Saturday 2 August 2014

Mapping deforestation on Borneo.

Industrial scale timber extraction began on Borneo in the 1970s and during the period 1980 to 2000 more timber was harvested from Borneo than from Africa and the Amazon Basin combined. In addition much forest has been cleared to make way for monoculture plantations, for the palm oil, rubber and timber industries, as well as being burned in forest fires.  For this reason the island is often assumed to be a hopeless case environmentally, where a once rich and globally important ecosystem has largely been destroyed and where remaining areas of forest are unlikely to be saved. An announcement by the Indonesian Government in 2011 that 45% of the original forest in the province of Kalimantan would be permanently protected was met with derision by environmental groups, who claimed that only 30% of Kalimantan’s forests remained. Despite this situation there is no overall data on deforestation on the island, which is split between the Indonesian province of Kalimantan, the Malaysian states of Sabah and Sarawak and the Sultanate of Brunei. 

In a paper published in the journal PLoS One on 16 July 2014, a team of scientists led by David Gaveau of the Center for International Forestry Research in Bogor, Indonesia, compared data from LANDSAT images from 1973 (the earliest year for which satellite data is available) and ALOS PALSAR images from 2010, in order to try to develop a clearer picture of the amount of forest that has been lost or converted to plantations over this time across the island.

Forest (dark green) and non-forest (white) in 1973. Gaveau et al. (2014).

Gaveau et al. estimate that in 1973 Borneo had about 558 060 km² of largely intact old growth forest, made up of Diptocarp-dominated lowland, hill and montane rainforests, freshwater and peat swamp forests, heath forests (kerangas) and Mangrove forests, largely dominated by Nypa Palms. These together covered 75.7% of the island.

By 2010 this coverage had been reduced by 168 493 km², a loss of 30.2% of the island’s forests leaving 389 566 km² of forest covering 28.4% of the island. The heaviest rates of loss have been in (more accessible) lowland forests, however this has changed over time, with logging advancing into more inaccessible highland areas. 75 480 km² of forest (about 10% of the surface area of the island) has been replaced with Palm oil or timber plantations.

Areas of forest loss during 1973–2010 (red). Gaveau et al. (2014).

This deforestation has not been even across the island, with the loss of 39.5% of the forests in Sabah, 30.7% in Kalimantan, 23.1% in Sarawak and only 8.3% in Brunei. Gaveau et al. note that this may in part be driven by climate; the forests of Sabah and Kalimantan are much drier than those of Sarawak, and easily affected by fires once deforestation begins to open up the forest, while the much wetter climate of Sarawak tends to prevent this.

42% of remaining forests on Borneo are in areas designated for timber production, and can therefore be expected to be logged in the future. A further 16% of the forests are in areas that have been designated for conversion to other uses (agriculture etc.) and will presumably also be lost. Only 11.9% of the forest lies in areas designated to be protected from logging (5.6% of lowland forest, the most threatened environment). 17% of the forest within national parks and other protected areas has also been logged, although this constitutes a mixture of illegally logged forests and forests which were logged prior to the designation of the area as national park (for example in the Sebangau National Park) and which hopefully will be enabled to regenerate.

Gaveau et al. also observe that the Borneo has large areas of ‘logged forest’, which have been targeted for timber extraction but not clear cut (i.e. loggers have removed some large, valuable trees but otherwise left the forest intact). They suggest that in the absence of the potential to save large areas of forest completely, such logged forest should become a priority for environmentalists, and the sustainable use of forests promoted over clear felling.

Remaining intact forest (dark green), remaining logged forest (light green), and industrial oil palm and timber plantations (Black) in 2010. Gaveau et al. (2014).

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