Rates of urbanisation vary considerably among the 22 Pacific Island countries and territories. Some of the highest percentages of urban populations are in smaller countries while the opposite holds true for the larger states in Melanesia. However, Melanesia boasts the largest urban centres in the region and Melanesian countries tend to have many more towns and cities, reflecting their larger populations and land areas. At the same time the urban atolls of South Tarawa and Majuro boast some of the highest population densities in the world, despite these countries being relatively small.
Growth in the number of urban residents has led to the emergence of informal settlements where inhabitants have little security of land tenure and the sites are often on marginal land that is highly exposed to the effects of extreme events such as tropical cyclones, floods and coastal erosion. It is likely that climate change will cause greater numbers of people to migrate to urban areas as their home locations become increasingly less habitable. Many will find themselves again living in exposed locations. Additionally, having little land tenure security, high levels of unemployment or underemployment, crowding, lack of infrastructure (including safe water and sanitation), crime and lack of access to land for food are likely to render many of these migrants vulnerable to the effects of climate change. As climate change continues to unfold, urban areas in the Pacific Islands region may find themselves particularly at risk. Urban planning which takes the likelihood of climate change into account is critically important.