The Birling Gap has suffered years-worth of erosion and damage in just a few weeks as a result of the wild winter storms, the National Trust has said.
The high winds and waves that repeatedly battered the UK in a series of storms have left cliffs crumbling, beaches and sand dunes eroded, defences breached, and shorelines and harbours damaged.
At Birling Gap which marks the start of the white chalk cliffs of the Seven Sisters, and has a cafe, car park, hotel and cottages, the speed of erosion has been "breathtaking", according to Jane Cecil, National Trust general manager for the South Downs.
"We've had about seven years of erosion in just two months. As a result of this loss of coastline, we are having to act now and take down the sun lounge and ice cream parlour, safeguarding the integrity of the rest of the building. We have to think long term," she said.
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The National Trust owns more than 740 miles of coastline around England, Wales and Northern Ireland, around a 10th of the total coastline for the three countries.
Peter Nixon, director of land, landscape and nature at the National Trust, said what was happening at the organisation's sites was "a very good canary of what is happening in the broader environment and the absolute imperative we understand what our changing climate means to us".
He said the recent extremes had been surprising, but were to be expected with a changing climate, and while huge storms had caused years-worth of damage in one go in the past, their frequency seemed to be increasing as well as their intensity.
"We're expecting more extremes, less predictability, more stormy events, combined with an underlying issue of rising sea levels," he said, adding that sea levels were rising because the south of England was sinking and the ocean was expanding as a result of warming temperatures.
He warned against falling into the trap of believing "we can engineer our way out of this", which in the majority of cases he said he did not think was true.
The National Trust did not rule out the use of hard sea defences, but he said there was a need to be aware of the impact they could have on the coast, the difficulty of maintaining them in the long term in the face of the forces of nature working against them, and what happened if they failed.
"We all have to be sensitive to those who have become dependent on artificial defences, but if you keep up defending, you build up the risk of a catastrophic event.
"A false sense of security in artificial defences can lead you to a catastrophic collapse, as opposed to a managed impact."
He added: "You can't hold the line everywhere, it's physically impossible and it's not good for society."
Mr Nixon said not enough funding or focus was going towards long-term planning to help coastal communities adapt to potential changes to the coastline, and said government, local authorities and organisations needed to help people whose lives and businesses were dependent on engineered defences to adjust to what was happening around them.
The National Trust has a role to play in increasing understanding of how nature is changing the coasts, and to demonstrate how those changes could be managed.
He pointed to places where "soft defences" such as coastal marshes were taking out the power of storm surges and preventing flooding inland.
And he said that people who might be shocked at the changes they saw the next time they visited one of their well-loved coastal sites should see the alterations as a process of natural change.
"If you would have come here 30 years prior it would have been different, but we need to expect a greater rate of change," he said.