Rewetting Tropical Peatlands

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Rewetting Tropical Peatlands

Gepubliceerd op
2 september 2014

Natural peat swamps are important biodiversity reservoirs, carbon stores and hydrological buffers. They contain a wide variety of trees, including highly important economic species, and provide habitats for various endangered species. In their natural state these peatlands are carbon sinks, but many are turning into carbon sources right now. Alterra Wageningen UR is working on solutions, for example on systems for more adequate water management. This method has been approved now as a new Verified Carbon Standard methodology.

Photo: Man-made logging canal in a peatswamp forest

Tropical peatlands cover worldwide around 45 million hectares. Large areas of these rather unknown but very important lands in Southeast Asia are under threat from land clearance, degradation and fire, jeopardising their natural functions as reservoirs of biodiversity, carbon stores and hydrological buffers. Utilisation of this resource for agriculture or plantation crops requires drainage that, unavoidably, leads to irreversible subsidence resulting in loss of peat emitting as CO2 to the atmosphere. When continued, it results in severe disturbance of the substrate and creates problems for cultivation and peoples’ livelihoods.

Dam construction using locally available material
Dam construction using locally available material

Adequate water management proves to reduce carbon losses caused both by drainage and fires. Once peatlands are degraded by legal or illegal drainage canals, it is necessary to construct dams to restore their hydrological integrity. Drainage channels must be blocked or water flow along them retarded to prevent water tables dropping substantially below the peat surface for any length of time. Only rewetting of the peat restores its natural resource functions, decreases peat oxidation and reduces fire risk.

Dam made of locally available material (3 m long, 1 m wide and 2.5 m deep)
Dam made of locally available material (3 m long, 1 m wide and 2.5 m deep)

The Alterra model Simulation of Groundwater (SIMGRO) shows that a cascade of closely spaced dams is most effective for water control. The differences in water levels over each dam should be limited to about 30 cm to reduce seepage and to prevent erosion. Dams have to be adopted to the characteristic high hydraulic conductivity (high water flow) and low bearing capacity (structurally weak) of tropical peat. Simple dams constructed from locally available material proved to be effective in maintaining high water tables.

Navigation by boat in a logging canal
Navigation by boat in a logging canal

The procedure to rewet tropical peatlands has been approved as a new Verified Carbon Standard (VCS) methodology. The methodology was developed in close collaboration between WWF Indonesia and WWF Germany, Remote Sensing Solutions GmbH, Alterra Wageningen UR, Winrock International and TerraCarbon LLC. 

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