Half of the world’s tree biodiversity is unprotected and is increasingly threatened by human activities

Abstract

Although trees are key to ecosystem functioning, many forests and tree species across the globe face strong threats. Preserving areas of high biodiversity is a core priority for conservation; however, different dimensions of biodiversity and varied conservation targets make it difficult to respond effectively to this challenge. Here, we (i) identify priority areas for global tree conservation using comprehensive coverage of tree diversity based on taxonomy, phylogeny, and functional traits; and (ii) compare these findings to existing protected areas and global biodiversity conservation frameworks. We find that ca. 51% of the top-priority areas for tree biodiversity are located in current protected areas. The remaining half top-priority areas are subject to moderate to high human pressures, indicating conservation actions are needed to mitigate these human impacts. Our findings emphasize the effectiveness of using tree conservation priority areas for future global conservation planning.

Paleoclimate and current climate collectively shape the phylogenetic and functional diversity of trees worldwide

“…In this study, we used the world tree species list 56 and species range maps compiled by 47,57 . Briefly, the world tree species checklist (GlobalTreeSearch, GTS 56 ) was used to extract the global tree species list for the current study.…”

“…The estimated range maps of the 46,752 tree species were rasterized to 110 km equal-area grid cells (∼1 degree at the Equator), a resolution commonly used in global diversity studies (e.g., 45 ), using the letsR package 93 . For detailed information on the range map estimations and external validation, see 47 .…”

“…As many of the species’ trait were missing, we imputed missing values via an gap-filling algorithm with Bayesian Hierarchical Probabilistic Matrix Factorization (BHPMF, 106–108 ), which is mostly based on both trait-trait correlation matrix and the phylogentic signal of traits (Refer to ref. 47 for the detailed gap-filling procedure). In this process, all the 21 traits were used to maximally benefit from the correlations among them.…”

“…Due to the non-equivalency between the facets of diversity 44–47 , the responses of SR, PD and FD to different climatic conditions may vary. For example, warm and humid climates are hypothesized to increase diversification rates 48,49 , dispersal and establishment 50 , and decrease extinction 27,51 , thus increasing SR and PD, but not necessarily FD, as comparable climates more likely predispose species towards similar functional traits 25,52–55 .…”

“…We subsequently analyze the relative roles of past and present climates in shaping global patterns of tree SR, FD, and PD. We first compiled the most updated dataset of tree species including occurrence records, functional traits, and tree phylogeny, covering 46,752 tree species or 80.5% of the species in the GlobalTreeSearch list 47,56,57 . We subsequently mapped global tree SR, FD, and PD.…”