Ancient seawall shows how ancestors tried to cope with rising seas

ATLIT, Israel (Reuters) - An ancient seawall erected thousands of years ago along the Mediterranean coast at the end of an ice age is the oldest evidence of civilization trying to defend itself against rising sea levels, a team of researchers said on Wednesday.

The 100-meter (yard) wall, built 7,000 years ago out of boulders in what is now northern Israel, was an early attempt by villagers to fend off the perils of a changing climate.

In this case it was in vain. The Neolithic village was long ago overtaken by the sea as it swelled from glacial melting at the end of the last ice age. Today the shoreline is much higher and the research was conducted under water.

All that remains of the wall are some of the boulders, brought by ancient settlers from a riverbed more than a kilometre away, lining the seabed in a pattern that would fit a coastal defence.

"The environmental changes would have been noticeable to people during the lifetime of a settlement across several centuries," said marine archaeologist Ehud Galili of the University of Haifa.

"Eventually, the accumulating yearly sea level necessitated a human response involving the construction of a coastal protection wall similar to what we’re seeing around the world now," he said.

The Israeli coast has been populated by a myriad of civilisations over the millennia, many of whose remains are now under water. Marine archaeologists have uncovered countless treasures, including shipwrecks, harbours and dwellings.

The work was conducted by researchers from the University of Haifa, Flinders University in Australia, the Israel Antiquities Authority and the Hebrew University. It was published in the journal PLOS ONE.

According to the researchers, sea levels were rising faster when the Neolithic village existed around the end of the Stone Age, up to 7 millimetres a year, than they have so far under contemporary climate change.

"This rate of sea-level rise means the frequency of destructive storms damaging the village would have risen significantly,” said Galili.

Climate experts say sea levels are rising around 3 millimetres per year now, and the rate is accelerating as global warming caused by the burning of fossil fuels causes seas to expand and ice sheets to melt.

A landmark report on oceans by the U.N.-backed Intergovernmental Panel on Climate Change found in September that sea levels could rise by one metre (3.3 feet) by 2100 - 10 times the rate in the 20th century - if greenhouse gas emissions keep climbing. The rise could exceed five metres by 2300.



(Reporting by Rami Amichay and Ari Rabinovitch in ATLIT, with additional reporting by Matthew Green in LONDON; Editing by Peter Graff/Mark Heinrich)