Ironwood (Eusideroxylon zwageri) is an exceptional tree and wood in the rainforests of the Indonesian archipelago. It belongs to the family Lauraceae with thousands of tropical plants, including the laurel tree and avocado tree. The local name of Ironwood is Ulin.

Ulin trees grow in lowland rainforests with high precipitation – 2500-4000 mm/yr. They grow relatively slowly, at approximately the same pace as pine trees in Northern Sweden. It may take 100 years for an Ulin tree to reach 30 cm diameter, despite the favourable climate conditions in a rainforest. At the same time, they are hardy and live long – there are specimens that are estimated to be over 1,000 years old with a diameter greater than 2 meters and height of 45 meters.

The wood is very hard and resistant, which is necessary for trees that grow to old age in the rainforest. Ulin wood is heavy and sinks in water. As the Ulin wood resists termites and rot, it has long been used in challenging environments such as for boat hulls and in marine constructions. Because of its hardiness, Ulin is also an essential part of the construction of traditional long-houses on Borneo by the Dayak people.

Ulin has also a place in the local mythology as it is believed to protect against attacks by tigers and elephants.

The tough Ulin wood is in demand on the world market. Many years of logging and trade has put Ulin on the red list of threatened species. Indonesia has established export restrictions, and illegal logging and trade is known to occur. Because of the slow growth of Ulin trees, plantations have not been considered a profitable option, despite the high market price of the wood. Instead, Ulin trees are felled in natural forests where oversight and control often are insufficient.

Planting an Ulin tree symbolises that we value longterm perspectives in forestry. It also provides the reflection that we must balance social, economic and environmental benefits from the forest, as major contributions to overall sustainable development. Along this line, CIFOR’s work aims to ensure and demonstrate that forestry contributes to all 17 Sustainable Development Goals (SDGs) agreed by the United Nation’s Member States. Sweden and Indonesia are leading forestry countries, both taking great responsibility for future climate, biological diversity and sustainable management of forest resources.