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An international team of coastal scientists has rejected suggestions that half of the world’s beaches could go extinct over the course of the 21st century and that Australia was one of the highest-risk countries with 40% of its beaches threatened with extinction.
The claim was made by researchers led by the European Commission Michalis Vousdoukas, of the Joint Research Commission, in a paper entitled “Sandy coasts threatened with erosion” published in Nature climate change in March 2020. However, academics from Australia, the UK, France, South Africa, New Zealand, and the US reviewed the data and methodology behind the original study and say they strongly disagree with its conclusion.
They have now published a rebuttal to the article in the same journal and concluded that with the global data and numerical methods available today, it is impossible to make such comprehensive and far-reaching predictions.
Crucial to their disagreement with the original document’s conclusions is the fact that they argue that there is the potential for beaches to migrate to land as sea levels rise and coasts recede.
The key notion behind this is that if beaches have room to move to under the influence of sea level rise – referred to as accommodation space – they will retain their overall shape and form but in a more landward position.
The new research says beaches backed by hard coastal cliffs and engineering structures, such as dikes, are likely to disappear in the future due to rising sea levels because these beaches are unable to migrate to land. They will first experience “coastal compression” resulting in a decrease in width and eventually drown. This will happen on beaches like Collaroy in Sydney and Wamberal on the Central Coast, NSW, Australia.
However, beaches backed by low coastal plains, shallow lagoons, salt flats and dunes, as is the case with most Australian beaches, will migrate to land due to rising sea levels. In these cases, the shoreline will recede, but it is still likely that they will remain, albeit somewhat raised in elevation and located towards the land, and will certainly not be “extinct”.
Co-author Honorary Professor Andrew Short of the School of Geosciences at the University of SydneyThe Faculty of Science, which has studied all 12,000 Australian beaches, said: “I found no evidence of widespread erosion, let alone accelerated erosion of Australian beaches.
“Since most have ‘room to move’, the vast majority should be able to slowly adapt and adapt to sea level rise, certainly up to 2100 and beyond.”
Coastal structures such as dikes prevent beaches from naturally adapting to sea level rise by migrating to land, and in such contexts, removal of structures (managed realignment) or nature-based solutions (e.g. sand replenishment) they may be the only ways to safeguard the future of these beaches. This is the case with Australian beaches such as Collaroy and Wamberal.
While beaches may not be commonly threatened in Australia, the same cannot be said for coastal homes.
‘In NSW, the hazard lines have been mapped for 2020, 2050 and 2100 on all beaches, so we know what to expect during extreme storm events with sea level rise,’ added Professor Short.
“These are reviewed every five years as more data becomes available and reviewed by the state government.”
Andrew Cooper, a professor of coastal studies at Ulster University and lead author of the new paper, said new methods are needed to predict the impacts of sea level rise on the coast.
“This will require better coastal morphology datasets and a better understanding of shoreline response mechanisms in certain settings,” he said.
“As the sea level rises, the retreat of the coast must and will happen, but the beaches will survive. The biggest threat to their existence is the coastal defense structures that limit their ability to migrate. “
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