The rise of the sea

When people think about the most devastating potential impacts of climate change, rising sea level is probably the first thing that comes to mind, and for good reason. According to the Intergovernmental Panel on Climate Change (IPCC), global sea level has been rising at about 2mm per year for the better part of the last century. The IPCC projects that sea level will rise about another 30cm to 40cm by the end of the century; however, the latest research is making these projections look overly optimistic. It is estimated that nearly one quarter of the world's population lives within 100km of the coast less than 100m above sea level, making sea-level rise a global concern.

SIDS will be among the worst hit by rising sea level for obvious reasons. A larger percentage of their populations live near the coast and their small economies are usually highly dependent upon activities centred on the ocean. Rising sea level causes many problems for SIDS, which includes, but is not limited to:

• displacement of large percentages of the population, which causes stress for not only the displaced, but also for the receiving communities;

• flooding and coastal erosion, which destroys vital infrastructure;

• saltwater inundation of agricultural land, which threatens food security and forces island farmers to switch to more salt-tolerant crops;

Box 14.2 Climate change refugees to be resettled in Papua New Guinea

The world's first climate change refugees will be relocated from their Pacific island home to Papua New Guinea by March next year.

The Solomon Islands Broadcasting Corporation says 40 families from north of Ontong Java in the Solomon Islands' Malaita Province will be relocated to Bougainville. Flooding has made parts of their islands completely uninhabitable and the islands are expected to be fully submerged by 2015. The relocation is estimated to cost the Autonomous Bougainville and Papua New Guinea government millions of dollars over the next six years. One third of the 1500 residents have refused to leave the islands.

Source: ABC News (2008)

• saltwater intrusion into vital groundwater supplies, which threatens water security and decreases the availability of freshwater for drinking, sanitation and irrigation; and

• amplification of damage from intense storms due to the weakening of natural barriers.

Many SIDS are already feeling the impact. Much of the land area of Tuvalu's nine islands is regularly inundated by rising tides every year, internally displacing many people, contaminating meagre groundwater supplies, and forcing residents to grow more salt-tolerant subsistence crops. The Maldives recently attracted media attention when its president announced that the country would be setting aside funds from its tourism industry to purchase a new homeland should the need arise (see Box 14.1).

It was reported that portions of the Solomon Islands are nearly uninhabitable due to flooding, requiring the evacuation of many families to Papua New Guinea (see Box 14.2).

According to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, global sea level rose at an average of 1.8mm per year from 1961 to 2003, and at an average of 3.1mm per year from 1993 to 2003. What causes sea level to rise? Since 1997, thermal expansion has contributed to 57 per cent of sea-level rise, the decrease in glacier and ice caps about 28 per cent, and the loss of polar ice sheets 15 per cent. The principal reason is, thus, the increase in average temperatures (air and ocean), which was exacerbated by anthropogenic greenhouse gas (GHGs) emissions.

Island settlements have many features in common, one of which is the high proportion of coastal settlements. In the Pacific or Caribbean islands, for instance, over 50 per cent of the population is located within 1.5km of the shore, and all major infrastructure, such as airports, or economic activities are also in floodable areas on the coast. As a result, they are highly vulnerable to a rise in sea level. Tuvalu, for example, is cut from the world up to 2 weeks a year during the high tide seasons, which completely flood the island of Funafuti and its airport strip.

Sea-level rise will affect these societies on many levels. First, coastal flooding will increase. This will trigger increased erosion of coastal land surfaces. According to scientific studies, islands with substantial human modification (e.g. modern infrastructure) are much more vulnerable to coastal erosion as the natural ecosystems have been replaced by modern structures and can no longer fulfil their ecological roles.

Since most infrastructure is on the coast, the damage from erosion and flooding is likely to be burdensome for these fragile economies. As traditional housing and building have been replaced with modern structure, the cost to repair the damage has increased. What is more, mitigation measures against sea-level rise, such as building sea walls, are extremely costly.

Another negative effect of sea-level rise is increased salinity of soils and contamination of freshwater aquifers. As a result, agricultural output, especially from traditional crops, is likely to decrease. This is a serious threat, especially since population is increasing. What is more, as saltwater enters further in the islands, freshwater lenses and freshwater aquifers will increasingly be contaminated by saltwater, leading to water scarcity. This is particularly problematic since this phenomenon will be combined with the likely decrease in precipitation. Many islands are starting to invest in desalinization plants. However, their high cost is prohibitive for many islands who cannot afford to invest in these life-saving infrastructures without outside financial help.

The predictions are not optimistic. The projected increase ranges from 0.19m to 0.58m by the end of the 21st century relative to 1980 to 1999. This increase is, of course, very problematic for islands, such as the Maldives, Tuvalu, Kiribati, and other atoll-formed nations that culminate at 3 m. Tide phenomena, thermal expansion and extreme weather events will contribute to making life in these islands increasingly difficult, if not impossible.

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