Beaches with space to migrate will survive rising sea levels
In March, researchers reported in the journal Nature Climate Change that half of the world’s beaches could vanish by the end of this century. But now, an international team of scientists led by the University of Plymouth has published a counter-argument in the same journal, explaining that there is potential for beaches to migrate landwards as sea level rises and shorelines retreat.
After re-examining the data, the experts say they strongly disagree with the initial conclusion that many beaches will simply disappear under the threat of sea level rise and erosion. The researchers argue that if beaches have space to move, or “accommodation space,” they will retain their overall shape and form but in a more landward position as sea levels rise.
The study authors acknowledge that beaches backed by coastal cliffs and structures such as seawalls are, in fact, likely to disappear due to future sea-level rise because they are unable to migrate landward. First, they will experience a “coastal squeeze” and lose much of their width, and will eventually drown.
On the other hand, beaches that are backed by low-lying coastal plains, sand dunes, or shallow lagoons will migrate landward as the sea level rises. The shoreline will retreat, and the beaches may be a bit raised in elevation, but they will not vanish.
The researchers point out that there is currently no information available globally on the number of beaches that fall into either category, which makes it impossible to quantify what proportion of the world’s beaches will disappear between now and 2100.
“New methods are needed for predicting impacts of sea-level rise on the coast. This will require better datasets of coastal morphology and improved understanding of the mechanisms of shoreline response in given settings,” said study lead author Professor Andrew Cooper.
“As sea level rises, shoreline retreat must, and will, happen but beaches will survive. The biggest threat to the continued existence of beaches is coastal defence structures that limit their ability to migrate.”
Earlier this year, study co-author Professor Gerd Masselink led a research group which found that island “drowning” is not inevitable as sea levels rise.
“Sea level is currently rising and will continue to rise at an increasing rate for many years to come. This will lead to more coastal erosion and it is crucial that we anticipate the future loss of land and take this into account in coastal management and planning to avoid putting more buildings and coastal infrastructure in harm’s way,” said Professor Masselink.
“In the UK, Coastal Change Management Areas (CCMAs) are becoming increasingly important as a planning tool. CCMAs are areas that are likely to be affected by coastal change in the future and development in these areas should be avoided. This will then enable the coastline to respond naturally to sea-level rise, preventing coastal squeeze and loss of beaches.”
Beaches that have coastal structures such as seawalls will be prevented from naturally adjusting to rising sea levels and migrating landward. To safeguard the future of these beaches, removal of the structures or nature-based solutions may be the only solutions.
The research is published in the journal Nature Climate Change.