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Ce rapport est l'un des principaux résultats de l'atelier régional Sea'ties Pacifique qui s'est tenu du 10 au 12 juillet 2023 à Nadi (Fidji). L'atelier a été organisé par la Plateforme Océan & Climat, le Programme régional océanien de l'environnement (PROE), et le Pacific Climate Change Pacifique (PCCC), avec le soutien financier du Fonds de coopération économique, sociale et culturelle pour le Pacifique (« Fonds Pacifique », Ministère de l’Europe et des Affaires Etrangères), du PCCC, et du PROE par le biais du programme d’assistance technique de l’Initiative Kiwa. Le rapport fournit une vue d'ensemble des défis actuels en matière d'adaptation dans la région du Pacifique, ainsi que des initiatives inspirantes pour les relever. Les conclusions de ce rapport s'appuient sur les points de vue exprimés lors d’entretiens et sur les discussions de l'atelier lui-même. Il souligne et démontre à quel point, dans une région où de nombreuses îles sont de faible altitude, où la grande majorité de la population vit au bord de l'océan et où la côte s'urbanise rapidement, l'élévation du niveau de la mer reste une question existentielle et qu'il est primordial d'accélérer les mesures d'atténuation et d'adaptation.

Atoll islands are often perceived as inevitably lost due to rising sea levels. However, unlike other islands, atoll islands are dynamic landforms that have evolved, at least historically, to vertically accrete at a pace commensurate with changing sea levels. Rather than atoll islands’ low elevation per se, the impairment of natural accretion processes is jeopardising their persistence. While global marine impacts are deteriorating coral reefs, local impacts also significantly affect accretion, together potentially tipping the scales toward atoll island erosion. Maintaining atoll island accretion requires intact sediment generation on coral reefs, unobstructed sediment transport from reef to island, and available vegetated deposition sites on the island. Ensuring the persistence of atoll islands must include global greenhouse gas emission reduction and local restoration of accretion proce

The three most invasive rat species, black or ship rat Rattus rattus, brown or Norway rats, R. norvegicus and Pacific rat, R. exulans have been incrementally introduced to islands as humans have explored the world’s oceans. They have caused serious deleterious effects through predation and competition, and extinction of many species on tropical islands, many of which are biodiversity hotspots. All three rat species are found in virtually all habitat types, including mangrove and arid shrub land. Black rats tend to dominate the literature but despite this the population biology of invasive rats, particularly Norway rats, is poorly researched on tropical islands. Pacific rats can often exceed population densities of well over 100 rats ha?1 and black rats can attain densities of 119 rats ha?1, which is much higher than recorded on most temperate islands. High densities are possibly due to high recruitment of young although the data to support this are limited. The generally aseasonally warm climate can lead to year-round breeding but can be restricted by either density-dependent effects interacting with resource constraints often due to aridity. Apparent adverse impacts on birds have been well recorded and almost all tropical seabirds and land birds can be affected by rats. On the Pacific islands, black rats have added to declines and extinctions of land birds caused initially by Pacific rats. Rats have likely caused unrecorded extinctions of native species on tropical islands. Further research required on invasive rats on tropical islands includes the drivers of population growth and carrying capacities that result in high densities and how these differ to temperate islands, habitat use of rats in tropical vegetation types and interactions with other tropical species, particularly the reptiles and invertebrates, including crustaceans.