Some Islands Prove Resistant to Sea-Level Rise

South Farallon Island, located west of San Francisco, California. (Jan Roletto / NOAA)

(CN) — Scientists have long warned of the potential dangers rising sea levels could pose to coral reef islands, but new research released Wednesday suggests that those islands may be far more adaptable than we gave them credit for.

In a study published in the journal Science Advances, an international team of researchers led by the University of Plymouth in the U.K. reveals that, for the first time, advanced numerical modeling methods and physical experiments have shown that coral reef islands may be capable of adapting to — and subsequently surviving — a rise in sea levels.

Of the numerous threats that climate change presents to the world, few have captured the attention of researchers and climate experts as much as rising sea levels. For years, scientists have reported that as more ice melts from the polar ice caps and moves into the oceans, sea levels will inevitably and dangerously rise around the world.

This has resulted in much fear for island and coastal communities, particularly for islands that rest above coral reef platforms. Previous research has shown that these areas could be among the hardest hit by rising ocean tides, with many warning that water levels could rise so much that entire islands could find themselves flooded and swallowed by the sea.

But new research may suggest that there is more to the picture.

Researchers built a scale model of the Fatato Island, part of the Funafuti Atoll in Tuvalu, and subjected it to a series of lab experiments that helped to simulate how the island would respond to rising ocean waters.

What researchers found was that as sea levels rose, islands composed largely of gravel could naturally evolve to meet the rising water. As the water begins to crest over the island’s boundaries, such as during storm events, sediment and gravel from underneath the island has the ability to wash up and resettle the island’s surface. This results in an increase in island elevation.

According to the study, this process could leave an island and its community relatively protected from rising sea levels.

Gerd Masselink, professor of coastal geomorphology at Plymouth and study lead, recognizes that for some time, previous research efforts have pointed to the climate change challenges coral reef islands are faced with going forward and how widely accepted the idea is regarding islands being lost to rising sea levels.

“In the face of climate change and sea level rise, coral reef islands are among the most vulnerable coastal environments on the planet,” Masselink said with the release of the study. “Previous research into the future habitability of these islands typically considers them inert structures unable to adjust to rising sea level. Invariably, these studies predict significantly increased risk of coastal flooding and island inundation, and the concept of ‘island loss’ has become entrenched in discourses regarding the future of coral reef island communities.”

But Masselink suggests that these viewpoints may need to change. Research shows that we need to stop looking at coral reef islands as static, unchangeable objects with no interest in evolving, and instead look at them as being naturally capable of adapting to their own changing environments in order to survive.

Masselink stresses that coral reef islands have been shaped by thousands of years of exposure to nature, and that in that time frame, they have learned how to sustain themselves.

“It is important to realize that these coral reef islands have developed over hundreds to thousands of years as a result of energetic wave conditions removing material from the reef structure and depositing the material towards the back of reef platforms, thereby creating islands,” Masselink said.

“The height of their surface is actually determined by the most energetic wave conditions, therefore overtopping, flooding and island inundation are necessary, albeit inconvenient and sometime hazardous, processes required for island maintenance.”

Researchers warn that this does not mean that all islands are inherently protected from the dangers of rising sea levels.

The research findings were specific to coral reef islands that are made up of coral-reef material, such as gravel and sand, given that those islands are able to use those materials to help increase their elevation through adaptation. The same principle, Masselink says, does not apply to rocky islands.

Researchers also point out that in the event that a coral reef island was able to adapt to rising ocean water, communities would still need to focus on flood-proof housing and other infrastructure efforts to help island communities adapt. This livability also may need to be viewed in a more short-term basis, depending on the factors of each individual island.

Paul Kench, dean of science at Simon Fraser University in Canada, says that while each island may need to be evaluated on its adaptability on a case-by-case basis, simply understanding how they respond to sea level rise can significantly help island communities better understand their choices as they navigate the future.

“Understanding how islands will physically change due to sea level rise provides alternative options for island communities to deal with the consequences of climate change,” Kench said. ”It is important to stress there is no one-size-fits-all strategy that will be viable for all island communities – but neither are all islands doomed.”

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