Ecoregions

Sumatran peat swamp forests

October 16, 2011, 4:28 pm

The Sumatran peat swamp forests are a distinctive forest type, and their biodiversity is characteristic of the associated habitat.

caption Satellite view of peat swamp forest (center) on Sumatra across from Bangka Island (Photograph by USGS)

The peat swamp forests in Indonesia are less threatened than the freshwater swamp forests. This is partly because of their low nutrient levels, which limit the productivity of their vegetation, including agricultural crops. However, despite their poor productivity in the past five years, significant areas of peat swamp forests have been burned in Indonesia, and less than one-half of these forests remain.

Location and General Description  

This ecoregion represents the peat swamp forests along the eastern coast of the island of Sumatra, Indonesia, as well as the Riau archipelago. Based on the Köppen climate zone system, this ecoregion falls in the tropical wet climate zone.

caption Source: WWF

The peat swamp forests of Sumatra have similar characteristics to those in Borneo and Peninsular Malaysia. Peat soil is composed of more than 65 percent organic matter. Most peat deposits found behind mangroves along the coast are ombrogenous, or rain-fed peat swamps. Peat swamp forests are formed when rivers drain into the inland edge of a mangrove and the sediments are trapped behind the tangle of mangrove roots. These areas begin to build up and flood less often as the coastline extends outward. The peat deposits usually are at least 50 centimeters (cm) thick but can extend up to 20 meters (m). Peat swamps are domed and are rarely flooded. Because peat swamps are not drained by flooding, they are nutrient deficient and acidic, with a pH usually less than 4. Compared with other moist forest ecoregions, peat forests-at least in the lowlands-are not as species-rich and are not high in endemism.

There is not a single type of peat swamp forest but rather a gradation of forests types along a nutrient gradient. The edges of peat swamp forests are relatively nutrient-rich, whereas the center is nutrient-poor. Likewise, the forest becomes smaller with an even canopy, moving from the edges to the center. Whereas Borneo has up to six types of peat swamp forest, Sumatra retains only two: a mixed peat swamp forest and a pole forest.

Both mixed swamp forest and pole forest have few tree species, but a pole forest may have a higher density. Mixed swamp forests tend to have a larger average diameter and basal area. Some characteristic species from these forests include Tristania obovata, Ploiarium alternifolium, Polyalthia glauca, Stemonurus secundiflorus, Radermachera gigantea, Salacca conferta, Livistona hasseltii, and Cyrtostachys lakka. Palms are not common, but several species generally are confined to these forests. The emergent Livistona hasseltii is characteristic, as is the bright-red sealing wax palm Cyrtostachys lakka.

Biodiversity Features

Peat swamp forests do not support an abundance of terrestrial wildlife, and none of the mammals are considered endemic. The Sumatran tiger (Panthera tigris) is Indonesia's largest terrestrial predator and is critically endangered. The Sumatran tiger lives in lowland and montane rain forest and frequent peat swamp forests throughout Sumatra. An estimated 500 Sumatran tigers remain in Sumatra. There are three Level II Tiger Conservation Units (TCUs) in Sumatra that overlap this ecoregion. The Asian elephant (Elephas maximus) is found in numerous populations throughout Sumatra. However, only five populations have more than 200 individuals, but habitat loss has placed the survival of many of these populations at risk. The number of bird species tends to be lower in peat swamp forest than in the surrounding lowland rain forests, and there are no endemic or near-endemic species.

Current Status

More than half of the habitat in this ecoregion has been cleared, especially in the southern portion, where only a few blocks of habitat remain. Large areas of swamp have been drained, mainly for transmigration settlements and large-scale development projects, making this a highly vulnerable ecoregion. There are thirteen protected areas that extend into the ecoregion to cover 4,730 square kilometers (km2) (5 percent) of the area (Table 2). However, many of the protected areas are proposed, and the official status is still uncertain. Of the gazetted protected areas, only Berbak is greater than 1,000 km2.

 Table 1. WCMC (1997) Protected Areas That Overlap with the Ecoregion.

Protected Area

Area (km2)

IUCN Category

Bakau Selat Dumai [AA0124]

320

PRO

Bukit Batu

230

PRO

Siak Kecil

940

PRO

Danau Tanjung Padang

110

PRO

Giam Duri [IM0157]

200

PRO

Pulau Burung [AA0124]

260

I

Berbak [AA0124]

1,310

II

Istana Sultan Siak

240

PRO

Danau Belat/Besar Serkap

80

PRO

Sarang Barung

40

PRO

Kerumutan

110

IV

Kerumutan Lama

40

PRO

Padang Sugihan

850

IV

Total

4,730

 

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

Types and Severity of Threats

In some areas of southern Sumatra, the peat swamp has been drained for transmigration and other major development projects. The drainage of one area dries neighboring areas. Therefore, fires are common, preventing natural succession and promoting the development of extensive, nearly monospecific stands of paperbark (Melaleuca cajuputih). In areas where the peat itself is burned, small, shallow lakes form and become covered with floating islands of grasses and herbs. Large-scale plantations, illegal logging, and timber enterprises have also led to increasing deforestation with resultant erosion and sedimentation of nearby rivers. Coconuts are grown along the coast, and drained swamps are used for pineapple plantations. Logging concessions cover almost 80 percent of the ecoregion's remaining habitat and pose a serious threat to habitat integrity and conservation.

Justification of Ecoregion Delineation

Whitmore and MacKinnon showed large extents of peat swamp forests along the northern coast of Sumatra, especially in Riau Province. We delineated the Sumatran Peat Swamp Forests to represent these forests but extracted the smaller patches of freshwater swamp forests into the Sumatran Freshwater Swamp Forests and the mangroves in theSunda Shelf Mangroves.

MacKinnon's biounit 21 largely corresponds to Udvardy's Sumatra biogeographic province. However, Udvardy did not include the Nicobar Islands. Eight ecoregions overlap Udvardy's Sumatra biogeographic province: Sumatran Lowland Rain Forests, Sumatran Montane Rain Forests, Mentawai Islands Rain Forests, Sumatran Peat Swamp Forests, Sumatran Freshwater Swamp Forests, Sundaland Heath Forests, Sumatran Tropical Pine Forests, and Sunda Shelf Mangroves.

Additional Information on this Ecoregion 

 

Disclaimer: This article contains 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.

 

 


 

 

Glossary

Citation

Fund, W. (2011). Sumatran peat swamp forests. Retrieved from http://www.eoearth.org/view/article/156326

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