South Western Ghats montane rain forests

Content Cover Image

Tamil Nadu, India (Photograph by © WWF-Canon/Mauri Rautkari)

Introduction

The South Western Ghats Montane Rain Forests 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. 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.

Location and General Description

caption WWF

This ecoregion represents the montane rain forests above 1,000 meters (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 kilometers (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 millimeters (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. This produces local variations in habitat types and localized centers of endemism. 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. The forest communities are characterized by Cullenia exarillata, Mesua ferrea, Palaquium ellipticum, Gluta travancorica, and Podocarpus wallichiana. 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.

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. 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.

Biodiversity Features

caption Nilgiri Tahr (Hemitragus hylocrius), south-western Ghats, India (Photograph by G.S.Rawat)

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.

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-hectare (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-kilometer (km) stretch of shola-grassland mosaic, from the Nilgiri Hills to the Ashambu Hills. 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. The largest population of tahr, estimated at 250-300 animals, now resides in the Grass Hills of the Anamalai Sanctuary.

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 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.

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.

The ecoregion is included within the Western Ghats EBA (123).

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 square kilometers (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

60

IV

Talakaveri

250

PRO

Brahmagiri

190

PRO

Aralam

50

IV

Karimpuzha

230

PRO

Mukurty National Park

60

PRO

Silent Valley

110

II

Megamalai

120

PRO

Periyar

540

IV

Anamalai

600

IV

Eravikulam

70

II

Parambikulam

260

IV

Idukki

80

IV

Shenduruny

300

IV

Kalakad-Mundanthurai

290

IV

Peppara

40

IV

Total

3,250

 

 

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. Four reserves-Periyar, Anamalai, Eravikulam, and Megamalai (proposed)-extend into the adjacent South Western Ghats Moist Deciduous Forests.

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.

Types and Severity of Threats

caption Nilgiri Hills, India (Photograph by © WWF-Canon/Mauri RAUTKARI)

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. 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. 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 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. We used the 1,000-m contour from a Department of Environmental Management (DEM) and MacKinnon's 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.

Additional information on this ecoregion

 

 

 

Disclaimer: This article is taken wholly from, or contains information that was originally published by, the World Wildlife Fund. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the World Wildlife Fund should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.

 

 

 

Glossary

Citation

Fund, W. (2014). South Western Ghats montane rain forests. Retrieved from http://www.eoearth.org/view/article/156148

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