Mark Spalding, president of The Ocean Foundation, has said that underwater cultural heritage such as shipwrecks are a potential environmental “time bomb”, due to the vast oil deposits many of them hold.

Writing in National Geographic, Spalding said that shipwrecks from World War II account for 75 per cent of oil leakages on the seabed while the 140 million barrels of oil sitting on the ocean floor inside shipwrecks could potentially create a “catastrophic” spill.

Wrecks experiencing metal fatigue are the main cause for concern, according to Spalding, who blamed corrosion, storm damage, harm from dynamite fishing, damage from anchors and bottom trawling gear, earthquakes, looting and intrusive exploration from archeologists and tourist divers as the lead causes of the issue.

World War II alone produced around 7,800 wrecks that are cause for concern, though the sites are popular attractions for tourist divers and researchers.

International treaties on underwater cultural heritage mean nations must work together where appropriate to protect each underwater cultural heritage site. There is, however, a grey area as to who is responsible from a legal and financial perspective.

Maritime law says that the flag of the vessel sunk, particularly for military vessels, gives sovereignty for that flag country over the vessel, meaning the shipwreck has sovereign immunity, preventing other nations from claiming jurisdiction over it. The issue that arises is the question of whether that immunity is extended to environmental harm from leaks and whether or not it is the obligation of the origin country to operate a clean up before a leak occurs.

“Our work to protect and manage underwater cultural heritage should always avoid harm to natural resources on the wreck, or anywhere in the countries where the wrecks are situated,” said Spalding.

“What will it take to produce the political will to be proactive and mitigate the risk of leaks and spills before it creates substantial environmental and socioeconomic damages for the countries in which these wrecks exist?

“We want those who are concerned with protection of underwater cultural heritage to also be concerned about potential environmental harm from leaking shipwrecks. In the same breath, we need those who are concerned about environmental conservation to understand that protection of cultural heritage is as important to many people as well.”