Regeneration of fire degraded peatswamp forest in Berbak National ...

Regeneration of fire degraded peatswamp forest in Berbak National Park and implementation in replanting programmes
logging on biodiversity and ecosystem balance, there are significant indirect effects as well.
Research indicates that the majority of El Niño associated forest fires occur in areas that are
degraded through logging as opening up of the forest canopy increases susceptibility to forest
fires (Giesen, 2004; Siegert et al., 2001 a ).
Cultivation of peatswamp forests
Over the years large surfaces of peatswamp forest have been reclaimed for agricultural and
silvicultural purposes. Most land is used for oil palm plantations, smaller areas are planted with
commercial (pulp) timber species, coconut and rice. Naturally abiotic conditions of peat soils are
unfavourable for crop growth, and consequently active measures are regularly undertaken to
improve soil quality. One of the most influential measures is drainage and in many agricultural
areas extensive networks of canals are constructed to enable crop growth. As hydrology of peat
soils is very sensitive to disturbance, drainage has a huge impact on peat properties, both within
the agricultural land as well beyond it’s borders in other parts of the catchment. A direct effect of
drainage is subsidence and deterioration of the upper peat layer through oxidation. This poses a
serious threat to peat soils, as deterioration can destroy a peat soil within one or two decades, or
even faster, leaving no more than a poor mineral subsoil that is even less suitable for crop growth.
Field studies indicate that both subsidence and oxidation cause a decrease of 20 to 50 centimetres
in the first years after drainage. In subsequent years this rate decreases to approximately two
centimetres per year, the exact rate depending on the water regime of the area. CO2 emission in a
drained peatswamp in Southeast Asia is significant and is expected to strongly contribute to the
green house effect (Rieley & Page, 2004). In a Malaysian peatswamp forest emission was found
to be significant, and is estimated to be up to 26,5 tons per hectare per year (Wösten et al., 1997).
In other regions similar or even higher rates were found. Drainage strongly influences
susceptibility to fires, as drained peat soils burn readily. The effects of these fires can be very
destructive mainly in El Niño years when extreme drought further increases fire risk. In 1997
fires destroyed more than 13 million hectares in Indonesia, mainly agricultural land and logged
concession areas, but also adjacent pristine forests (figure 2.3). Recovery of those burnt areas is
difficult and they are very sensitive to repetitive burning. Disappearance of peat through
oxidation and fire further increases drainage, thus creating an almost irreversible positive
feedback process. Saline intrusion and coastal erosion may follow degradation of the peat soil,
posing another threat to people and nature.
Figure 2.3 Fires initiated to clear land from vegetation for
agriculture or building purposes, easily turn into wild fires that can
destroy thousands of hectares.
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