The vulnerability of low-lying island states and territories to warming environments and rising seas is a powerful image of the impacts of climate change on those who contributed little to its causes. But beyond this vulnerability, small island nations have also been driving mitigation and adaptation efforts and have steered climate negotiations towards more effective action over the last decades. In this issue of Nature Climate Change, we focus on climate research conducted on small island states and territories and on what needs to be done to further advance their ability to adapt to changing environments.

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Many factors make small islands within the major global oceans vulnerable to global warming. The most prominent is that many of these islands do not have much elevation, which leads to an increased risk of flooding and coastal erosion as sea levels rise. In addition, the islands’ economies often rely heavily on the health of the marine environment around them, for example, through fishery that makes up much of the locally sourced food supply, and together with tourism, constitutes a major part of many islands’ economies1. Hence, increases in ocean acidification, marine heatwaves, tropical cyclones and other weather extremes that harm physical structures and threaten the survival of biological species directly affect key sectors of these communities’ functioning.

But island states and territories are not only subject to massive environmental changes, they have also been pivotal in advancing climate action globally. From the early days of climate negotiations in the 1990s, island states have pushed for ambitious climate policy, despite having contributed only negligibly to the emissions causing warming.

As comparatively small and scattered states, their negotiating power is limited when acting alone. Thus, they have made coalition forming and coordinated action a key part of their approach. They have created groups of island states such as the Alliance of Small Island States, but also broader coalitions with other countries such as the High Ambition Coalition, the Climate Vulnerable Forum and the Vulnerable Twenty (V20) Group, all of which played important roles in climate negotiations2,3.

For example, island states promoted a target of limiting warming to 1.5 °C long before COP21 and the coalitions they formed were instrumental in its inclusion in the Paris Agreement2. Similarly, loss and damage were always a key concern for highly vulnerable islands who were at the core of coalitions pushing for a designated loss and damage fund at COP27 (ref. 3). As such, small island states have transformed vulnerability to leadership through a focus on cooperation and coordinated action.

This leadership is not only seen at international negotiations on climate policies. On 21 May 2024, the International Tribunal for the Law of the Sea published an advisory opinion in which it stated that greenhouse gas emissions are “pollution of the marine environment” and need to be mitigated by its signatory states. This decision followed a request for an advisory opinion from the Commission of Small Island States on Climate Change and International Law, formed by Antigua and Barbuda and Tuvalu in 2021 and later joined by Palau, Niue, Vanuatu and Saint Lucia. This is one of the first decisions made by an international court on responsibility for greenhouse gas mitigation and thus opens another route for juridical enforcement of climate action through international law4.

Island states and territories are also regions of active research in many different scientific fields. In a Viewpoint in this issue, nine researchers from different islands around the world highlight the diversity of research and climate action conducted on islands, discussing key research and policy questions in their regions.

Also in this issue, in a Comment, Evans and colleagues argue that a better representation of small islands in climate models is needed to fully understand the different ways they are affected by climate change. Besides the successes of island states on different areas of international climate policy, there are still open issues on how they can translate climate research to domestic policies on the islands themselves. These issues are discussed in more detail in a Correspondence by Luetz and colleagues.

More than in most other regions, climate change poses an existential threat to small island states and territories. The articles in this issue are just a small sample showing the many ways in which communities living on these islands are facing this threat. They could have referred to their small contribution to emissions, but instead they stepped up and advanced climate action on all scales, from local initiatives to global cooperation.