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Invasive alien species (IASs) on islands have broad impacts across biodiversity, agriculture, economy, health and culture, which tend to be stronger than on continents. Across small-island developing states (SIDSs), although only a small number of IASs are widely distributed, many more, including those with greatest impact, are found on only a small number of islands. Patterns of island invasion are not consistent across SIDS geographic regions, with differences attributable to correlated patterns in island biogeography and human development. We identify 15 of the most globally prevalent IASs on islands. IAS impacts on islands are exacerbated through interactions with a number of other global change threats, including over-exploitation, agricultural intensification, urban development and climate change. Biosecurity is critical in preventing IAS invasion of islands. Eradication of IASs on islands is possible at early stages of invasion, but otherwise is largely restricted to invasive mammals, or otherwise control is the only option. Future directions in IAS management and research on islands must consider IASs within a broader portfolio of threats to species, ecosystems and people’s livelihoods on islands. We advocate for stronger collaborations among island countries and territories faced with the same IASs in similar socio-ecological environments.

In this review, I look at governance beyond the national level and consider how well island conservation issues are addressed in international conventions and agreements, both global and regional. I focus primarily on small island developing states (SIDS) and look at conventions to which they are parties, in which their needs are specifically mentioned and which have actions directly targeted to SIDS. I also discuss the evolution of international soft law in agreements and action plans to respond to island issues, the role of the secretariats that have been set up by international conventions to support SIDS conservation action and the protection and recognition provided to island protected areas listed under international conventions.

Despite a growing body of literature on integrated land–sea management (ILSM), very little critical assessment has been conducted in order to evaluate ILSM in practice on island systems. Here we develop indicators for assessing 10 integrated island management principles and evaluate the performance of planning and implementation in four island ILSM projects from the tropical Pacific across different governance structures. We find that where customary governance is still strongly respected and enabled through national legislation, ILSM in practice can be very effective at restricting access and use according to fluctuations in resource availability. However, decision-making under customary governance systems may be vulnerable to mismanagement. Governmentled ILSM processes have the potential to design management actions that address the spatial scale of ecosystem processes and threats within the context of national policy and legislation, but may not fully capture broad stakeholder interests, and implementation may be poorly coordinated across highly dispersed island archipelagos. Private sector partnerships offer unique opportunities for resourcing island ILSM, although these are highly likely to be geared towards private sector interests that may change in the future and no longer align with community and/or national objectives. We identify consistent challenges that arise during island ILSM planning and implementation and offer recommendations for improvement.