Would you think of perfumes when observing orangutans? Our Post-Release Monitoring team members do! While out on patrol from Camp Nles Mamse in the Kehje Sewen Forest, East Kalimantan, they come across many exciting tree species with remarkable properties.

One of them is the tengkaras tree or agarwood (Aquilaria malaccensis). Agarwood is highly sought after and sold as a raw material in producing perfumes. However, due to overexploitation, it is now an endangered species.

Destructive harvesting is the main threat to the survival of agarwood. Loggers often cut the tree down first to determine if it has enough quality material to harvest. As a result, many felled tengkaras trees are left untouched and wasted if found not to contain the right amount of the precious wood. 

Only some agarwood trees produce the wood for perfumes.

The problem: Not all tengkaras trees produce agarwood for perfumes. It is formed only under unique conditions, stimulated by the fungal infections of parasites from the Ascomycetes group, like Phaeoacremonium.

Many of our team members previously worked as agarwood seekers. However, after being educated on the importance of nature conservation, they now understand how vital it is to ensure the sustainable use of these trees. So, even when the PRM team needs to cut through bushes and branches with machetes on patrol, they take extra care not to slash any precious agarwood.

The endangered giant

The same need for protection applies to the ulin (Eusideroxylon zwageri), a large, hardy tree native to Borneo that grows in lowland, tropical rain forests. It is dark in colour, resistant to termites and seawater, and often referred to as the Bornean ironwood.

Bornean ironwood trees grow as high as 50 metres, with diameters up to 2.2 metres! Its buttress roots extend up to four metres high along the trunk, and the straightness and length of its trunk make it an ideal and uniform building material. It is used, for example, for constructing houses, bridges, power poles, bearings and maritime buildings.


However, the Bornean ironwood grows slowly, with seed germination alone taking anywhere from six to 12 months. Therefore, using ironwood trees must be balanced with conservation efforts and follow a sustainable management plan to safeguard the species’ survival.

We hope that stricter regulations and supervision, both by the central and local governments, will prevent the illegal logging of Bornean ironwood. 

May both of these magnificent tree species grow forever in the forests of Borneo!


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