America has told China to stop work on man-made islands but Beijing says its aim is to make dangerous waters safer

Dozens of long, flat boats swarm across turquoise waters, inside the pale, curving arc of a new island they have created from open sea in just a few months.

The Chinese dredger barges can reach up to 30 metres below the surface, cutting out and scooping up huge quantities of sand and coral for land reclamation projects. The technology is sophisticated, but the idea is simple: debris is collected from the seabed and piled up until it creates an island.

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Sometimes the slurry is pumped straight from the boats in heavy plumes, landing between barriers marking off what will become solid ground. If the areas being dredged and reclaimed are too far apart, it is loaded on to smaller boats that ferry it over before dumping it in place.

Decades old, the technology has been used around the world to build projects ranging from Hong Kong’s main airport and entire districts of Singapore to the ostentatious villa settlements on Dubai’s Palm Islands – man-made islands which form the shape of a tree.

But what was once largely a practical concern of urban planners and developers has been thrust into the international spotlight by Beijing’s decision to use the technology to consolidate its presence on a string of islands in the South China Sea. In barely two years, more than 2,000 acres, an area more than twice the size of New York’s Central Park, has been carved from what were open stretches of the South China Sea.

The area is a busy shipping route connecting to the Strait of Malacca and the Pacific and is believed to have rich oil and gas deposits, meaning that the tiny specks of land that dot it have been contested by many neighbouring powers for decades.

Some countries, including Vietnam, Malaysia and Taiwan, have used land reclamation to expand or plan expansion of the islands so that they can better support human life and, by extension, troops and other military capacity.

However, China is the only power to have begun turning reefs, which are under water at high tide and therefore not considered land under international law, into permanent islands.

This weekend Beijing’s conversion of open ocean it claims as its own into land that could be used to claim even more ocean triggered a serious escalation in the long-running dispute.

US defence secretary Ashton Carter yesterday demanded an “immediate and lasting halt” to the reclamation projects after stepping up surveillance flights and a naval presence around the new islands. His demand has been supported by other regional powers alarmed at the speed of the developments.

“China has reclaimed over 2,000 acres, more than all other claimants combined, and more than in the entire history of the region. And China did so in only the last 18 months,” Carter told the Shangri-La regional dialogue in Singapore. “It is unclear how much farther China will go. That is why this stretch of water has become the source of tension in the region and front-page news around the world.”

China’s breakneck pace of island construction is partly a result of technological improvements. The country has become a world leader in land reclamation, creating more than 10,000 square kilometres along its coastline, but managing projects on a remote ocean outcrop is much harder than pushing out the shoreline by a few hundred kilometres near home.

Facebook Twitter Pinterest A US navy crewman aboard a surveillance aircraft views a computer screen purportedly showing Chinese construction on the reclaimed land of Fiery Cross Reef. Photograph: Reuters

“Technical constraints were a factor in the past for the reclamation of islands. The islands were too far away from the mainland for any construction work to be carried out,” said Du Xiaojun, researcher at the National Institute for South China Sea Studies.

Reefs are ideal locations for land reclamation because they rise far above the surrounding seabed, making them accessible to dredger barges. Recently released photos show more than 30 such ships clustered around one of the new islands, explaining the dramatic speed of the expansion.

One ship working in the South China Sea, tracked by Jane’s Defence Weekly, can suck up 4,500 cubic metres of debris an hour from the seabed. It has recently been at work on perhaps the most controversial aspect of the disputed expansion, runway construction.

One of the peculiarities of Beijing’s longstanding claim over the two South China Sea island chains, the Paracels and the Spratlys, is that they lie so far from the country that it has been effectively impossible for the Chinese military to patrol the area from its existing bases hundreds of nautical miles away.

But tarmac is already being laid on Fiery Cross Reef for an airstrip which is potentially long enough to support most military and surveillance planes. Even more disturbingly for China’s regional rivals, the airstrip may be intended as part of a wider web of bases and supply stations.

Plans on the website of the China State Shipbuilding Corporation laid out details of an airstrip complex at the Johnson South Reef, with a CGI image of the outpost containing windmills for power and greenhouses for food, although they have been taken down.

Beijing insists that the reclamation projects are part of an effort to support civilians and shipping in an area which has both heavy traffic and difficult weather and has brushed off reports that recent US satellite photos showed two artillery vehicles on one.

It’s obviously unfair for the west to question China’s intentions in its reclamation projects Xu Liping, researcher at the Institute of Asia-Pacific Studies

“The Nansha [Spratly] Islands is in a distant sea area with busy shipping routes and vulnerable to marine perils,” Ouyang Yujing, head of the foreign ministry’s department of boundary and ocean affairs told the official Xinhua news agency.

He listed China’s responsibilities for “maritime search and rescue, disaster prevention and mitigation, marine scientific research, meteorological observation, ecological environment preservation, safety of navigation and fishery production”.

Objections to the plan are born of fear and discrimination, say officials and analysts in China. They argue that other nations’ projects to boost their claims on disputed outposts, from expansion to sponsoring civilian communities, have gone largely unchallenged.

“It’s obviously unfair for the west to question China’s intentions in its reclamation projects. It shows that the west has wilfully misjudged the situation in the South China Sea,” said Xu Liping, researcher at the Institute of Asia-Pacific Studies inside the Chinese Academy of Social Sciences, a leading government thinktank.

However, no other power has created dry land from stretches of open sea and, whatever their current use, Beijing’s top generals and politicians are well aware of the islands’ vital strategic importance to a country that is aiming to project its naval power ever further from its shores.

The various outcrops claimed by China cover just 13 square kilometres in total, but are key to controlling 2m square kilometres of sea and critical routes to the Pacific, according to a recent US state department assessment of Beijing’s claims. Analysts, including Xu, describe them as one of China’s “core interests”, and the government has flirted with officially giving the area that status, which would put it on a par with areas such as Tibet and Taiwan, and therefore be seen as critical to national sovereignty and a possible trigger of military action.

Facebook Twitter Pinterest An uneasy relationship: US secretary of state John Kerry (left) and Chinese foreign minister Wang Yi shake hands after a meeting in Beijing in May to discuss the South China Sea issue. Photograph: Ng Han Guan/AP

That hardline view may have been behind a recent editorial in the Global Times, a fiercely nationalist government-controlled paper which warned that war was inevitable if the US tried to stop the reclamation projects. Beijing has since said that the paper speaks only for itself and that the government is focused on maintaining peace and stability in the area, but there is little question that the tabloid’s stance has been embraced by some hardliners within the Chinese military and government.

“The Global Times’ editorial has expressed a certain view,” Xu said. “China is determined to defend its sovereignty in the South China Sea and others should not test its bottom line or challenge its core interests.”

Beijing’s arguments have the weight of decades of history. The current claims were first expressed in recognisable form on a government map created several years before the communists swept to power in 1949, according to a US state department report .

However, they are somewhat vague, defined by a “nine-dash line”, drawn on maps without detailed coordinates and never officially submitted to an international body. The lines often sit closer to the coast of nearby countries than to the nearest island on which China is anchoring its claim.

Washington has always said that it takes no position on the sovereignty dispute, but objects to the islands because China is using the tiny new territories to take control of surrounding air and water, with a string of military warnings to stay away from one island recently captured on film by CNN.

“Turning an underwater rock into an airfield simply does not afford the rights of sovereignty or permit restrictions on international air or maritime transit,” said Carter, warning that China may find decades of dusty agreements far harder to transform than the sea itself.

He added: “America, alongside its allies and partners ... will not be deterred from exercising these rights.”

Additional research by Luna Lin