Location and General Description
This ecoregion represents the lowland evergreen and semi-evergreen rain forests of the western side of Arakan Yoma and Tenasserim ranges along the west coast of Myanmar. A small area extends into southeast Bangladesh. It falls within the tropical wet climate zone of the Köppen climate system (National Geographic Society 1999).
The copious monsoonal rainfall results in very lush vegetation (MacKinnon 1997). Most of the dominant tree species are characterized by dipterocarp species such as Dipterocarpus alatus, D. turbinatus, D. obtusifolius, D. pilosa, Anisoptera glabra, Hopea odorata, Lagerstroemia calyculata, L. floribunda, L. speciosa, Parashorea stellata, Pentace birmanica, and Swintonia floribunda, with undergrowth of Calamus palms and the creeping bamboo Temostachyon helferi (WWF and IUCN 1995). In the southern part (Tenasserim portion) of the ecoregion, there are some Heritiera-dominated brackish and fresh-water habitats along the Tenasserim river. The former is characterized by Bruguiera parviflora, Aquilaria agallocah, Sonneratia griffithii, and Cynometra mimosoides and the latter by Amoora cucullata, Dysophyllum cochinchinensis, D. turbinatus, Intsia bijuga, Barringtonia acutangula, and Combretum trifoliatum. There are also large tracts of mixed delta scrub and low forest (ken-byauk), where the principal tree species are Elaeocarpus hygrophilus, Calophyllum amoenum, Litsea nitida, Eugenia spp., and Diospyros burmanica, with a dense undergrowth of Calamus erectus and Pinanga gracilis.
Although low in endemism, it has a rich fauna and flora, largely as a result of its lush vegetation, extensive range of habitats from mangroves to mountains, and position as a corridor between the Sundaic, Indochinese, and Indian sub-regions (MacKinnon 1997). Among the several threatened and endangered mammals of conservation significance are the tiger (Panthera tigris), Asian elephant (Elephas maximus), Malayan tapir (Tapirus indicus), wild dog (Cuon alpinus), sun bear (Ursus malayanus), clouded leopard (Pardofelis nebulosa), leopard (Panthera pardus), Asiatic golden cat (Felis temmincki), and gaur (Bos gaurus).
The ecoregion overlaps with three Level I TCUs (Dinerstein et al. 1997). One near-endemic mammal occurs here, the disc-footed bat (Eudiscopus denticulus), and an endemic pipistrelle (Pipistrellus lophurus) (table 1). More than 350 bird species are found in the diverse habitats of this ecoregion, although none are considered ecoregional endemics.
Table 1. Endemic and Near-Endemic Mammal Species.
Vespertilionidae Eudiscopus denticulus
Vespertilionidae Pipistrellus lophurus*
An asterisk signifies that the species' range is limited to this ecoregion.
The Sumatran rhinoceros was once part of this diverse forest ecosystem, but they have been extirpated from this ecoregion for more than fifteen years. The last Sumatran rhinoceros in this ecoregion was caught in 1984 in Arakan Yoma and its horn sold to a traditional Chinese medicine shop in Yangon.
Most of the seasonal evergreen forest and almost all the freshwater swamp of this ecoregion has been cleared for agriculture (MacKinnon 1997), especially along the fertile, densely populated plains of the Irrawaddy (IUCN 1991). Heavy degradation is evident around Myeik (Mergui) and Dawei (Tavoy) (WWF and IUCN 1995). Further north, large tracts of forest have been cut, including the gorges of the Thanlwin (Salween) River where it enters the Andaman Sea at Mawlamyine, an area that once harbored many local or endemic species of orchids, begonias, and other herbs (WWF and IUCN 1995). This ecoregion is inadequately protected; there are five proposed protected areas that cover about 2,700 km2 (4 percent) of the ecoregion area (table 2). Of these one, Pegu Yomas, shared with Irrawaddy Moist Deciduous Forests [IM0117], accounts for almost 2,500 km2. Along Myanmar's western coast, extensive areas of forest remain that are worthy of conservation and should be brought under protection and managed effectively to increase representation in this diverse ecoregion.
Table 2. WCMC (1997) Protected Areas That Overlap with the Ecoregion.
Protected Area Area (km2) IUCN Category
Pegu Yomas [IM0117] 2,490 PRO
Naaf River WS 140 ?
Mohingyi 130 PRO
Dipayon 20 PRO
Letkokkon 4 PRO
Ecoregion numbers of protected areas that overlap with additional ecoregions are listed in brackets.
Types and Severity of Threats
The continued development of flat, lowland areas for irrigated paddy rice and subsistence crops such as hill rice, cassava, yams, and vegetables on hilly ground will be a major threat in the future (MacKinnon 1997). Forests are being exploited extensively for timber because the country is hungry for foreign currency.
Wildlife trade and poaching are a major threat to the rapidly declining large mammals and medicinal plants in both regions of Arakan and Tenasserim coasts. Tigers are almost extinct in the northern part of the ecoregion along the Arakan Yoma because of intense demand in China and Thailand.
Justification of Ecoregion Delineation
MacKinnon's Burmese coast biounit is represented by four ecoregions: the Myanmar Coastal Rain Forests [IM0132] (lowland rain forests), Irrawaddy Freshwater Swamp Forests [IM0116], Myanmar Coastal Mangroves [IM1404], and Mizoram-Manipur-Kachin Rain Forests [IM0131] (montane semi-evergreen forests). The Myanmar Coastal Rain Forests [IM0132] encompass the lowland rain forests in the southern extent of the Burmese Monsoon Zone Biounit (09).
References for this ecoregion are currently consolidated in one document for the entire Indo-Pacific realm.
Indo-Pacific Reference List
Prepared by: U Tin Than and Eric Wikramanayake