Gunung Leuser: the forest that holds Sumatra together

Gunung Leuser National Park protects a large block of rainforest along the Barisan mountains of northern Sumatra, in Aceh and North Sumatra. It is part of the Tropical Rainforest Heritage of Sumatra, a UNESCO World Heritage site, and it is one of the most important conservation areas in Southeast Asia. The park is named after Mount Leuser, a remote peak of about 3,400 metres.

The park is only part of the story. The wider Leuser ecosystem covers about 2.6 million hectares of forest, peatland and rivers, and it is the last place where Sumatran orangutans, tigers, elephants and rhinos still live together. The forest is under pressure from roads, plantations and logging, and the future of these species depends on keeping it connected.

The park and the ecosystem

Gunung Leuser National Park covers about 7,900 square kilometres, from the coast near Singkil to the high mountains of the interior. It was established in 1980 by combining several reserves, and it has been a UNESCO World Heritage site since 2004, together with Kerinci Seblat and Bukit Barisan Selatan. The park is managed by the Indonesian government, with support from conservation organisations.

The wider Leuser ecosystem is larger than the park and includes areas that are not formally protected. It stretches across Aceh and North Sumatra and includes lowland forest, peat swamp, karst and alpine meadows. Its rivers supply water to millions of people, and its forests store carbon and prevent flooding. The ecosystem is one of the most biodiverse places on earth, with more than 10,000 plant species and hundreds of bird and mammal species.

The wildlife

Leuser is the last stronghold of the Sumatran orangutan, with an estimated 13,000 to 15,000 animals in the wild. It also holds the Sumatran tiger, the Sumatran elephant, the Sumatran rhino and the Sunda clouded leopard, all of them critically endangered or endangered. The chance of seeing any of these large mammals is low, but the forest is full of other life: gibbons, leaf monkeys, macaques, hornbills, pheasants, frogs, snakes and insects.

The plants are as important as the animals. Rafflesia arnoldii, the world's largest flower, grows in the forest, as does the towering Amorphophallus titanum. The park's orchids, palms and figs support the animals, and the fig trees are a keystone species, fruiting at different times and feeding everything from birds to orangutans.

Bukit Lawang and Ketambe

There are two main access points for trekkers. Bukit Lawang, in North Sumatra, is the busiest, with a concentration of guesthouses, guides and the old orangutan rehabilitation centre. It is easy to reach from Medan, and the treks range from half a day to several days. The forest around Bukit Lawang is secondary and regenerating, but it is rich in wildlife and the river is beautiful.

Ketambe, in Aceh, is quieter and wilder, and it is the base for longer treks into the interior. The village has a research station and a handful of guesthouses, and the forest around it is primary rainforest. The treks are more demanding, the wildlife is less habituated, and the experience is closer to a real expedition.

Threats and conservation

The Leuser ecosystem is under serious pressure. Roads, illegal logging, palm oil plantations and smallholder clearing have fragmented the forest, and the construction of the Ladang-Gayo road and other projects has opened up previously remote areas. Poaching is a threat to tigers and rhinos, and human-wildlife conflict is a problem where villages border the forest.

Conservation efforts involve the national park authorities, local communities, NGOs and international donors. The Leuser Ecosystem Management Agency and groups such as the Sumatran Orangutan Society and the Frankfurt Zoological Society work on patrols, reforestation, ecotourism and community livelihoods. Tourism, done well, gives local people a reason to protect the forest, which is why the ethics of trekking matter.

Trekking and practicalities

Treks require permits, guides and, for longer routes, porters and camping equipment. Most visitors do a two- to four-day trek from Bukit Lawang or Ketambe, sleeping in the forest or in simple camps. The terrain is steep, humid and muddy, and the heat is intense. Leeches are common, especially in the wet season, and the rivers can rise quickly.

You need sturdy shoes, quick-dry clothing, a rain jacket, insect repellent, a headlamp, water purification and a first-aid kit. Do not trek alone, and do not trek if you are ill: human respiratory diseases can be fatal to orangutans. Choose an operator that follows the park rules on distance, feeding and waste.

Getting there and a plan

For Bukit Lawang, fly to Medan and drive three to four hours. For Ketambe, fly to Medan or Banda Aceh and drive to Kutacane, then continue to the village; the journey is long and the roads can be rough. The dry season, May to September, is the best time for trekking, though the forest is wet year-round.

Three days is the minimum for a trek, and five to seven days allows a deeper route. The park is not a place for a quick visit, and the best experiences come from slowing down, listening and letting the forest decide what you see.

• Day 1: arrive at Bukit Lawang or Ketambe, arrange permits and guides, short acclimatisation walk.
• Days 2 to 4: trek into the forest, camp, and return by river or road.
• Add days for a longer route, a village stay or a visit to the hot springs.
• Carry cash, a headlamp and water purification; there are no shops in the forest.

Questions people actually ask

Can I visit Gunung Leuser without a trek?

The park is forest, so the main way to experience it is on foot with a guide. Bukit Lawang has short walks and river activities, and the park office can arrange half-day trips. There is no road access to the interior.

Will I see a tiger or rhino?

Almost certainly not. Sumatran tigers and rhinos are extremely rare and avoid people. You are more likely to see orangutans, gibbons, monkeys, hornbills and insects. The park is worth visiting for the ecosystem as a whole, not for a checklist.

How fit do I need to be for a Leuser trek?

Reasonable fitness is enough for a two- to three-day trek, but the terrain is steep, humid and muddy. Longer routes require good fitness and a tolerance for discomfort. Tell your guide honestly about your level.

Is it ethical to trek in Gunung Leuser?

It can be, if you choose a responsible operator. Keep your distance from orangutans, never feed or touch them, do not trek when you are ill, and avoid operators that promise close encounters. Tourism gives local communities a stake in protecting the forest.