The case is part of a wider international movement seeking to assign responsibility to major companies for the climate damage hurting the livelihoods of millions of people, especially in the Global South.

More than two years after four residents of Pari filed suit against the world's largest cement firm, two of them have travelled to Switzerland to take part in a preliminary hearing in the landmark case.

The hearing to determine whether or not the court will consider the complaint will take place on Wednesday in Zug, where the firm is headquartered.

Holcim insists it is "deeply committed to taking action on climate", but maintains that "the question of who is allowed to emit how much CO2" should be "a matter for the legislature and not a question for a civil court". 

Environmentalists say cement production is responsible for around eight percent of global CO2 emissions, and allege that Holcim figures among the 100 largest CO2 emitters among all companies worldwide.

The company thus bears significant responsibility for climate-related loss and damages, the suit maintains, in a case that could be a milestone for plaintiffs from developing countries who take on industrial giants.

"I hope the case will become inspirational... for climate victims" around the world, plaintiff Asmania told reporters in the Swiss city of Lausanne ahead of the hearing, speaking through a translator.

Environmentalists have said most of the 42-hectare island of Pari could be underwater by 2050 due to rising sea levels. 

The islanders say saltwater floods have in recent years surged in scale and frequency, battering homes and damaging livelihoods. 

Asmania, a 42-year-old mother-of-three, who like many Indonesians goes by one name, has already lost her seaweed farm due to flooding, which has also ravished her fish farm, sweeping in dirt and oil that kill off the babies.

This year, she began with 500 small fry, "and there are only nine left", she said, adding that income "is zero".

Another plaintiff, 54-year-old mechanic and beach manager Arif Pujianto, also said climate impacts were taking a dire toll. 

"The climate crisis is the biggest threat to my life," he said through a translator.

He described how severe flooding of Star Beach had shrunk the pristine stretch of sand by nine meters since 2021, driving away tourists vital for his income.

At the same time, tidal floods now regularly reach his bamboo house, rotting the walls and contaminating his well, forcing him to purchase drinking water for his family at a high price.

The small workshop where he repairs motorcycles and diesel engines has also been repeatedly flooded, rusting his equipment, he said.

If the Swiss court refuses to take the case, Arif said he feared he would lose his beach, his island and even his life.

Environmental litigation against governments and fossil fuel firms seen as responsible for the greatest CO2 emissions has surged in recent years, but the case marks the first such action against a major cement company.

It is also the first filed by Indonesians against a foreign company for climate-related damage, and the first instance of a Swiss company being sued for its alleged role in such damage.

The four plaintiffs in the case are seeking 3,600 Swiss francs ($4,500) each from Holcim for damages and protection measures such as planting mangroves and constructing breakwater barriers.

Swiss Church Aid (HEKS), an NGO helping the islanders, stressed that the amount was only equivalent to 0.42 percent of the actual costs -- in line with estimates that Holcim is responsible for 0.42 percent of global industrial CO2 emissions since 1750. 

In addition, the plaintiffs are demanding a 43-percent reduction in Holcim's greenhouse gas emissions by 2030 and a 69-percent reduction by 2040, with HEKS saying this was in line with the Paris Climate Agreement's goal of limiting global warming to 1.5 degrees Celsius, compared to the pre-industrial era.