Indonesia plans to build a “giant sea wall”, more than 500 kilometres long, to defend Java’s north coast from rising sea levels.

The proposal includes a large lagoon behind the colossal concrete wall, raising significant questions about the feasibility and cost of such a giant project.

Indonesian civil society groups say the sea wall could prompt more sand mining, degrade mangroves and affect livelihoods of fishing communities. There are fears the project will worsen existing ecological destruction caused by industrialisation. While desperate to avoid flooding, these groups don’t see a wall as the solution.

Indonesia is significantly affected by climate change, often in the form of severe and regular floods.

So, what is the best way to respond?

What is Indonesia proposing?

The sea wall plan has been framed as a flagship economic project on Java’s north coast. It will cost at least US$80 billion and take decades to build. Construction is planned to start in September 2026.

The sea wall will be overseen by several government agencies and subject to scrutiny from Indonesia’s Corruption Commission (KPK). Whether such scrutiny will be effective is an open question.

The massive cost is slated to come from provincial and national budgets, along with public-private partnerships with countries such........

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