Dipterocarpaceae is a tropical to subtropical tree family with 521 species (GlobalTreeSearch, bgci.org/resources/bgci-databases/globaltreesearch). Borneo is the centre of dipterocarp diversity, with 269 accepted species of which 162 are endemic. Dipterocarp species play a dominant ecological role in the major habitat of Borneo—lowland mixed dipterocarp forest—and in montane, heath (kerangas) and various types of peat swamp forest. They are also important as a source of timber.

In October 2021, The Red List of Bornean Endemic Dipterocarps was published (bgci.org/resources/bgci-tools-and-resources/the-red-list-of-bornean-endemic-dipterocarps), reporting the IUCN Red List status of all 162 endemic species: 99 species (62%) are threatened with extinction (18 Critically Endangered, 34 Endangered and 47 Vulnerable) and the other 63 species are categorized as Near Threatened, Data Deficient or Least Concern. Ninety-four per cent of species have a decreasing population trend, with most threatened species considered to have experienced a population decline of > 30% over three generations (IUCN Red List criterion A). Industrial agriculture was identified as the major threat to these dipterocarps and is the main driver of population decline. Other threats include timber harvesting, road construction and increasing occurrence of fires and droughts.

These conservation assessments, which are a contribution to the Global Tree Assessment (bgci.org/our-work/projects-and-case-studies/global-tree-assessment), were completed by a partnership between Botanic Gardens Conservation International, Universiti Brunei Darussalam, Sabah Forestry Department, Universiti of Malaysia Sabah, Forestry Department Sarawak, Bogor Botanic Gardens, The Indonesian Institute of Sciences (LIPI) and Arboretum Sylva Untan (Pontianak, Kalimantan). All these organizations carry out research on and conservation of dipterocarps both in situ and ex situ. This work is showcased in seven case studies in the report.

Only 47 of the 162 endemic species are held in ex situ collections, but 146 species (90%) occur in protected areas. Priorities for the group are investment in and maintenance and expansion of in situ conservation, particularly for the 15 threatened species that do not occur in either protected areas or ex situ collections.

Dipterocarps are under serious threat in their centre of diversity and a range of conservation actions are needed to protect them. To mobilize and inspire conservation efforts for this group, conservation recommendations are outlined in the report, including details of the Global Conservation Consortium for Dipterocarps, established in early 2021, which aims to develop a network of dipterocarp experts to coordinate action and share knowledge and expertise.