Leuser Ecosystem
Asia > Indonesia > Leuser Ecosystem
Summary
- Sumatran orangutans (Pongo abelii) are present in the Leuser Ecosystem.
- It has been estimated that 13,846 (CI: 11,561-16,805) individuals occur in the site.
- The orangutan population trend is decreasing.
- The site has a total size of 2.6 million ha.
- Key threats to orangutans are deforestation, construction of roads and planned construction of hydroelectric power plants, poaching, and capturing of young orangutans for the illegal pet trade.
- Several NGOs are involved in the implementation of conservation interventions; for example, the Human-Orangutan Conflict Response Unit rescues and relocate orangutans trapped by humans.
Site characteristics
The site is located in the provinces of Aceh and North Sumatra, at the northernmost tip of Sumatra, Indonesia. The area is extremely rich in biodiversity; more than 200 mammal species, 580 bird species, and an estimated 10,000 plant species, including 17 endemic genera, can be found at the Leuser Ecosystem. Within Leuser, the coastal peat swamp forests of Tripa, Kluet, and Trumon-Singkil harbour the highest densities of orangutans. In addition to Sumatran orangutans, the Leuser Ecosystem is also home to the last remaining viable populations of Sumatran tigers, Sumatran rhinoceros, and Sumatran elephants (Sumatran Orangutan Conservation Programme). The Leuser Ecosystem is designated as a National Strategic Area for its environmental function. This designation does not exclude non-forest uses, but stresses the importance of sustainable management (Singleton et al. 2018). The Gunung Leuser National Park is found within the Leuser Ecosystem, which is also designated a Man and Biosphere Reserve, and is part of the Tropical Rainforest Heritage of Sumatra World Heritage Cluster Site by UNESCO (Singleton et al. 2018). The park supports only 25.3% of Sumatra’s Orangutans. Also within the Leuser Ecosystem, is the 1,025 km² Singkil Swamps Wildlife Reserve (Singleton et al. 2018).
Table 1. Basic site information for Leuser Ecosystem
| Area | 2.6 million ha |
| Coordinates | 3.630896 N, 97.378969 E |
| Designation | National Strategic Area |
| Habitat types | Subtropical/tropical dry forest, plantations, subtropical/tropical heavily degraded former forest |
IUCN habitat categories Site designations
Ape status
The peat-swamp forests of the Leuser Ecosystem hold the highest Sumatran orangutan densities (Wich et al. 2016). The species is predicted to decline across a variety of land-use scenarios; as many as 4,500 individuals could vanish by 2030 (Wich et al. 2016).
Table 2. Ape population estimates in Leuser Ecosystem
| Species | Year | Abundance estimate (95% CI) | Density estimate [ind./ km²] (95% CI) | Encounter rate (nests/km) | Area | Method | Source | Comments | A.P.E.S. database ID |
|---|---|---|---|---|---|---|---|---|---|
| Pongo abelii | 1999-2013 | 13,846 (11,561-16,805) | 0.73 | Leuser Ecosystem | Line transects (Distance) | Wich et al. 2016 |
Threats
Key threats to orangutans at the Leuser Ecosystem include habitat destruction, habitat fragmentation, hunting, and the illegal pet trade (SOCP). New roads are continuously being cut through the habitat. In addition to habitat encroachment, palm oil concessions, and new hydro electric schemes and geothermal energy plants are proposed in critical areas (SOCP). As a by-product of land-conversion and increased proximity to humans, orangutans are sometimes killed due to human-wildlife conflict situations, for example, when orangutans raid farmlands (Singleton et al. 2018).
Table 3. Threats to apes in Leuser Ecosystem
| Category | Specific threats | Threat level | Quantified severity | Description | Year of threat |
|---|---|---|---|---|---|
| 1. Residential & commercial development | Unknown | ||||
| 2. Agriculture & aquaculture | Unknown | ||||
| 3. Energy production & mining | 3.3 Renewable energy | Low | Proposed construction of several new hydroelectric power plants leading to habitat loss (Wich pers. comm. 2020; SOCP). | Ongoing (2020) | |
| 4. Transportation & service corridors | 4.1 Roads & railroads | Medium | The construction of roads is causing forest loss and forest fragmentation (Wich et al. 2016). | Ongoing (2016) | |
| 5. Biological resource use | 5.1 Hunting & collecting terrestrial animals | Low | Poaching/persecution. Orangutans are captured or killed when they leave the forest and enter agricultural land or areas that have been recently deforested (Wich et al 2016; Singleton et al. 2018). | Ongoing (2018) | |
| 5.3 Logging & wood harvesting | Medium | Deforestation as a result of land-cover changes (Wich et al. 2016). | Ongoing (2016) | ||
| 6. Human intrusion & disturbance | Unknown | ||||
| 7. Natural system modifications | Unknown | ||||
| 8. Invasive & other problematic species, genes, diseases | Unknown | ||||
| 9. Pollution | Unknown | ||||
| 10. Geological Events | Absent | ||||
| 11. Climate change & severe weather | Unknown | ||||
| 12. Other options | 12.1 Other threat | Present, but threat severity is unknown | Capturing young orangutans for illegal pet trade (SOCP). | Ongoing |
Conservation activities
A number of NGOs are active in the implementation of conservation activities, including the Sumatran Orangutan Conservation Programme (SOCP), the Orangutan Information Center (OIC), the Leuser International Foundation (LIF), and HAkA.
Table 4. Conservation activities in Leuser Ecosystem
| Category | Specific activity | Description | Year of activity |
|---|---|---|---|
| 1. Residential & commercial development | 1.2. Relocate primates to non-residential areas | The Human-Orangutan Conflict Response Unit rescue, relocate, and confiscate orangutans in human-orangutan conflict situations (OIC). | Ongoing |
| 2. Agriculture & aquaculture | Not reported | ||
| 3. Energy production & mining | Not reported | ||
| 4. Transportation & service corridors | Not reported | ||
| 5. Biological resource use | Not reported | ||
| 6. Human intrusion & disturbance | Not reported | ||
| 7. Natural system modifications | Not reported | ||
| 8. Invasive & other problematic species, genes, diseases | Not reported | ||
| 9. Pollution | Not reported | ||
| 10. Education & Awareness | Not reported | ||
| 11. Habitat Protection | Not reported | ||
| 12. Species Management | Not reported | ||
| 13. Livelihood; Economic & Other Incentives | Not reported |
Conservation activities list (Junker et al. 2017)
Challenges
Table 5. Challenges reported for Leuser Ecosystem
| Challenge | Source |
|---|---|
| Lack of law enforcement | Singleton et al. 2018 |
| Lack of national protection | Singleton et al. 2018 |
| Lack of management | Wich pers. comm. 2020 |
Research activities
Documented behaviours
Table 6. Ape behaviors reported for Leuser Ecosystem
| Behavior | Source |
|---|---|
| Not reported |
External links
Leuser International Foundation
HAkA
OIC
SOCP
Relevant datasets
References
Singleton, I., Wich , S.A., Nowak, M., Usher, G. & Utami-Atmoko, S.S. 2017. Pongo abelii (errata version published in 2018). The IUCN Red List of Threatened Species 2017: e.T121097935A123797627. http://dx.doi.org/10.2305/IUCN.UK.2017-3.RLTS.T121097935A115575085.en
Page completed by: Serge Wich & A.P.E.S. Wiki team Date: 30/12/2020