The Jakarta administration is set to begin the development of the so-called giant seawall along the city's northern coast in September, as part of Indonesian President Prabowo Subianto's 500-kilometer megaproject aimed at protecting flood-prone communities from Banten to East Java against rising sea levels.

Jakarta Governor Pramono Anung said he "fully supports the project", which will stretch 19 km along Jakarta's northern coast, up from the initial 12-km plan, and is projected to cost around $1 billion annually over the eight years of construction.

The entire giant seawall project is expected to cost up to $80 billion and take around 20 years to complete.

Pramono said Jakarta is committed to helping finance the construction. President Prabowo last year specifically asked the city to fund the Jakarta segment, citing its "very large regional budget".

In an interview with The Jakarta Post on Jan 20, Pramono reiterated his commitment to a hybrid seawall design that combines concrete structures with nature-based solutions such as mangrove restoration to mitigate flooding and erosion.

"Despite the name 'giant seawall', I will still develop mangrove ecosystems along Jakarta's sections of the wall," he said.

Previously, during a mangrove planting event at the Angke protected forest in North Jakarta in February last year, Pramono said that more than half of Indonesia's mangrove forests had disappeared over the past 30 years, including in Jakarta, calling the situation "a very serious threat".

First proposed in 1994, the seawall aims to curb seawater intrusion amid climate-driven sea level rise and worsening land subsidence along Java's coast. Prabowo revived the long-stalled plan through a 2025 presidential regulation designating the seawall as a national strategic project.

However, environmental groups have criticized the plan, with the Indonesian Forum for the Environment calling it a "false solution" to the climate crisis that could marginalize fisheries and coastal communities.

Yonvitner, a fisheries and marine science professor at Bogor Agricultural University, said that concrete coastal defenses are unavoidable as erosion continues along Java's shoreline.

"We need mitigation instruments to deal with rising sea levels and accelerating land subsidence. One of them is constructing a giant seawall," Yonvitner said.

But he noted that the project's design remains undisclosed, making it difficult to assess potential risks.

Yonvitner agreed that concrete barriers alone would be insufficient to halt seawater intrusion, underscoring the need to integrate artificial structures with natural measures, including expanding green coastal ecosystems, to allow coastal communities to sustain their livelihoods.

"The project should not be dominated by concrete barriers. There must be space for mangroves and waterways for fishing boats," he said.

The Jakarta Post, Indonesia