Seabirds play critical roles on islands. By catalysing terrestrial and marine productivity through guano nutrient input, seabirds support natural island functioning. In the Indo-Pacific, atolls comprise one-third of all islands but only ~0.02% of island area. The importance of atolls as seabird nesting grounds has been historically neglected except on a few key atolls. We compiled a global dataset of seabird surveys on atolls and modelled seabird distribution and nutrient deposition on all Indo-Pacific atolls. We found that atolls are breeding sites for 37 species, ranging from a few dozen to more than 3 million individuals per atoll. In total, an estimated 31.2 million seabirds nest on atolls, or ~25% of the tropical seabirds of the world. For 14 species, more than half of their global populations nest on atolls. Seabirds forage more than 10,000–100,000 km² around an atoll and deposit, on average, 65,000 kg N and 11,000 kg P per atoll per year, thus acting as major nutrient pumps within the tropical Indo-Pacific. Our findings reveal the global importance of atolls for tropical seabirds. Given global change, conservation will have to leverage atoll protection and restoration to preserve a relevant fraction of the tropical seabirds of the world.

海鸟在岛屿上发挥着关键作用。通过鸟粪营养输入催化陆地和海洋生产力，海鸟支持自然岛屿的功能。在印太地区，环礁占所有岛屿的三分之一，但仅占岛屿面积的 ~0.02%。环礁作为海鸟筑巢地的重要性在历史上一直被忽视，除了几个主要的环礁。我们编制了一个环礁海鸟调查的全球数据集，并模拟了所有印太环礁的海鸟分布和营养沉积。我们发现环礁是 37 个物种的繁殖地，每个环礁从几十个到超过 300 万只不等。据估计，总共有 3120 万只海鸟在环礁上筑巢，占世界热带海鸟的 ~25%。对于 14 个物种，它们全球种群的一半以上在环礁上筑巢。海鸟在一个环礁周围觅食超过 10,000-100,000 平方公里，平均每年每个环礁沉积 65,000 公斤氮和 11,000 公斤磷，因此是热带印太地区的主要营养泵。我们的研究结果揭示了环礁对热带海鸟的全球重要性。鉴于全球变化，保护工作必须利用环礁保护和恢复来保护世界上相关部分的热带海鸟。