For years, China has been piling sand onto coral reefs in the South China Sea and turning them into solid land, some of it big enough to hold runways. The short answer is control: permanent outposts let China be present, watch, and enforce its claims across a sea it says is largely its own. Several neighbors claim the same waters, and an international court has already ruled against much of China’s position, which is why the islands keep making headlines.
What China Wants From the South China Sea
The islands serve a strategic goal bigger than any one reef. China is working to build a regional order that raises its status and influence. Control over Taiwan and the East and South China Seas is a primary driver of that strategy.1RAND Corporation. Land-Based, Multi-Domain Anti-Access/Area Denial Forces Power in the South China Sea also helps China pursue control of key shipping lanes reaching into the Indian Ocean.2World Affairs. CHINESE STRATEGY IN THE SOUTH CHINA SEA
The claim itself rests on a map line. Chinese maps show the nine-dash line, a U-shaped string of dashes that loops around most of the sea. Vietnam, the Philippines, Malaysia, Brunei and Taiwan claim parts of the same waters.3The Wall Street Journal. Vietnam Is Building Islands to Challenge China’s Hold on a Vital Waterway Countries tend to strengthen a claim by showing they actually administer a place: staffing it, patrolling it, building on it. That is why a physical outpost counts for more than a map. Ships come and go, but an island stays and can be staffed year-round. Most of these features were reefs or rocks that barely broke the surface before the dredgers arrived.
The claim is also a matter of national pride. After the 2016 ruling against China, Chinese social media filled with maps of the nine-dash line captioned that not an inch could be lost.4The Diplomat. The South China Sea Case and China’s New Nationalism
Military Bases at Sea
Satellite images show that China dredged sand and fill to create large artificial islands that now host naval bases.5JScholarship. ASSESSING THE CHINESE NAVAL INFRASTRUCTURE CHANGES IN THE SOUTH CHINA SEA USING GEOSPATIAL INTELLIGENCE These bases have ports, long runways, aircraft hangars, watchtowers, radar and communications sites, and missile shelters.6JScholarship. ASSESSING THE CHINESE NAVAL INFRASTRUCTURE CHANGES IN THE SOUTH CHINA SEA USING GEOSPATIAL INTELLIGENCE Since 2014 China has built combined civilian-military bases on its outposts in the Spratly and Paracel Islands.7Asia Maritime Transparency Initiative. Chinese Power Projection Capabilities in the South China Sea It has deployed mobile surface-to-air missiles and anti-ship cruise missiles there.8Asia Maritime Transparency Initiative. Chinese Power Projection Capabilities in the South China Sea
“Civilian-military” is the description because the same runway can serve supply planes or fighter jets, and the ports host coast guard, fishing and naval vessels alike. This dual use lets China describe the sites as civilian while keeping its military options open.
Together, the bases sharply expanded China’s ability to monitor and project power across the whole sea.9Asia Maritime Transparency Initiative. Chinese Power Projection Capabilities in the South China Sea Radar on a reef far from the coast can watch ships and aircraft that would be out of range of mainland radar. A runway in the middle of the sea lets aircraft refuel and land, so patrols last longer and cover more water.
Turning a reef into an island follows a rough sequence. Dredgers suck sand and broken coral from the seabed around the reef, and the material is pumped onto the reef until it stands above high tide. China’s dredging ship Tian Kun Hao, 140 meters long, can pull up about 6,000 cubic meters of sand an hour from 35 meters below the surface, by Chinese state media’s account.10CNBC. Beijing has a new ship that can build artificial islands. That’s worrying some neighbors New projects begin with docks, berths and construction access so supply and construction ships can work, before any airstrip or missile appears.11The Lowy Institute. China is remaking the South China Sea with a return to island-building Runways, buildings and weapons follow once the ground is stable.
Is China’s Island-Building Legal
The Philippines took China to court and won. On July 12, 2016, a tribunal hearing the Philippines’ case against China ruled unanimously and largely in Manila’s favor.12Global Challenges. South China Sea: War on the Horizon? It found China’s nine-dash line, its land reclamation, and other activities in Philippine waters unlawful.13U.S.-China Economic and Security Review Commission. South China Sea Arbitration Ruling: What Happened and What’s Next? China argued that centuries of use of the sea gave it rights inside the line. But the tribunal held that any historic rights ended once the UN Convention on the Law of the Sea took effect, since they don’t fit that treaty, which China has also joined.14Global Challenges. South China Sea: War on the Horizon?
Building on a reef doesn’t create ocean rights. Under the sea treaty, a natural island can claim an exclusive economic zone, waters up to 200 nautical miles out where that country controls fishing and drilling. Rocks that can’t support people or an economy on their own get no such zone.15Global Challenges. South China Sea: War on the Horizon? Reefs that are underwater at high tide get no maritime zone of their own.16Global Challenges. South China Sea: War on the Horizon? The tribunal ruled that Mischief, Subi and Second Thomas Shoal are submerged at high tide, and that Fiery Cross, Johnson, Cuarteron and Scarborough Shoal are mere rocks.17Global Challenges. South China Sea: War on the Horizon? Piling sand on these features does not, legally, turn them into islands with their own economic zones; under the treaty what counts is the feature’s natural state before building.
The tribunal’s reach had limits. The case was about how the sea treaty applies to features and activities, so it did not rule on who owns which reef. That is how it could say a reef creates no economic zone without handing sovereignty to anyone. The Philippines could bring the case because it concerned waters it says fall within its own economic zone.
The ruling hasn’t stopped construction. China refused to take part in the case and rejects the award, and there is no international police force to enforce such rulings.
Pressure Without War
China uses coast guard ships, naval forces and a maritime militia in what’s called a gray-zone approach: escalating pressure without crossing into open war.18Marine Policy. China’s gray zone actions in the East Asia region, employing coast guard, naval forces, and maritime militia, has drawn attention for its non-military tactics that escalate conflict without crossing into open warfare Island bases give these vessels nearby ports to refuel and stay on station.
On the water, this looks like coast guard ships shadowing or blocking another country’s boats near disputed reefs, or large groups of fishing boats, some acting as militia, crowding an area. Each incident is small enough that firing back would look like escalation. Over time, presence quietly becomes control.
Second Thomas Shoal is a well-known flashpoint. The Philippines keeps a small group of personnel on an old ship there, and Chinese vessels have tried to obstruct resupply boats. Scarborough Shoal has seen repeated coast guard encounters, with Chinese ships blocking or shadowing Filipino fishing boats. These clashes typically involve water cannon, blocking maneuvers and close sailing rather than gunfire.
What Is at Stake for Trade, Energy and Fish
About 80% of world trade by volume moves by sea,19ChinaPower Project. How Much Trade Transits the South China Sea? and the South China Sea carries roughly one-third of global shipping.20ChinaPower Project. How Much Trade Transits the South China Sea? China, Taiwan, Japan and South Korea depend on it to reach the Strait of Malacca and the Indian Ocean.21ChinaPower Project. How Much Trade Transits the South China Sea?
That leverage comes from geography. Ships heading between East Asia and the Indian Ocean must funnel through narrow passages like the Strait of Malacca. A powerful military presence near those routes could in theory slow or inspect traffic during a crisis, and the ability to threaten that, even without acting, gives a country leverage.
Oil and gas matter, but less than headlines suggest. The sea holds an estimated 11 billion barrels of oil and 190 trillion cubic feet of gas in known and probable reserves.22Asia Maritime Transparency Initiative. South China Sea Energy Exploration and Development Most of it lies near the coasts, not under the disputed reefs.23Asia Maritime Transparency Initiative. South China Sea Energy Exploration and Development Even China’s higher estimates are modest next to its demand of about 12.8 million barrels of oil a day.24Asia Maritime Transparency Initiative. South China Sea Energy Exploration and Development
Fish and cables add to the stakes. Overfishing, reef damage and pollution are shrinking fish stocks,25Recent Developments in the South China Sea Dispute. Natural resources and inter-state cooperation and competition in the South China Sea so competition among Chinese, Vietnamese and Filipino fishermen is growing and could drive future conflict.26Climate-Diplomacy. Fishing Dispute in the South China Sea Undersea internet cables crossing the sea are also a new area of US-China rivalry.27Journal of Cultural Analysis and Social Change. Undersea Cables in the South China Sea: A New Frontier of Us-China Strategic Competition and The Dilemma for Southeast Asian Countries
How the US and Neighbors Respond
US warships and planes conduct freedom of navigation operations, sailing or flying through waters to challenge claims the US considers excessive.28The Belfer Center for Science and International Affairs. Freedom of Navigation in the South China Sea: A Practical Guide The program dates from 1979 and its message has stayed consistent.29Journal of Quantitative Analysis in Sports. Why Is China Building Islands in the South China Sea? In one, a US destroyer passed the Paracels without asking permission, rejecting limits set by China, Taiwan and Vietnam.30U.S. Navy. U.S. Navy Destroyer Conducts Freedom of Navigation Operation in the South China Sea
The US says it does not take sides on who owns the reefs, but it insists on the rights of passage the sea treaty gives all ships. Such a challenge is a legal message more than a military move, and it does not stop construction.
China isn’t the only island-builder. Over four years, Vietnam turned remote rocks and reefs in the Spratlys into fortified artificial islands.31The Wall Street Journal. Vietnam Is Building Islands to Challenge China’s Hold on a Vital Waterway The Philippines and Malaysia have held back from major building, though they may follow if rivals operate from the Spratlys en masse.32Center for Strategic and International Studies. The Ripple Effects of Vietnam’s Island-Building in the South China Sea
Diplomacy runs alongside. ASEAN countries and China have been negotiating a Code of Conduct since a draft text in 2018.33ASEAN. Priority Areas of Cooperation After nearly two decades of talks, the Philippines has signaled agreement is close.34The Diplomat. South China Sea Code of Conduct: A Deal Is Not Enough A deal alone won’t settle who owns what, and its value depends on whether it is binding and enforced.
The Damage to Coral Reefs
All the new land was built on coral reefs, destroying those ecosystems on a massive scale.35PubMed Central. Island building in the South China Sea: detection of turbidity plumes and artificial islands using Landsat and MODIS data Corals are animals that rely on algae living in their tissue, and those algae need sunlight to feed them. Sediment stirred up by dredging clouds the water and blocks that sunlight, weakening the algae.36PubMed Central. Island building in the South China Sea: detection of turbidity plumes and artificial islands using Landsat and MODIS data The fine sediment also settles on coral, which can cover and suffocate it. Plankton levels in the area dropped from 2016 through 2018, and sinking sediment likely smothered nearby reefs.37PubMed Central. Evidence of Environmental Changes Caused by Chinese Island-Building
Clam harvesting adds harm. Giant-clam harvesters drag weighted propellers across the seabed, scarring reefs.38Conservation news. Island-building and overfishing wreak destruction of South China Sea reefs Giant clams are already at risk of extinction.39Conservation news. Island-building and overfishing wreak destruction of South China Sea reefs
A dredged reef does not simply grow back. Once a reef is buried under fill, the living surface is gone and cannot regrow under the new land. Even nearby reefs that are only damaged need years of clean water to recover. Reefs are also nurseries for many fish the region’s fishermen rely on, so losing them deepens the fish shortage that fuels disputes.
Is China Still Building, and What Comes Next
China has returned to island-building, including new work at Antelope Reef in the Paracels.40The Lowy Institute. China is remaking the South China Sea with a return to island-building Satellite tracking has found new, unreported reclamation at Barque Canada Reef and the ships involved.41Mitsubishi Research Institute, Inc.. Satellite Data Points to More Land Reclamation in South China Sea
Outsiders can tell because researchers compare satellite images over time to spot new sand deposits, dredging ships and construction. Tracking ship signals helps identify which vessels are working at a site. That is how new work gets reported even when governments do not announce it.
Another possible step is an air defense identification zone, airspace where a country asks incoming aircraft to identify themselves in advance. China declared one over the East China Sea in November 2013.42Foreign Policy Association. Will Beijing Declare Another Air Defense Zone? It hasn’t declared one over the South China Sea, partly because existing flight-control coverage already serves its needs.43南海战略态势感知计划. Why Is There No South China Sea Air Defense Identification Zone? Beijing says it could declare one if foreign military flights increase.44南海战略态势感知计划. Why Is There No South China Sea Air Defense Identification Zone?