Kayah-Karen Montane Rainforests

The world’s smallest mammal lives in the deep recesses of limestone caves in this Kayah-Karen Montane Rain Forests ecoregion. This tiny animal, known as Kitti’s hog-nosed bat or bumble-bee bat, is about the size of a bumblebee, and is so taxonomically unique that it was assigned to its own genus. 

Because of its small size and cryptic nature, very little is known about its biology and even its distribution, but current knowledge indicates that the entire world population is restricted to a few caves in Myanmar and Thailand. The ecoregion also supports Asia’s largest land mammal, the Asian elephant, and many other species of sizes in between. 

This ecoregion lies along the northern part of the Tenasserim Mountain Range, which forms the border between Thailand and Myanmar. Geologically, the mountains are made up of limestone, heavily dissected and incised by weathering since the Paleozoic era, over 300 million years ago. The terrain consists of overhanging cliffs, sinkholes, and caves typical of tropical karst landscapes and steep hillsides that rise to ridges over 2,000 m.

The climate is warm, wet, and seasonal, although winters can become cool in the high elevations. Annual rainfall averages about 2,000 mm. The west-facing slopes in Myanmar bear the brunt of the monsoons from the Bay of Bengal and receive more rainfall, while the east-facing slopes in Thailand are in the rain shadow and thus drier. 

The low elevation forests are dominated by teak, species of Dipterocarpus, and oak. A distinctive plant in these forests is the Malayan urn vine, an epiphyte growing on trees and with modified leaves in which ants live and return the favor by protecting the plant against herbivorous animals. 

The forests in the higher elevations are a mix of large evergreen deciduous trees in the Magnoliaceae and Lauraceae families. Further up and along the ridges, the forests are characterized by subtropical and even temperate trees, including members of the oak and birch families, such as Castanopsis, Quercus, Lithocarpus, and Schima. Rhododendrons grow in the highest elevations. 

Almost 170 species of mammals are known from this ecoregion. In addition to the largest and smallest mammals, other species of conservation importance include the tiger, gaur, banteng, clouded leopard, Malayan tapir, wild dog, Asiatic black bear, Phayre’s Leaf-monkey, Sunda and Chinese pangolins, and the Eastern hoolock gibbon with their haunting calls that reverberate across the valleys. 

An incredible 568 bird species have been recorded from this ecoregion, including the Burmese yuhina which is endemic to the ecoregion. Other birds that are of conservation importance and indicators of habitat integrity are Lady Amherst’s pheasant, Hume’s pheasant, green peafowl, plain-pouched hornbill, rufous hornbill, wreathed hornbill, and white-winged duck, just to name a few.

About 72% of the ecoregion’s forest cover still remains, but some may be degraded due to shifting cultivation. Protected areas cover about 27% of the ecoregion; thus, the potential for conservation is high. But the anthropogenic threats are now increasing as agricultural lands and plantations are encroaching into forested areas. Logging bans in Thailand have led to illegal logging in Myanmar, where protection is more lax. Poaching of high value wildlife is also increasing, especially as demand from China rises.

The priority conservation actions are to: 1) promote sustainable logging and prevent illegal logging in Myanmar; 2) encourage farmers to adopt environmentally friendly agricultural methods; and 3) work with the local ethnic and tribal groups to implement conservation actions and the protection of wildlife of high conservation priority.

Citations

1. Wikramanayake, E, E. Dinerstein, et al. 2002. Terrestrial Ecoregions of the Indo-Pacific: A Conservation Assessment. Island Press.
2. Critical Ecosystems Partnership Fund. 2012. Ecosystem Profile. Indo-Burma Biodiversity Hotspot. 2011 Update. https://www.cepf.net/Documents/final.indoburma_indochina.ep.pdf Accessed Dec 2017.
3. Greater Mekong Subregion Atlas of the Environment. 2nd ed. Asian Development Bank. 2012. https://www.adb.org/sites/default/files/publication/30074/gms-atlas-environment-2nd-edition.pdf. Accessed Dec 2017.