Migration from the island of Nias to the West Batang Toru forests over the last two decades has been largely spontaneous. These settlers have opened up primary forests for agriculture and hunt many species of local wildlife, including orangutans. Currently at least eight Nias communities have been established inside the protected forest in the Batang Toru area, leading to the loss of more than 2,200 ha of orangutan forest habitat in specifically ...

Values for the various non-carbon ecosystem services (water, regulation of floods and landslides, fisheries, prevention and limitation of fires, agriculture, tourism, and non-timber forest products (NTFP) and biodiversity) were calculated with a discount rate of 4% over a 30-year period. Total value for ecosystem services beyond climate regulation being USD 3,735/ha.

Some timber concessions overlap orangutan habitat in a number of key locations. If left to recover after logging, orangutans will gradually return to former concessions. But if the land is converted to monoculture plantations this will no longer be possible.

Net present value (NPV) is in millions of USD over a 30-year period (2000-2030) at a 4% discount rate. The NPV for local communities under a deforestation scenario would be 3,132 million USD and under a conservation scenario 5,341 million USD. The analysis shows that the local community would benefit most from a scenario under which the forest is conserved, negative effects on ecosystem services are avoided and payments for ecosystem services ar...

Overall population growth in the region has been very rapid during the past nine decades. In 1920, the human populations of Aceh and North Sumatra provinces were 736,348 and 1,961,678, respectively (Volkstelling 1922). By 2008, these had risen dramatically to 4,293,915 and 13,042,317 (BPS 2010a).

Most Sumatran orangutan habitat is protected by Indonesian law. The government has created a very comprehensive system of functional forest categories, and institutions responsible for managing its forests. Some areas remain highly threatened, however, including the Batang Toru Forest (production forest), and the Tripa Swamp Forest (not part of the formal forest estate).

Oil palm plantations depend on the microclimate conditions generated by nearby forests, and the rivers emanating from orangutan habitat. Not all plantations concessions on the map have been cleared and planted yet. The majority of concessions are oil palm, but the map also contains rubber and other plantation crops. The establishment of many of these plantations has resulted in significant losses in orangutan habitat, since they have been created...

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.