Peatlands in South East Asia
Tropical peatlands are one of the most critical ecosystems in South East Asia. It is important for biodiversity conservation, climate regulation and for the support it provides for human welfare.
Peatlands cover over 400 million ha worldwide, occur in about 180 countries and represent a third of the global wetland resource. Approximately 10% of the world's peatland area is tropical with about 60% of this in South East Asia alone, predominantly in Indonesia. The area of tropical peatlands in the region is estimated to cover c. 30 million ha.
Peatland Degradation
In South East Asia, up to 70% of tropical peat swamp forests have been significantly affected by unsustainable forest harvesting, deforestation, drainage and land clearing for agriculture. This trend of peatland loss and degradation will continue if there are no interventions. With the current rate of loss, intact and functioning peatlands will disappear completely within a few decades.
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Peatlands are the single largest terrestrial store of carbon. It stores more carbon than the vegetation of the whole world, which is equivalent to 75% of all carbon in the atmosphere. There is no doubt that their continued degradation will accelerate global climate change.
Environmental Challenges
In South East Asia, about 7 million ha of tropical peatlands have been cleared and drained for agriculture and forestry in recent years. The oxidation of the topsoil results in the emission of carbon dioxide in the range of 50-100 tonnes per ha/year; or approximately 350-700 million tonnes/year.
Fire in drained peat areas spreads easily and can last for months. In 1997/98, flames engulfed about 2.2 million ha of peatlands in Indonesia, contributing 10-20% (1-2 billion tonnes) of the world's CO2 emissions. Smoke from the peat fires spread throughout South East Asia and is estimated to have caused an economic damage worth US$10 billion, in addition to affecting the health of millions of people.
Tropical peatlands form mostly on low-lying water-logged land where a lack of oxygen prevents dead plant tissue from decomposing completely. This dead plant matter then accumulates to form layers of peat.
Tropical peatlands are areas in the tropics covered with peat soil. Unlike many temperate peatlands, the typical plant community in tropical peatlands is forest. A single peat swamp forest can hold a diverse range of forest types, all of which might differ from the range found in other peat swamps. The type of forest in a peat swamp varies according to peat depth, nutrient supply and the amplitude and period of flooding.
In peatlands, there is a close connection between water, peat and the vegetation growing on the land. If any one of these components is changed, the nature of the peat is fundamentally affected.
What is Peat?
Peat is defined as a soil type containing at least 65% organic matter. In the tropics, it is formed from decayed leaves, stems and roots of plants that have accumulated in a water-saturated environment in the absence of oxygen.
Peat accumulates in layers year after year to form a deposit which can amount up to 20m thick. These deposits develop over different geological times; recent deposits remain as peat while earlier deposits transform over millions of years into lignite and coal. The layers of peat can often show the succession of vegetation over thousands of years.
Peat comprises more than 90% water; this enables peatlands to have a unique ability to store large amounts of water. Peatlands are essentially water bodies, although trees can grow and people can walk on them.
Forests formed on peat soils are called peat swamp forests. They possess unique vegetation assemblages adapted to the high degree of water logging, low pH and low nutrient conditions.
Formation of Tropical Peatlands
Peat is formed when leaves, tree roots and wood from vegetation in a forest fall to the ground, which is covered in water. These leaves, tree roots and wood only partly decompose because the rate of chemical breakdown (decay) is slowed down by the presence of water. Peat forms when the rate at which the vegetation (or organic matter) accumulates in the ground is higher than its chemical breakdown. Peat is generally considered to be partly decomposed vegetation.
Water is an important factor in the formation of peat because it slows down the rate of plant decay. The water table is held permanently high through high precipitation (rainfall) or by ground or surface water flow.
In the tropics, peat accumulates with a rate of about 0.5-2 mm per year (or 5-20m over 10,000 years). Most peatlands which exist today were formed in the last 10,000 years since the last ice age.
Tropical peatlands are found in the region between the tropics of Cancer and Capricorn in South America, Africa, India, Papua New Guinea and South East Asia. In South East Asia, there are about 30 million ha of tropical peatlands.
Approximate Peat Distribution in South East Asia
The largest area of peatlands in South East Asia is found in Indonesia which has an estimated 21 million ha, followed by Malaysia with c. 2.5 million ha. Thailand has a comparatively small area of peat (c. 60,000 ha) mostly in the southern provinces, whilst Viet Nam has an area of peat about 36,000 ha mainly in the Lower Mekong Delta. Two peatland areas were identified in the Philippines recently at Agusan Marsh and Leyte Sab-a, totalling c. 11,000 ha. Myanmar has at least 3,500 ha, Lao PDR 20,000 ha and Brunei Darussalam 100,000 ha.
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