Saturday, August 11, 2012

The Sabangau Forest

The Sabangau Forest is in southern Borneo, near Palangka Raya, in the Indonesian province of Central Kalimantan. Centered on the blackwater Sabangau River, it is bounded by the Katingan River to the west, Kahayan River to the east, Java Sea to the south and the main Palangka Raya-Sampit road to the north. The ecosystem covers an area of approximately 9,000 km2 of tropical peatland and most (6,300 km2) remains forested. Sabangau forms part of a great swathe of tropical peatlands that cover almost the entire lowland river plains of southern Borneo. It is the largest area of lowland rainforest remaining in Borneo.

The main habitat of the area is tropical peat-swamp forest. This is often decribed as a "dual ecosystem", with a diverse tropical forest ecosystem standing atop a thick peat layer. Peat is formed in heavily-waterlogged, acidic consitions, which prevents the complete breakdown of plant material. It is thus the partially-decayed remains of fallen leaves, branches and trees. The peat layer in Sabangau has formed slowly over 20,000 years and is up to 15 m deep in places. Being made almost completely of plant matter, peat is a major store of carbon. When drained, it begins to break down and oxidise, and becomes very susceptible to fire, releasing large amounts of carbon dioxide into the atmosphere: the current total peatland CO2 emissions in South-east Asia are estimated to be equal to almost 8% of global emissions from fossil fuel combustion, from just 0.1% of the global land area  (Hooijer et al., 2006). When CO2 emissions from degraded peatlands are included, Indonesia is the world's third biggest emitter of greenhouse gases after the USA and China (it is 21st excluding peat emissions).  Preserving tropical peatlands in their natural state is therefore one of the most effective ways of limiting global warming. Logging, peat drainage and fire all disturb the ecosystem's natural balance and, unfortunately, these all occur when peat-swamp forests are converted to oil palm plantation and other forms of agriculture. 

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In 1996, 50,000 hectares in the north of the Sebangau River catchment area was protected as the Natural Laboratory of Peat Swamp Forest (NLPSF or LAHG). The NLPSF is managed by CIMTROP (the Centre for the International Cooperation in Sustainable Management of Tropical Peatlands), an Indonesian research and conservation institution based at the University of Palangka Raya (UNPAR). Setia Alam Field Station, within the NLPSF, is situated 20 km southwest of Palangka Raya in the upper reaches of the Sabangau River.

Setia Alam Field Station is sited just inside the edge of the forest on the site of a former logging concession.  The NLPSF contains three forest classes: the mixed swamp forest (MSF), with a large diversity of tree species up to a maximum of 35 metres tall on peat approx. 6m deep, which spans the forest edge and reaches up to 5-6 km into the forest. The low pole forest (LPF), characterised by trees of height 10-15 m, then extends from 6-11 km into the forest. Furthest into the forest is the tall interior forest (TIF), on a peat layer up to 13 m thick and characterised by the highest diversity of tree species, with emergents up to 45 m tall.

The human population in the transmigration settlements on the southern Sabangau River numbers ~2,000; only one other permanent community of 100 residents on the Sabangau River exists in the west of the catchment. Fifteen large villages of 200-2,000 residents are found along the length of the Katingan River, with the large town of Kasongan marking the north-western boundary of the catchment. Several smaller villages occur along this river, together with the large transmigration settlement of Pegatan at the mouth of the river and temporary communities formerly up to 3,000 people centred on timber sawmills, although these are starting to dwindle as migrant workers return home following the cessation of illegal logging in the region.

The eastern Sabangau catchment is smaller and much more heavily degraded. The route of the trans-Kalimantan highway runs close to the Kahayan River, between Palangka Raya and Pulang Pisau, with many small settlements along its length. The northern boundary is marked by the provincial capital of Palangka Raya (ca. 100,000 residents); south of this is the large village of Kereng-Bangkerai (ca. 5,500 residents) on the northern bank of the Sabangau River. The entire area forms Block C of the failed Mega Rice Project, a program that planned to convert this area of deep peatland into rice padi. A large network of wide, deep, canals completely traverses this area, ostensibly built to provide irrigation, but, in fact, a major reason for the project’s failure. The project was abandoned before any forest was cleared in this region, but the drained and dried out peat has burnt regularly since 1997 and much of the forest in this area has been destroyed. Canals have partitioned the remaining forest. The area is still officially designated for agriculture, although no effort or investment has been put towards this since the cessation of the Mega Rice Project. Protection efforts are urgently required in this area to save the remaining large patches of forest, and conserve the biodiversity and carbon stored within.