Biodiversity and Conservation Priority Setting for the Vascular Flora of New Guinea

Aims New Guinea is one of the world’s most floristically diverse islands, but its plant collection records are very uneven. We aim to identify which areas have the highest diversity of vascular plant genera, and which areas have the highest deforestation risk. Combining these findings we highlight priority regions for research and conservation. Location New Guinea Time period 1900–2021 Taxa studied Tracheophyta (Vascular plants) Methods We obtained collection records and environmental variables and prepared a cost-distance map of New Guinea to indicate accessibility. We modelled the joint distribution of 1,156 genera with the ‘Hmsc’ package in R to predict biodiversity across space, accounting for collection bias. We combined these results with a genus-level phylogenetic tree to predict phylogenetic endemism. We then modelled deforestation risk with the ‘R-INLA’ package, using forest clearance data and variables including cost-distance. We compared actual and predicted deforestation, and made predictions for 2021–25. Finally, we developed a combined measure of predicted biodiversity plus deforestation risk. Results A mean Spearman’s rank correlation of 0.462 was obtained on five-fold cross-validation of the genus biodiversity model; bias-correction shifted the predicted distribution of biodiversity towards western New Guinea, but had less effect on estimates of phylogenetic endemism. Predictions of relative deforestation probability were accurate over 5 and 10 years (Spearman values 0.66 and 0.71). We postulate a ‘deforestation debt’ to explain the persistence in accuracy. Over time, the areas which survive early deforestation gradually become more rewarding targets and the proportion of at-risk forest lost to clearance accumulates. Main conclusions We present a method for rapid assessment of biodiversity and deforestation risk in data-deficient tropical forest regions. Areas of high predicted biodiversity such as the Merauke and Jayapura lowlands are at high near-term risk from commercial deforestation, requiring urgent interventions to record and preserve threatened species.