FREE 1 | Causes and consequences of functional rarity from local to global scales

Rarity has always fascinated conservation and evolutionary biologists with the goal to uncover species characteristics causing extinction risk. Recently, some results suggest that rare species may over-contribute to the diversity of traits within communities thus supporting irreplaceable roles while others show that rare species are functionally redundant with common species. Beyond the rarity of species, the rarity of functions played by species, coined as functional rarity, is thus key to understand the impact of biodiversity decline on ecosystem functioning. However, functional rarity still lacks a clear definition and a quantitative framework while its emergence and maintenance within communities is largely unknown. 

The aim of the FRB-CESAB FREE 1 working group was to advance the concept of functional rarity and examine the causes and consequences of functional rarity from local to global scales. 

This document summarizes in a few pages the group’s context and objectives, the methods and approaches used, the main findings, as well as the impact for science, society, and both public and private decision-making.