Location and General Description
Myanmar Coastal Mangroves [IM1404] ecoregion is found in the Irrawaddy delta. The mouth of the Irrawaddy River was some 170 miles inland near Prome 300,000 years ago. On the islands of Twante, Myaungmya, and Bassein, lateritic ridges stood above the water. The delta is composed largely of alluvium, and a large area is occupied by volcanic rocks.
The mangrove flora consists of three separate regions: the Rakhine mangroves, Irrawaddy mangroves, and Taninthayi mangroves. The Rakhine mangroves are made up primarily of Rhizophora mucronata, R. candelria, Sonneratia spp., Kandelia rheedeii, Bruguiera spp., Xylocarpus granatum, X. moluccensis, Nipa fruticans, and Phoenix paludosa. The Irrawaddy mangroves consist of Rhizophora mucronata, R. conjugata, Bruguiera parviflora, B. gymnorhiza, B. cylindrica, Heritiera formes, Sonneratia apetala, S. griffithii, S. caseolaris, Xylocarpus granatum, X. molluccensis, Ceiops roxburghiana, C. mimosoides, Avicennia officinalis, Kanddelia rheedii, and Excoecaria agallocha. Finally, the Taninthayi mangroves contain Rhizophora spp., Sonneratia caseolaris, Ceriops tegal, Xyloxarpus granatum, Avicennia officinalis, and Bruguiera spp.
Several mammal species occur in this ecoregion but in small and scattered populations. Wild elephants (Elephas maximus) are represented by a small population of approximately 150 animals. Rakhine is one of the last regions where Asian elephants still roam wild. During the dry summer elephants come down from the mountains to the mangroves to drink salt water (Thet Tun, pers. comm., 1999). The population estimate for Rakhine State in 1990-1991 was between 750 and 1,100, with the country total between 4,115 and 4,639 (U Ga 2000)
The tiger used to be plentiful all over the country some forty years ago but has been persecuted to the point of extirpation. There are at most 150 tigers remaining in Myanmar, and it is unknown how many, if any, use the dwindling mangroves (Saw Tun Khaing, pers. comm., 2000). Tiger (Panthera tigris), leopard (Panthera pardus), wild dog (Cuon apinus), and otter (Lutra spp.) were reported by Salter in 1982 but probably have been extirpated or survive only in low numbers. As a result, sambar (Cervus unicolor), hog deer (Cervus porcinus), mouse deer (Tragulus javanicus), barking deer (Muntiacus muntjak), tapir (Tapirus malayanus), and wild boar (Sus scrofa), prey species for many predators, are abundant in the reserved forests. According to Salter (1982), the Malayan tapir (Tapirus indicus) was rapidly decreasing to the point of extinction in Myanmar. However, they still survive in parts of the Taninthayi mangroves.
Bird life in the mangroves is rich in migrants and resident waterbirds. A few resident waterbirds include the oriental darter (Anhinga melanogaster), little cormorant (Phalacrocorax nigers), reef heron (Egretta sacra), dusky gray heron (Ardea sumatrana), ruddy shelduck (Tadorna ferruginea), bronze-winged jacana (Metopidius indicus), lesser sand plover (Charadrius mongolus), great stone plover (Esacus magnirostris), black-winged stilt (Himantopus himantopus), spotted greenshank (Tringa guttifer), lesser black-back gull (Larus fuscus), and common moorhen (Gallinula chloropus). One of the most highly threatened residents is the edible-nest swiftlet (Collocalia fuciphaga), found inhabiting rocky limestone caves. The nests, which are an expensive delicacy, are highly valued and collected.
The southern part of the delta contains the last population of crocodiles (Crocodylus porosus) in the ecoregion. The river terrapin (Batagur baska) has also been reduced to a few small populations on offshore islands as a result of egg overcollection.
Mangrove forests are subject to severe degradation because there is no clear-cut land-use system. Forestlands have been converted to agriculture and other development activities, not only in this ecoregion but throughout Myanmar. Irrawaddy is one of the most heavily silted rivers in the world. The sedimentation rate was 299 million tons per year, and it ranked fifth behind the Yellow, Ganges, Amazon, and Mississippi rivers in silt deposition. Today the sedimentation rate in getting worse as deforestation and agricultural erosion continue. If the situation between 1977 and 1986 is maintained, it is estimated that all the mangrove forests will disappear in fifty years.
A new Forest Policy, Forest Act, and Wildlife Protection Act are in force today. However, implementation of conservation and protection activities is poor, with a shortage of staff to police and monitor the few protected areas proposed (table 1). This is primarily because of an inadequate budget.
Table 1. WCMC (1997) Protected Areas That Overlap with the Ecoregion.
Protected Area Area (km2) IUCN Category
Letkokkon 4 PRO
Meinmahla Kyun 120 PRO
Kadonlay Kyun 1 PRO
Ecoregion numbers of protected areas that overlap with additional ecoregions are listed in brackets.
Types and Severity of Threats
The entire ecoregion is under severe threat of conversion and illegal settlements. Rice yields decline on reclaimed mangroves within a few years, and new areas are cut. Fertilizer on reclaimed mangroves causes more harm than good because of the accumulation of acid sulfate over time. Mangroves are being intensively cut for firewood, charcoal burning, and nontimber produce. Mangroves are increasingly converted to fish and prawn aquaculture to meet the demand of an increasing population.
Wildlife poaching is rampant. Wild elephant, tiger, sun bear, monkey species, wild boar, banteng, and sambar are being intensively hunted. Tigers are often killed for the bones and skins for sale to wildlife traders in Thailand and China. There is no control over the extraction of forest resources despite forest reserves having legal protected status. Illegal logging is more prevalent than legal logging concessions.
Justification of Ecoregion Delineation
MacKinnon divided the Indochina bioregion into fifteen biogeographic subunits nested within seven major biounits. Each of these biounits and biogeographic subunits contains a mix of biomes. For instance, the Burmese coast biounit (04) is made up mostly of tropical wet evergreen forests but also includes tropical montane evergreen forests, semi-evergreen rain forests, dry dipterocarp forests, and large areas of freshwater swamp forests and mangroves in the Irrawaddy River delta. We assigned these distinct habitat types to separate ecoregions. Thus MacKinnon's Burmese coast biounit is represented by four ecoregions: the Myanmar Coastal Rain Forests [IM0132], Irrawaddy Freshwater Swamp Forests [IM0116], Myanmar Coastal Mangroves [IM1404], and Mizoram-Manipur-Kachin Rain Forests [IM0131].
This region does not correspond well to Udvardy's biogeographic provinces. The Irrawaddy Freshwater Swamp Forests [IM0116] and Myanmar Coastal Mangroves [IM1404] are contained within Udvardy's Burman rain forest.<
References for this ecoregion are currently consolidated in one document for the entire Indo-Pacific realm.
Indo-Pacific Reference List
Prepared by: U Saw Han and Saw Tun Khaing