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Beaches can survive sea-level rises subject to space remaining for movement - Daily News Egypt

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Beaches can survive sea-level rises subject to space remaining for movement

Previous research claimed half of world's beaches could become extinct over course of 21st Century

An international team of coastal scientists has dismissed suggestions that half of the world’s beaches could become extinct over the course of the 21st century. The claim was made by European researchers in a paper published, in March 2020, in Nature Climate Change.

However, a group of academics from the UK, France, South Africa, Australia, New Zealand, and the US, have re-examined the data and methodology that underpinned the original study. As a result of the in-depth study, they say they strongly disagree with its conclusion.

They have now published a rebuttal to the article in the same journal, concluding that, with the global data and numerical methods available today, it is impossible to make such global and wide-reaching predictions.

Critically to their disagreement with the original paper’s conclusions, they say there is potential for beaches to migrate landwards as sea level rises and shorelines retreat. The key idea behind this is that, if beaches have accommodation space, or space to move into under the influence of rising sea levels, they will retain their overall shape and form but in a more landward position.

The new research says that beaches backed by hard coastal cliffs and engineering structures, such as seawalls, are indeed likely to disappear in the future, due to sea-level rise as these beaches are unable to migrate landward. They will first experience a ‘coastal squeeze’, resulting in a decrease in width, and will eventually drown.

However, beaches backed by low-lying coastal plains, shallow lagoons, salt marshes and dunes will migrate landward as a result of rising sea level. In these cases, the shoreline will retreat, but the beaches are still likely to remain, albeit a little raised in elevation and located landward. Should this happen, the findings found that the beaches will not go “extinct”.

The new paper says there is currently no information available globally on the number of beaches which fall into either category. As such, it is impossible to quantify what proportion of the world’s beaches will disappear between now and 2100.

“Climate change will exacerbate the effects of coastal erosion processes, which threatens densely populated areas,” said Michalis Vousdoukas, a researcher at the European Commission’s Joint Research Centre (JRC) and lead author of the older study. 

He said that, in the best scenarios, Egypt will lose between 35.1% and 50.5% of its sandy beaches due to erosion, meaning the erosion of about 1,000 km of Egyptian sandy beaches. The percentage is likely to be even higher in countries such as Saudi Arabia and Libya.

Vousdoukas added that the UK is expected to lose 27.7% of its sandy beaches, according to the best estimates, and 43.7% according to worst case scenarios. Australia is also expected to be the most affected, as about 15,000 km of its beaches are at risk, followed by Canada, then Chile, Mexico, China, and the US. It is also expected that more than 680 million Indian citizens living in the country’s low-lying coastal region will be affected by coastal erosion and climate change.

“The study provides first-of-their-kind forecasts regarding sand beach erosion, taking into account human interventions as well as the effects of climate change and natural factors,” said Vousdoukas.

The researcher also said that there is still a glimmer of hope, as greenhouse gas emissions can be reduced to prevent 40% of the coastline retreat. This requires, however, an international commitment to the Paris Climate Agreement and related protocols, alongside some coastal protection measures to protect populated areas.

Andrew Cooper, Professor of Coastal Studies at Ulster University and the paper’s lead author, said, “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. 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.”

Co-author Professor Gerd Masselink, from the University of Plymouth’s Coastal Processes Research Group, led a study earlier this year 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, which 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,” Masselink said, “In the UK, Coastal Change Management Areas (CCMAs) are becoming increasingly important as a planning tool.”

He added, “CCMAs are areas that are likely to be affected by coastal change in the future and development in these areas should be avoided, as this will then enable the coastline to respond naturally to sea-level rise, preventing coastal squeeze and loss of beaches.”

Coastal structures, such as seawalls, prevent beaches from naturally adjusting to rising sea levels by migrating landward and in those settings. The removal of the structures as part of managed realignment, or nature-based solutions such as beach nourishment, may be the only methods to safeguard the future of these beaches.

The older study has also been criticised by other researchers such as Jeffrey Kargel, a senior research scientist at the University of Arizona.

Kargel told Daily News Egypt that, although the methodology of the study is good and its conclusions are valid, it did not take into account some detailed changes. These changes include the sediment supply and the increase in the production and transport of sand and silt due to the increased melting glaciers.

The older study also did not take into account: increased surface runoff of corrosion and more sediment supply from expanded agricultural areas; increased sediment supply from dam construction; and reduced sediment transport due to dams in many parts of the world.

Kargel said that the melting glaciers do not directly affect Egypt, but affect places such as Greenland and Alaska, which are geographically closer to glaciers.

“Construction of dams is the most important for Egypt, due to the construction of the High Dam in Aswan, and then there will be a giant reservoir for the huge dam in Ethiopia,” he said, “When the silt is blocked by reservoirs, this will be an obstacle to the construction of the delta areas, and thus the delta will drop and seawater will submerge its coast with its cities and villages, which will represent a major problem for Egypt.”

But he also believes that the Egyptian Delta, despite the problems it faces, is “lucky” because it is not subject to hurricanes.

Topics: beaches Sea level

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