Islands Harbour Nearly 20% of Earth's Biodiversity, Yet Remain Overlooked in Conservation Strategies

Although they account for just 7% of the Earth's land surface, island ecosystems harbor almost 20% of the world's biodiversity. From sea-level rise to biological invasions, islands are facing multiple pressures associated with ongoing global change, and yet they are still overlooked in global biodiversity conservation strategies.

Scientists from the Écologie, Société et Évolution (ESE) laboratory (AgroParisTech-Paris/CNRS/Université Paris Saclay) and the Center for the Synthesis and Analysis of Biodiversity (CESAB) have completed the first global assessment of the exposure of islands larger than one square kilometer (0.39 square miles) to global change.

The research is published in the journal Proceedings of the National Academy of Sciences.

Climate change dominates island threats by 2050

Their findings are alarming: by 2050, climate change will be the dominant threat for 65% of island ecosystems; land-use change will be the primary threat for 22%, particularly in the Pacific (Micronesia and Fiji), the Baltic Sea, the Bay of Bengal and Southeast Asia; biological invasions will be the main threat for 13%, posing a heightened risk to temperate islands such as those in Northern Europe.

The team also identified the countries and regions most disproportionately exposed to these risks, based on the number of islands located there. France has an unusually high number of "exposure hotspots"—islands highly exposed to all three threats—including in French Polynesia and certain islands in mainland France. This places it among the 25% of countries most exposed. The Seychelles, Bangladesh, China, Fiji, Micronesia, Denmark, Sweden, India and Japan are also affected.

Targeting protection at exposure hotspots

In response to these findings, the authors call for stronger protection of islands in the 31 countries identified as having a disproportionately high number of exposure hotspots, through locally tailored strategies.

Ecosystem restoration and the development of protected areas are among the solutions that can both limit the impacts of climate change and reduce opportunities for the establishment of invasive alien species. The exposure maps produced by this research are valuable tools for prioritizing action.