Developing countries vulnerable to the worst ravages of global heating have spent the past week at United Nations climate talks urging more support from wealthy nations.

The Pacific state of Kiribati has a very specific and unusual demand – that its islands be physically raised up to escape the encroaching seas.

The plan to dig up huge clumps of sand and rocks from the seabed and layer them upon the thin coral atolls that make up Kiribati’s sparse landmass will cost “in the billions” of dollars, the country’s president, Taneti Maamau, told the Guardian.

Kiribati has secured a more modest amount from the World Bank to help protect its tenuous water supply but Maamau argues that the rich countries that have done the most to cause the climate crisis should pay out far more to help save this slice of Pacific island life.

“We’ve asked donors to help – the physical land is limited but we have a lot of sea area, we can reclaim those areas and raise them high,” he said. “[Developed countries] should act, because time is short for us. Every day counts, a delay of a day means loss to us. It’s time for action, we demand action now.

“For too long we have waited and waited and then the negotiation prolongs, maybe it’s one way of delaying loss and damage,” Maamau said of the animating issue for developing countries – a proposed form of finance given from rich countries to poor to help pay for climate damages – at the Cop27 talks in Egypt. “I hope they listen now, because they have to honour their commitments and pledges. They need to open their ears more clearly, and their minds. The wealthy countries are after all responsible for what we are now facing.”

Kiribati (pronounced Ki-ri-bahss, a local translation of “Gilberts”, its name under British colonial rule) is comprised of 33 coral atolls scattered across a huge expanse of ocean in the central Pacific ocean, between Hawaii and Australia. It covers more than 1.3m sq miles, making it one of the world’s largest nations when sea area is included, but is one of the smallest in terms of land, with most of its 120,000 population crammed into the narrow outcrops that make up Tarawa, its capital.

No part of Kiribati’s land rises more than two metres above the ocean, making it one of the most vulnerable places in the world to the sea level rise being driven by global heating. Several small islands have already been inundated by water, with parts of others eroded by the advancing tides. Intruding salt water threatens the ability to grow crops and risks the fresh groundwater that sits upon the porous reefs that form the basis of the islands.

The flooding is “scary at times”, according to Maamau, and has caused a “huge outcry” from the population of Kiribati to act. His government has decided that fortifying the islands is the best option, a departure from the previous president, Anote Tong, who championed a concept of “migrate with dignity”, where people would form growing expat communities in places like Australia and Fiji to escape the rising seas.

“If you move people to Fiji, they are also facing the same issue with climate change,” Maamau said. “So where can we go? The whole world is facing a climate crisis. There is no safe place. The option is to give the people their preference.”

The Kiribati public are largely in favour of staying and fighting for their survival, Maamau said. “They say, ‘We’ve been here for over 2,000 years, how can you convince us that our islands are going to disappear?’”

Sea level rise will be relentless this century, and beyond, even if planet-heating emissions are constrained. The global average will rise by up to a metre by 2100, maybe more if the huge ice sheets at the poles break up faster than expected. This, according to hired consultants, will require Kiribati’s land to be raised by three to five metres to cope with storm surge, although the government considers this too high as it will impact people’s ability to access the sea, a key resource for food and income.

Anything up to three metres is acceptable to Maamau, although this will still require a huge operation to dredge the seabed (only one dredger, donated by Japan, is currently available) to bolster the coastlines. Rocks from Fiji have already been imported to defend areas eroding. In the lagoon that abuts Tarawa, sand and gravel naturally accumulates and could be accessed, although the task will be more complicated on more remote and sparsely populated islands.

“If it’s realistic anywhere it’s realistic in Tarawa, elsewhere you’d need to move communities to central locations to protect them,” said Simon Donner, a climate scientist and coral expert who has conducted research in Kiribati. “In the outer islands it becomes less feasible. But in many ways the other options are worse.”

It’s a widespread misconception, Donner said, that low-lying islands like Kiribati will simply drown under the rising seas. The flooding will shift and remould the islands rather than completely sink them, unless sea level rise is extreme, but the devastation wrought upon day-to-day life makes this process an “existential threat” to civilisation in Kiribati, he said.

“With a lower rate of sea level rise it’s conceivable the island itself survives but I’m not sure how the communities survive without a huge investment in adaption,” Donner said. This is technically possible, he said, pointing to China’s development of artificial islands for military purposes in disputed areas of the South China Sea.

“But this is a question of resources. If Kiribati was off the coast of Los Angeles you’d say it was doable. It’s possible if you throw enough resources at it, but who is going to do it for Kiribati? Sadly, it’s going to be down to how much rest of the world cares.”

Kiribati’s desire to generate new investment has enmeshed it within broader geopolitics, with Tong, who was president until 2016, accusing Maamau’s government of “cooking something with China”. Last year the government opened the Phoenix Islands Protected Area, one of the world’s largest marine reserves, to commercial fishing, where Chinese trawlers can fish for tuna. It’s also been speculated that China wants a military base within Kiribati territory, although both Beijing and Maamau have denied this.

“The western countries, those we thought we were very close with, have left us for so long, so we have to fill the gap,” said Maamau. “When Taiwan comes, and when China comes, they bring a lot. As donors, we have to deal with them.”

Donner said there were some “pretty disturbing” things happening in Kiribati, including the dismissal of the country’s chief justice to be replaced by the attorney general, leading to concerns over conflict of interest (Maamau denies any laws have been broken in this).

“That’s not good but I wouldn’t blame them for turning to China, because it’s not like countries that colonised them are helping them,” he said. “The whole thing is heartbreaking, really.”