Drained peatlands in Sarawak, Malaysia will be increasingly flooded due to subsidence

Published: 3 June 2015

Deltares experts are investigating how deforestation and drainage for oil palm plantations of tropical peatlands in Sarawak, Malaysia will cause subsidence in the future. The lowering of land surface will cause increased water management problems and flooding in coming decades.

Almost entire area at risk of flooding in 100 years

In the Rajang River Delta along the coast of Sarawak, the Malaysian part of Borneo, the cover of industrial oil palm plantations increased from 6 % to 47 % between 2000 and 2014. The remaining non-plantation area is also mostly drained, so that the entire area is now subsiding.

New flood model results show that flood risk was already present in 29 % of oil palm plantations by 2009. This is projected to increase to 42 % in 25 years, 56 % in 50 years, and 82 % in 100 years. It is predicted that at some point in coming decades, as flood conditions continue to get worse, oil palm production will have to be abandoned in most of the area. It is recommended that to ensure a more sustainable future for the area, and other tropical peatlands like it, non-drained land use alternatives should be considered such as flood tolerant production species.

Land loss due to drainage of peatlands is global phenomenon

Since peat is not ‘land’ in the common sense, but an unstable mix of water (90%) and carbon (in the vegetation remains), it will inevitably disappear when drained. As the bottom of the peat is often near sea level, inundation and loss of agricultural production is common in such areas. This land loss is the reason that expansion of peatland drainage for agriculture was ceased in Europe and the USA by the mid-20th century. In Malaysia and Indonesia, however, development of peatlands for agriculture (mostly oil palm and Acacia plantations) has only recently started.