The Importance of Islands for the Protection of Biological and Linguistic Diversity

TLDR

Islands cover only 5.3 % of land yet harbor ~19 % of birds, 17 % of rodents, 17 % of flowering plants, and 27 % of languages, while hosting 61 % of extinct species and 37 % of critically endangered species, making them a high‑priority conservation focus due to invasive species and habitat loss. Proven management actions can reduce these threats, benefiting both local peoples and species diversity on islands.

Abstract

Islands make up 5.3% of Earth's land area yet maintain an estimated 19% of bird species, 17% of rodents, 17% of flowering plants, and 27% of human languages. Species diversity is disproportionately threatened on islands in relation to the islands' proportion of both global land area and species, with 61% of all extinct species and 37% of all critically endangered species confined to islands. Languages are disproportionately threatened on islands in relation to land area with 11% of extinct languages and 25% of critically endangered languages on islands. Islands are a priority area for integrated conservation efforts because they have 14 times greater density of critically endangered terrestrial species and 6 times greater density of critically endangered languages than continental areas. Invasive species and habitat loss are the largest threats to island terrestrial species diversity. Proven management actions can reduce these threats, benefiting both local peoples and species diversity on islands.