About 24 per cent of sandy beaches worldwide are eroding, while 27 per cent are growing, showed the findings published in the journal Scientific Reports.
The view from space provided researchers with a more accurate picture of just how much of Earth's shorelines are beaches.
They found that about a third (31 per cent) of all ice-free shorelines are sandy or gravelly and Africa has the highest proportion of sandy beaches (66 per cent) and Europe has the lowest (22 per cent).
The results showed that beaches in Australia and Africa are experiencing more erosion than growth, a process scientists call accretion.
The opposite is true for all other continents. Asia is experiencing the highest rate of overall accretion, the team discovered.
This is most likely due to artificial coastline development in China and land reclamation, or draining land and making it suitable for human use, in places such as Hong Kong and Singapore, according to the authors.
"At this point we think the continental differences in beach erosion and accretion are largely influenced by human interventions along the coast," said Arjen Luijendijk, a coastal development expert at Deltares, an independent research institute studying deltas, river basins and coasts in the Netherlands.
The team of scientists and engineers from the Netherlands used Machine Learning (ML) to "teach" their classification software to accurately identify sandy beaches from images taken by Landsat satellites from NASA and the US Geological Survey.
This allowed them to quickly and automatically examine 30 years of data and determine how many of Earth's beaches are sandy instead of rocky or icy, and how those sandy beaches are changing with time.
In the past, answering these questions required years of expensive, labour-intensive research, and the results of previous attempts to measure Earth's beaches varied widely.
"It only took about two months' calculation time to generate this data set of annual shorelines between 1984 and 2016 for the entire world," Luijendijk said.
"The alternative of taking aerial images, placing the images in world coordinates, and sometimes manually detecting shorelines, takes weeks or months to capture a coast longer than 50 miles," Luijendijk added.
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