The first global-scale assessment of its kind, a recent study has provided a comprehensive report on “the state of the world’s beaches”: some are stable, some are actually growing, but a significant percentage are quickly eroding – especially in the regions researchers say we should be the most concerned about.
Of the world’s 20 megacities, 15 are located along the world’s coastlines. Not only do coastal zones the world over provide ample resources for the developed cities and populations within, they offer high aesthetic value for those living along them. Nowhere is this truer than along the world’s beaches, the sandy portions of the world’s coastal regions.
The world’s sandy shorelines are worth protecting both for their economic and aesthetic value, and for the fact that they are among the highest populated regions in the world. Surprisingly, given this reality, no reliable data exists on how many beaches there are across the globe, nor – more importantly – how these sandy shorelines are changing over time.
That was until recently, when researchers from Delft University and the University of Twente in The Netherlands developed what is arguably the first comprehensive assessment of the world’s beaches, including information on the number of coastal regions that are sandy, their rates of both erosion and accumulation, as well as the impact of human activity on these rates of change.
The study, published Friday in Nature Scientific Reports, used global satellite images taken over a period of 33 years, from 1984 to 2016, in order to find the occurrence of beaches across the world’s coastlines, with the help of specialized classification software. An automated algorithm was then used to measure the rate of change of these shorelines, in metres per year, across the three decades studied.
Statistical analysis showed that, out of all the world’s (ice-free) shorelines, 31% are sandy beaches. Continent-specific data were also reported on in the study: for instance, just 22% of Europe’s coasts are sandy, compared to 66% of Africa’s. 48% of the world’s beaches were reported on as stable, and 28% were found to be accreting, or accumulating sand. However, 24% of the world’s beaches appear to be eroding at a rate of 0.5m/year. 16% of the world’s beaches are eroding at a rate of over 1m/year, and approximately 7% are undergoing “severe erosion”, ate a rate of 3 or more metres per year.
For those beaches listed under the World Database for Protected Areas, which includes both terrestrial and marine-protected areas, it was found that the majority of beaches in marine-protected areas are eroding, a data point “raising cause for serious concern”, according to the researchers involved in the study.
The researchers responsible for this assessment cite several human causes for changes to the world’s beaches. Sand mining, as well as the development of coastal structures around the world, both have a significant impact on the erosion of the world’s beaches. On the other hand, sand nourishment systems in certain parts of the world contribute to the widening of certain sandy shorelines. Climate change continues to threaten the world’s beaches, a situation expected to worsen in the future.
Towards a solution to these issues, the authors of the report express hope for advancements in both imaging technology and data analysis techniques that will allow researchers to better monitor the world’s beaches, an activity these researchers stress is vitally important going forward.
“Reliable assessments of the occurrence of sandy coasts and their rates of shoreline change are basic necessities for effective spatial planning, sustainable coastal development, coastal engineering projects, and mitigation of climate change impacts along high value coastlines around the world.”