Development of tropical peatlands
Tropical peatlands occur in three main regions, Central and South America, Africa, and South East Asia. Around 62% of the world’s tropical peatlands are found in the Indo-Malaya region (80% Indonesia, 11% Malaysia, 6% Papua New Guinea, and smaller areas in Brunei, Vietnam, the Philippines, and Thailand). Indonesian peatlands are found on the three islands of Sumatra (8.3 million ha), Kalimantan (6.3 million ha), and Papua (4.6 million ha). These peats developed in low-lying areas like deltas, floodplains, or shallow lakes such as meander oxbows of great rivers. Development seems to follow general hydrosere successional stages with eutrophic open water colonised by water plants and transformed into a waterlogged swamp with grasses and shrubs. This gradually morphs into peat-forest and the peat continues growing and accumulating to the point that in some areas a raised, convex-shaped dome is formed. Some peat may be pushed out to the dome fringes or zones in-between the core accumulations. The peat growth may rise to four metres in coastal peats and to eighteen metres in inland sites.
With tropical peat formation, the early stages are mostly topogenous or min-erotrophic as they receive nutrients from rivers or groundwaters. However, like with temperate peats, as the deposit deepens and the peat-dome elevates above the surrounding water table, they become ombrotrophic. Water input is then exclusively from rainfall and so this becomes a low-nutrient system. With calcium particularly in short supply, the peat is highly acidic. At this stage, biodiversity may be reduced and any tree growth is stunted.
Inland and coastal peats differ greatly in age with many coastal peat sites beginning to form during the mid-Holocene Epoch (around 8,000 years ago) whereas some inland peatlands are older and began in the Late Pleistocene Age (c. 26,000 years ago). In coastal zones, the initiation of peat formation was strongly influenced by a rise in the sea level which in turn was affected by factors and events like the El Nino being less intense and by glacial-related changes which triggered alternating periods of inundation and of drying up of the seas. As ice sheets thawed, the coastline moved inland as the sea level rose. The oldest coastal peats in tropical Asia today are about 8,000 years old.
Kates of growth over long periods of time in the inland peatlands were sometimes very slow and varied from a few millimetres per year to maybe only 0.05 millimetres. The inland sites are driven mostly by climate and some topographic influences but little or no effect of any rising of the sea level. Sites are located about twelve to twenty metres above modern sea level, and historically this has not risen more than about six metres in the last 100,000 years.
Examples of tropical peat-forest and issues in South East Asia
Indonesia has about 50% of the world’s tropical peat-swamp forest which were formerly major components of ecosystems there with 16.5 to 27 million hectares. In their original state, Indonesian peat-swamp forests were carbon-sequestering systems. However, these forests have been lost to deforestation felling, drainage, and conversion to agricultural lands and other functions. The reduction has compromised the ecosystem service functions
Over recent decades, the Indonesian government has pursued the ‘Mega Rice Project (MRP)’, whereby it has sanctioned the draining of over one million hectares of Borneo peat-swamp forest which was converted to agriculture. Indeed, between 1996 and 1998, over 4,000 kilometres of drainage and irrigation channels were cut. At the same time, deforestation rapidly accelerated through both legal and illegal logging and also burning to remove the trees. Infrastructure such as roads, railways, and water channels for legal forestry, also facilitated the areas to become accessible for illegal cutting and the government did little or nothing to prevent this.
Across the MRP region, the forest cover fell from 65% in 1991 to 46% in 2000, with ongoing clearance since that time. Assessments suggest that virtually all sellable timber trees have been taken from within this area. The intention had been that the cut channels would irrigate the region whereas in practice they drained it and today where the forest floor once stood up to two metres deep in water, it is bone dry. Late in the day, and after considerable damage, the Indonesian government halted the MRP. However, the region is now dominated by huge numbers of fires from burning peat and burning trees and the lowlands north-west and south-east of the region are shrouded by thick, grey smoke. In many areas, this adverse environmental impact has seriously affected a potentially lucrative tourism economy for the country.
The wider environmental impacts are even more drastic with research for the European Space Agency finding 2.57 billion tons of carbon released to the atmosphere in 1997 alone because of burning peat and associated vegetation in Indonesia. The estimate suggests an amount close to 40% of the mean annual global carbon emissions from fossil fuels. This is a major factor in the greatest annual increase in atmospheric carbon dioxide concentration since data records started in 1957. Catastrophic fires in 2002 to 2003, further released 200 million to one billion tons of carbon into the atmosphere, and these were associated with government corruption and illegal business activities. The effect on tourism across a wide area of South East Asia was devastating as palls of thick smoke clouded
FIGURE 4.2 Indonesian peat-swamp forest by Wilter Malandi showing a huge tropical tree.
a wide region internationally. A further consequence now is that from being a centre for carbon storage worldwide, Indonesia is today the world’s third-largest carbon emitter. This is mostly due to the felling, draining, and burning of its ancient peat-swamp forests.
A key issue for conservationists and scientists is to find ways to highlight the significance of the forest resources and their peat. For peat-swamp forests there need to be alternative ways to make these areas productive for local people, including indigenous communities, but in ways which are environmentally sound and sustainable (Figure 4.2).
Peat-swamp forest in Kalimantan
Kalimantan is the expansive Indonesian part of Borneo and has extensive peat-swamp forests, with huge trees up to seventy metres high. These are totally different landscapes from the familiar peatlands of northern temperate and boreal areas where sphagnum mosses, grasses, sedges, and shrubs dominate. The anaerobic, seasonally flooded peat-beds can be up to twenty metres deep with a spongy, unstable, waterlogged, substrate that is highly acidic (pH 2.9 to 4.0) and nutrient-poor. The water in the forest is dark brown because of tannins leached from fallen leaves and the peat, and these are also called ‘black-water swamps’. Even in the dry season the peat is waterlogged with pools of water standing amongst the trees. The actual water level on the peat is generally around twenty centimetres under the surface, but this may fall to about forty centimetres under exceptionally dry periods like El Nino conditions. This lowering of the water table makes the sites vulnerable to deliberate and accidental fires.
The peat-forest histosol soils have a high carbon content with typically 70% to 99% organic material. In temperate peatlands this high carbon content is maintained by wetness and low temperatures, whereas in tropical peatlands it is stabilised by waterlogging. Therefore, any changes to water status here can trigger major carbon release into the atmosphere.
Conservation and preservation
Conservation of tropical peat-swamp forest has had limited success and the efforts pale when compared to the widespread devastation of commercial logging and deforestation. There are attempts by conservation bodies like ‘Borneo Orangutan Survival’ for example, to preserve the peat-swamp forest of Mawas using carbon finance and debt-for-nature-swap. Habitat disturbance from deforestation has dramatic impacts on orangutan populations in mixed swamp-forest. The presence of a large, self-sustaining orangutan population in Kalimantan’s peat-swamp forests, for example, emphasises the need for greater and effective measures. Furthermore, the orangutans are merely the iconic biodiversity headline species in forests which have superabundant endemic species including large numbers as yet unknown to science. As the forests burn we are losing species we don’t even know we have. Currently, around 6% of the original peat-forest is in protected landscapes, the largest being Tanjung Put-ing and Sabangau National Parks. At the same time, logging is on-going and intensifying elsewhere.
Palm oil agribusiness is the main driver for East Asian deforestation along with illegal logging in places like South Sumatra. Surveys indicate that complete removal will have occurred by 2030. Projects initiated under concepts such as ‘reducing emissions from deforestation and degradation’ (REDD) address deforestation as a global issue. Destruction impacts on biodiversity and livelihoods of forest-dependent communities but is also a major climate change driver which leads to around 20% of global greenhouse gas releases. REDD projects are intended to address forest destruction and to provide protection from agricultural encroachment. The idea is that such initiatives should benefit biodiversity and improve environmental quality for surrounding communities.
Organizations like Wetlands International are now working with the Indonesian government to provide improved policy and spatial planning guidance on these issues. The intention is to deal with issues of the unsustainable palm oil expansion in Indonesian peatlands and the destruction of mangrove swamps. Perhaps, rather controversially, the projects engage with palm oil industrialists who are at the heart of this problem. The idea, however, is to promote ‘best management practices’ for tropical peat-swamp forests and engage local communities who often are unaware of key aspects of natural resource management. Work in the field tries to support local people in restoring mangroves and peatlands.