Evrim Yazgin
Cosmos science journalist
New research highlights the importance of the tiniest islands in the world for seabirds.
Seabird colony survey data collected over 55 years was used to estimate the numbers of birds nesting on the 280 atolls in the Indo-Pacific. The study, published in the journal Nature Ecology and Evolution, also measures the nutrient contribution of the birds to the ecosystem.
Atolls are ring-shaped coral reef islands that enclose a lagoon. They form when a sinking extinct volcano subsides, leaving behind the coral reef that has grown around its rim.
Of the about 440 atolls in the world, most are in the Pacific Ocean. Their combined surface area only makes up about 0.02% of the total island area in the Indo-Pacific region.
However, the new study shows that their importance to seabirds far outweighs their relatively small total area.
“We calculated that over 31 million seabirds – about 25% of the world’s tropical seabirds – are nesting on atolls,” says first author Sebastian Steibl from the University of Auckland in New Zealand. “At least 14 seabird species have more than half of their global populations nesting on atolls.”
This is also just a fraction of historical populations using the atolls for breading and nesting.
The authors also note the importance of seabirds and, by extension, the atolls they rely on for the broader ecosystem.
“Seabirds are globally important mediators of ecological connectivity between land and sea,” they write. “They transport nutrients in the form of guano from marine feeding grounds to terrestrial nesting sites.”
The research highlights the importance of conserving seabird colonies and the atolls amid growing environmental challenges such as warming oceans and rising sea levels.
“Protecting atolls is therefore not only important for seabird conservation – in turn, seabirds on atolls are also supporting the functioning of the atolls themselves, which might be key to building resilience against climate change,” Steibl says.
“Many atoll islands that bear legacies of colonial exploitation are today uninhabited,” the authors of the paper say. “Building on the here-established global importance of atolls for seabird conservation, these uninhabited atoll islands offer themselves as prime target sites for future seabird conservation and restoration initiatives.”
Such restoration initiatives could include targeting invasive species for removal to encourage more seabird nesting.
