South China Sea

The South China Sea is a marginal sea of the Western Pacific Ocean. It is bounded in the north by South China, in the west by the Indochinese Peninsula, in the east by the islands of Taiwan and northwestern Philippines (mainly Luzon, Mindoro, and Palawan), and in the south by Borneo, eastern Sumatra, and the Bangka Belitung Islands, encompassing an area of around 3,500,000 km² (1,400,000 sq mi). It communicates with the East China Sea via the Taiwan Strait, the Philippine Sea via the Luzon Strait, the Sulu Sea via the straits around Palawan, the Java Sea via the Karimata and Bangka Straits, and directly with the Gulf of Thailand. Additionally, the Gulf of Tonkin is part of the South China Sea.

$3.4 trillion of the world's $16 trillion maritime shipping passed through the South China Sea in 2016. Oil and natural gas reserves have been found in the area. The Western Central Pacific accounted for 14% of the world's commercial fishing in 2010.

The South China Sea Islands, collectively comprising several archipelago clusters of mostly small uninhabited islands, islets (cays and shoals), reefs/atolls, and seamounts numbering in the hundreds, are subject to competing claims of sovereignty by several countries. These claims are also reflected in the variety of names used for the islands and the sea.

Etymology

The South China Sea is the common name used in English and many other languages for this body of water. European explorers first became interested in it as a route to China and other trading places. In the 1500s, Portuguese sailors called it the China Sea, but later it was renamed the South China Sea to tell it apart from nearby waters.

Ancient Chinese texts from around 1000 BCE called it the Nanfang Hai or Southern Sea. Over time, different Chinese dynasties used various names for it. In Southeast Asia, it was once known as the Champa Sea after the Champa kingdom in what is now Central Vietnam. During World War II, Japan controlled most of the sea. Today, different countries have different names for parts of it. For example, Vietnam calls it the East Sea, while the Philippines recently started using the name West Philippine Sea for the part near its shores. In 2017, Indonesia named the northern part of its area the North Natuna Sea.

Hydrography

The South China Sea touches several places, including People's Republic of China, Republic of China (Taiwan), the Philippines, Malaysia, Brunei, Indonesia, and Vietnam. Many important rivers flow into it, such as the Pearl, Red, and Mekong Rivers.

The sea is deep, with an average depth of 1,212 metres, and its deepest point reaches about 5,560 metres.

Geology

See also: Tectonics of the South China Sea

The South China Sea sits above an old land area that sank under the water. During times when there was less water on Earth, called ice ages, the sea level was much lower and the island of Borneo was connected to Asia.

The South China Sea began to form about 45 million years ago when a piece of land moved away from southern China. Around 30 million years ago, the seafloor spread out, creating the shape of the sea we see today. This process stopped about 17 million years ago.

Scientists have different ideas about how the sea formed. Some believe that when India moved into Asia, it pushed Indochina to the southeast, helping the sea open. Others think Indochina did not move much. Studies show that faults in the northwest part of the sea were active early on, supporting the idea that movement played a role. Since then, rivers like the Mekong River, Red River, and Pearl River have added lots of mud and sand to the sea. Some of these areas have oil and gas.

Islands and seamounts

See also: South China Sea Islands and list of islands in the South China Sea

The South China Sea has more than 250 small islands, atolls, cays, shoals, reefs, and sandbars. Many of these are underwater during high tide, and none have people living on them naturally. Some stay completely under the water all the time.

Important groups of these features include the Spratly Islands, the Paracel Islands, Pratas Island and the Vereker Banks, the Macclesfield Bank, and the Scarborough Shoal.

The Spratly Islands cover a large area, about 810 by 900 km. The biggest island here is Taiping Island, which is just over 1.3 kilometres long and only about 3.8 metres above sea level.

The largest single underwater feature in this area is called Reed Tablemount, or Reed Bank. It is a wide underwater mountain, about 100 kilometres across. It used to be an island, but rising sea levels after the last ice age covered it about 7,000 years ago. Today, it lies just 20 metres below the surface.

Trade route

The South China Sea has been an important trade route for many centuries, connecting northeast Asia, China, southeast Asia, India, and the West. Many old shipwrecks on the ocean floor show that trade has been busy there for a long time. In 2016, trade worth $3.4 trillion passed through the South China Sea, which was part of the world's $16 trillion in maritime shipping. By 2019, the sea carried trade equal to 5 percent of the world's total economy.

Natural resources

Scientists estimated in 2012–2013 that there is not much oil or natural gas in some parts of the South China Sea, like near the Paracel and Spratly Islands. Most of the oil and natural gas is found closer to shorelines that no one argues about.

In 2010, fishing in the western part of the Pacific Ocean, including the South China Sea, provided 14% of the world’s fish catch. This was a big increase from less than half that amount in 1970.

In May 2017, China made a discovery by getting methane from special icy structures in the South China Sea, but using this for business might take many years.

Territorial claims

Main articles: Territorial disputes in the South China Sea, Spratly Islands dispute, Timeline of the South China Sea dispute, and Regional reactions to China's maritime activities in the South China Sea

Several countries have made competing claims over the South China Sea. These disputes are considered some of Asia's most potentially dangerous points of conflict. Both the People's Republic of China and the Republic of China (ROC, commonly known as Taiwan) claim almost the entire sea as their own, using what is known as the "nine-dash line". This claim overlaps with the claims of virtually every other country in the region.

Countries with competing claims include:

• Indonesia, Vietnam, China, and Taiwan over the waters northeast of the Natuna Islands
• The Philippines, China, and Taiwan over Scarborough Shoal.
• Vietnam, China, and Taiwan over the waters west of the Spratly Islands. Some or all of the islands themselves are also disputed between Vietnam, China, Taiwan, Brunei, Malaysia, and the Philippines.
• The Paracel Islands are disputed between China, Taiwan, and Vietnam.
• Malaysia, Cambodia, Thailand, and Vietnam over areas in the Gulf of Thailand.
• Singapore and Malaysia along the Strait of Johore and the Strait of Singapore.

China and Vietnam have both been strong in pursuing their claims. China and South Vietnam each controlled part of the Paracel Islands before 1974. A brief conflict in 1974 resulted in China taking full control of the Paracel Islands. The Spratly Islands have been the site of naval clashes, including one in March 1988 where over 70 Vietnamese sailors were killed. Disputing claimants regularly report clashes between naval vessels, and these now also include airspace incidents.

ASEAN, in general, and Malaysia, in particular, have been keen to ensure that the territorial disputes within the South China Sea do not escalate into armed conflict. Joint development authorities have been established in areas of overlapping claims to develop the area together and divide the profits equally without settling the issue of sovereignty over the area. China has preferred to resolve competing claims bilaterally, while some ASEAN countries prefer multilateral talks.

The overlapping claims over Pedra Branca or Pulau Batu Putih, including the neighbouring Middle Rocks, by both Singapore and Malaysia were settled in 2008 by the International Court of Justice, awarding Pedra Branca/Pulau Batu Puteh to Singapore and the Middle Rocks to Malaysia. In July 2010, US Secretary of State Hillary Clinton called for China to resolve the territorial dispute. China responded by demanding that the US keep out of the issue.

In September 2011, India's state-run explorer, Oil and Natural Gas Corporation (ONGC) said that its overseas investment arm ONGC Videsh Limited had signed a three-year deal with Petrovietnam for developing long-term cooperation in the oil sector and that it had accepted Vietnam's offer of exploration in certain specified blocks in the South China Sea. In response, Chinese Foreign Ministry spokesperson Jiang Yu issued a protest.

In 1999, Taiwan claimed the entirety of the South China Sea islands under the administration of Lee Teng-hui.

In May 2014, China established an oil rig near the Paracel Islands, leading to multiple incidents between Vietnamese and Chinese ships.

The US, although not a signatory to UNCLOS, has maintained its position that its naval vessels have consistently sailed unhindered through the South China Sea and will continue to do so.

In November 2025, Australia raised concerns over China's military expansion in the South and East China Seas, citing increased risks to trade routes.

2016 arbitration

In January 2013, the Philippines initiated arbitration proceedings against China over issues surrounding the nine-dash line, characterization of maritime features, and EEZ. China did not participate in the arbitration.

On 12 July 2016, an arbitral tribunal ruled in favor of the Philippines on most of its submissions. It clarified that it would not "rule on any question of sovereignty over land territory and would not delimit any maritime boundary between the Parties" but concluded that China had not historically exercised exclusive control within the nine-dash line. It also concluded that China's historic rights claims over the maritime areas inside the nine-dash line would have no lawful effect outside of what is entitled to under UNCLOS. It criticized China's land reclamation projects and its construction of artificial islands in the Spratly Islands. Finally, it characterized Taiping Island and other features of the Spratly Islands as "rocks" under UNCLOS, and therefore are not entitled to a 200 nautical mile exclusive economic zone. The arbitral tribunal decision was ruled as final and non-appealable by either country.

China rejected the ruling, calling it "ill-founded". China’s response was to ignore the arbitration result and to continue pursuing bilateral discussions with the Philippines.

Taiwan, which currently administers Taiping Island, the largest of the Spratly Islands, also rejected the ruling. As of November 2023, 26 governments support the ruling, 17 issued generally positive statements noting the ruling but not calling for compliance, and eight rejected it. The governments in support are Australia, Austria, Belgium, Canada, the Czech Republic, Denmark, Finland, France, Germany, Greece, India, Ireland, Italy, Japan, the Netherlands, New Zealand, the Philippines, Poland, Portugal, Romania, Slovakia, South Korea, Spain, Sweden, the United Kingdom, and the United States; the governments in opposition are China, Montenegro, Pakistan, Russia, Sudan, Syria, Taiwan, and Vanuatu. The United Nations itself does not have a position on the legal and procedural merits of the case or on the disputed claims, and the Secretary-General expressed his hope that the continued consultations on a Code of Conduct between ASEAN and China under the framework of the Declaration of the Conduct of Parties in the South China Sea will lead to increased mutual understanding among all the parties.