Mounting threats to food and water security, infrastructure, and public health and safety will have a negative impact on many communities across the Pacific Islands. Because Pacific Islands are almost entirely dependent upon imported food, fuel, and material, the vulnerability of ports and airports to extreme events, sea level rise, and increasing wave heights is of great concern. Sea level rise and flooding are also expected to overwhelm sewer systems and threaten public sanitation, endangering public health.

Ocean temperatures in the Pacific region exhibit strong year-to-year and decadal fluctuations, but since the 1950s, they have also exhibited a warming trend, with temperatures from the surface to a depth of 660 feet rising by as much as 3.6°F. Future sea surface temperatures are projected to continue increasing through 2100, even if current emissions of heat-trapping gases are substantially reduced.

Projected climate changes will significantly alter the distribution and abundance of many native marine, terrestrial, and freshwater species in the Pacific Islands. On low islands, native vegetation and the fauna it supports may change as periodic flooding increases the salinity of groundwater. On high islands, existing climate zones are generally projected to shift upslope in response to climate change.

The Pacific Island region faces a range of challenges associated with sea level rise. Higher water levels threaten coastal structures and property, groundwater reservoirs, coral reef ecosystems, harbor operations, wastewater systems, airports, and other resources of social and economic concern. Low islands are especially vulnerable given their limited elevation above present-day sea level.

On even the smallest islands, freshwater is necessary to support plants, animals, and any human inhabitants. On developed islands, natural sources of water must also support agriculture, industry, and tourism. Relatively high demand for these uses means that water supply is constrained and may become more limited as climate changes.