An $80 billion sea wall stretching more than 500 kilometers (311 miles) along Java's north coast is at the core of a potential decades-long effort to protect Indonesia's economic heartland from worsening floods and sea level rise.

If completed, it would be one of the biggest coastal defense projects on the planet. But critics say it could also create an entirely new set of environmental and social problems, as The Conversation reported.

What's happening?

Indonesia is planning to build the massive concrete barrier off the shoreline of the world's most populous island, with construction expected to start in September. The proposal also calls for a large lagoon behind the barrier, The Conversation noted.

Everything about the wall is huge. The outlet noted it's expected to cost at least $80 billion, take decades to finish, and draw funding from provincial and national budgets as well as public-private deals, including support from countries such as the United Arab Emirates.

Supporters see the project as a response to a crisis. Indonesia is increasingly facing severe flooding linked to the changing climate, while parts of coastal Java are also sinking because of land subsidence.

Still, civil society groups and researchers are raising serious doubts about whether the wall will actually solve the problem, per The Conversation. They warn it could spur sand mining, damage mangroves, harm fishing communities, and deepen ecological damage already associated with industrial development.

Why does it matter?

The biggest issue is that flooding in Java is not being driven by rising seas alone. Researchers say land subsidence, the gradual sinking of land, is a major factor. It's linked to groundwater overuse, heavy building loads, mangrove loss, and previous coastal engineering.

A giant wall could reduce flooding in some places while leaving the root causes untouched, as The Conversation explained. In some instances, infrastructure can even shift risk from one community to another instead of eliminating it.

The authors of The Conversation piece's own research from villages in central Java found that raised roads, seawalls, and home-repair grants helped some households but did not fully solve flood risk. Roads and walls sometimes redirected water into lower-lying homes, while grants often fell short of the full cost of raising houses, leaving low-income families behind.

There are also concerns related to food. The Conversation explained that without river cleanup and wastewater upgrades, the planned lagoon could turn into a low-oxygen body of water behind the wall; saltwater intrusion is already affecting farmland.

What's being done?

Researchers, Indonesian media, and advocacy groups are calling for a broader approach instead of a single megaproject, per The Conversation.

That would include consultation with communities that would live with the wall's effects along with integrated coastal management that considers fisheries, farming, ecosystems, and housing together.

They also argue that groundwater extraction must be regulated and enforced more effectively. If the land keeps sinking, even extremely expensive flood barriers could prove to be temporary fixes. The human activities at the heart of rising sea levels and subsidence — such as polluting energy sources and industrial practices — are all part of the picture.

"The best question is not 'wall or no wall,' but if it is possible to construct a giant sea wall that works as intended," the authors concluded.

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