Why does China want the Senkakus?

China’s claims to the Japan-held Diaoyu/Senkaku islets are commonly denounced as a product of its hyper-nationalism and restless search for resources.

There may, however, be another equally plausible reason for the growing brinkmanship in the East China Sea: shrinking oceans.

Although the two nations have roughly the same amount of coastline, Japan enjoys a total exclusive economic zone (EEZ) of 4.5 million square km in the high seas, five times more than its much bigger and more populous neighbour. And Japan’s maritime domain has vastly expanded in the last three decades.

Until very recently, the high seas were commonly owned. But since the United Nations Convention on the Law of the Sea was ratified exactly 30 years ago, 162 countries have carved up the oceans into EEZs, giving them special rights to up to 350 nautical miles (650 km) beyond their territorial waters.

Nations such as Britain, France and Japan, with residual territories from far-flung colonial empires have arguably done far better out of this arrangement than China, which ranks between the Maldives and Somalia as a territorial maritime power.

Tokyo takes these EEZs very seriously. Consider its jurisdiction of a string of islands extending into the Pacific. At the farthest reaches is Okunotorishima (literally “remote bird island”), almost 2,000km from the capital, roughly the same distance from London, England to Reykjavik, Iceland.

Essentially two coral reefs, the territory shrinks at high tide so that “one is about the size of a double bed and the other a small room,” according to a new paper by Gavan McCormack, emeritus professor at the Australian National University.

Since 1987, he says, Tokyo has invested $600 million in an attempt to shore up the reef and stop it from disappearing under the rising seas.

The rewards are clear: an EEZ attached to a fixed point on the dubiously defined “island” would give Tokyo 400,000 square kilometres and a theoretical maximum of 1.3 million square kilometres – three and a half times the total land area of Japan.

Tokyo’s nationalisation of the Diaoyus/Senkakus, about 1,900km from the capital, should be put in this context.

American and Japanese military plans for the region (the US intends to concentrate 60 percent of its navy in the Pacific by 2020) increases the strategic importance of the islets, which are administratively part of the Okinawa chain, host to the heaviest concentration of US military forces in Japan.

Says McCormack: “From the Chinese viewpoint the Okinawan islands resemble nothing so much as a giant maritime Great Wall … potentially blocking naval access to the Pacific Ocean.”

Put like that, this seemingly unintelligible spat in the East China Sea begins to make more sense.