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An international study published in Current Biology shows that human population density has a more marked impact on the phylogenetic and functional diversity of species than it does on species richness. As well as causing species loss, man has thus considerably reduced the diversity of functions performed by fish communities and diminished the wealth of their evolutionary history.

Literal biodiversity reservoirs, coral reefs and associated ecosystems are in grave danger from natural and man-made disturbances. The latest World Resources Institute assessment is alarming with 75 % of coral reefs reported as endangered worldwide, a figure that may reach 100 % by 2050. The numbers are concerning, particularly as coral reefs provide sustenance and economic benefits for many developing countries and fish biodiversity on coral reefs partly determines the biomass available for human consumption.

An ecosystem’s richness is measured both in taxonomic biodiversity terms (number of different species) as well as by the number of lineages or functions performed by many ecosystem goods and services. The study results showed a sharp drop in functional and phylogenetic diversity levels, with the increase of the number of inhabitants per sq. km of reef, while species richness was barely affected.

The research shows that species numbers are a poor indicator of anthropogenic pressure, while two other biodiversity components are far more heavily affected by human density. These components make up the tree of life, i.e. the diversity of biological traits and phylogenetic lineages that are essential for coral systems to function.

Référence : S. D’agata, D. Mouillot, M. Kulbicki, S. Andrefouët, D. R. Bellwood, J. E. Cinner, P. F. Cowman, M. Kronen, S. Pinca, L. Vigliola. Human-Mediated Loss of Phylogenetic and Functional Diversity in Coral Reef Fishes, Current Biology, 2014.