Islands are true treasures of biodiversity. Although they represent only 7% of the Earth's land surface, they are home to nearly 20% of all the planet's species. However, this richness also makes them one of the most fragile ecosystems in the face of the effects of global change. Rising temperatures, sea levels, land transformation, and the arrival of invasive species are threats looming over these territories, often overlooked in international conservation strategies.
Now, an international team led by the French National Centre for Scientific Research (CNRS) and with participation from the National Museum of Natural Sciences (MNCN-CSIC) has taken a key step toward understanding the scope of these threats. The results, published in the journal PNAS, offer the first global assessment of islands' exposure to global change, with projections to 2050. And the conclusion is stark: climate change will be the main threat to 65% of island ecosystems.
Climate change, the main threat to two out of every three island ecosystems
The study analyzed 16.578 islands larger than one square kilometer worldwide. For each island, its exposure to three major drivers of biodiversity loss was calculated: climate, changes in land use, and biological invasions. The data reveal that rising temperatures and sea-level rise will be the factors that most affect the majority of island ecosystems, far more than the other two.
Specifically, climate will be the primary threat to 65% of the islands. This is followed by changes in land use, which will affect 22% of the territories, particularly in regions such as Micronesia, Fiji, the Baltic Sea, the Bay of Bengal, and Southeast Asia. Finally, invasive alien species will be the predominant risk for the remaining 13%, with a particularly high incidence in the temperate islands of Northern Europe.
Researchers warn that most islands will face not just one threat, but several at once. In fact, by 2050 many will simultaneously suffer the effects of climate change, land transformation, and biological invasions , further complicating their conservation.
Critical points: where it will hit hardest
The team has also identified the areas with the highest levels of cumulative exposure. These are the 5% of islands at greatest risk, which the authors call hotspots. They are located in Seychelles, French Polynesia, Bangladesh, China, Fiji, Micronesia, Denmark, Sweden, India, and Japan. In total, 31 countries have a disproportionately high number of these hotspots, requiring protection strategies tailored to local circumstances.
Ana Benítez-López, a researcher at the MNCN-CSIC and co-author of the study, emphasizes that “it is necessary to increase the protection of islands in these countries through strategies adapted to each specific situation.” She adds that “ecosystem restoration and the creation of protected areas are among the solutions that can both limit the impacts of climate change and reduce the effect of invasive alien species.”
The maps generated allow for the identification of risk level on each individual island, something unprecedented until now. Until now, global threat analyses were based on coarse-grained continental scales, which overlooked island territories due to their small size. Now, those responsible for the study are confident that these tools will help prioritize conservation efforts where they are most needed.
The situation in the Spanish islands
The study also focuses on Spain. Of the 28 islands analyzed, three have been identified as critical exposure points: Arosa Island, La Toja Island, and Conejera Island. They are not large archipelagos, but their vulnerability is high. In the case of Arosa, the exposure is distributed similarly among climate change, invasive species, and changes in land use , making it a particularly complex case.
On the islands of La Toja and Conejera, however, the main threats are invasive species and changes resulting from urbanization. This data reflects that the problem is not exclusive to the tropics, but also affects territories near the Iberian Peninsula. The authors emphasize that the precision of the maps allows conservation efforts to be targeted to specific locations , avoiding the dispersion of resources.
Tools for conservation and next steps
Beyond the data, the study provides a practical tool: cumulative exposure maps that can track progress toward international biodiversity goals. Researcher Martin Philippe-Lesaffre, also from the MNCN-CSIC, emphasizes that “the exposure maps we have developed are valuable tools for prioritizing conservation actions .”
The next step, according to the authors, is to incorporate other threats that are currently underrepresented, such as pollution from plastics, pesticides, and artificial light , as well as the overexploitation of natural resources. This will provide an even more comprehensive view of the impact of global change on ecosystems that, despite their importance, remain insufficiently represented in international strategies.
In short, the study demonstrates that islands are natural laboratories where climate change manifests itself with particular severity . And that protecting them is not only a matter of environmental justice, but also a smart strategy for preserving an essential part of the planet's biodiversity.
