Diospyros barberi, Memecylon subramanii, Memecylon gracile, Goniothalamus rhyncantherus, and Vernonia travancorica (Ramesh 1999).

The montane shola-grassland complexes occur between 1,900 and 2,220 m. These consist of stunted montane forests surrounded by undulating grasslands. The upper story of the forests is characterized by Pygeum gardneri, Schefflera racemosa, Linnociera ramiflora, Syzigium spp., Rhododenron nilgiricum, Mahonia nepalensis, Eleocarpus recurvatus, Ilex denticulata, Michaelia nilagirica, Actinodaphne bourdellonii, and Litsea wightiana (Karunakaran et al. 1998). A low, twisted second story of Ilex wightiana, Rapanaea wightiana, Ternstroemia gymnanthera, Symplocos spp., and Microtropis spp. and a dense shrub layer of saplings of Strobilanthes, Psychotria, and Lasianthus spp. usually is present. The grasslands that surround the shola forests consist of several fire- and frost-resistant grasses: Chrysopogon zeylanicus, Cymbopogon flexuosus, Arundinella ciliata, Arundinella mesophylla, Arundinella tuberculata, Themeda tremula, and Sehima nervosum (Karunakaran et al. 1998).

Biodiversity Features
The levels of endemism in these montane forests are truly astounding. More than half the tree species are endemic, especially among the Dipterocarpaceae and Ebenaceae. The majority of the fifty endemic plant genera are also monotypic. But the distribution of richness and endemism is not uniform. There are localized areas that harbor exceptional levels of diversity and endemism. For instance, the Agasthyamalai and Nilgiri hills, recognized as centers of plant diversity, are exceptional for plant richness (WWF and IUCN 1995).

A high proportion of the trees in these forests are dioecious breeding systems. In the shola forests in particular, dioecy is quite prevalent among the Lauraceae and Moraceae. Therefore, many of the tree populations are especially vulnerable to deforestation and other disturbances because of mate isolation and reduction of numbers of mates. In the Cullenia-dominated stands, for instance, a large proportion of trees have less than five individuals in a 10-ha area, making them locally rare.

This ecoregion harbors almost 20 percent of India's mammal fauna. The seventy-nine mammal species attributed to the ecoregion include ten endemics (table 1). Three of these are strict endemic species (i.e., limited to this ecoregion), and the others are considered to be near-endemic species (i.e., shared with adjacent ecoregions).

Table 1. Endemic and Near-Endemic Mammal Species.

  Family Species
Soricidae Suncus montanus
Pteropodidae Latidens salimalii
Cercopithecidae Trachypithecus johnii
Viverridae Viverra civettina
Viverridae Paradoxurus jerdoni
Bovidae Hemitragus hylocrius*
Sciuridae Funambulus layardi
Sciuridae Funambulus sublineatus
Muridae Mus famulus*
Muridae Vandeleuria nilagirica*

An asterisk signifies that the species' range is limited to this ecoregion.

The Salim Ali fruit bat (Latidens salimalii) and the rodent Platacanthomys lasiurus represent monotypic, endemic genera. The rare and endemic Nilgiri tahr (Hemitragus hylocrius) is currently limited to a narrow, 400-km stretch of shola-grassland mosaic, from the Nilgiri Hills to the Ashambu Hills (Mishra and Johnsingh 1998). At lower altitudes the tahr also use patches of grassland that grow on rock-sheeted substrates. Tigers, leopards (Panthera pardus), and wild dogs (Cuon alpinus) are the natural predators of Nilgiri tahr. However, the population decline of the tahr has been caused by heavy hunting pressure and habitat conversion (Mishra and Johnsingh 1998). The largest population of tahr, estimated at 250-300 animals, now resides in the Grass Hills of the Anamalai Sanctuary (Mishra and Johnsingh 1998).

The charismatic endangered lion-tailed macaque (Macaca silenus) and Nilgiri macaque (Semnopithecus johnii) are other endemic species that need intact habitat and are highly threatened by habitat conversion. This ecoregion also harbors India's largest Asian elephant (Elephas maximus) population (Sukumar 1989) and contains critical habitat for tigers (Panthera tigris). It overlaps with two Level I TCUs (Dinerstein et al. 1997). The survival of the tiger and elephant is threatened by habitat fragmentation.

Among the other threatened species are the sloth bear (Melursus ursinus), gaur (Bos gaurus), and wild dog (IUCN 2000).

The bird fauna in the ecoregion is estimated at 309 species. Ten species are near-endemics and three are strict endemics (table 2).

Table 2. Endemic and Near-Endemic Bird Species.

  Family Common Name Species
Columbidae Nilgiri wood-pigeon Columba elphinstonii
Bucconidae Malabar grey hornbill Ocyceros griseus
Corvidae White-bellied treepie Dendrocitta leucogastra
Turdidae White-bellied shortwing Brachypteryx major
Pycnonotidae Grey-headed bulbul Pycnonotus priocephalus
Timaliidae Grey-breasted laughingthrush Garrulax jerdoni
Timaliidae Rufous babbler Turdoides subrufus
Muscicapidae Black-and-rufous flycatcher Ficedula nigrorufa
Muscicapidae Nilgiri flycatcher Eumyias albicaudata
Sylviidae Broad-tailed grassbird Schoenicola platyura*
Timaliidae Nilgiri laughingthrush Garrulax cachinnans*
Motacillidae Nilgiri pipit Anthus nilghiriensis*
Psittacidae Malabar parakeet Psittacula columboides

An asterisk signifies that the species' range is limited to this ecoregion.

The broad-tailed grassbird (Schoenicola platyura) and Nilgiri pipit (Anthus nilghiriensis) are high-elevation grassland species (Grimmet et al. 1998).

The ecoregion is included within the Western Ghats EBA (123) (Stattersfield et al. 1998).

The high endemism levels seen among the mammals and birds extend to other taxonomic groups as well. About 90 of India's 484 reptile species are endemic to these forests, including eight endemic genera (Brachyophidium, Dravidogecko, Melanophidium, Plectrurus, Ristella, Salea, Teretrurus, and Xylophis). The amphibian fauna exhibits even greater levels of endemism: almost 50 percent of India's 206 amphibian species are endemic to this ecoregion, among which are six endemic genera (Indotyphlus, Melanobatrachus, Nannobatrachus, Nyctibatrachus, Ranixalus, and Uraeotyphlus).

Current Status
Nearly two-thirds of the natural forests in this ecoregion have already been cleared. The remaining habitat is fragmented, except for one large intact habitat block in the southern area of the ecoregion. About 3,200 km2 of the ecoregion is already included within sixteen protected areas (table 3).

Table 3. WCMC (1997) Protected Areas That Overlap with the Ecoregion.

  Protected Area Area (km2) IUCN Category
Pushpagiri [IM0135] 60 IV
Talakaveri 250 PRO
Brahmagiri 190 PRO
Aralam 50 IV
Karimpuzha 230 PRO
Mukurty National Park 60 PRO
Silent Valley 110 II
Megamalai [IM0150] 120 PRO
Periyar [IM0150] 540 IV
Anamalai [IM0150] 600 IV
Eravikulam [IM0150] 70 II
Parambikulam 260 IV
Idukki 80 IV
Shenduruny 300 IV
Kalakad-Mundanthurai 290 IV
Peppara [IM0150] 40 IV
Total 3,250  

Ecoregion numbers of protected areas that overlap with additional ecoregions are listed in brackets.

Among these, Periyar, Anamalai, and Kalakad-Mundanthurai represent three important reserves. Parambikulam, Anamalai, and Eravikulam lie adjacent to each other and form a large protected area complex that harbors important Nilgiri tahr populations (Mishra and Johnsingh 1998). Four reserves-Periyar, Anamalai, Eravikulam, and Megamalai (proposed)-extend into the adjacent South Western Ghats Moist Deciduous Forests [IM0150].

Despite 15 percent of the intact habitat being within the protected area system, the management status and threats to these protected areas vary enormously. For example, the Mukurty National Park in Tamil Nadu has no human inhabitants but contains small abandoned plantations, whereas Kerala's Parambikulam Wildlife Sanctuary has several large commercial plantations within it (IUCN 1991).

Types and Severity of Threats
The threats to this ecoregion's natural habitats and biodiversity are manifold. Some of the major threats include conversion of forests into tea, coffee, potato, teak, Eucalyptus, and cardamom plantations, as well as road construction, tourism pressures, and livestock grazing (Rodgers and Panwar 1988; WII 1999). Illegal taking of timber is high and is considered a major threat to the remaining forests. Many people own guns for crop protection that they also use for poaching.

The Nilgiri and Cardamom hills in particular harbor high levels of richness and endemism as well as some of the most important populations of elephants and tigers. These areas are especially affected by the tea, coffee, and rubber plantations. Shifting cultivation has begun to clear patches of old-growth forest (Kendrick 1989). In the Anamalais, fig trees from the sholas are felled or lopped to feed camp elephants. Because many of these species are dioecious, this affects the sexual selection among trees and causes reproductive isolation. Fig trees are also keystone food resources for several species (from giant squirrels to hornbills), and their removal results in cascading ecological effects on the frugivore community.

Hydroelectric power development along the rivers in this ecoregion is also a serious threat. In addition to inundating critical habitat, dam construction also causes tremendous habitat destruction and disturbances.

The mountains, especially in the south, are mineral-rich. Therefore, mining is a potential future threat that should be addressed with preemptive measures.

Justification of Ecoregion Delineation
In an earlier analysis of conservation units of India, Rodgers and Panwar (1988) placed the Western Ghats Mountain Range into a single biogeographic unit. But they acknowledged that the entire mountain range was too large to represent a single unit for conservation planning and divided the mountain range into northern and southern areas, using the Wyanad as a transition zone. Here the moister southern Cullenia-dominated forests grade into the drier northern dipterocarp forests. In our analysis, we also used this transition to make a more explicit division of the northern and southern ecoregions in the Western Ghats. But in keeping with our definition of ecoregions (i.e., to represent distinct habitat types and lowland and montane forests in separate ecoregions), we placed the montane forests to the south of the Wyanad area in the South Western Ghats Montane Rain Forests [IM0151]. We used the 1,000-m contour from a DEM and MacKinnon's (1997) map of original vegetation to define the boundary between the montane rain forests and moist deciduous forests. This ecoregion falls into Udvardy's Malabar rain forest biogeographic province.

References
References for this ecoregion are currently consolidated in one document for the entire Indo-Pacific realm.
Indo-Pacific Reference List

Prepared by: Prepared by Gopal S. Rawat, Ajay Desai, Hema Somanathan, and Eric D. Wikramanayake
Reviewed by:

 

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