China’s playing Monopoly in the South China Sea—only, instead of building hotels on Pacific Avenue, it’s constructing helipads and, in some cases, whole new islands.

In less than a year, shallow reefs in the Spratly Islands have sprouted white-sand outcrops, sporting what look to be Chinese military facilities, according to satellite imagery published this week by IHS Jane’s Defence Weekly, a consulting company. The Spratlys are more strategic than they are substantial; under international law, the archipelago could have exclusive claim to the bounteous fishing grounds in the surrounding seas, and to the potentially oil-rich seabed—which may explain why China and five other Asian countries claim the islands.

The new reclaimed islands are only the latest Spratly rockpiles and reefs that, since February 2014, China has willed into existence by heaping sand atop of them–to the alarm among China’s neighbors.

IHS Jane’s Defence Weekly ©CNES 2015, Distribution DS/IHS: 1570064 Airbus Defence and Space satellite imagery shows the brisk clip at which China has turned Gaven Reefs into a helipad-supporting island.

Military experts say China’s beefed-up reefs are aimed at enforcing sovereignty claims (paywall) to the waters. A US government report notes that the airstrip China recently built at the aptly named Mischief Reef would allow the People’s Liberation Army to vastly expand the reach of its air defense.

"China’s First Airstrip in the Spratly Islands Likely at Fiery Cross Reef," Ethan Meick, using Google Maps; adapted from David Shlapak, “Chinese Air Superiority in the Near Seas,” in Peter Dutton, Andrew S. Erickson, and Ryan Martinson (eds.), China’s Near Seas Combat Capabilities (China Maritime Studies, U.S. Naval War College, February 2014) Comparison of current operational distances of PLA bases with airstrips fromTaiwan versus the Spratly Islands (distances in nautical miles).

Fish, oil, and natural gas

One of the military initiatives China’s likely to undertake once it’s done building the islands is to implement an air-identification zone (a.k.a. ADIZ), says Peter Dutton, director of the China Maritime Studies Institute at the U.S. Naval War College. But China’s Spratly ambitions likely go way beyond mere military might, he adds.

“It certainly also means supporting the fishing fleet, oil and natural-gas exploration, the ability to support law enforcement and coast guard, in addition to military activities,” says Dutton. “The islands being built up in the South China Seas really do present a major problem for other claimants in the region in that regard, because China simply outclasses them in every dimension of state power needed to reinforce [its claims].”

Asia Maritime Transparency Initiative and the Center for Strategic and International Studies

Sand fight

One conspicuous element of the Spratly controversy is the timing: China’s building spree has been recent and furious. Land reclamation itself isn’t strictly illegal, says Mira Rapp Hooper, director of the Asia Maritime Transparency Initiative (AMTI) at the Center for Strategic and International Studies—in fact, Vietnam and Malaysia have reclaimed Spratly land in the past. Other claimants have also built on disputed Spratlys; until 2014, China was the only one, other than Brunei, without an airstrip.

The main reason that ”China’s current activities strike many states as especially destabilizing,” says Rapp Hooper, is “because they are taking place on six different land features, very quickly, and with the clear intent of creating artificial islands where none existed before.”

Rock, reef, or island?

That still doesn’t explain China’s sudden need to build, though. Rapp and her AMTI colleagues have a theory: in addition to building up military might, China’s also trying to stymie a legal challenge to its claimed Spratly jurisdiction that the Philippines brought in 2013.

historicair/Wikipedia, CC-BY-3.0 UNCLOS territorial jurisdictions.

To understand why, it helps to grasp an arcane yet critical piece of the UN law of the sea (UNCLOS, pronounced “un-claws”), which lays out coastal states’s rights over adjacent waters and seabed. UNCLOS grants a country jurisdiction over its “territorial waters,” which extend 12 nautical miles (22 kilometers, 14 miles) from its shores, as well as the sole right to exploit resources within an “exclusive economic zone,” (EEZ) extending another 200 nautical miles, and the right to seabed resources in the “continental shelf,” which can reach up to 350 nautical miles.

In other words, even a one-palm island can be incredibly valuable if it’s in the middle of valuable seas—and the Spratlys certainly are. This likely explains why, even though China’s nearest legal shores are hundreds of miles from the Spratlys, the archipelago forms part of the lower bound of Beijing’s notorious Nine-Dash Line, the huge sweep of the South China Seas within which China claims sovereignty.

But UNCLOS doesn’t make it quite so easy for countries to parcel up the sea in search of tuna and crude. An island must be naturally formed—and not reclaimed—land that sits above water at high tide—otherwise it gives the claimant country no right at all. Meanwhile, rocks that can’t “sustain human habitation or economic life of their own” grant their owners no more than the 12-nm territorial sea.

“Tampering with the evidence”

These rules have been little tested, though. In January 2013, the Philippines brought brought a case against China to the Permanent Court of Arbitration in The Hague, asking the tribunal to rule on whether six of the Spratlys that China is building on are indeed islands—or whether they’re rocks or reefs. The tribunal will announce sometime this year whether it has jurisdiction over the case, and if it finds it does, is expected to rule in 2016.

China has declined to participate, at least not formally. However, its out-of-the-blue land reclamation spree might still relate to the case, argues Jay Batongbacal, a director of the University of the Philippines Institute for Maritime Affairs and Law of the Sea, in an AMTI blog post. To rule, the court will need to review detailed surveys of the six Spratly maybe-islands. By obscuring what they used to look like, China’s dramatic makeover effectively “tampers with the evidence” the court needs to review to reach its decision. This wouldn’t ordinarily be such a problem. However, “accurate surveys in the South China Sea are notoriously lacking, and will prove impossible for features permanently modified by Chinese expansion,” says CSIS’s Gregory Poling on the AMTI blog, noting the court will require rigorous geological surveys, not the satellite imagery making the rounds on Twitter.

More distant ambitions?

UWC’s Dutton is less concerned about the lack of evidence; he says the US compiled solid documentation prior to the Chinese reclamation. But he brings up another potential spur driving China’s South China Seas buildup. When Taiwan holds its presidential elections in January 2016, experts say the Kuomingtang Party, which traditionally favors closer relations with China, is likely to lose to much less pro-China Democratic Progressive Party.

“If you turn the map, there’s a very interesting, almost direct axis line between the islands China’s been reclaiming in Spratlys and Taiwan and the Senkaku/Diaoyu islands,” he says. “If I were a Taiwanese security planner, that would have caught my attention.”