Technological developments and high industrial demand affect the availability of raw materials. Synthetic or artificial raw materials may be viable and always available. However, natural raw materials are limited in number and require time to recover. Excessive exploitation and utilization of natural resources not accompanied by a qualified conservation program have resulted in several species of flora and fauna facing the threat of extinction, one of which is Keruing.

Keruing (Dipterocarpus spp.) is one of Southeast Asia’s most economically valuable tree species. As the third largest genus in the Dipterocarpaceae family, keruing is distributed in various countries such as China, Sri Lanka, Burma, Indochina, Thailand, and Indonesia. In Indonesia, 38 species of keruing mainly grow in the primary forests of Kalimantan and Sumatra. The diversity of flora in Indonesia, especially the Keruing plant, has attracted the attention of a research team led by Dr. Arida Susilowati from the Universitas Sumatera Utara, Indonesia. The team consists of researchers from the Universitas Sumatera Utara and the Ministry of Forestry and Environment of the Republic of Indonesia, with members Henti Hendalastuti Rachmat, Deni Elfiati, Asep Hidayat, Adhi Nurul Hadi, Anita Zaitunah, Darin Nainggolan, and Ida Mallia Ginting.

“Keruing is a large tree with a height of up to 40-50 meters and a trunk diameter of 100-150 cm. A straight trunk and hairy branches characterize this tree. Keruing wood is widely used in the wood processing industry because of its strength and durability,” Dr. Arida explained.

Keruing wood is known for its high density, which makes it resistant to pressure and impact. Therefore, it is often used to manufacture various high-quality wood products such as flooring, furniture, and building construction. Furthermore, kerning wood is resistant to pest infestation and extreme weather conditions, making it a popular choice for outdoor applications, including deck and bridge construction.

In addition, keruing also produces valuable oleoresins and oils. Keruing oil, which contains compounds such as humulene and oleanolic acid, is used as a medicine and fragrance ingredient.

However, the high demand for keruing timber, oil, and oleoresin has led to overexploitation of the species. Illegal timber harvesting and habitat disturbance have further exacerbated the situation. As a result, 25 keruing species in Indonesia are on the IUCN red list, ranging from vulnerable to critically endangered.

Gunung Leuser National Park in North Sumatra, Indonesia, is one of the most critical habitats for keruing. The area has high biodiversity and is home to various animal and plant species, including the keruing. However, research on keruing ecology in Gunung Leuser National Park is still very limited. “The high level of exploitation of keruing trees without any conservation efforts, it is not impossible that this tree will become extinct in the next few years,” said Dr. Arida Susilowati, a researcher from the Universitas Sumatera Utara. “In fact, we can utilize this keruing tree in various aspects, not only the ecosystem but also the economy and health.”

Research conducted by Dr. Arida Susilowati’s team in collaboration with the North Sumatra Ministry of Environment and Forestry identified three keruing species, namely D. haseltii, D. costulatus, and D. elongatus. These three species show different distributions at various growth stages. D. haseltii is classified as endangered (EN), D. costulatus as near threatened (NT), and D. elongatus as critical (CR).

Furthermore, Dr. Arida and the team’s research results say that seedlings are essential indicators for the ecosystem’s natural regeneration of tree species. Forty-seven species, totaling 1,042 individuals, were found at the seedling stage in Gunung Leuser National Park. However, only Dipterocarpus haseltii was found from the keruing species. Then, at the sapling stage (tree saplings with a size of more than 1.5 m and a diameter of less than 10 cm), 43 species with a total of 1,250 individuals were found, but only one species of D. haseltii and D. elongatus were found. At the pole stage, no keruing species were found.

The decreasing presence of keruing trees indicates that the natural regeneration of keruing has been disrupted. This disturbance is caused by human activities such as illegal logging and land clearing for plantations, which have occurred since the 1920s. The felling of valuable keruing trees and clearing the forest canopy reduces the population of parent trees essential for regeneration.

“The continuous land clearing since 1920, causing many disasters and hazards, or what we also call anthropogenic, greatly affects plant diversity and plant species distribution patterns,” concluded Dr. Arida Susilowati. Furthermore, the regeneration of keruing is also influenced by seed availability, with keruing flowering and fruiting every five to six years.

Although keruing is commonly found in Gunung Leuser National Park, part of a protected national park, this tree still has significant disturbances and extinction threats. Therefore, Dr. Arida Susilowati and her team said their research findings emphasize the importance of biodiversity protection in the Gunung Leuser National Park area and propose integrating keruing conservation with ecotourism to increase community awareness and involvement in conservation. “We hope that this research can help in efforts to conserve and restore the keruing population,” Dr. Arida Susilowati concluded.