Abstract
The mangrove biome stands out as a distinct forest type at the interface between terrestrial, estuarine, and near-shore
marine ecosystems. However, mangrove species are increasingly threatened and experiencing range contraction across the
globe that requires urgent conservation action. Here, we assess the spatial distribution of mangrove species richness and
evolutionary diversity, and evaluate potential predictors of global declines and risk of extinction. We found that human
pressure, measured as the number of different uses associated with mangroves, correlated strongly, but negatively, with
extinction probability, whereas species ages were the best predictor of global decline, explaining 15% of variation in
extinction risk. Although the majority of mangrove species are categorised by the IUCN as Least Concern, our finding that
the more threatened species also tend to be those that are more evolutionarily unique is of concern because their
extinction would result in a greater loss of phylogenetic diversity. Finally, we identified biogeographic regions that are
relatively species-poor but rich in evolutionary history, and suggest these regions deserve greater conservation priority. Our
study provides phylogenetic information that is important for developing a unified management plan for mangrove
ecosystems worldwide.