Indigenous knowledge of New Guinea's useful plants: a review.
We present the first large-scale synthesis of indigenous knowledge (IK) on New Guinea's useful plants based on a quantitative review of 488 references and 854 herbarium specimens. Specifically, we assessed (i) spatiotemporal trends in the documentation of IK, (ii) which are New Guinea's most useful ecosystems and plant taxa, (iii) what use categories have been better studied, and (iv) which are the best studied indigenous groups. Overall, our review integrates 40,376 use reports and 19,948 plant uses for 3434 plant species. We find that despite a significant increase in ethnobotanical studies since the first reports of 1885, all islands still remain under-investigated. Lowland and montane rainforests are the best studied habitats; legumes, palms, and figs are the most cited plant families; and Ficus, Pandanus, and Syzygium are the most useful genera. Medicinal uses have received the greatest attention and non-native species have the highest cross-cultural consensus for medicine, underscoring the culturally enriching role of non-native taxa to New Guinea's pharmacopeia. Of New Guinea's approximately 1100 indigenous groups, 217 are mentioned in the literature, and non-endangered groups remain better studied. We conclude that IK can contribute significantly to meet rising demands to make New Guinea's landscapes "multifunctional" and boost the green economy, but ambitious strategies will still be needed to mainstream IK and improve its documentation.