DigitalGlobe

The speed and scale of China’s island-building spree have alarmed other countries with interests in the region. China announced in June that the creation of islands — moving sediment from the seafloor to a reef — would soon be completed. Since then, China has focused its efforts on construction. So far it has constructed port facilities, military buildings and an airstrip on the islands, with recent imagery showing evidence of two more airstrips under construction. The installations bolster China’s foothold in the Spratly Islands, a disputed scattering of reefs and islands in the South China Sea more than 500 miles from the Chinese mainland.

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The new islands allow China to harness a portion of the sea for its own use that has been relatively out of reach until now. Although there are significant fisheries and possible large oil and gas reserves in the South China Sea, China’s efforts serve more to fortify its territorial claims than to help it extract natural resources, said Mira Rapp-Hooper, formerly the director of the Asia Maritime Transparency Initiative at the Center for Strategic and International Studies, a Washington research group,

Though too small to support large military units, the islands will enable sustained Chinese air and sea patrols of the area. The United States has reported spotting Chinese mobile artillery vehicles in the region, and the islands could allow China to exercise more control over fishing in the region.