Worldwide, more than 200 million people and counting live along coastlines that are less than five metres above sea level.
In 2014, the global sea level was 66 millimetres above the 1993 average, and continues to rise at a rate of about 3mm a year, driven not only by the melting ice caps, but because water expands as it warms.
But the old notion of building ever stronger defences is not the answer, Prof Robert Brown from Plymouth University’s School of Architecture says. Sea walls merely push the problem elsewhere.
If a sea wall fails, the cost can be high. And – as some residents of Dawlish in South Devon have complained – a sea wall cuts you off from the sea view, which is why you went to the coast in the first place.