Sumatran orangutan habitat is restricted to the westernmost tip of Indonesia. Boxes indicate the case study areas Tripa and Batang Toru. The case of Sumatran orangutan serves as a useful example to illustrate how the fate of one of our nearest relatives is closely tied to ours.

Most of the Sumatran orangutan's forests inland play a key role in ensuring downstream freshwater supplies, since the non-alluvial inland areas of the region tend to have very little or no underlying groundwater resources.

If only the most important orangutan habitat is examined – i.e. forest below 1,000 m – for the 1985-2007 period, the rate of loss was even higher, at 28% and 49% for Aceh and North Sumatra respectively. When only the most species-rich forests (below 500 m) are considered, forest loss between 1985 and 2007 was 36% for Aceh and 61% for North Sumatra. For the carbon-rich peat swamp forests the loss was 33% for Aceh and 78% for North Sumatra.

In Batang Toru, land use changes and deforestation led to an overall loss of around 10 tonnes of carbon per hectare between 1994 and 2009. Due to its exploitation for the cultivation of oil palm, the peat area of Tripa had to face a much more important decrease of 66 tonnes of carbon per hectare in the time period 1990-2009. In terms of CO2 emissions, it corresponds to an overall emission per year of 634,903 tCO2.

Orangutans are also still regularly killed or captured. This occurs for three main reasons: first, even today some people still hunt orangutans for food, most notably in the non-Muslim parts of North Sumatra. Second, when orangutans enter farms or plantations at the for-est edge, for example to feed on fruit trees or other crops, they are often shot or otherwise killed, and any surviving infant eventually ends up in trade or as someone’s illegal ...

Between 1985 and 2007, 49.3% of all forests on the island were lost. In the provinces of Aceh and North Sumatra the figures were 22.7% and 43.4%, respectively. Most forest loss has occurred in the lowlands, the very areas where orangutan density is highest.

A generalized diagram of how multinational networks exploit natural resources by developing numerous temporary subsidiaries and use corruption and security firms to ensure rapid exploitation and maximum profits. Arms trading has been reported from the Democratic Republic of the Congo, while the bribes and “security firms” also play a major role in Indonesia. This graphic is republished from "The last stand of the Orangutan" Rapid Response Assessm...

For a range of land uses that occur in Tripa (forests on peatland) and Batang Toru (forest on non-peatland) the profitability and carbon stocks were determined. Undisturbed forest clearly has the highest carbon stock while rice fields have the lowest.

Sumatran orangutans live in lowland tropical rainforests, with precipitation normally between 1,680 mm and 4,070 mm annually. Western regions receive much more rain than those in the east, as prevailing winds from the Indonesian ocean are forced upwards, cooling rapidly and condensing water vapour, which then falls as precipitation.

The area where orangutans occur can be separated into two main habitat types: forest on peat-lands (Tripa) and forests on mineral soils (Batang Toru), and the results are presented for these types separately. Values for carbon were calculated according to Butler et al. 2009 model using a discount rate of 6.5% and voluntary market prices (mean USD 13.33t/CO2, range USD 9.43-17, forest carbon report). Under the fixed scenario the carbon price remai...

Some of the richest above-ground carbon stocks are found in forests occupied by Sumatran orangutans. The total carbon stored in the above-ground woody biomass of a tropical forest varies between 170 and 250 tonnes of carbon per hectare.

Approximately 50% of Sumatran orangutan habitat is inside conservation areas directly managed by the Ministry of Forestry, and 78% lies within the boundaries of the vast Leuser Ecosystem Conservation Area.

Only areas with very low human population densities harbour orangutans. In Aceh and North Sumatra, human settlements are still primarily concentrated in the relatively flat coastal zones, particularly along the north and east coasts, and in alluvial areas elsewhere.

Roads, both existing and planned, are a major threat to Sumatran orangutans as they increasingly fragment populations, making them more vulnerable and less viable. Often such roads are crossing protected areas such as the Gunung Leuser National Park.

Sumatran orangutans occur in two main forest habitats, those on dryland mineral soils and those on wet coastal peat. The three main peat areas are Singkil, Kluet and Tripa on the west coast of Aceh province.

Orangutan habitat overlaps the catchments of 44 major rivers in Sumatra, each of which reaches the coast and discharges into the sea. Thus it is very important to guarantee proper functioning of ecosystem services related to water.

Illegal transport and organization of illegal logging by syndicates. Much of the timber is re-sold during transport and thus changes ownership en route, obliterating tracking efforts to trace origins and diluting import-export figures.

An estimated 88% of Sumatran orangutan habitat is on land classified by Indonesian Government studies (RePPProT) as completely unsuitable for cultivation of major crops such as oil palm, rubber, robusta coffee or cocoa. Only 1.3% of orangutan habitat is deemed ideal for one or more of these crops, while 10.7% could be suitable with significant inputs, such as fertilizer and irrigation.

The main driver for forest loss on peat areas in the Leuser Ecosystem was oil palm development between 1985 and 2007, while for forest on non-peatlands other land uses than oil palm contributed more to land use changes.

Sumatran orangutan habitat overlaps 2 Provinces and 21 Districts, presenting many challenges for integrated development policies. 78% of the species’ present range lies within Aceh, and the remaining 22% in North Sumatra. A total of 13 districts in Aceh, and eight in North Sumatra, contain forests where wild Sumatran orangutans still occur.