Deforestation of Primate Habitat on Sumatra and Adjacent Islands, Indonesia

Jatna Supriatna1,2, Asri A. Dwiyahreni2, Nurul Winarni2, Sri Mariati3,4 and Chris Margules2,5

1Department of Biology, FMIPA Universitas Indonesia, Depok, Indonesia
2Research Center for Climate Change, Universitas Indonesia, Depok, Indonesia
3‘Postgraduate Program, Trisakti Institute for Tourism, Pesanggrahan, Jakarta, Indonesia
4Conservation International, Indonesia

5Centre for Tropical Environmental and Sustainability Science, College of Marine and Environmental Sciences, James Cook

University, Cairns, Australia

Abstract: The severe declines in forest cover on Sumatra and adjacent islands have been well-documented but that has not slowed the rate of forest loss. Here we present recent data on deforestation rates and primate distribution patterns to argue, yet again, for action to avert potential extinctions of Sumatran primates in the near future. Maps of forest loss were constructed using GIS and satellite imagery. Maps of primate distributions were estimated from published studies, museum records and expert opinion, and the two were overlaid on one another. The extent of deforestation in the provinces of Sumatra between 2000 and 2012 varied from 3.74% (11,599.9 ha in Lampung) to 49.85% (1,844,804.3 ha in Riau), with the highest rates occurring in the provinces of Riau, Jambi, Bangka Belitung and South Sumatra. During that time six species lost 50% or more of their forest habitat: the Banded langur Presbytis femoralis lost 82%, the Black-and-white langur Presbytis bicolor lost 78%, the Black-crested Sumatran langur Presbytis melalophos and the Bangka slow loris Nycticebus bancanus both lost 62%, the Lar gibbon Hylobates lar lost 54%, and the Pale-thighed langur Presbytis siamensis lost 50%. Two species, the Pagai langur Presbytis potenziani and the Pagai macaque Macaca pagensis, both from the southern part of the Mentawai islands, are not represented in national parks or protected areas at all, and a further five species are found in only one protected area. The causes of deforestation are many and varied, but by far the leading causes are logging, followed by fire and/or conversion to plantations. Enforcement of existing regulations protecting primates, disentanglement of land claims and overlapping boundaries, a halt to logging in existing forests, a halt to road building through forests, clarification of how traditional adat law relates to protected areas, and the creation of new, enforceable laws pro­tecting species from trade and exploitation will all be needed if Indonesia is to uphold the commitments to primate conservation that it has already made.

Keywords: deforestation, Indonesia, primates, primate habitat, Sumatra


There are 22 primate species that occur on Sumatra and its neighboring islands. Three are ranked as Critically Endan­gered on the IUCN Red List of Threatened Species (Pagai macaque Macaca pagensis, Pig-tailed langur Simias concolor, and Sumatran orangutan Pongo abelii) (Roos et al. 2014; Supriatna and Ramadhan 2016), and a further ten are listed as endangered (Siberut macaque Macaca siberu, Black Suma­tran langur Presbytis sumatrana, Mitred langur P. mitrata, Black-and-white langur P. bicolor, Black-crested Suma­tran langur P melalophos, Siberut langur P siberu, Kloss’s gibbon Hylobates klossii, Lar gibbon H. lar, Agile gibbon H.

agilis, and Siamang Symphalangus syndactylus). Nine of the 22 species are endemic (MacKinnon and MacKinnon 1980; Brandon-Jones et al. 2004; Roos et al. 2014).

Sumatra was still densely forested as recently as 1950, but then clearing began in the lowland areas where topography and soil fertility were most favorable to human settlement and agriculture. Clearing for plantations and clearing for crops and settlements associated with transmigration programs in the 1970s and 1980s occurred largely in the lowlands or on gently sloping foothills (Whitten et al. 1987). Estimates vary, but recent sources suggest that Sumatra has lost 5 million ha of forest between 1990 and 2000 (Gaveau et al. 2012) and a further 3 million ha between 2000 and 2012 (Margono et al. 2014) for a total of 8 million ha due to legal and illegal logging, conversion of natural forests to industrial planta­tions, and forest encroachment by communities. The analysis reported here estimates that 3.5 million ha were lost between 2000 and 2012. The difference of 500,000 ha is likely due to our use of the Ministry of Forestry classification of forest and non-forest.

Sumatran forests are suffering one of the highest rates of destruction in the world (Collins et al. 1990; Margono et al. 2014). There are now only small scattered remnants of undisturbed lowland forest outside of protected areas. This lowland forest is the home of most Sumatran primates. Many (for example, orangutans, gibbons, some restricted range and endemic langurs, and some macaques) are sensitive to distur­bance caused by logging, hunting and other human activities (Yanuar and Chivers 2010). Consequently, these species have little chance of surviving in highly fragmented or disturbed forests. For example, tree availability, as a source of food and nesting sites, is one of the most influential factors affecting the density of orangutans (van Schaik et al. 2001; Ancrenaz et al. 2005).

The many documented declines in forest cover and there­fore primate habitat (for example, Supriatna et al. 2001, 2002; Mittermeier et al. 2007; Mariati et al. 2014; Supriatna and Mariati 2014), have largely been ignored by government and the private sector. Forest loss has continued to proceed at a high rate. Here we present recent data on the extent of defor­estation and primate distributions and propose actions that will be necessary if extinctions in the near future are to be averted.


Mapping forest loss

Forest loss, or deforestation, is defined as the change from forest cover in 2000 to non-forest cover in 2012. We used the deforestation data from the Ministry of Forestry. Landsat 7 Enhanced Thematic Mapper (ETM) satellite images from 2000 and 2012 were used to calculate changes in the forest cover that coincided with the distribution of each primate spe­cies. Images of Sumatra were selected from 2000 and 2012, with cloud cover less than 50%, and all forested areas such as parks, protected forest, company concessions and other for­ested lands were included. This covered primary and second­ary forest but did not include tree crops or production forest. Forest cover results were then validated using Google Earth ( and ESRI online base map (www. from the same time period. The rate of defores­tation was also calculated using the formula described by Puyravaud (2003). The formula is based on Compound Inter­est Law and is considered more intuitive than the one pro­posed by FAO (see Puyravaud 2003). It is as follows: r = 1/(t2 -11) x Ln (a2/a1)

where r is the rate of change, and a1 and a2 are the forest cover estimates at time t1 and t2 respectively.

Primate distributions

Primate surveys in different parts of Sumatra have been carried out by many researchers, including Crockett and Wilson (1980), Kawamura and Megantara (1986), Supriatna et al. (1996), Supriatna and Hendras (2000), Supriatna et al. (2001), Whittaker (2005, 2006), Geissmann et al. (2006), Supriatna and Gursky-Doyen (2010), and Supriatna and Mar­iati (2014). Additional data on taxonomic status and distribu­tions were gathered from Groves (2001), Brandon-Jones et al. (2004), Mittermeier et al. (2013), and Roos et al. (2014). We examined all records of primates on Sumatra in the Bogor Museum, and updated the distribution data of Groves (2001). These were published in Supriatna and Ramadhan (2016). Ground-truthing of these geo-referenced distribution maps was conducted throughout Sumatra between 2012 and 2014, except for the southern islands (Pagai and Sipora) of the Mentawai archipelago. Survey locations were chosen using the following criteria: areas likely to have species that had not been studied intensively, for example, species recently described; areas with species whose systematics had recently been revised; areas that had been recently logged and/or con­verted to plantations; and areas that had been recently burnt by forest fires. Further aspects of primate ecology and conserva­tion status were gathered from primatologists who have stud­ied these issues in the field (Indra Yustian, Sunarto, Tatang Mitrasetia, pers. comm.) and the considerable experience of most of the present authors, especially the senior author.

Based on primate distribution data from these sources, we plotted the current known distributions of each primate species. We then overlaid these geo-referenced distribution maps onto current forest cover maps and maps of forest lost between 2000 and 2012. In this way, we mapped changes in available habitat for all primate species and calculated current available habitat, defined as forest cover.


Extent of forest loss

Deforestation in the provinces of Sumatra between 2000 and 2012 ranged from 3.74% to 49.85%, with a total of 3,547,740.60 ha (22.08 %) lost (Table 1). The highest rate was found in the provinces of Riau, Jambi, Bangka Belitung, and South Sumatra (Fig. 1). Most clearing took place in al­ready degraded production forests and not in primary con­servation forests, except in Tesso Nilo National Park in Riau Province, where the highest rate of forest loss was found (9.28% per year, Mariati et al. 2014). In the rest of Riau province, deforestation occurred mainly in production forests, which were converted to acacia and oil palm plantations. Il­legal logging was widespread in the Giam Siak and Rimbang Baling protected areas and in Tesso Nilo National Park (Su­priatna and Mariati 2014). Similar trends have occurred in Jambi Province in the mid-western part of the island, close to Bukit Tigapuluh National Park, where many companies have converted their forest concessions into plantations of acacia and oil palm.

In North Sumatra, most forest was lost in the region of the Rawa Singkil Game Reserve, on the southern border of Gunung Leuser National Park. It is located between Gunung Leuser National Park and Batang Gadis National Park (Fig.1). Several companies converted their forest concessions into oil palm plantations. Illegal logging has also affected many areas in the Gunung Leuser National Park itself. All of those affected areas are the habitat of the Critically Endangered Sumatran orangutan Pongo abelii, as well as other primates, such as Thomas’s langur Presbytis thomasi, the Lar gibbon Hylobates lar, and the Siamang Symphalangus syndactylus.

Figure 2 shows the trend in the rate of forest loss between 2000 and 2012. All provinces show rates of forest loss trend­ing downward. Even provinces with relatively low total forest loss, such as Aceh and Lampung (Table 1) are showing the same downward trend. In Lampung, where there is little forest cover left, this suggests the possibility that none will remain in the near future. Way Kambas National Park may even be at risk. In Aceh, where there is still substantial forest cover remaining, it shows how the opportunity that exists now to arrest decline is disappearing.

Table 2 shows the percentage of forest lost across the range of each Sumatran primate species. The greatest impact was on the Banded langur Presbytis femoralis, in Tesso Nilo Forest and on Kampar Peninsula, both in Riau. This species