Area and location
Tropical peatland, one of the least known ecosystems of the world covers between 30 and 45 Mha, which is approximately 12% of the global peatland resource by area. Brunei, Indonesia and Malaysia contain nearly 70% of the total resource while the island of Borneo has about one quarter of the total (11 Mha). Indonesia contains the largest area of peat in the tropical zone with estimates ranging from 16 to 27 Mha. Central Kalimantan province (Indonesia) has still approximately 3 Mha of largely tropical rain forest covered peatland, but is also base of many failed peat conversion projects. In Malaysia peat covers 2.7 Mha of which 1.7 Mha is located in Sarawak.
Global carbon store
Tropical peat swamp forests have sequestered carbon dioxide (CO2) from the atmosphere into the peat up to 24,000 years, and thus reduced the greenhouse effect in the global scale. Peat deposit thickness can exceed 20 m, and the mean peat depth of about 5 m is exceeding that of our boreal peatlands. It has been estimated that if the tropical swamps form about 13% of the global mire area, but the amount of the carbon in tropical peat can form up to one third of the carbon of all mires on our planet. Large part of the plant biomass produced by wet environment adapted peat swamp forest vegetation, especially litter from tree roots, is allocated to water saturated peat where the organic matter decay rate is slow. This creates potential for accumulation of dead organic matter i.e. peat formation.
Land use change and carbon loss
Use of peat for agriculture requires drainage in order to improve oxygen availability for the roots of cultivated plants. Simultaneously, improved aeration in the peat profile promotes decomposition of surface peat and the litter from replacement vegetation does not end up into wet peat for substituting the oxidised organic material. Due to felling and drainage the natural carbon sinks have now transformed increasingly into pulp tree and oil palm plantations, and form now one of the biggest causes of the climate change of our planet.
According to a recent report (Delft Hydraulics report, 2007), Indonesia’s peatlands drained for agriculture and plantation production (some of which have become abandoned mismanaged areas) release every year about 2,000 million tons of CO2. This carbon outflow to the atmosphere elect this country at third largest emitting nation in the global green house gas emission statistics, immediately behind the leading USA (5,783 Mt) and China (4,140 Mt) in the year 2003. If the emissions from drained peatlands are ignored, Indonesia will have a 21st place in these statistics with 295 Mt CO2 emissions, and this position would be resulted basically from use of fossil fuels. If expansion of drainage areas in Indonesia continues with present speed on peatlands, CO2 emissions into the atmosphere may double or triple during the next 10-15 years and possibly turns Indonesia to the largest emission source in the world.
It has been estimated that drainage and drainage related fires free up to 100 tons of carbon dioxide per hectare annually. This would lead to 700 million tons CO2 release every year from the 7 million hectares cultivated peatlands established in the Southeast Asia. Fire is been still largely used in land clearance for cropping vegetation and escaped fires cause repeatedly large CO2 emissions almost every year. For example, it has been estimated the peat fires raged in Indonesia have freed 3,000-9,400 million tons of carbon dioxide into the atmosphere in 1997-1998, which is comparable with 15 – 40% of the global fossil fuel emissions in that year. At that time the global atmospheric CO2 concentration had the largest ever measured increase since the follow-up measurements started in 1950’s; statistically about half of that record CO2 rise can be explained by fires that smouldered half year in peatlands of Southeast Asia.
Towards wise use
Valuable materials, timber, rattan, natural gum and many medicinal plants, have been collected from peat swamp forests in Southeast Asia for a long time. The shallower peat owing forest areas have been used in cultivation. The growth of human population has compelled during the last few decades to take to the cultivation still more rugged and further-away peat swamp forests. The yield has remained low and it has been difficult to get products to the market because of long distances. Large areas of peat swamp forest have to be used as a production land also in the future but their limitations and the consequences of the use must be taken into consideration. The present use of tropical peatlands is unsustainable. The operational life time of reclaimed peat is determined by the intensity of drainage, fires and the thickness of the peat layer. The subsidence of peat in warm humid climate will be about 5 cm per year even after 20 years from initial drainage. Because of the subsidence the production possibilities can last only for a few decades before infertile subsoil is reached – in many places on coastal areas, eventually, salty water and poisonous sulphate subsoil stop further land use. The best lasting alternatives of the use of tropical peat swamp forests have been proven to be light selective felling performed without drainage and also cultivation by plants which can survive in relatively wet soil.
Key words in finnish: trooppinen suo, trooppiset suot, hiilidioksidi, turve, biomassa, Kaakkois Aasia, pinta-ala, hiili, kestävä käyttö, biodiveristeetti, maankäyttö, maankäyttömuutos
Further information concerning tropical peat will be provided by
Jyrki Jauhiainen and Harri Vasander
Meet also our other Peatland Ecology Group members in University of Helsinki at http://blogs.helsinki.fi/peatlanders/front-page/
