Indonesian islanders plant mangroves, seek justice as seas rise

• Residents on Pari Island sue Swiss cement maker Holcim
• Climate change blamed for warmer, higher sea
• Mangroves help protect Indonesia's eroding coastline

PARI ISLAND, Indonesia - Under the scorching midday sun, Asmania and several women from Indonesia's Pari Island walk toward Rengge Beach, a shoreline slowly receding from the rising sea, to plant dozens of young mangrove seedlings.

The Women's Group of Pari Island hopes the mangroves, which also absorb planet-heating greenhouse gas emissions, will protect the coastline from worsening tidal floods, rising sea levels and stronger waves.

"The sea is not like it used to be. It's hotter, rougher, and it scares us," said Asmania, a mother of three, as she dug with her hands into the sand beneath the shallow sea.

Home to just 1,000 residents, Pari Island near the capital Jakarta is at the centre of a globally significant court case over the impact of climate change on its beaches.

Asmania, who goes by a single name, and three other residents sued cement giant Holcim in Switzerland in 2023, accusing it of failing to cut emissions as their island faced repeated floods.

Cement production contributes about 7% of the world's total carbon dioxide (CO2) emissions, according to the Global Cement and Concrete Association.

A court in the town of Zug, where Holcim has its headquarters, has not yet ruled on whether to hear the case.

Sinking island

An archipelago with some 81,000 kilometres of coastline, Indonesia is highly vulnerable to erosion as the sea level has risen about 4.25 millimetres a year since 1992, threatening to submerge small islands like Pari.

About 11% of Pari's 42 hectares has already been lost to the sea, and the whole island could be underwater by 2050, according to environmental group Indonesian Forum for the Environment and Swiss Church Aid, a nonprofit working on climate justice, which are supporting the suit against Holcim.

Although Holcim has not operated cement plants in Indonesia since 2019, Asmania believes it has contributed to rising sea levels.

"This is not about distance. This is global damage caused by Holcim's emissions," she said. "It's unfair because we are the ones suffering from the impact."

Asmania first came to Pari Island in 2005 when the sea was clear, cool and rich in life and allowed people to farm seaweed and fish. She noticed the water turning warmer in 2010.

"The sea water was bluish-green and cool enough to grow seaweed at a depth of about 30 centimetres," she said.

"In 2023, our seaweed harvest failed. It all melted from the seawater heat," said Asmania, showing a clump of seaweed with white patches.

Her husband Sartono said only seven of the 400 young groupers he released into his farm in August remained two months later.

Sea surface temperatures in Indonesian waters have risen steadily since 1982, warming by about 0.19 degrees Celsius (0.34 Fahrenheit) per decade due to climate change, according to a 2025 study published in the journal Frontiers in Marine Science.

Push for accountability 

The Cantonal Court of Zug held a preliminary hearing in September, but did not decide whether the case can proceed, leaving its future uncertain.

"While in our opinion the question of who is allowed to emit how much CO2 is a matter for the legislature and not a question for a civil court, Holcim is deeply committed to taking action on climate," a spokesperson told Context in an email, pointing to the company's use of decarbonisation technology.

Although the case may not change international law, it reflects a rising trend of communities testing corporate accountability across borders, said Glenn Wijaya, a Jakarta-based lawyer who specialises in mining, energy and renewable projects.

"There is growing global momentum where people affected by the climate crisis are filing lawsuits against companies, particularly major emitters," he said.

In May, a German court rejected a Peruvian farmer's appeal for damages against RWE, a German energy utility he accused of putting his home at risk through climate change. But it set a precedent by ruling that companies were liable for emissions.

Mustaghfirin, 53, another plaintiff in the Holcim case who only uses one name, said catching fish has become increasingly difficult in recent years due to unpredictable sea currents and weather.

In the 2000s, he could catch 40 to 60 kg of fish a day. Since 2020, he's caught no more than 10 kg.

"Fishermen rely on nature. If we treat nature well, it will treat us well in return," he said.

"Mangroves can prevent erosion, absorb carbon and serve as breeding grounds for fish, sea cucumbers and crabs."

More than half of the total fish catch in weight in Indonesia is of mangrove-dependent species, according to a 2022 World Bank report. With tourism and carbon sequestering, it estimated the value of each hectare of mangroves to be between $15,000 to almost $50,000 per hectare annually.

Indonesia is the world's second-most biodiverse country, and home to 20% of the world's mangroves. Resembling upside-down tree roots, the vegetation acts as a buffer to waves, a nursery for fish and other animals and a carbon sink.

Over time, trapped sediment can form new land and expand coastal areas. Mangrove roots also act as natural barriers, absorbing up to 90% of wave energy.

"They hold back sediments from land runoff and seawater, helping to stabilise the coastline and prevent erosion," said Fery Kurniawan, a lecturer in aquatic resource management at the Bogor Agricultural Institute in West Java province.
But it can be difficult for them to thrive.

Seedlings must have at least a third of their shoots above water for photosynthesis, said Jeanny Sirait, a Greenpeace campaigner in Indonesia.

"For every 10 mangroves planted, only about five are likely to survive due to these natural risks," she said.

Despite the challenges, Asmania said she will keep restoring mangroves at Rengge beach in a bid to save the island.

"Planting mangroves is our way of holding on," she said.

(Reporting by Leo Galuh; Editing by Jack Graham and Ayla Jean Yackley. )