This serial World Heritage site comprises three widely separated nationally protected areas along the Bukit Barisan mountain range, which runs along the western side of the island of Sumatra. The sites are Gunung Leuser National Park in the northern provinces of Nanggroe Aceh Darussalam and Sumatra Utara; Kerinci Sablat National Park in the south-central provinces of Sumatra Barat, Jambi, Sumatra Selatan and Benkulu; and Bukit Barisan Selatan National Park in the far southern provinces of Sumatra Selatan, Bengkulu and Lampung, partly bordering the south-west coast.
The composite site, straddles the equator along the Bukit Barisan mountain range. This runs 1,650 km down the western side of the island studded with active volcanoes. The eastern side of Sumatra is predominantly lowland and in the past has periodically been linked to the Asian mainland.
Gunung Leuser National Park in the north is 150 km long, over 100 km wide and is predominantly mountainous. It covers most of the West Barisan, West Alas and East Barisan ranges and is almost divided by the Alas valley graben. Kerinci Sablat National Park in the centre extends 350 km down the spine of the Bukit Barisan. Three-quarters of the park is steep. Its highest point is the magnificent Gunung Kerinci - at 3,805 m, the highest peak in Sumatra and highest volcano in Indonesia. It is active. Nearby Gunung Tujuh is an outstandingly beautiful crater lake at 1,996 m. Bukit Barisan Selatan National Park is also 350 km long but only 45 km wide on average. The northern two-thirds are mountainous, averaging 1,500 m with a high point at Gunung Pulung of 1,964 m. The southern half is lower; 90 km of it is a peninsula and the park borders the sea for half its length. Dozens of rivers originate in the park and there are several lakes and hot springs.
The Indonesian archipelago contains 10% of the world's flowering plants and Sumatra, the third largest island, is the location of the Sumatran Islands Lowland and Montane Forests Ecoregion and part of the WWF's Sundaland hotspot. Its forests are among the largest tropical rainforests in South-East Asia, comparable with those of Borneo and Papua New Guinea.
Animal diversity in Sumatra is impressive, with some 180 mammal species in the nominated sites, and some 450 bird species.
Sumatra has a high level of endemism, which is well represented in the nominated sites. It is evidence of the land bridge/barrier between the Sumatran biota and that of mainland Asia due to changes in sea level. Some of the animal distributions may also be evidence of the effect of the Mount Toba tuff eruptions 75,000 years ago. The Sumatran orangutan for example, is not found south of Lake Toba nor the Asian tapir north of it. The altitudinal range and connections between the diverse habitats in these areas must have facilitated the ongoing ecological and biological evolution. Key mammals of the parks are the Sumatran tiger, Sumatran rhino, orangutan, Sumatran elephant; also Malayan sun-bear and the endemics Sumatran grizzled langur, Hoogerwerf's rat. Rare birds noted in the site's nomination are Sumatran ground cuckoo, Rueck's blue flycatcher, Storm's stork and white-winged duck.