On the northern coast of Java, fisherman Ahmad Sarif sees the sea steadily swallowing land at high tide every time he comes home from work in Bogorame village.

Sarif, a village elder, told Nikkei Asia earlier this month that Bogorame, part of the broader Timbulsloko area, spanned roughly 400 hectares in the 1980s. Today, most of it lies submerged, forcing residents in the Timbulsloko community of more than 3,300 people to raise the height of the wooden platforms their homes are built on every few years in a desperate effort to escape the floods. That often fails when high tide comes.

The northern coastline of central Java is experiencing extreme land subsidence, sinking at a rate of 10 to 20 centimeters annually, far surpassing that of Jakarta, a phenomenon that partly explains why Indonesia is constructing a new capital city, Nusantara, amid the jungles of Borneo.

Now Indonesian President Prabowo Subianto is reviving an ambitious, long-stalled plan to build a 500 kilometer seawall to try to protect vulnerable coastal communities like Bogorame and the businesses that sustain them. A September 2025 presidential regulation designated what was dubbed the “Giant Seawall” a national strategic project at an estimated cost of $80 billion, with the funding yet to be sourced. If the undertaking can surmount engineering, financial and political issues — and be completed in the estimated 20 years it will take to build — Indonesia will have built the world’s longest seawall.

In the district of Demak, where Bogorame sits, industrial zones and villagers alike grapple with chronic coastal flooding. The growing risk of extreme weather events triggered by climate change, like November’s epic floods in Sumatra, threatens to make an impossible situation all the more hopeless, experts say.

In Bogorame, Sarif lost his shrimp pond to encroaching waters in 2009 and now spends his days wading into murky waves to fish for whatever shrimp he can catch, often returning empty-handed. “I have to head back home the moment I return to the village, because if I don’t, the pathways will already be under water,” said Sarif, 36.

According to the Centre for Strategic and International Studies Indonesia, climate change has evolved into a structural threat to the nation’s agricultural system, mostly in the form of erratic and extreme rainfall. From 2020 to 2024, climate change inflicted 544 trillion rupiah ($32 billion) in economic losses across Indonesia, the Centre estimates. Agriculture took 78 trillion rupiah of that blow, while coastal and marine sectors bled even more.

The world’s most populous island, home to close to 160 million people, Java is an economic powerhouse that hosts everything from furniture factories to automotive plants.

According to official estimates, Java’s northern coast alone contributes an estimated $368 billion to gross domestic product each year. This amounts to about a quarter of Indonesia’s total GDP, but it is now at risk from the onslaught of climate threats. The situation is also imperiling Prabowo’s ambitious target of 8% GDP growth by 2029, a goal many critics already dismiss as unrealistic.

First proposed more than 30 years ago, the Giant Seawall project never broke ground. Now, work on a wall stretching 500 kilometers across the northern Java coast is reportedly set to start in September, with a construction timeline of roughly 20 years.

Some observers say the Giant Seawall cannot succeed without ancillary projects, particularly improving the supply of clean water, which currently meets less than two-thirds of demand according to local officials.

For Raj Kannan, president director of Deloitte Consulting, “coastal protection measures must be implemented alongside groundwater management and improved urban planning. … The objective is therefore not simply to build a wall, but to deploy a range of solutions that protect communities, sustain economic activity along the coast and safeguard critical agricultural areas from saltwater intrusion.”

Due to the lack of clean water infrastructure, unregulated industrial, commercial and residential extraction of groundwater exacerbates land subsidence, officials say. In Demak, subsidence has been acute, influenced by the nearby city of Semarang’s fast expansion, which has brought in more manufacturing companies, homes and fish farm operations.

One key issue regarding the seawall project that observers have identified is political stability: Since construction will take many years, the seawall needs support from future governments, not just the current one.

Another is the financial commitment required. There is still no clear national budget for the project. Without one, the government cannot show potential private investors and international partners that it is serious.

In Bogorame, village chief Sarif is not the only one to have lost his shrimp farm to rising waters and mud. Countless other residents have also abandoned the farms and ponds that once sustained them. Mangroves still line parts of the shoreline, but many have already died, suffocated by the mud.

“The shrimp pond has lost its yield, and now we never know what the tide will bring,” Sarif said. “The fish have become nearly impossible to find because they’ve lost their habitat. The mud has killed off much of the mangroves, and that’s where the fish used to live.”

The encroaching recently forced Sarif to raise the floor of his home by at least 1.5 meters. The father of two and his father had already raised the house by two meters. Still, water finds its way inside, sometimes seeping through what used to be the house’s roof, now the kitchen floor.

The rising sea claims more than homes; it is drowning livelihoods. Businesses across the region are fighting for survival as the water reshapes the local economy.

“Climate change has been impacting 30% to 40% of the businesses in the area,” Frans Kongi, chairman of the Central Java Provincial Executive Board of the Indonesian Employers Association, told Nikkei.

Kongi noted that the immediate business impact is a cycle of severe disruption, from which production is repeatedly halted as companies divert resources to pump out invading seawater. The local government has escalated its response in recent years by deploying larger pumps, Kongi said. However, this intervention merely manages the symptom, not the cause.

“This operational paralysis has translated into severe financial losses for the business sector,” Kongi said. “The disruption extends beyond idle production lines. Critical supply chains are severed, where inbound raw materials are stranded by flooded roads, while outbound shipments for domestic and export markets fail to meet delivery commitments.

“These systemic breakdowns in logistics further compound the economic damage, creating losses that ripple far beyond the immediate flood zone.”

According to a 2024 research report by a group of Indonesian academics, the annual economic impact of coastal erosion in the three most severely affected beach zones in Karawang Regency district in West Java was estimated at $1.6 million.

The relentless pressure of rising seas is forcing a structural shift. Some factories, finding continued operation impossible, have ceased operations entirely. These businesses have shuttered coastal sites and relocated to safer grounds within Central Java. In 2023, PT Fuji Metec relocated its production site from Tanjung Mas on the northern coast of Semarang, near Demak due to coastal tidal flooding, resulting in 500 layoffs, the Tribun Jateng newspaper reported.

However, such permanent moves remain the exception: The capital required to establish a new facility poses a formidable barrier for most smaller companies.

Didit Herdiawan Ashaf, head of the North Coast of Java Management Authority (BOPPJ), said last month in a briefing that the government has completed studies in Jakarta Bay and across Central Java for the construction of the Giant Sea Wall.

“The President’s (Prabowo’s) directive is to protect the north coast of Java comprehensively,” Ashaf said. “This is not merely about constructing a seawall, but about safeguarding a civilization that has thrived here since the first century.”

The BOPPJ, under the Coordinating Ministry for Infrastructure and Regional Development, has assembled a broad coalition of experts to confront coastal erosion and land subsidence. Working alongside universities and environmental organizations, the agency draws on international consultants from Japan, South Korea, China, the Netherlands and other parts of Europe to develop technical solutions.

“Java’s northern coast holds so much that it demands protection, not only the 17 to 20 million people living there, but also national assets (in contribution to GDP) valued at roughly $368.3 billion,” Ashaf said.

Beyond flood protection, the Giant Seawall is designed to serve as a multipurpose infrastructure hub, supporting a toll road, mass rapid transit rail lines, solar power generation, and a clean water supply with reservoirs on the wall’s inner side.

Observers say securing clean water is a critical issue in the Giant Sea Wall plan, one that requires immediate action. If the government pushes forward while ignoring rampant groundwater extraction, the project risks failure from the start, observers say, as sinking land will eventually undermine everything it aims to protect.

“Public water services currently cover only about 60% of (Jakarta) demand, leaving a 40% shortfall,” said Yus Budiyono of the National Research and Innovation Agency (BRIN). “Over nearly a decade, progress in expanding this coverage has remained inadequate.”

Deloitte’s Kannan said the Giant Sea Wall, combined with reclaimed land, could help protect critical economic zones while also generating economic value. The project is ambitious but necessary for the economy along the Java coast, he added.

“The project has also been positioned as a national priority, and the establishment of the North Java Sea Wall Authority signals strong intent from the government,” Kannan said. “In addition, parts of the project … could generate economic returns through land reclamation, commercial development and energy generation, which may help attract private investment.”

Skepticism about the project and its implications for the country isn’t hard to find.

Speaking to Nikkei Asia on condition of anonymity, an official from a foreign development agency described the Giant Sea Wall as “actually an adaptation measure for Jakarta sinking, whereas the mitigation measures that should be pursued are those to prevent the sinking itself.”

Regarding the government’s plan to store fresh water between the seawall and land, the official said, “Trapping water in specific locations cannot be considered a secure water resource strategy.”

In the meantime, the battle for survival continues on the northern Java coastline. In Bogorame, village elder Sarif is not for giving up on his home, whatever it takes.

“I hope the community won’t lose their hope of preserving the land,” he said, bemoaning the uncertain climate. “Because for me, I love my homeland.”