In the Tripa peat swamps, companies are operating seven large concessions of between 3,000 and 13,000 hectares. Tey are converting the remaining forests on peatlands into oil palm plantations. Te concessions cover more than 75 percent of Tri- pa’s total area of 62,000 hectares. While almost certainly host- ing as many as 1,000 orangutans or more in the early 1990s, when still covered in pristine peat swamp forest, there are thought to be less than 280 (Wich et al. 2008) still surviving in the remaining 17,000 hectares of forest (Tata and van Noord- wijk 2010) (Map 11). Under current trends, all of Tripa’s forest and its orangutans will have disappeared by 2015-16 (Tata and van Noordwijk 2010).
Although large-scale agricultural expansion is the most highly visible threat to Sumatran orangutan habitat, small-scale agricul- tural encroachment remains a serious problem and contributes greatly to forest loss in the Leuser Ecosystem. Te main driver for forest loss on peat areas in Leuser was oil palm development, while for forest on non-peatlands other land uses than oil palm contributed more to land use changes (Figure 2, Map 12).
A total of 102 fires – the main indicator associated with small- scale slash and burn farming – were detected in Sumatran orangu- tan habitat between November 2000 and April 2010. Both habitat types were affected and 50% of these fires took place just between 2008 and April 2010 (NASA/University of Maryland 2002).