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Papua New Guinea has a diverse tree flora. Now for the first time we know that 460 (36%) of its endemic tree species are threatened with extinction in the wild. These trees require immediate conservation action, through a variety of methods. Protection of trees is essential in Papua New Guinea as many people across the country rely on them for their livelihoods. Additionally, the extinction of these species would mean the loss of unique biodiversity. With the majority of forest cover still remaining in Papua New Guinea, it presents an almost unique opportunity to save tree diversity at a large scale and should therefore be at the forefront of the conservation agenda. Summary• Papua New Guinea is one of the world's most tree diverse countries, with over 1,200 endemic tree species. However, forests within the country face a range of threats but the impact of these threats on individual tree species has yet to be studied. Without identifying which species are threatened, where they are and their major threats it is not possible to effectively prioritise conservation actions for the trees of Papua New Guinea.

Abstract— This paper presents Artocarpus buyangensis, a newly-described species known only from Manus Island, Papua New Guinea. A member of Artocarpus subgenus Artocarpus phylogenetically placed near A. section Artocarpus series Rugosi, A. buyangensis most closely resembles Artocarpus elasticus and A. sericicarpus, neither of which is found east of the Moluccas. The new species thus represents a substantial eastward expansion for the A. series Rugosi clade. Long-distance dispersal, perhaps by birds, is suggested as a possible explanation for the origin of A. buyangensis.

The genus Diospyros (Ebenaceae) is highly diverse throughout Malesia, and New Guinea is thought to host c.46  species. Here we present a taxonomic treatment of a group of vegetatively similar species from the region, characterised by the large, chartaceous leaves that develop a peculiarly dark colour when dried. As a result of examination of herbarium collections, we describe two species new to science, Diospyros multimaculata and D. tehno; we exclude the presence of D. rostrata from New Guinea; and we provide a key to these and the three other species with a similar habit, namely, D. janowskyi, D. fusicarpa and D. pulchra.

Three species of Pleuranthodium were encountered and collected during a survey of gingers at Mount Wilhelm, Chimbu Province, Papua New Guinea. Based on new material, the only previously known Pleuranthodium from this area, P. piundaundense, is described in more detail highlighting new diagnostic characters and its known distribution range is expanded based on identification of older specimens at Edinburgh from two other provinces. Two species so far only known from Mount Wilhelm could not be identified after studying all protologues, types and material from several herbaria. These are here described as new species, P. corniculatum and P. sagittatum. A key with both floral and vegetative characters is provided to all three species. Pleuranthodium corniculatum is distinct in having apical appendages on the calyx, and P. sagittatum has a wrinkled calyx. All species are described and illustrated, and conservation assessments are made.