Climate
change presents U.S.-affiliated islands with unique challenges. Small
islands are vulnerable to sea-level rise, coastal erosion, extreme
weather events, coral reef bleaching, ocean acidification, and
contamination of freshwater resources with saltwater. The islands have
experienced rising temperatures and sea level in recent decades.
Projections for the rest of this century suggest continued increases in
air and ocean surface temperatures in both the Pacific and Caribbean,
an overall decrease in rainfall in the Caribbean, an increased
frequency of heavy downpours nearly everywhere, and increased rainfall
during the summer months (rather than the normal rainy season in the
winter months) for the Pacific islands. Hurricane wind speeds and
rainfall rates are likely to increase with continued warming. Island
coasts will be at increased risk of inundation due to sea-level rise
and storm surge with major implications for coastal communities,
infrastructure, natural habitats, and resources.
A note on the emissions scenarios
None of the emissions scenarios used in this report assume any policies
specifically designed to address climate change. All, including the
lower emissions scenario, assume increases in heat-trapping gas
emissions for at least the next few decades, though at different rates.
Key Issues
Air Temperature Change, Observed and
Projected, 1900 to 2100 relative to average of 1960 to 1979
The
availability of freshwater is likely to be reduced, with significant
implications for island communities, economies, and resources.
Most
island communities in the Pacific and Caribbean have limited sources of
freshwater. Many islands depend on freshwater lenses below the surface,
which are recharged by precipitation. Changes in precipitation, such as
the significant decreases projected for the Caribbean, are thus a cause
of great concern. Sea-level rise also affects islands water supplies by
causing saltwater to contaminate the freshwater lens and by causing an
increased frequency of flooding due to storm high tides. Water
pollution (such as from agriculture or sewage), exacerbated by storms
and floods, can contaminate freshwater supplies, affecting public
health.
Caribbean Precipitation Change
Modeled Annual Total, 1900 to 2100
Island
communities, infrastructure, and ecosystems are vulnerable to coastal
inundation due to sea-level rise and coastal storms.
Flooding
will become more frequent and coastal land will be permanently lost as
the sea inundates low-lying areas and the shorelines erode. Loss of
land will affect living things in coastal ecosystems. For example, the
Northwestern Hawaiian Islands, which are low-lying and therefore at
great risk from rising sea level, have a high concentration of
threatened and endangered species, some of which exist nowhere else.
Hurricanes and other storm events cause major impacts to island
communities including loss of life, damage to infrastructure and other
property, and contamination of freshwater supplies. With further
warming, hurricane and typhoon peak wind intensities and rainfall are
likely to increase, which, combined with sea-level rise, would cause
higher storm surge levels.
Climate changes affecting coastal and marine ecosystems will have major implications for tourism and fisheries.
Coral
reefs are particularly sensitive to the impacts of climate change as
even small increases in water temperature can cause coral bleaching.
Ocean acidification due to rising carbon dioxide levels poses an
additional threat to coral reefs and rich ecosystems they support.
Fisheries feed island people and island economies. Nearly 70 percent of
the world’s annual tuna harvest comes from the Pacific Ocean. Climate
change is projected to cause a decline in tuna stocks and an eastward
shift in their location.
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