In addition to sequestering carbon, trees stabilize soils and provide habitat and resources for numerous species. The extent to which currently protected areas preserve tree diversity is not well known. Wen-Yong Guo et al. quantified human pressure on trees and the amount of protection in their existing ranges by analyzing a global database of 46,752 tree species. The authors found that, on average, 50.2 of a given species' range is unprotected, with 6,377 species occurring outside protected areas. Additionally, 83.3 of species are exposed to moderate to high human pressure as indicated by overlapping ranges with the Global Human Modification Map, which estimates the spatial extent and magnitude of human activity. The authors also found that areas of high species and phylogenetic diversity as well as functional diversity, or the variability in traits such as wood density, overlapped with priority areas set by three conservation prioritization frameworks. In particular, the Global 200 Ecoregions framework exhibited high overlap with the top 17 of priority areas for tree diversity. According to the authors, priority areas for protecting trees reflect conservation priority areas for overall biodiversity, but a large fraction of tree species fall outside protected areas and are under considerable human pressure. — T.H.D.
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