These Pacific Islands are building walls to stop rising seas. Will it work?

Australia Broadcast Center

3 days ago

The sea used to wreak havoc as it crashed into Simeona Tapeneko's village in Samoa.
Water would flood the houses in Lauli'i, on the north coast of the country's most populated island, overwhelming an old seawall built offshore.
"Many things — including our homes — were severely damaged," Mr Tapeneko said.
"The waves also destroyed the graves of deceased family members."
When builders laid the last rock of a new seawall there in May, ending six months of construction, Lauli'i breathed a collective sigh of relief.
Mr Tapeneko said the $1.9 million wall, funded by the New Zealand government, would protect the homes from storm surges.
It's one of many Pacific Island communities building seawalls to defend themselves against rising sea levels.
One of Marshall Islands' most populated islands, Ebeye, is buttressing its coast with a wall of rock shipped from Dubai and funded by the World Bank and Green Climate Fund.
New seawalls also protect low-lying atolls in Tuvalu, and more will appear in Kiribati, Tonga, Solomon Islands, Fiji and other island nations, many with funding from the Australian government and international development organisations.
They're a source of hope for countries grappling with sea level rise — which scientists say will continue even if the world limits global temperature rises to 1.5 degrees Celsius above pre-industrial times.
Coastal engineers say places like the Netherlands have long used engineering to hold back the sea from low-lying lands — and that the Pacific could do the same.
But researchers in climate change adaptation say seawalls are usually a costly, short-term fix in a region with limited money.
"A seawall along an eroding coastline is really only a stopgap measure, because we know that [sea level rise] is projected to continue well beyond the end of this century, perhaps by about another 200 or 300 years," Patrick Nunn, a University of Sunshine Coast climate scientist, said.
Not far from the shores of Lauli'i, its old seawall sits mostly submerged in water.
Leota Vaimauga, a village chief, estimates it lasted for 10-15 years before it was overwhelmed by the sea.
And while he's relieved the village has a new seawall, he expects Lauli'i will need to replace it in another decade, depending on the weather and the stability of the new barrier.
Climate adaptation researchers say seawalls have a clear downside that makes them hard to sustain in rural areas.
"You have to keep elevating them, have to keep extending them, and so they're very economically costly," Jon Barnett, a climate adaptation researcher at the University of Melbourne, said.
Most seawalls in rural coastal areas are funded and built by local communities, and have been too expensive to maintain, researchers say.
Professor Nunn calculates that on average, the structures will collapse after 18 to 24 months.
A study he co-authored in 2021 describes the Pacific's rural coastlines as "littered with the remains of collapsed seawalls".
Climate adaptation researchers also say seawalls have side effects, like diverting erosion to other parts of the coast, forcing waves to scour the seafloor at their seaward side, and pooling water on their landward side.
Professor Nunn said rural villages in the Pacific's higher volcanic islands could better use the labour and resources spent on seawalls on a longer-term solution — relocating further inland and upslope.
But he said seawalls can offer important psychological benefits for communities losing land to rising seas.
They also provide time for them to consider whether to relocate, researchers and coastal engineers say.
It's something Queensland University of Technology climate change adaptation researcher, Annah Piggott-McKellar, observed in one Fiji village that relocated after building a series of seawalls.
"Land is … a way of life. It's a part of who people are," she said.
But Dr Piggott-McKellar said there was also a risk that seawalls give false hope.
"Having that realistic conversation and understanding of what a seawall might be there to do is going to be important."
For the Pacific's low-lying atolls, new seawalls come with fanfare.
In Marshall Islands, 65,000 tonnes of rock shipped from the United Arab Emirates will form a new 1.81 kilometre barrier on the seaward side of Ebeye island.
Hall Contracting, which is building the multi-million-dollar seawall, said it was due to be completed by December.
"The houses in Ebeye are built right up against the ocean … in large storm events those houses can be affected," company CEO and director Cameron Hall said.
"This seawall will protect them."
Mr Hall said seawalls have an important role to play for Pacific Island nations as sea levels rise.
"It's a problem that developed nations have created … and if there's an engineering solution, why wouldn't we do it for them?"
The work is logistically challenging, requiring builders to move machinery to remote atolls, and source material for the seawalls.
In Tuvalu, Hall Contracting dredged sand from the lagoon by the capital Funafuti to build seven hectares of new or "reclaimed" land protected by a seawall of sandbags.
It also constructed a seawall of interlinked hexagonal concrete blocks along part of the coast at Nanumea, another Tuvalu atoll.
It's all part of Tuvalu's coastal adaptation project, funded by the Tuvaluan and Australian governments and the Green Climate Fund, aiming to keep the nation inhabitable.
But a group of Nanumeans is championing a proposal to save their home for the longer-term.
Local engineer Truman Lomi has worked on a concept for the Nanumea Salvation Seawall Project for years.
It involves building a barrier around the entire island — rather than just a section.
He said the barrier would protect the entire coast from large, powerful waves.
For now, it requires funding for a feasibility study.
His granddaughter Ashleigh Chatelier, a member of the Nanumea Salvation Seawall group, said the project also carried a message about Tuvalu's ability to adapt to climate change.
"Unfortunately, we are restricted in terms of the funding of this project, but the reality is that this is a community-led resilience project and it essentially has come from the roots of Nanumea."
Countries have long used engineering to protect, or reclaim, land from the sea.
In the Netherlands, dams and dykes keep vast, low-lying areas from flooding.
The Maldives, in the Indian Ocean, has reclaimed land from rising seas, although at huge financial and environmental costs.
"An engineering solution is possible," Francois Flocard, coastal engineer at the University of New South Wales' Water Research Laboratory, said.
"It's [about] understanding, as a community and as a society, where does it make sense to be applied?"
Professor Barnett says there are other options for communities where seawalls are too costly to build and maintain.
One is to try restoring and conserving ecosystems in a way that lets islands respond naturally to sea level rise.
"That doesn't mean they're going to be easy to live on," he said.
"Shorelines are going to change, the topography of islands is going to change. Some bits are going to erode, some bits are going to grow.
"But the adaptation options there are probably much cheaper."
Some Pacific Island nations are also creating nature-based barriers, using mangroves, sloping rock walls and vetiver grass to block rising seas.
In some ways, Professor Barnett said, all action is good action compared to the paralysis on climate change adaptation in some countries.
Leaders in countries like Tuvalu are being told there is only decades until their nations are uninhabitable, he said.
"You've got to protect the capital. You have to have an airport. You have to have a hospital. You have to have schools.
"It seems perfectly reasonable to engage in the kinds of urban defensive strategies."