The South China Sea is one of the most highly contested and stressed marine regions on Earth. Surrounded by nine nations (with more than 270 million people along its coasts), the South China Sea is a nearly enclosed marginal and tropical sea. It is bounded in the west by mainland Asia—principally China, Vietnam, and Malaysia—and in the east by islands: Taiwan, the Philippines, and Borneo.
Nearly half its seabed is continental shelf in water depths less than 650 feet; a single deep basin with several depths to more than 16,400 feet makes up only 16 percent of the South China Sea. The Taiwan and Luzon Straits in the northeast link the South China Sea to deeper Pacific waters; shallow basin waters in the south link with water masses from the Indian Ocean through the Strait of Malacca. Overall, the South China Sea performs key roles in water mass exchanges between the Indian and Pacific Oceans, with regional climate implications.
The Pearl River, China’s third-longest and second-largest river by volume of water, empties into the northwest corner of the South China Sea just south of Hong Kong. This large freshwater inflow has significant influences on the regional oceanography and contributes to considerable pollution in coastal waters drawn from the Pearl River’s huge watershed in southern China.
The oceanographic data record (some physical observations date back to 1919), indicates the South China Sea surface waters circulate in a cyclonic direction in winter, but reverse for a largely anticyclonic motion in summer—the result of seasonal, reversing monsoon winds. The South China Sea experiences severe, occasionally extreme, storms and typhoons and very dynamic oceanographic and atmospheric conditions. All ship operations in the South China Sea—fishing, offshore drilling, naval missions, and large commercial ship transits—are challenging, and mariners experience a highly variable and sometimes hostile marine environment.
The legal and governance issues of the South China Sea are complex and contentious. China’s nine-dash-line claim, and the other maritime states declaring their overlapping 200-nautical-mile exclusive economic zones under the U.N. Convention on the Law of the Sea, tend to dominate Asian and global dialogues. However, any review of current marine uses and future resource potential indicates that the South China Sea is globally important. It is home to one of the world’s largest fisheries, although it is under great threat from overfishing, pollution, and warming coastal waters. This fishery remains critical to regional food security.
The South China Sea is one of the world’s busiest waterways for global trade, with ships carrying an estimated 30 percent of global crude oil consumed and one third of shipping cargoes passing through it every year. Furthermore, its seabed is believed to hold huge oil and gas reserves, although what value they will have in the future is debatable in an era of global energy adaptation and efforts to reduce hydrocarbon use.
Profound environmental change is coming to the South China Sea. Warming waters and ocean acidification are already affecting the region’s marine ecosystem and its fishery. Coral reefs are exhibiting the stresses associated with warmer waters, and marine biodiversity is being compromised by coastal pollution and climate change stressors. Future sea level rise will inundate most of the small islands and reefs within the South China Sea and will have immense effects on coastal infrastructure around the basin, including major port cities. Recent research has revealed an increase in the strength of tropical storms (forced in part by warmer surface waters), which does not bode well for this marginal sea. All is not dire, but the challenges are many, and close cooperation among the nine surrounding nations will be crucial—not the norm for this highly contested marine space.
The South China Sea undoubtedly will remain a globally important coastal sea and international waterway. However, complex and rapid environmental changes will surely reshape and perhaps limit its resource potential and capacity to support a growing regional population.