The machair – fertile low-lying grassy plains found on the Atlantic coastlines of Ireland and Scotland, particularly the Outer Hebrides – will be among the environments under threat according to new research into melting ice sheets and glaciers.
Scientists from the British Antarctic Survey and Bristol University, who are collaborating on the European Ice2sea programme, said there were still some uncertainties over melting processes, but predicted there is just a 5% chance of ice melt contributing more than 33in of sea level rise up to 2100.
Once other factors are taken into account, such as the increase in volume of the oceans as they warm, the best guess for overall rise in sea levels globally could be from 2.4in up to 27in, the researchers said.
Professor David Vaughan, of the British Antarctic Survey, who is co-ordinating the programme, said: "Today, as the glaciers and ice sheets lose their ice, the water they once held has melted and flowed in to rivers and seas, increasing their volume and raising global sea levels.
"Current rates of sea level rise are already having impacts on the most vulnerable communities and ecosystems.
"It is likely some future ice loss and sea level rise is now unavoidable. But nevertheless, understanding why changes are occurring today and how they could increase in the future is the first step in maintaining the security of our coastal regions for future generations."
The last global review of climate science published in 2007 by the Intergovernmental Panel on Climate Change (IPCC) estimated sea levels could rise 7in to 23in by 2100, but there were gaps in the scientific knowledge.
The research by the Ice2sea team is based on "medium" projections for greenhouse gas emissions which the world is outstripping, and the researchers suggested an even warmer climate would lead to higher sea level rises and bigger storm surges.
And they said rises in sea levels would not stop after 2100, with increases between 2100 and 2200 likely to be much greater than during the 21st century.
Sea level rise will vary from region to region, with the Pacific, where there are many low-lying islands, expected to experience the greatest increases and European coastlines likely to see a sea level rise of less than the global average.
However, this will still have an impact on coastal areas such as the Thames Estuary, where the Thames Barrier provides protection to London from storm surges so high they would only be expected once in a thousand years.
If the sea level in the estuary was to rise by 20in, without action being taken to provide further flood protection, the barrier could be expected to be overtopped by a storm once every 150 years.
If sea levels rose by 40in, the barrier could be breached every 12 years, said the report by the Ice2sea programme, made up of experts from 24 leading institutions in Europe and beyond.
The Environment Agency has developed a plan to adapt flood defences to maintain protection to London.