Why wartime wrecks are slicking time bombs

New Scientist
September 1, 2010
By Mick Hamer

Thousands of ships sunk in the second world war are seeping oil – and with their rusty tanks disintegrating, “peak leak” is only a few years away

THE battle for Guadalcanal was one of the pivotal moments of the second world war. The Japanese occupied Guadalcanal, the largest of the Solomon Islands, in August 1942. When the Americans landed a few months later, the Japanese set out to reinforce their troops by sea. The struggle for naval supremacy that followed was confused and bloody, but by February 1943 the battle was over and the Japanese had evacuated their remaining troops.

The battle has a hidden legacy, however. Before the war, the stretch of water north of Guadalcanal was called Sealark Sound. Now it is known as Iron Bottom Sound, because of the number of wrecked ships there. One of these is the 6800-tonne Japanese freighter Hirokawa Maru, lying stranded off what would otherwise be an idyllic, palm-fringed Pacific island beach. Every now and then the ship leaks oil, threatening coral reefs, marine life and subsistence fishing.

Compared with the spill from BP’s Deepwater Horizon field in the Gulf of Mexico, the oil from the Hirokawa Maru is a drop in the ocean. But this is not an isolated case of one ship blackening the shores of one Pacific island. The second world war saw the greatest-ever loss of shipping: more than three-quarters of the oil-containing wrecks around the globe date from the six years of this war. Sunken merchant ships are scattered around trade routes, the victims of attack by U-boats and other craft aiming to disrupt enemy nations’ supply lines (see map). Then there are the naval ships sunk during great engagements such as the attack on Pearl Harbor and the battle of Chuuk Lagoon, the Japanese base in the Pacific where the US sank over 50 Japanese ships. In some locations these hulks are already leaking oil, threatening pristine shorelines, popular beaches and breeding grounds for fish. This year, for example, oil has begun to leak from the Darkdale, a British naval tanker that sank in 1941 near the island of St Helena in the south Atlantic Ocean. It was carrying more than 4000 tonnes of oil when it went down.

So how long have we got before there is a sharp increase in leakage from this lost fleet, and how big a problem could it be? What, if anything, can we do about it – and who will foot the bill?

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