South Western Ghats montane rain forests

The South Western Ghats montane rain forests are an ecoregion of southern India, covering the southern portion of the Western Ghats range in Karnataka, Kerala and Tamil Nadu, at elevations over 1000 meters. They are cooler and wetter than the lower-elevation South Western Ghats moist deciduous forests, which surround the montane rain forests.

South Western Ghats montane rain forests
Ecoregion territory (in purple)
Ecology
RealmIndomalayan
Biometropical and subtropical moist broadleaf forests
BordersMalabar Coast moist forests, North Western Ghats montane rain forests and South Western Ghats moist deciduous forests
Geography
Area22,545 km2 (8,705 sq mi)
CountryIndia
StatesKarnataka, Kerala and Tamil Nadu
Conservation
Conservation statuscritical/endangered
Protected5,998 km² (27%)[1]

Setting

The ecoregion is the most species rich in peninsular India, and is home to numerous endemic species. It covers an area of 22,600 square kilometers (8,700 sq mi). It is estimated that two-thirds of the original forests have been cleared, and only 3,200 square kilometers, or 15% of the intact area, is protected.

The southern portion of the Western Ghats contains the highest peaks in the range, notably Anai Mudi in Kerala, at 2695 meters elevation. The Ghats intercept the moisture-laden monsoon winds off the Arabian Sea, and the average annual precipitation exceeds 2,800 mm. The northeast monsoon from October to November supplements the June to September southwest monsoon. The South Western Ghats are the wettest portion of peninsular India, and are surrounded by drier ecoregions to the east and north.[2]

Flora
Satyrium nepalense in Silent Valley National Park

The cool and moist climate, high rainfall, and variety of microclimates brought about by differences in elevation and exposure supports lush and diverse forests; 35% of the plant species are endemic to the ecoregion. Moist evergreen montane forests are the predominant habitat type. The montane evergreen forests support a great diversity of species. The trees generally form a canopy at 15 to 20 m, and the forests are multistoried and rich in epiphytes, especially orchids. Characteristic canopy trees are Cullenia exarillata, Mesua ferrea, Palaquium ellipticum, Gluta travancorica, and Nageia wallichiana. Nageia is a podocarp conifer with origins in the ancient supercontinent of Gondwana, of which India was formerly part, and a number of other plants in the ecoregion have Gondwana origins. Other evergreen tree species of the montane forest include Calophyllum austroindicum, Garcinia rubro-echinata, Garcinia travancorica, Diospyros barberi, Memecylon subramanii, Memecylon gracile, Goniothalamus rhynchantherus, and Vernonia travancorica.[2]

The other major habitat type in the ecoregion is the shola-grassland complex, found at elevations of 1,900 to 2,220 m. Shola is a stunted forest, with an upper story of small trees, generally Pygeum gardneri, Schefflera racemosa, Linociera ramiflora, Syzygium spp., Rhododendron nilgiricum, Mahonia napaulensis, Elaeocarpus recurvatus, Ilex denticulata, Michelia nilagirica, Actinodaphne bourdillonii, and Litsea wightiana. Below the upper story is a low understory and a dense shrub layer. These shola forests are interspersed with montane grasslands, characterized by frost- and fire-resistant grass species like Chrysopogon zeylanicus, Cymbopogon flexuosus, Arundinella ciliata, Arundinella mesophylla, Arundinella tuberculata, Themeda tremula, and Sehima nervosum.[2]

Fauna

The ecoregion supports India's largest elephant population, along with populations of threatened tiger (Panthera tigris), leopard (Panthera pardus), sloth bear (Melursus ursinus), gaur (Bos gaurus), and dhole or Indian wild dog (Cuon alpinus). The rare and endemic Nilgiri tahr (Nilgiritragus hylocrius) is limited to a 400 km band of shola-grassland mosaic, from the Nilgiri Hills in the north to the Agasthyamalai (Ashambu) Hills in the south. The lion-tailed macaque (Macaca silenus) and Nilgiri langur (Semnopithecus johnii) are endangered endemic primate species.[2]

90 of India's 484 reptile species are endemic to the ecoregion, with eight endemic genera (Brachyophidium, Dravidogecko, Melanophidium, Plectrurus, Ristella, Salea, Teretrurus, and Xylophis). Almost 50% of India's 206 amphibian species are endemic to the ecoregion, with six endemic genera (Indotyphlus, Melanobatrachus, Nannobatrachus, Nyctibatrachus, Ranixalus, and Uraeotyphlus).[2]

Protected areas

A 2017 assessment found that 5,998 km², or 27%, of the ecoregion was in protected areas. Another 62% is forested but outside protected areas.[1] A 1997 assessment found 13 protected areas in the ecoregion, covering an area of over 3,200 km².[3] Several of the protected areas in the northern portion of the ecoregion are included within the Nilgiri Biosphere Reserve, and the Agasthyamala Biosphere Reserve covers the southern portion.

References
  1. Eric Dinerstein, David Olson, et al. (2017). An Ecoregion-Based Approach to Protecting Half the Terrestrial Realm, BioScience, Volume 67, Issue 6, June 2017, Pages 534–545; Supplemental material 2 table S1b.
  2. Wikramanayake, Eric; Eric Dinerstein; Colby J. Loucks; et al. (2002). Terrestrial Ecoregions of the Indo-Pacific: a Conservation Assessment. Washington, DC: Island Press.
  3. Wikramanayake, Eric; Dinerstein, Eric; Loucks, Colby J. (2002). Terrestrial Ecoregions of the Indo-Pacific: a Conservation Assessment. Washington, DC: Island Press. p. 326–328. ISBN 978-1559-639-23-1.

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