Scientists warn nearly 50% of beaches could vanish from coastal erosion and rising sea levels. Learn how human activity impacts biodiversity and why protection is vital.
Scientists have issued a warning that nearly half of the world’s beaches could disappear due to rising sea levels and increasing human activity. As coastal areas become more developed, beaches are being squeezed from both sides, placing immense stress on these natural environments. This threat not only endangers the wildlife that relies on sandy shores but also harms local economies that depend on fishing and tourism. Moreover, coastal communities face a heightened risk of flooding as their natural defences weaken.
Disappearing Oceans
This warning was given by Professor Omar Defeo, a marine scientist from the University of the Republic (UdelaR) in Uruguay. He shared his insights during the opening sessions of the FAPESP Day Uruguay symposium, which took place in Montevideo on November 13.
Defeo explained that what we refer to as a beach is actually a complex system composed of three interconnected zones. The dune zone is located above the high tide line, where wind moves sand to form dunes, which can resemble small hills or “sand mountains.”
The beach zone lies between the high and low tide marks, and it alternates between being dry and submerged. The submerged zone stretches from the low tide line to the point where waves begin to break. These three zones constantly exchange sand. Wind carries sand from the upper, dry parts of the beach to the water’s edge, while waves push sand back onto land. This natural process maintains the stability of the coastal system.
Dunes serve as a vital natural barrier. They act as a buffer against storm waves, reducing their impact on the land. However, when structures are built on or near the dunes, this natural protection is compromised.
Study Across 30 Beaches
Defeo and his team found that disturbing any part of the beach system has far-reaching effects. Collaborating with Brazilian scientists supported by FAPESP, they conducted a study on biodiversity at 90 sites across 30 beaches in northern São Paulo, Brazil.
Their findings, published in Marine Pollution Bulletin, revealed that crowded beaches with many visitors had the most negative impact on animal species inhabiting the sand, particularly in the submerged zones. Construction on the sand and mechanical cleaning methods also reduced the number and variety of species present.
Interestingly, they discovered that while fewer species survived in urban areas, the total number of individual animals often increased. This is because certain hardy species, such as polychaetes (a type of worm), thrive on organic waste left by humans and can dominate when other species decline.
Defeo said, “Above all, the study showed that human impacts aren’t restricted to the place where they occur [on dry sand]. Stressors such as construction and high numbers of visitors on the upper part of the beach negatively affect biodiversity in the lower and submerged areas.”
Another global study led by Defeo, published in Frontiers in Marine Science, examined 315 beaches worldwide. The results showed that about 20% are experiencing intense, extreme, or severe erosion. The researchers evaluated factors like sea level rise, changes in wind patterns, and wave behaviour. They also found that human activities worsen erosion, especially on steep-sloped beaches where waves hit the shore with more force, and on beaches that fall between steep and gentle types.
The study highlights a central message: protecting beaches is not just a local concern but a shared regional and global responsibility. Without coordinated efforts, scientists warn that many of the world’s iconic sandy shores may vanish within decades.