Indonesia: Kalimantan’s Lowland Peat Forests Explained

Indonesia: Kalimantan’s Lowland Peat Forests Explained

4 December 2009

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Indonesia —

Earth’s tropical rainforests are a critical component of the world’s carbon cycle yet cover only about 12% of its terrestrial land. Accounting for 40% of the world’s terrestrial carbon and 50% of the world’s gross primary productivity,[1]. the production of organic compounds primarily through photosynthesis, tropical rainforests also are one of the engines driving Earth’s atmospheric circulation patterns.

Asia is home to roughly 17% of the world’s rainforests and to a large percentage of the world’s biodiversity. Asia’s forests also have some of the highest deforestation rates [2]. In fact, fragmentary secondary forests in Asia now are greater than all remaining old-growth primary rainforests in SE Asia [3]. This means that secondary lowland forests, such as Kalimantan’s peat forests, must play a key role in biodiversity conservation, carbon emissions mitigation, and sustainable economic development.

Borneo’s Speciation

Tropical forests, home to over 50% of the world’s species,[4]. are experiencing unprecedented deforestation. Indonesia’s forests on Borneo are being deforested at a rate of roughly 2% a year [5]. It is estimated that the forests on Indonesia’s part of Borneo, which is called Kalimantan, will be deforested by about 2020 [6]. Kalimantan’s forests have two broad ecological zones. In the lowland peat forests, dipterocarp trees can reach over 60 meters, or roughly 200 feet, and each tree is host to up to 1,000 insect species [7]. In the highland mountains, the forests are little explored or understood.

Borneo has the highest documented tree diversity on Earth, with 1,175 species counted in one 52 hectare plot in Lambir Hills National Park, Sarawak, Malaysia [8]. In fact, more than 6,000 endemic plant species, 15,000 plant species, 2,000 species of orchids, 265 dipterocarp tree species, and an estimated 700 tree species have been recorded thus far in Borneo. For comparison, there are roughly only 50 tree species in Northern Europe [9].

Borneo’s Deforestation

The island of Borneo is Earth’s third largest island, approximating 74,392,500 ha2 (square hectares). Three countries share the island: Indonesia, Sultanate of Brunei Darussalam, and Malaysia.
Figure 1: Extent of Deforestation in Borneo 1950-2005, Projection to 2020 [2]Borneo  74,392,500 ha Indonesia  54,000,000 ha Brunei Darussalam  576,500 ha Malaysia  19,816,000 ha In Figure 1: Extent of Deforestation in Borneo 1950-2005, Projection to 2020, Borneo’s rate of deforestation, primarily in Indonesia, can be understood as catastrophic and unprecedented. The amount of land deforested in the last 20 years is about the same size as Texas and California combined, or the total landmass of Spain or France. This astounding rate of deforestation has resulted in an increase in Indonesia’s carbon emission load, due to peatland fires and related decomposition of peat, to over 2 billion tons of carbon annually. This is equivalent to three times the German economy and greater than Russia’s annual carbon emission rate [12]. Borneo’s forests, which only 20 years ago were dipterocarp primary tropical rainforests, now are a patchwork quilt of palm oil plantations, degraded forested land, and timber plantations [13].

Since 1983, Indonesia has experienced many disastrous periodic forests fires during each El Niño Southern Oscillation (ENSO) period. In 1997-98, an area the size of Connecticut and Rhode Island burned.

Borneo’s ecological system has characteristically been driven by ENSO-related microclimate changes, with extensive drought in each ENSO period. The drought conditions cause the dipterocarp trees to synchronously bloom and then bear fruit, contributing food to vertebrate populations that in turn feed larger vertebrates further up the food chain.

Because of unparalleled uncontrolled and unmitigated deforestation, Kalimantan now experiences a destructive cycle related to ENSO. ENSO causes widespread drought that is enhanced by deforestation, lack of leaf transpiration, and draining of the lowland peat forests [14].

The dry peat soil then is the fodder for remarkable forest fires that degrade millions of hectares of Kalimantan’s rainforest. In fact, the forest fires are so large they can be seen from space (see Figure 2: Borneo’s Fires from Space September 22, 1997). During 1997-98, more than 5 million hectares of rainforest burned in the province of East Kalimantan [15]. This burned area is an equivalent area to Connecticut and Rhode Island combined.
These forests fires would not have been as large if the forests had not been drained or disturbed. Rainforest trees can trap transpired moisture that originates from the surrounding biomass, thereby increasing humidity and decreasing fire risk [16]. Also, most tropical trees have thin bark, and the bark of saplings is even thinner. Because of this, seedlings and saplings are easily damaged by fire. Regeneration of burned tropical rainforests requires sustained periods without severe fire disturbance. Otherwise, mortality and regeneration are affected [17].
Figure 2: Borneo’s Fires from Space September 22, 1997 [19] Once a fire has occurred, the same forest is prone to secondary fires because of ecosystem changes. ENSO events in 1982-83 and 1997-98 had a significant effect on the rainforest ecosystems of Borneo with increased fire damage. Furthermore, these events are expected to increase in severity as global warming and associated climate changes accelerate [18].

Most commercial timber in Borneo’s lowland peat forests is composed of dipterocarp trees, roughly 90%. Dipterocarp trees are dense – 50 to 120 m3 per hectare. When they are logged, about 80% of the canopy is destroyed [20]. In a primary dipterocarp forest, the above ground biomass is approximately 500 tons per hectare [21]. It is estimated that only about 7% of the carbon released by the destruction of tropical rainforests is reabsorbed through photosynthesis back into the fallow remaining rainforests [22]. In fact, the volume of dipterocarp timber exports from Borneo measured in cubic meters is greater than all tropical wood exported from Latin America and Africa combined since 1980 [23].

While there are many reasons a forest may burn, the critical factors are forest clearance and draining of peat forests [24]. It is estimated that during the fires of 1997-98, 2.18 – 2.57 GT carbon were released into the atmosphere as a result of fires throughout the Sumatra and Kalimantan. This is about 40% of the emissions of fossil fuels from car emissions annually globally,[25]. with a cost to the local economy of roughly $9 billion USD [26]. This made Indonesia the third largest carbon-emitting nation globally [27].  

Kalimantan’s Peat Forest Ecosystem

Peat forests are defined as terrestrial lands in which over 80% of the area is covered by peat soil. Peat soil contains at least 30% organic matter by weight with greater than 40 cm in a cumulative layer [28]. Peat forests are wetlands with a thick layer of decomposing organic matter. Peat forests occupy only 3% of Earth’s surface yet their carbon storage rate is approximately 525 gigatons of carbon. Peat forests therefore could store 15% of Earth’s terrestrial carbon [29].

The hydrologic routing in Kalimantan’s peat forests is dominated by ombrotrophic waters (from precipitation) with some phreatotrophic waters (from groundwater). Kalimantan’s waters are mainly palustrine and riverine. Yet little is known about the hydrarch succession within Kalimantan’s lowland peat forests.

Sixty-eight percent of the world’s tropical peat forests are in the area of the South China Sea, including Indonesia [30]. Tropical peat forests represent 10% of the world’s peat forests and 8% of the world’s wetlands. This is an equivalent area of 500,000 km2. Tropical peat forests account for about 40% of the carbon storage capacity in the world’s peat forests, equivalent to 200 GT carbon. Kalimantan contains 68,000 km2 of peat forests [31]. Accordingly, Indonesia’s Kalimantan peat forests have a carbon storage capacity of 27 GT carbon, and during ENSO years, which are characteristic of relative drought in Kalimantan’s lowland peat forests, carbon fluxes increase as carbon is emitted from the drying peat soils [32]. Carbon is emitted because as the organic matter in peat soils dries, it goes through either aerobic or anaerobic decomposition, which releases CO2, CH4, and N2O into the atmosphere. Tropical peat forests in Kalimantan have relatively high temperatures, and some suggest that a rise in global temperatures will increase forest temperatures, increasing carbon release rates from decomposing woody debris [33]. But hydrological conditions dominate lowland peat forests as this relates to carbon storage.

In Kalimantan, there are no large seasonal changes in evapotranspiration [34]. Small variation in water table levels shows only a small change on soil CO2 flux rates [35]. This means that when the water table lowers through drought during an ENSO year or when peat forests are drained for large-scale agricultural endeavors such as palm oil plantations, CO2-releasing decomposition increases rapidly. The above analysis took into account microtopographically hummock and hollow peat surfaces.  Hummocks, areas where tree roots collect woody debris causing an increase in the level of organic carbon, are higher than hollows, which are depressed areas where water collects. Anoxic waterlogged peat that is located under the water table releases CH4. This suggests that water table decreases cause an increase in CH4 emissions. Assuming less than 5% change in peatland forest floor emissions for each 10% change in hummock/hollow microtopographic change, one can adjust data accordingly [36].

We face many challenges as we develop our global carbon-neutral economy. Sustainably developing the economy of Kalimantan in a fashion that protects our global carbon bank stored within its peat forests should be one of primary objectives as global governments convene in Copenhagen next week to discuss climatic disruption mitigation policy. Specifically, at the local level, Indonesia may choose to develop its information sharing capacity in rural Kalimantan by increasing democratic management techniques regarding forestry practices[37]. mimicking the success of the Katingan Peat Forest project[38]. while emphasizing sustainable economic development that does no further harm to the unique peat forests of Kalimantan.

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