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Southeastern Asia: Vietnam

The Southern Vietnam Lowland Dry Forests [IM0211] ecoregion is the single most degraded or otherwise converted dry forest ecoregion outside of India. Only India's East Deccan Dry Evergreen Forests [IM0204] are in worse shape. This ecoregion retains less than 10 percent of its forests, and only 2 percent are protected. The protected areas are surrounded by a burgeoning human population, and many of the "protected" forests are devoid of their fauna species because of intensive hunting pressures

  • Scientific Code
    (IM0211)
  • Ecoregion Category
    Indo-Malayan
  • Size
    13,500 square miles
  • Status
    Critical/Endangered
  • Habitats

Description
Location and General Description
The semi-arid coastal areas of southern Vietnam are the most arid in Vietnam because of the rainshadow effects of the plateaus of the southern Annamite Range, which restrict the flow of humid air in the early monsoon season. Mean annual rainfall is less than 1,500 mm in the coastal belt south of Nha Trang and below 800 m at Cape Padaran south of Phan Rang. These areas have been heavily affected by human activities and greatly altered.

The coastal region around Nha Trang, Cam Ranh Bay, and Phan Rang in southern coastal Vietnam is formed as a succession of small alluvial plains to the east of the Annamite Range and separated by low hills up to 1,000 m elevation formed of rhyolite or granite. The first woody community encountered away from the beach in southern Vietnam is generally a thicket community that gives way to a low scrubby forest further inland.

Areas with extensive coverage of unstabilized dunes support a distinctive community of shrubby trees with extensive root systems. On low dunes these species have a shrubby growth form. However, where a significant phreatophytic zone of freshwater develops at the base of these dunes, a true forest may develop with a variety of tree species reaching up to 12 m in height. Moist depressions within these dunes are dominated by Baeckia frutescens (Myrtaceae), Melaleuca leucadendron, and diverse graminoids.

Extensive areas of coastal dunes formed of stabilized red sands are a characteristic component of this coastal region around Cam Ranh Bay on granitic parent material. Two endemic species of Dipterocarpaceae, Hopea cordata and Shorea falcata, are known only from dune forests on these sands. These are two of only six endemic Dipterocarpaceae for all of Indochina, suggesting that many other endemic species may be found in this habitat if it is more carefully studied. Evergreen and semi-evergreen forest cover may be present on the coastal hills that reach higher elevations. A unique low forest or thicket community occurring on semi-arid slopes along the coast of southern Vietnam and notably rich in endemic species has been described near Phan Rang, Ba Ngoi, and Nha Trang, but it is heavily degraded today.

The low rolling hills of Binh Chau-Phouc Buu Nature Reserve, southwest of Phan Thiet, contain a variety of dry forest communities including notable tree endemics such as Lithocarpus dinhensis, Dalbergia bariensis, and the recently discovered Dipterocarpus caudatus. The forest is dominated by varying combinations of Dipterocarpus caudatus, D. intricatus, Shorea siamensis, and S. roxburghii.

Biodiversity Features
There are several large mammals of conservation significance in this ecoregion, including the endangered douc langur (Pygathrix nemaeus), red-cheeked gibbon (Hylobates gabriellae), and pileated gibbon (Hylobates pileatus) and potentially the tiger (Panthera tigris). The ecoregion also overlaps with a portion of the South Vietnamese Lowlands (144) EBA (Stattersfield et al. 1998) and contains two near-endemic bird species (table 1).

Table 1. Endemic and Near-Endemic Bird Species.

  Family Common Name Species
Phasianidae Germain's peacock-pheasant Polyplectron germaini
Timaliidae Grey-faced tit-babbler Macronous kelleyi

An asterisk signifies that the species' range is limited to this ecoregion.

Current Status
More than 90 percent of the habitat in this ecoregion has been cleared. There are ten very small protected areas (the average size is only 69 km2) in the ecoregion that cover less than 700 km2 (about 2 percent) of the ecoregion (table 2). Even these small protected areas do not have effective protection and are now insularized by forest clearing throughout the larger landscape, increasing the edge effects.

Table 2. WCMC (1997) Protected Areas That Overlap with the Ecoregion.

  Protected Area Area (km2) IUCN Category
Ban Dao Son Tra 50 IV
Cu Lao Cham 20 IV
Ba To 20 UA
Nam Hai Van 100 ?
Nui Thanh [IM0152] 40 UA
Deo Ca Hon Ron 210 UA
Rung Kho Phan Rang [IM0152] 50 IV
Deo Ngoau Muc [IM0152] 30 ?
Kalon Song Mao [IM0152] 70 IV
Binh Chan Phuoc Buu 100 IV
Total 690  

Ecoregion numbers of protected areas that overlap with additional ecoregions are listed in brackets.

Types and Severity of Threats
The main threats to this habitat are agriculture, exploitation of valuable hardwood trees and other plant resources, and the rampant hunting primarily to supply the huge commercial market in both Vietnam and China (WWF and IUCN 1995; Compton 1998).

Justification of Ecoregion Delineation
MacKinnon (1997) included the coastal habitats of Vietnam, Cambodia, and Thailand in the Coastal Indochina biounit (05), consisting of four subunits. Each of these subunits includes several biomes. We delineated several ecoregions based on the distribution of these biomes. Like MacKinnon, we chose the Hai Van pass to represent a transition from the tropical south and the subtropical north and placed the lowland dry coastal forests in the Southern Vietnam Lowland Dry Forests [IM0211].

References
References for this ecoregion are currently consolidated in one document for the entire Indo-Pacific realm.
Indo-Pacific Reference List

Prepared by: Eric Wikramanayake and Philip Rundel
Reviewed by:

 

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