The leaders of Southeast Asian nations recently took the extraordinary step of warning China that its island-building activities in the contested South China Sea “may undermine peace, security and stability” in the region.

That’s strong language from the usually reticent 10-member Association of Southeast Asian Nations, and shows just how high tempers are flaring over what has been called China’s “great wall of sand” in a strategically important area.

The commander of the US Pacific Fleet, Admiral Harry Harris, has described China’s island enhancement programme as part of a “pattern of provocative actions” towards smaller South China Sea states.

But island-building in regions like the Spratly Islands plays well to China’s nationalistic domestic audience and also appears to be aimed at reinforcing China’s territorial and maritime claims in a potentially resource-rich area. Such activities could, however, have dire consequences for the region’s marine environment and vital fisheries.

Ensuring stability and maritime security in this area is crucial to Australian and global interests. An estimated 60% of Australian trade passes through the South China Sea, with US$5 trillion in trade overall flowing through the region.

An island of one’s own

The Spratly Islands, located in the southern part of the South China Sea, are claimed in whole or in part by China, Taiwan, the Philippines, Malaysia, Brunei and Vietnam.

The Spratly Islands comprise over 120 islands, islets, rocks and reefs scattered over 240,000 square kilometres of maritime space.

These are insignificant fly specks on the map – but they are close to vital sea lanes. They also potentially give rise to broad maritime claims, within which valuable resources exist.

Around 10% of the global fishing catch is estimated to come from the South China Sea, making access to its waters critical to regional food security. There has also long been speculation concerning potential oil and gas resources underlying disputed waters – but that’s uncertain precisely because of the existence of the competing claims.

The nations fighting over the Spratly Islands care deeply about territory, no matter how tiny and seemingly intrinsically worthless. Safeguarding sovereignty claims therefore helps to underpin and legitimise the governments concerned.

China is something of a latecomer to the island occupation game. Taiwan is the most longstanding occupant of an island among the Spratly Islands group, having occupied the largest of the Spratly Islands, Itu Aba (all of 1.4km long and 370m wide), since 1956. The Philippines, Malaysia and Vietnam all occupied features in the 1960s and 1970s. China did not really get in on the act until 1980s.

As a result, China was left with the smaller, more tenuous features to occupy, often comprising extremely low elevation or at least partially submerged features. Of the eight features occupied by China in the Spratly Islands, five of them are no more than low-tide elevations (that is, features submerged at high tide but exposed at low tide). These do not even qualify for the definition of “island” under international law. The remainder are arguably mere rocks.

So building up and expanding these tiny features is an attractive option in order to add substance (literally) to China’s physical presence among the disputed islands of the South China Sea.

An island in the eyes of the law?

Can you build your own island? Certainly! But it won’t be the same as a “normal” island – not in the eyes of international law, anyway.

The United Nations Convention on the Law of the Sea, to which China and all of the South China Sea claimant states are party, draws a sharp distinction between naturally formed and artificial islands.

UNCLOS is explicit in stating that man-made structures do not possess the status of islands, have no territorial waters of their own and their presence does not impact on the delimitation of maritime boundaries.

While land reclamation may indeed be possible around features that already qualify as islands, simply building up a feature so that it is elevated above the high tide mark will not transform it into a “real” island.

China has painted its reclamation efforts as being of benefit to the region. For example, it has suggested that its newly reclaimed land will enhance China’s maritime search and rescue capabilities in an area prone to typhoons.

Beijing has assured the US that its reclamation efforts will not threaten freedom of navigation and overflight in the South China Sea. And it has suggested that other countries, including the US, might be able to use its new facilities “when conditions are ripe”. The other claimant states are unlikely to take up this offer, since to do so would imply that they recognise China’s right to build such facilities and thus its sovereignty claims.

More ominously, Chinese Foreign Ministry spokesperson Hua Chunying has said that while certain other countries were keeping silent regarding their own island construction activities, they “point the finger at China’s normal activities on its own territory”, something that was “an out-and-out double standard”.

It’s true that other claimant states have undertaken their own reclamation efforts on islands they occupy among the Spratlys, but what is distinctive about the Chinese activities is their scale and pace.

The US Pacific Fleet’s commander Admiral Harris has said that China had “created over four square kilometres of artificial landmass”. To put that in context, the combined total land area of the largest dozen Spratly Islands has previously been estimated to be less than half this area.

More conflict ahead

The sovereignty dispute over the Spratly Islands shows little sign of resolution, with the present furore just the latest in a string of incidents among the claimants.

While China is correct to point out that it is, essentially, only doing what others have done before, that is hardly a compelling justification.

In 2002 China and the other Spratly Islands claimants agreed to a Declaration on the Conduct of Parties in the South China Sea, which included an undertaking that they exercise self-restraint. But despite that, it seems China and other states are continuing their efforts to shore up power in this strategically important zone.

Finally, despite assurances from the Chinese that their land reclamation activities followed a “high standard of environmental protection", it is difficult to reconcile this with depositing tonnes of dredged sand on top of coral reef systems.

This is especially the case when these reefs are crucial to sustaining the viability of the fisheries of the South China Sea which, in turn, provide the primary protein intake for hundreds of millions of people around its shores.

Unfortunately, it seems that this great wall of sand is unlikely to wash away anytime soon.

This article was originally published on The Conversation.