International action is urgently required to save the world's historic shipwrecks from the ravages of commercial fishing, experts say.
Industrial trawling, capable of destroying fragile underwater heritage, is occurring on a scale that is creating an archaeological catastrophe comparable to the looting of the National Museum in Baghdad or the destruction of the Buddhas of Bamiyan, they warn. The seabed is often described as the world's greatest museum but it is estimated that 42 per cent of the globe's three million wrecks may have been damaged by trawling.
The scale of the devastation means the chances of repeating the recovery of vessels such as the Mary Rose are decreasing, while there are fears that HMS Victory – the 1737 predecessor to Nelson's flagship – has already been damaged by trawlers in the English Channel and is at risk of total destruction.
Dr Sean Kingsley of Wreck Watch International is calling for the creation of national "red lists" for shipwrecks of major international importance similar to those created by the International Council of Museums (Icom) for cultural objects.
But he said attempts to safeguard sunken vessels, some dating back to the earliest civilisations, were being hampered by a lack of political will and a shortage of funds.
"Thousands of shipwrecks worldwide lie in the path of fishing trawlers, but governments are failing to find even small change to require the damaging effects of a multibillion-dollar industry to be monitored," Dr Kingsley said. "The struggle to save even a small percentage of the world's most important shipwrecks is a fight over funds. Compared to marine ecosystems, from kelp to sharks, archaeology cuts an isolated figure in marine science. For a hugely romantic and adventurous field we are failing to get the message across that the sunken past matters."
It is estimated that an area of seabed the size of Brazil, Congo and India is trawled each year, disrupting sediment and causing potential damage to submerged wrecks. Recent research has suggested that more than half of the North Sea is at risk from beam trawling – one of the most damaging types of fishing – while in the North Adriatic it is believed that every square metre of the seabed has been swept by trawlers three times.
Unlike offshore dredging or pipeline cutting, fishing has no legal obligation to mitigate its impact on marine archaeology.
There are no laws or even best-practice initiatives on avoiding snagging or on reporting finds in international waters. The continued presence of trawlers in archaeologically rich waters has been compared to the ploughing of ancient battle sites by farmers, but marine finds often tell archaeologists much more about what life was like than those on land.
Experts call it the "Pompeii effect", when a culture and its artefacts are freeze-framed in a moment of calamity. Organic matter can be preserved for hundreds of years under mud and sand, and large objects on the seabed are much less likely to be looted or melted down.
However Dr Kingsley said he was realistic about the problems of enforcing exclusion zones on commercial fisheries which are already struggling with catastrophic rates of species decline.
Barrie Deas, the chief executive of the National Federation of Fishermen's Organisations, said modern GPS and chart plotting technology meant fishermen were able to avoid wrecks more easily than ever before, and it was in their interests to do so because they were a danger to their gear and crew.
"Protecting shipwrecks for historical and aesthetic reasons is a concern shared in the fishing industry as well," he added.
Over the centuries fishing has been a fertile source of marine archaeology. In the 18th century, oyster dredgers off Whitstable in Kent began recovering the first of hundreds of pots later identified as belonging to a Roman vessel sunk in the mouth of the Thames. Over the past decade Dutch trawlers have recovered 50 cannon weighing up to 2.3 tonnes.
But many such artefacts end up in London antiques shops and the location of the wreck remains unknown.
Sunken treasure: historic finds
The 465kg bronze Athlit Ram, the largest ballistic weapon known from the ancient world, lost in the 2nd century BC and found in 1980 off the coast of Israel. Archaeologists saved the ram from being melted down, but the wreck of the oared warship still awaits discovery.
HMS Victory, the 1737 predecessor to Nelson's flagship, was lost with all hands in 1744 in the English Channel. Armed with 100 bronze cannon, it was found in 2008, damaged by trawlers and still at risk.
A Victorious Youth, a life-size bronze statue made in Greece between 300-100 BC and caught in a trawler's nets off eastern Italy in 1964. The wreck and its contents await discovery.
The Eendracht, a 74-gun Dutch flagship sunk in the Battle of Lowestoft in 1665. Around 20 cannon have been snagged by trawlers, but the exact wreck site is unknown.