Sunda Shelf mangroves
Bako National Park, Sarawak, showing poor mangrove condition where shore erosion has occurred. @ C.Michael Hogan
The Sunda Shelf mangroves are some of the most biologically diverse mangroves in the world.
This ecoregion is generally found along portions of the coastline of Malaysian Borneo at the fringes of the South China Sea, Singapore Strait, Sulu Sea and Celebes Sea, as well as the Java Sea coast of Indonesian Borneo and the eastern shoreline of Sumatra.
They are home to the Proboscis Monkey (Nasalis larvatus), an endangered primate species of considerable interest. Like othermangrove forests in the region, they are under intense ecological threats from expansion of the human population,logging, shrimp farming, and agriculture conversion.
Location and General Description
The Sunda Shelf mangroves are found on the island of Borneo, fringe of the Riau Archipelago and the east coast of Sumatra. This mangrove ecoregion occurs on portions of the coastline of Malaysia (Geography of Malaysia), Brunei and Indonresia.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.
Source: World Wildlife Fund
There are five major mangrove types, or consociations, recognized in this region, based on the dominant species within the genera 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 metres (m) in height in many areas.
Biodiversity Features
Crab-eating macaque (Macaca fascicularis), Bako NP, Borneo, Malaysia. Source: 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 [[habitat]s]. 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 [[coastline]s] from erosion, accumulate sediment, and provide a nursery for numerous [[coast]al] fishes.
Last Glacial to Holocene Perspective
Pollen core research yields important information on the ecological change to the Sunda Shelf region over the last 25,000 years. During the Last Glacial Maximum sea levels were approximately 120 metres lower along the Sunda Shelf, leaving much of the present seabed to serve as a landbridge to near-shore islands. 
Aerial prop roots for mangroves on the foreshore,
Bako NP. @ C.Michael Hogan
The Holocene itself can be viewed to have an early segment (9900 to 5200 years before present; a middle segment (5200 to 2300 years before present); and a recent segment (2300 years before present to current time). The early Holocene segment witnessed sharp increases in mangrove species, especially for the Sonneratia and Rhizorora genera; at this same time montane rainforests almost disappeared from the region. The combination of these trends indicate that there was a pronounced warming that apparently endured through the mid-Holocene.
During the recent Holocene mangrove swamps and lowland rainforests declined on the Sunda Shelf, based upon pollen core records. During this recent epoch montane rainforests flourished along with ferns (especially Dicranopteris and Acrostichum genera). Pinxian Wang interprets the latter occurrences as due to a cooling climate and to human deforestation, pursuant to analysis by Li and Sun.
Current Status
Traditionally, mangroves have been harvested for fuelwood, charcoal, and timber, and, in some instances, these practises have 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).
|
| ||
|
|
Area (km2) |
IUCN Category |
|
Kuala Jambu Aye/Air |
140 |
PRO |
|
Kuala Langsa |
140 |
PRO |
|
Bakau Selat Dumai |
190 |
PRO |
|
Pulau Burung |
190 |
I |
|
Berbak |
200 |
II |
|
Bakau Muara Kampar |
350 |
PRO |
|
Tanjung Datuk |
130 |
PRO |
|
Kelompok Hutan Bakau Pantai Timur |
90 |
I |
|
Kulamba |
230 |
VI |
|
Muara Kayan |
320 |
PRO |
|
SAR (Sanctuary Reserve) |
50 |
II |
|
SAR (Sanctuary Reserve) |
340 |
UA |
|
SAR (Sanctuary Reserve) |
30 |
PRO |
|
SAR (Sanctuary Reserve) |
40 |
II |
|
Hutan Sambas |
20 |
PRO |
|
SAR (Sanctuary Reserve) |
50 |
IV |
|
Muara Kendawangan |
290 |
PRO |
|
Unnamed |
60 |
? |
|
Tanjung Penghujan NR |
170 |
PRO |
|
Tanjung Puting |
190 |
II |
|
Kelompok Hutan Kahayan |
560 |
PRO |
|
Pamukan |
320 |
PRO |
|
Teluk Kelumpang Selat Laut/Sebuku |
880 |
I |
|
Pleihari Tanah Laut |
410 |
IV |
|
Apar Besar |
1,000 |
PRO |
|
Pantai Samarinda |
140 |
PRO |
|
Total |
6,530 |
|
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
Bako National Park, Malaysia. Source: WWF and Canon The threats to the habitat remain the same as those that already have claimed vast areas of land: deforestation, 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. Water pollution, agriculture conversion, and oil extraction also threatened mangrove forests.
References
- Alistar I. Robertson. 1992. Tropical mangrove ecosystems. American Geophysical Union. 329 pages
- Li and Sun. 1999. Palynological records since Last Glacial Maximum from a deep-sea core in the southern South China Sea. Quat. Sci. Rev. 23: 2007-2016
- Pinxian Wang. 2009. The South China Sea: Paleoceanography and Sedimentology (Google eBook) Springer. 506 pages
- Eric D.Wikramanayake. 2002. Terrestrial ecoregions of the Indo-Pacific: a conservation assessment. Island Press. 643 pages
See Also
- Malaysia
- Ecoregions of Malaysia
- Malaysia Geography Collection
- Forests of Borneo
| Disclaimer: This article contains certain information that was originally published by the World Wildlife Fund. Topic editors and authors for the Encyclopedia of Earth have edited its content and added new information. The use of information from the World Wildlife Fund should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content . |
The Topic Editor of this article is Peter Saundry.
