Ecoregional Assessment of Biological Diversity in East Kalimantan

East Kalimantan Ecoregional Assessment: Chapter 2 – Target Ecological Systems
watercourses that divide them into numerous smaller patches which, when taken together,
constitute a single occurrence for the purpose of this ecological assessment.
East Kalimantan mangroves have been little studied but those of the Malaysian state of
Sarawak have been closely studied (Chai 1982). The species composition of Indonesian
mangroves reported in Whitmore (1984) and Tomascik et al (1997) provides a fairly
comprehensive description of the value of this community type to the ecology of the adjacent
marine environment.
Mangrove forests are highly productive natural ecosystems and tend to have a higher ‘litter’
production (of leaves, twigs, fruit and flowers) than lowland rainforests (Jiminez et al.
(1985). This litter is broken down by detritivores to enrich the surrounding waters,
particularly with nitrogen and phosphorus. The influence of mangroves on the nutrient levels
of other coastal ecosystems is also considered important as tides transport these nutrients to
other coastal areas (Ong et al. 1980).
Mangroves include a number of plant and animal species that are tolerant of the salt water
and mud environments. The mangal vegetation provides food, through leaf fall and decay
processes, as well as shelter to a unique and rich community of animals, particularly large
crustaceans and molluscs (Kartawinata et al. 1979). Mangroves are also important spawning
grounds and nurseries for prawns and many pelagic fish of commercial importance. Recent
observations by TNC ecologists suggests that this community may also be an important
protective feeding zone for hatchling sea turtles (EHB Pollard, pers. comm. 2003).
The Proboscis Monkey, Nasalis larvatus, Silver Langur, Presbytus cristata, Monitor Lizard,
Varanus salvator, and Crocodile, Crocodylus porosus also rely heavily on this aquatic forest
community. Mangroves also provide important feeding grounds for flocks of migratory
Palaearctic wading birds (MacKinnon et al. (1996). Other studies in Malaysia and Australia
also show that mangrove avifauna is distinct. For example in Borneo, Wells (1976) listed 21
species of birds that depended extensively or exclusively on mangroves.
Three main forms of mangrove system are represented in Kalimantan and elsewhere in
Borneo (Ong 1982, Tomascik et al. 1997). These are the coastal/delta form, the
estuarine/lagoon form and the island form. Mangrove forests occur along most of the
coastline of Borneo; however, they are being rapidly diminished in nature and extent by
human development processes. The greatest extent of remaining undisturbed mangroves on
Borneo is in East Kalimantan (MacKinnon et al. 1996, Tomascik et al.1997).
Conservation issues and threats
Mangroves are the most threatened of the coastal habitats in East Kalimantan. MacKinnon et
al. (1996: Table 3.1) report that the extent of this forest type in East Kalimantan has shrunk
from an original area of 950,000 ha to 750,000 ha in 1996. In addition, no large expanses of
mangroves are currently protected within existing conservation reserves. Only Kutai National
Park has a narrow belt of coastal mangrove.
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