Should small-ranged species always be prioritised for conservation?

Alarming trend in biodiversity decline has been observed due to anthropogenic drivers, reinforcing the need to identify priority species for conservation. We discuss the prioritisation of species with small distribution sizes for conservation through two often-neglected perspectives: exposure to human-driven threats and importance to biodiversity. To evaluate species exposure, we estimated the amount of human pressure they encounter within their distribution ranges. To estimate their distinctive contributions to ecosystem functions and services, we calculated decreases in phylogenetic diversity after sequential species exclusion. We found that small-ranged species are not the most exposed to human-driven threats, as phylogenetic diversity is not always more affected by the loss of small-ranged species when compared to broad-ranged species. We propose conservation strategies to cope better with small-ranged species' vulnerability and to identify species with higher conservation needs. Under species high exposure to human-driven threats, conservation initiatives would benefit from distinguishing the causes of small range size. Conservation efforts on species whose distribution is mostly limited by abiotic suitability could focus on ecosystem management, while a focus on species management could be more adequate for species whose distribution is mostly limited by the accessibility. We also discuss the use of a response–effect framework to improve our capacity to identify species more negatively impacted by human-driven threats and with more distinctive effects on ecosystem processes. Small-ranged species should be prioritised for conservation when a negative correlation between species' ability to cope with environmental change and the distinctiveness of their effects on ecosystem processes is found.