Peat swamp forest

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Satellite image of the island of Borneo on 19 August 2002, showing smoke from burning peat swamp forests

Peat swamp forests are tropical moist forests where waterlogged soil prevents dead leaves and wood from fully decomposing. Over time, this creates a thick layer of acidic peat. Large areas of these forests are being logged at high rates.

Peat swamp forests are typically surrounded by lowland rain forests on better-drained soils, and by brackish or salt-water mangrove forests near the coast.

Tropical peatlands, which coexist with swamp forests, have accumulated vast amounts of carbon as soil organic matter. Since the 1970s, however, deforestation and drainage have progressed on an enormous scale. In addition, El Niño and Southern Oscillation (ENSO) drought and large-scale fires, which grow larger under the drought condition, are accelerating peatland devastation. That devastation enhances decomposition of soil organic matter and increases the carbon release to the atmosphere as CO2. This phenomenon suggests that tropical peatlands have already become a large CO2 source, but related quantitative information is limited.[1]

In particular, tropical peat swamp forests are home to thousands of animals and plants, including many rare and critically endangered species such as the Orangutan and Sumatran Tiger.[2]

In Indonesia[edit]

Over the past decade[date missing], the government of Indonesia has drained some peat swamp forests on the island of Borneo for conversion to agricultural land. The dry years of 1997-8 and 2002-3 saw huge fires in the peat swamp forests. A study for the European Space Agency found that the peat swamp forests are a significant carbon sink for the planet, and that the fires of 1997-8 may have released up to 2.5 billion tonnes, and the 2002-3 fires between 200 million to 1 billion tonnes, of carbon into the atmosphere. Much of the emissions from peatlands in Borneo are due to changes in their hydrological regime, caused by drainage from nearby plantations (particularly oil palm). Peatland conservation and rehabilitation are more efficient undertakings than reducing deforestation (in terms of claiming carbon credits from REDD initiatives), due to the much larger reduced emissions achievable per unit area and the much lower opportunity costs involved.[3] Indonesia contains 50% of tropical peat swamps and 10% in the world.[4]

Habitat disturbance caused by logging was shown to affect orangutan density within mixed swamp forest. The orangutan population for a larger peat covered landscape unit (9200 km2), including the Sebangau catchment, was estimated to be between 5671 (±955) and 8951 (±1509) individuals, based upon the area of each forest type, the level of disturbance in each area and corrected to prevent overestimates. There is a presence of a very large, self-sustaining orangutan population in this region and emphasizes the urgent requirement for greater protection of Kalimantan's peat swamp forests in the light of recent and rapid habitat degradation.[5]

Peat formation is a true carbon sink, the carbon being sequestered out of the system and converted into peat through biological activity. Peat swamp forests originally represented major ecosystems in Indonesia and ranged between 16.5 – 27 million hectares. In their original state, Indonesian peat swamp forests sequestered between 0.01 – 0.03 Gigatonnes of carbon annually. These important ecosystems have however in recent years been reduced through drainage and conversion to agricultural lands and other activities. Their present status as carbon sequestering systems have thus also been reduced significantly. An understanding of the global importance of peat (and thus the urgency of maintaining peat swamp forests) and identifying alternative ways of making these areas productive in an environmentally sound and sustainable manner should have high priority among scientists and policy-makers alike. [6]

In Malaysia[edit]

It has long been assumed that the peat underlying tropical peat swamp forests accumulates because the extreme conditions (water logged, nutrient poor, anaerobic and acidic—pH 2.9–3.5) impede microbial activity. Litterbag studies in a tropical Malaysian peat swamp (North Selangor peat swamp forest) showed that although the sclerophyllous, toxic leaves of endemic peat forest plants (Macaranga pruinosa, Campnosperma coriaceum, Pandanus atrocarpus, Stenochlaena palustris) were barely decomposed by bacteria and fungi (decay rates of only 0.0006–0.0016 k day−1), leaves of M. tanarius, a secondary forest species were almost completely decomposed (decay rates of 0.0047–0.005 k day−1) after 1 year. Thus it is intrinsic properties of the leaves (that are adaptations to deter herbivory in the nutrient poor environment) that impede microbial breakdown. [7]


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