CCT Programme Manager authors paper proving atolls are globally important sites for tropical seabirds

CCT is delighted that their 'Healthy Islands, Healthy Reefs' (HIHR) Programme Manager, Dr Pete Carr, was one of the authors of a scientific paper out today that found seabirds need atolls, and atolls need seabirds. This is due to the promotion of atoll resilience to climate change being vital for seabirds, proven by 25% of the world’s tropical seabirds nesting on Indo-Pacific atolls. And for 14 species, including many tropical seabirds such as White Terns, Black Noddies, or Lesser Frigatebirds, over half of their global populations nest on atolls. 

The study, which modelled both seabird population sizes on atolls, as well as the reciprocal relationship between seabirds and atolls, can be read here: https://www.nature.com/articles/s41559-024-02496-4, 

It also reveals global conservation efforts often overlook the important contributions of atolls to the protection, restoration potential, and long-term survival of tropical seabirds. In particular, it found 37 different species of seabirds that breed on atolls, with populations ranging from a few dozen to over 3 million individuals per atoll. In total, an estimated 31.2 million seabirds nest on atolls, or about one-quarter of all the world’s tropical seabirds.

Seabirds forage over 10,000-100,000 km² around an atoll and deposit on average 65,000 kg of nitrogen and 11,000 kg of phosphorus per atoll per year, acting as major nutrient pumps within the tropical Indo-Pacific. Besides being seabird breeding sites, atolls can also be important roosting sites for migratory seabirds during their non-breeding season, which import additional nutrients to atolls.

Through their nutrient inputs, seabirds on atolls support groundwater and soil nutrient enrichment of the otherwise impoverished island soils, shape atoll vegetation, boost plankton and fish biomass in adjacent atoll reefs and lagoons, enhance coral growth rates, and can even facilitate local feeding aggregations of large marine species such as manta rays. 

So atolls can be resilient to climate change, seabirds are a good way to visualise the connection of these unique ecosystems and their intertwined ecology of reefs, lagoons, and islands. But despite, or perhaps due to their smallness, atolls are globally relevant to conservation as they offer tractable systems that allow implementing whole ecosystem restoration actions that may not be feasible on continental or high-island settings. The protection of atolls against climate change impacts will need to become a priority for seabird conservation in the tropics. 

Earlier research has also shown that atolls - if their ecosystem functions are intact - can keep pace with current rates of rising sea levels. That’s good news, Dr Carr and the other authors of this paper say, because conservation will have to simultaneously leverage atoll protection and restoration to preserve a relevant fraction of the world’s tropical seabirds. And protect and restore seabird populations to help atolls remain resilient to climate change. Which is what our key rewilding project, HIHR, aims to do.