March 2, 2020

expert reaction to sea level rise and beaches

A study, published in the journal Nature Climate Change, reports on the impact of climate change on the worlds sandy beaches.

Prof Mark Bateman, Professor in Palaeoenvironmental Reconstruction at the University of Sheffield, said:

“This paper focusses on a very hot topic concerning human induced sea-level rises and their potential impacts on coastlines. Two key novelties to the work are the fact that it takes a global perspective under different future climate scenarios and secondly that it focusses on sandy coastlines. The latter fits in with the wider the global sand crisis with over-exploitations of sand particularly in rivers in Asia causing significant environmental impacts. Sandy coastlines are particularly vulnerable to changes in sea-level as they will respond much quicker (in years or decades) than cliffed or rocky coastlines which might take hundreds or thousands of years to respond.

“Closer to home the UK already has some of the fastest eroding coastlines in the world (East Yorkshire and Norfolk coastlines). This work indicates whilst the UK will not be the worst affected (Australia) this process will speed up unless significant adaptive measures are put in place to mitigate against this. Given the importance of beaches for tourism, on-shore-off-shore infrastructural links, transport this new research has profound implications for future coastal planning.”

Dr Jennifer Brown, Marine Physics and Ocean Climate Group at the National Oceanography Centre, said:

“The authors highlight the important role beaches have in acting as a buffer between coastal populations and stormy seas. They demonstrate how future projections of changing beach volume will be critical for the development of coastal climate resilience and adaptation strategies. However, it is not only the loss of natural systems and shoreline retreat that is of concern, but also the impact of beaches becoming lower in front of sea walls. In the UK, beach-lowering increases the hazard from violent wave plumes transporting water and debris over a sea defence built to protect the population and infrastructure behind it.”  

Dr Suzana Ilic, Senior Lecturer at the Lancaster Environment Centre, Lancaster University, said:

“This new research shows that about 30% and 60% of low lying areas fronted by sandy beaches will be seriously threatened by erosion, due to climate change under the high emission of greenhouse gases by the middle and the end of the 21^st century respectively.

“This alarming prediction follows the 2019 IPCC report highlighting the acceleration of sea level rise, leading to an urgent requirement for implementing adaptive measures along sandy coastlines.

“It is encouraging to see that reducing emissions from a high to moderate level will result in a reduction of the projected shoreline retreat of 22% by 2050 and 40% by 2100.

“While some parts of sandy coastlines will grow, many countries will have 80% of their sandy coastlines affected by erosion. The latter countries where sandy beaches are important tourist attractions will face the major negative socio-economic impacts. Countries like Australia and the USA have a large proportion of sandy beaches and will see large changes.

“Sea level rise makes the largest contribution to the shoreline retreat on sandy coastlines, though in areas like the south-east coast of the UK, the contribution to shoreline change from storms is also significant.

“The authors addressed a number of the limitations of these predictions related to data availability, the methods used, the availability of computational resources, the spatial and temporal scales considered and the assumptions made in addressing contributions to the shoreline retreat by ambient changes, sea level rise and storms independently. All of these increase the uncertainties in the projected shoreline retreat. In addressing the computation of future shoreline changes in a probabilistic fashion, the authors accounted for some of the uncertainties but further data and improvements in methodology and assumptions are needed to reduce the uncertainties. 

“While this study is a good basis for future regional and local assessment of the shoreline change due to climate change, the downscaling will involve further challenges.  I would like to stress the following:

“The study demonstrates the value of the Earth Observation (EO) data; the 32 year-long dataset of Landsat satellite images were used to obtain trends in the ambient shoreline change; altimeter data provided by six satellites (ENVISAT and others) were used for the assessment of the predicted wave fields; also other global datasets were used for input of parameters needed for simulations. Without those resources, it would be impossible to conduct a study at a global scale.

“It is envisaged that with increasing availability of the EO data at higher spatial and temporal resolution and with the contribution of Data Science methods for computing and analysis, more accurate predictions at more detailed spatial regional and local scales will be possible.”

Prof Jeffrey Kargel, Senior Scientist, Planetary Research Institute, Tucson, Arizona, said:

“The study’s linkage of global coastal degradation to combustion is a landmark advance. However, the study has not incorporated an assessment of changes in sediment supply to coastal regions. Whereas the authors note that damming is reducing sediment supply in some regions, there are places where increased glacier melting is drastically increasing the supply of sand and other sediment to deltas and barrier islands and other coastal landforms. Alaska and Greenland are by far the two biggest regions where there are rapid increases in the sediment budget due to recent climate change, and this sediment supply will continue to increase. The Himalaya probably also are producing much more sediment as glaciers waste, but that sediment mostly is being trapped in reservoirs. Therefore, much new Himalayan sediment is not reaching the coasts, and consequently the deltas are subsiding, and as the paper shows, coastal erosion of the Indus and Ganges delta areas of South Asia is expected to be extremely rapid. Mitigation of the influence of reservoirs can only happen by allowing more sediment to be transported out of the reservoirs. 

“In the UK, the sediment supply by Pleistocene glaciers and the roles of glacial and postglacial changes in sea level are well known as having affected the coasts, including sandy dunes and barriers. Now a new cycle of increasing sea level is hitting. The erosion of the East Riding coastline is a particularly interesting study, by Sue Boyes and colleagues, with many villages having been lost to the sea since Roman times. That study also points the way to further erosion of the coast in that region. 

“This new study considers climate change effects on storms in addition to sea level and more local erosional influences and concludes that the possible increased storminess is not a dominating influence on coastal erosion, but sea level rise is. However, much has been learned in recent years about connections between climate change and hurricane intensity, and also the phenomenon of more numerous and more intense bomb cyclones spilling out of the Arctic into the North Atlantic. This winter’s repeated bomb cyclone impacts on the North Atlantic, including the UK, are perhaps a warning that climate change comes with increased extreme weather, and this will no doubt affect sandy coasts in the UK and around the world, even if sea level rise dominates coastal change.”

Prof Andrew Shepherd, Director of the Centre for Polar Observation and Modelling, University of Leeds, said:

“Between a quarter and a half of the UK’s sandy beaches will retreat by more than a hundred metres over the next century, depending on how rapidly the polar ice sheets melt. Unfortunately, ice losses from Antarctica and Greenland are both tracking the worst-case climate warming scenario, and so we should prepare for dramatic changes to our coastal landscape.”

Dr Sally Brown, Deputy Head of Life and Environmental Sciences at Bournemouth University, said:

“Much of the world’s coast is already eroding, which could get worse with sea-level rise. Building defences helps maintain coastline position, but defences are known to reduce beach width or depth over multiple decades. Responding to sea-level rise means looking strategically at how and where we defend coasts today, which may mean protecting only limiting parts of the coast. In the UK, where there are defences, beaches may already be lowering and thinning, which can increase risk. Beach nourishment schemes can help the problem, such as in Bournemouth, but these beaches need a regular top-up. Ultimately, we cannot nourish everywhere for ever, meaning that hard decisions need to be made about how much to spend and how to manage the coast in decades to come. This could affect those living on the coast, and tourists who enjoy the sandy beaches too. Sea-level rise will only make this situation worse.”

‘Sandy coastlines under threat of erosion’ by Michalis Vousdoukas et al. was published in Nature Climate Change at 4pm UK TIME on Monday 2 March 2020.

DOI: 10.1038/s41558-020-0697-0

Declared interests

Kargel: I have no conflicts of interest regarding this story. 

Brown: Nothing to declare

Ilic: There is no conflict of interest.

No others received.