Values of Peatlands in Indonesia
The unique peat swamp forest ecosystem plays a very important role in maintaining environmental balance. Peatlands are known to regulate hydrological processes. Peat lands prevent flooding by absorbing (like a sponge) heavy rainfall during the wet season. During dry season, they do the reverse and release the moisture back into the air gradually. Peatlands are also important for conserving biodiversity, as reserves for farming areas, as an alternative source of energy and for controlling global climate change. Tropical peatlands play an extremely important global role for carbon storage, climate moderation and for providing a range of other benefits such as biodiversity, water management, and livelihood support to local communities. The fundamental component of peatlands is water. As the water level decreases in peatlands, so does its capacity for sequestering and storing carbon.
Peat can contain up to 1,000% of water relative to its own dry weight (van Veen 1997; Sugandhy 1997). Its holding capacity is relatively high, especially for tropical lowland peat soils (Radjagukguk 1997). The moisture content of peat increases with depth (Franky et al. 1999) – it ranges from less than 400% in 0–30cm depth to more than 550% in 30–60cm depth. Andriesse (1988) suggested that the difference of moisture content was determined by decomposition levels and botanical origin.
The large variation in water retention between peat materials is a function of porosity, pore size distribution (Sanches and Logan 1992) and hydraulic conductivity (Andriesse 1988). Coarse fabric materials have large pores, whereas the most-decomposed sapric material has relatively small pores. The water retention capacity is positively correlated with the degree of decomposition. The particular attribute of peatlands is of importance for maintaining the hydrological function of the whole watershed (Sugandhy 1997; Sjors 1985). Groundwater levels and their fluctuations are important indices of the hydrological condition in peatlands (Umeda and Inoue 1994). In the tropics, water levels can rise up to one meter above the peat surface during the rainy season and can draw down to more than 1.5m below the surface in the dry season (Anonymous 1997).
Peat material has a unique characteristic of irreversible drying, high porosity and low vertical hydraulic conductivity. Dried peat can have a very low bulk density, which leads to it being easily eroded by rainfall, burning easily, difficulty in absorbing water and difficulty in replanting. Therefore, the hydrological function of peatlands would be disturbed when drainage occurs.
Peatlands encompass 2.5% of the total land area in the world or equal to approximately 400million ha. They are a unique habitat for various flora and fauna and commonly contain a very high endemism of plants. In Sumatra, more than 300 plant species were found in peatlands (Giesen, W. 1991). Among the high value plant species are: Jelutung (Dyera custulata), Ramin (Gonystylus bancanus), Meranti (Shorea spp), Kempas (Kompassia malaccensis), Punak (Tetramerista glabra), Perepat (Combretocarpus royundatus), Pulai Rawa (Alstonia pneumatophor), Terentang (Campnospherma spp), Bungur (Lagestroemia spesiosa), and Nyatoh (Palaquium spp) (Wibisono, I. T. C et al. 2004). Peatlands also provide habitat for various fauna including Sinyulong Crocodile (Tomistoma schlegelii), Sumatran Tiger (Panthera tigris sumatrae), Honey Bear (Helarctos malayanus), Tapir (Tapirus indicus), Mentok Rimba (Cairina scutulata), Bangau Tongtong (Leptoptilos javanicus). The latter is an endangered species listed in Appendix I of CITES and is classified as vulnerable in the Red Databook of IUCN. Peatlands are also a very suitable habitat for various fish species, namely Channa sp, Wallago leeri, Anabas testudineus, Trichogaster pectoralis and Trichogaster trochopterus. Nevertheless, the most important fish in peatlands is the ‘arowana’ (Scleropagus formosus), which is endangered due to over exploitation for its ornamental value (Wahjunto et al. 2004).
Biodiversity in peatlands is valuable for its future value. Undisturbed peatlands serve as a source of germ plasma, which has potential to improve the characteristics of existing plants and animals to become more resistant to diseases, more productive and require low input for optimum growth.
Global Climate Control
Peat is one of the best carbon stores, thus is of importance for climate change. The workshop on Vulnerability of Carbon Pools in Tropical Peatlands held in Pekanbaru, Riau, from 23-26 January 2006 noted that peatlands store about 30% of global soil carbon. Tropical peatlands is believed to store up to 30% of this amount.
On the other hand, burning peatlands release greenhouse gases to the atmosphere, particularly carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). These greenhouse gases form a ‘blanket’ in the atmosphere and absorb the long wave radiation of the earth surface, which leads to global warming. This could have serious impacts on various living mechanisms: diseases development in animals, human beings and plants; changes in plant productivity; drought and floods etc.
Peatlands have been used for agriculture in Indonesia for over a hundred years. Indigenous people of Dayak, Bugis, Banjar and Malays groups have traditionally practiced agriculture in peatlands by selecting a proper location and selective commodities with respect to its natural holding capacity. They build non-continuous canals and use rivers for both peatland management and transportation; environmental problems arising from these practices have been negligible in the past.
As the population increased, the need for agricultural lands also increased to fulfill increasing demands for agricultural commodities, including rice, vegetables, poultry, fish and other dietaries. In the last few decades, demand on extension of agricultural area was not only limited to commodities for self-consumption but also for other market-oriented commodities such as oil palm, pulp and paper and other wood-based products. These demands have increased the pressure on peatlands. By the end of the 1980s, extensive areas of peatlands in Indonesia were being drained and converted to oil palm and forest plantations.
Maltby (1997) concluded that due to the high sensitivity of tropical peat swamp forests, development of tropical peat lands entails on site and off-site effects, especially in regards to climatic and hydrological changes. Tropical peatlands is susceptible to rapid damage and degradation from human activities upon it and is irreversible if converted (Sjors 1985). The damage would have several effects such as subsidence, and would induce rapid decomposition and loss of peat (Umeda and Inoue 1994).