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Sunda Shelf mangroves

Introduction

Bak National Park, Malaysia. (Photograph by WWF and Canon)

The Sunda Shelf Mangroves are some of the most biologically diverse mangroves in the world. They are home to the unique proboscis monkey. Like other mangrove forests in the region, they are under intense threats from logging, shrimp farming, and agriculture conversion.

Location and General Description

The Sunda Shelf Mangroves are found on the island of Borneo and the east coast of Sumatra. The climate and physical conditions vary widely in this region, giving rise to a high diversity of plant and animal species found in these forests. However, the region generally has high humidity, seasonal wind and precipitation, high temperatures, and high annual rainfall. Tidal fluctuations have large variations over short distances.

There are five major mangrove types, or consociations, recognized in this region, based on the dominant species of Avicennia, Rhizophora, Sonneratia, Bruguiera, and Nypa. The relative occurrence of each type is based on fluctuations in soils, salinity, and the tidal regime. Typically mangroves display a zonation or succession of forests, with each zone being dominated by one of the consociations. On the seaward sediments, Avicennia-Sonneratia forest dominates. Moving inland, there is softer and deeper mud sediment dominated by Rhizophora-Bruguiera forests. Further inland, the soils become firmer and the forests display a greater species diversity. In areas with a substantial freshwater influence, Nypa palms dominate. Mangrove forests reach 50 meters (m) in height in many areas.

Biodiversity Features

Crab-eating macaque (Macaca fascicularis), Bako National Park, Borneo, Malaysia. (Photograph by Jakob Damborg)

Mangrove diversity in terms of endemics or richness is not great. More than 250 birds are listed for this ecoregion, but many of them are transitory, some migrants, and some year-round inhabitants. Determining an exact count for this diverse ecoregion is difficult because of the transitional nature of the habitat.

The mangroves of Borneo are home to the proboscis monkey (Nasalis larvatus), which is one of the few large mammals limited to mangrove and peat swamp forest habitats. Proboscis monkeys eat primarily young leaves and the seeds of unripe fruit. To digest this diet, they have developed highly complex sacculated stomachs with specialized bacteria.

Although mangroves lack outstanding species diversity, they provide vital ecological functions by being at the interface between the terrestrial and marine realms. Mangroves stabilize coastlines from erosion, accumulate sediment, and provide a nursery for numerous coastal fishes.

Current Status

Traditionally, mangroves have been harvested for fuelwood, charcoal, and timber, and in some instances this has been done sustainably. However, in recent decades mangroves have been severely degraded by deforestation, agriculture, urban development, fishing, and shrimp farming despite the many protected areas that include mangrove forests (table 1).

Protected areas have not addressed many of the conversion threats facing mangrove systems. Many protected areas have been encroached upon for consumptive uses and have not afforded real protection in recent decades.

Types and Severity of Threats

The threats to the habitat remain the same as those that already have claimed vast areas of land: logging, aquaculture, agriculture conversion, and urbanization.

Many mangroves reside in logging concessions or are being cut down for commercial charcoal production. Production of woodchips and pulp is increasing, and more chip mills are being built. Shrimp farming continues to threaten vast mangrove forests. Other aquaculture practices include cockle culture and exploitation of the finfish, bivalve, and crab fisheries. Pollution, agriculture conversion, and oil extraction also threatened mangrove forests.

Additional Information on this Ecoregion

• For a shorter summary of this entry, see the WWF WildWorld profile of this ecoregion
• To see the species that live in this ecoregion, including images and threat levels, see the WWF Wildfinder description of this ecoregion.
• World Wildlife Fund Homepage