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Will Pacific Island Nations Disappear as Seas Rise? Maybe Not

Will Pacific Island Nations Disappear as Seas Rise? Maybe Not

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Reef islands can grow and change shape as sediments shift, and studies show that many of them are in fact growing in size, not shrinking, as sea level inches upward.

Low-lying stretches of atoll islands such as Fongafale, Tuvalu's most populous island, are sometimes overwashed by the highest spring tides, called king tides, which occur a few times a year.  (Photo by: Jocelyn Carlin, Panos Pictures)

Low-lying stretches of atoll islands such as Fongafale, Tuvalu’s most populous island, are sometimes overwashed by the highest spring tides, called king tides, which occur a few times a year. (Photo by: Jocelyn Carlin, Panos Pictures)

“If you were faced with the threat of the disappearance of your nation, what would you do?”

That’s the question Enele Sopoaga, the prime minister of the tiny Pacific Island nation of Tuvalu, asked fellow world leaders at the United Nations climate summit in Lima, Peru, in December.

It’s a question that leaders of Pacific Island states have been asking for decades. As a warming climate drives sea levels upward, low-lying island nations face an uncertain future—or no future at all, say these leaders, who warn of their nations’ imminent disappearance.

Officials in Tuvalu, 600 miles (965 kilometers) north of Fiji, have been some of the most vocal critics of the world’s large greenhouse gas emitters—industrialized nations such as the United States and China—which they accuse of not doing enough to curb emissions, contributing to the melting of ice sheets and rising seas.

“I carry a huge burden and responsibility,” Sopoaga told the climate summit delegates in Peru. “It keeps me awake at night. Will we survive? Or will we disappear under the sea?”

These are desperate questions. But how real is the threat? Are island nations like Tuvalu, where most of the land is barely above sea level, destined to sink beneath the waves, like modern-day Atlantises?

Not necessarily, according to a growing body of evidence amassed by New Zealand coastal geomorphologist Paul Kench, of the University of Auckland’s School of Environment, and colleagues in Australia and Fiji, who have been studying how reef islands in the Pacific and Indian Oceans respond to rising sea levels.

NG MAPS SOURCES: USGS/EROS; P.S. KENCH ET AL. , GEOMORPHOLOGY

NG MAPS SOURCES: USGS/EROS; P.S. KENCH ET AL. , GEOMORPHOLOGY

They found that reef islands change shape and move around in response to shifting sediments, and that many of them are growing in size, not shrinking, as sea level inches upward. The implication is that many islands—especially less developed ones with few permanent structures—may cope with rising seas well into the next century.

But for the areas that have been transformed by human development, such as the capitals of Kiribati, Tuvalu, and Maldives, the future is considerably gloomier. That’s largely because their many structures—seawalls, roads, and water and electricity systems—are locked in place.

Their analysis, which now extends to more than 600 coral reef islands in the Pacific and Indian Oceans, indicates that about 80 percent of the islands have remained stable or increased in size (roughly 40 percent in each category). Only 20 percent have shown the net reduction that’s widely assumed to be a typical island’s fate when sea level rises.

Some islands grew by as much as 14 acres (5.6 hectares) in a single decade, and Tuvalu’s main atoll, Funafuti—33 islands distributed around the rim of a large lagoon—has gained 75 acres (32 hectares) of land during the past 115 years.

More than 6,000 Tuvaluans cram onto Fongafale, a boomerang-shaped sliver of land on the edge of a vast lagoon. The highest elevation on Fongafale is only a few yards above sea level, making the island vulnerable to rising seas. (Photo by: Koene/Hollandse Hoogte, Redux)

More than 6,000 Tuvaluans cram onto Fongafale, a boomerang-shaped sliver of land on the edge of a vast lagoon. The highest elevation on Fongafale is only a few yards above sea level, making the island vulnerable to rising seas. (Photo by: Koene/Hollandse Hoogte, Redux)

Two-thirds of the reef islands in the study migrated lagoon-ward as their ocean-side coastlines eroded and sediment built up on the side facing the lagoon. One of Funafuti’s islands shifted more than 350 feet (106 meters) over 40 years.

Reef islands, Kench says, are among the most dynamic landforms on Earth. And Tuvalu’s are some of the most dynamic on record.

With a scant ten square miles (26 square kilometers) of dry land, Tuvalu is one of the smallest countries in the world. Although there are many atolls and islands in the group, which lies midway between Australia and Hawaii, more than half of Tuvalu’s 12,000 people live on just one island—Fongafale—on the eastern rim of Funafuti atoll.

Reef Loss, Island Gain

Some climate specialists believe that rising sea-surface temperatures and increasing ocean acidity may have an even more damaging impact on coral reefs than that caused by sea-level rise.

Since the beginning of the industrial period, some 250 years ago, the acidity of tropical surface waters has risen by 30 percent. Sea-surface temperatures have increased by about 1.8°F (1°C) during the past century.

High water temperatures kill corals, and acidification affects their ability to produce their skeletons, since calcium carbonate dissolves in acid. Laboratory experiments suggest that the calcification rate of some corals could decrease by a third over the next three to five decades.

Yet a reef’s loss of living coral can be an island’s gain—at least in the short term. In 1998, when a worldwide coral bleaching event killed up to one-sixth of the world’s reefs, a huge repository of coral rubble became available for island building. If heat-related coral die-offs occur in coming decades, the sediment supply for islands is likely to increase.

But Kench cautions that scientists don’t yet have a clear understanding of how changes in ocean chemistry will affect coral reefs, or how that might translate to islands. “We don’t have a good handle on the time lag between when coral is killed and when it becomes available to an island as sand,” he says.

Over the time scales that matter to island nations—the next few decades when they’ll be seeking to adapt to land changes—the critical factor, Kench says, is the reworking of sands and gravels around the reef islands.

“And that’s controlled by wave processes and whether there’s sediment available. If sand is still being produced, islands are able to adjust and maintain their area.”

(Read the full story from National Geographic.)

Avatar of Coral Triangle Written by Coral Triangle

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