Isau-Isau

Isau-Isau Wildlife Sanctuary (Suaka Margasatwa Isau-Isau, also recorded as Isau-Isau Pasemah) is an approximately 121 km² protected area of hill forest in the highlands of Muara Enim and Lahat regencies, South Sumatra, Indonesia, lying on the eastern slopes of the Barisan range about 30 km from the town of Muara Enim. ^[1] Established in 1978 as Isau-Isau Pasemah Nature Reserve and redesignated as a Wildlife Reserve in 2014, it conserves a compact block of hill and montane forest that serves as wildlife habitat and as a protective forest cover for the steep, water-yielding slopes of the surrounding districts. The reserve is home to the world's largest flower, Rafflesia arnoldii, and supports a range of threatened Sumatran species including Sumatran tigers and the world's rarest lagomorph. It is administered by the South Sumatra Natural Resources Conservation Agency (BKSDA Sumatera Selatan).

Despite its modest size, Isau-Isau supports a notable range of Sumatran hill-forest wildlife, including Sumatran tigers, clouded leopards, Malayan tapirs, siamangs, and the Sumatran striped rabbit (Nesolagus netscheri) — the world's rarest lagomorph. ^[1] Other primates include gibbons, leaf monkeys, and macaques, along with wild boar, muntjac and sambar deer, sun bears, and smaller carnivores like civets and leopard cats. The forest and its streams sustain a variety of birds, including hornbills, partridges, raptors, and montane songbirds, as well as amphibians and reptiles in the cool, moist watercourses. As a relatively small upland sanctuary embedded in a farmed landscape, Isau-Isau's value lies in providing a forested refuge and habitat connectivity for hill and montane species.

The sanctuary protects hill and lower montane rainforest on the slopes of the Barisan range, with mixed broadleaf and dipterocarp trees at lower elevations grading into laurel- and oak-rich montane forest higher up. Notable flora includes Rafflesia arnoldii, the world's largest flower, and at least 22 species of orchids, one endemic to South Sumatra. ^[1] Dense understorey vegetation, rattans, tree ferns, and abundant epiphytes characterise the moist forest interior. The forest cover plays an important hydrological and protective role on the steep terrain, guarding against erosion and helping regulate streamflow into surrounding valleys.

Isau-Isau lies within the Barisan mountain system, the volcanic and tectonically active range that forms the backbone of Sumatra, produced by the subduction of the Indo-Australian plate. Its terrain is hilly to mountainous, with steep ridges and incised valleys carved into uplifted Tertiary sedimentary and volcanic rocks and overlain by weathered, often fertile volcanic-influenced soils. Elevations range from approximately 300 to 1,400 metres, with fast-flowing streams draining the slopes toward the lowlands of Muara Enim and Lahat. ^[1] The combination of steep gradients, erodible soils, and high rainfall makes forest cover important for slope stability, reinforcing the reserve's role in protecting both the landscape and the water resources of the surrounding agricultural region.

As a highland reserve with elevations from approximately 300 to 1,400 metres, Isau-Isau experiences a cooler and wetter climate than the South Sumatran lowlands, with mild temperatures and frequent cloud and mist on the higher slopes. Rainfall is high year-round, with a generally wetter season from around November to April and a comparatively drier stretch between May and October, though the montane forest stays humid throughout. Temperatures fall with increasing elevation, and the upper slopes can feel distinctly cool, especially in the mornings. This moist, temperate-feeling climate sustains the lush hill forest and the perennial streams that make the sanctuary an important local water source.

The highlands around Isau-Isau lie within the culturally rich Pasemah and Semende uplands of South Sumatra, areas inhabited by communities with long traditions of highland farming, coffee growing, and rice cultivation, and the wider region is noted for ancient megalithic remains. Over the twentieth century, expanding coffee gardens, farms, and settlements increasingly bordered the forested hills, while logging and land conversion reduced surrounding forest cover. The reserve's establishment reflected concern both for conserving wildlife and for protecting the forested catchments on which the densely farmed valleys depend, set against a backdrop of steadily intensifying highland agriculture.

Isau-Isau was originally protected as Isau-Isau Pasemah Nature Reserve in 1978, later formally redesignated as a Wildlife Reserve in 2014, covering roughly 121 km² (about 12,144 hectares) of hill forest on the slopes of the Barisan range in South Sumatra. ^[1] It was established to conserve wildlife and to safeguard the protective forest cover of steep, erosion-prone slopes important for water supply to the surrounding districts of Muara Enim and Lahat. The reserve has since been managed by the South Sumatra Natural Resources Conservation Agency (BKSDA), which carries out patrols and works to contain encroachment from coffee and crop cultivation. Its history is part of the wider effort to retain upland forest along the spine of southern Sumatra.

Isau-Isau is a conservation reserve rather than a developed tourist destination, and its appeal lies in its hill forest, ridges, and clear mountain streams, which offer scope for nature observation, birdwatching, and the study of upland ecosystems. The reserve's exceptional biological highlights include Rafflesia arnoldii and the critically endangered Sumatran striped rabbit, making it of particular interest to naturalists and researchers. ^[1] The surrounding Pasemah and Semende highlands are scenic, with coffee landscapes and cultural heritage that draw broader regional tourism. Within the sanctuary there are no formally developed visitor trails, viewpoints, or facilities, and any exploration of the forest typically requires local guides or coordination with conservation staff.

Access to Isau-Isau is via Muara Enim, a regency town about 30 km away connected by road and rail to Palembang and other parts of South Sumatra, with the surrounding highlands reached along secondary roads through farming country. The sanctuary itself has minimal tourist infrastructure, with conservation management focused on patrol activities rather than visitor services, and no developed lodging or visitor centre inside the reserve. Accommodation and basic services are available in Muara Enim and nearby towns. Travel into the forest involves steep terrain (elevations 300–1,400 m) and is best done with local guides, making the reserve most suitable for nature-focused and research-oriented visitors.

Conservation efforts at Isau-Isau aim to protect its hill forest, the wildlife it shelters — including Sumatran tigers, clouded leopards, Malayan tapirs, and the Sumatran striped rabbit — and the water catchments that sustain surrounding farming communities. ^[1] As a relatively small reserve in a heavily cultivated highland landscape, it faces pressures from encroachment for coffee and crop cultivation, illegal logging, and forest fragmentation on steep slopes. Managed by the South Sumatra Natural Resources Conservation Agency, conservation work includes patrols, boundary maintenance, and engagement with local communities to balance livelihoods with forest protection. Keeping the forest intact is regarded as crucial for biodiversity, for preventing erosion and landslides, and for maintaining the streamflow on which the densely settled valleys below depend.