Rising sea levels, fueled by global warming, are putting immense pressure on our world’s coastlines. This leads to a phenomenon known as “coastal squeeze,” where beaches are trapped between rising seas and human-made structures like seawalls. As a result, these vital ecosystems and natural barriers are disappearing at an alarming rate, threatening coastal communities and the environment alike, and we at Unhurry®️ are committed to publishing science-backed research about it.
Sea level rise is expected to cause chronic shoreline retreat, affecting over 10% of the world’s population in low-elevation coastal zones (LECZ). Sandy beaches supported by man-made structures are more vulnerable to substantial beach area loss due to restricted landward migration, affecting ecosystem services. However, the global extent of ‘hardened’ sandy coastlines at risk of ‘severe beach loss’ has not been comprehensively quantified. Here, using products and geospatial datasets derived from satellite imagery, we find that, 33% of the world’s sandy coastline is currently hardened. Analysis of the results by IPCC AR6 regions show that the most hardened coastal regions are the Bay of Bengal, Western & Central Europe, the Mediterranean, Western North America, and East Asia. Linking coastal hardening information with existing shoreline retreat projections, we find that under SSP5-8.5, up to 26% of the world’s sandy coastline (~52,100 km) is likely to face severe beach loss by the end of the 21st century. Under a moderate emissions scenario (SSP2-4.5), this projection decreases to 21% (~42,080 km), highlighting the potential mitigation gain. The results also show that the vast majority of projected severe sandy beach losses are in high and upper-middle-income countries, with up to 82% of severe losses under SSP5-8.5 and up to 81% under SSP2-4.5 by the end of the 21st century, relative to the total length of sandy coastline, including both hardened and natural coastlines. The IPCC AR6 regions with the highest projected sandy beach losses include Eastern North America, Northern South America, the Mediterranean, the Bay of Bengal, Western Africa, and South-east Asia.
Sandy beaches are more than just a place for recreation; they are vital coastal ecosystems, natural barriers against storm surges, and a significant part of the world’s economy. However, a study published in Nature Communications reveals a stark and troubling reality: these precious coastlines are being silently eroded by an unseen hand—coastal hardening.
In their groundbreaking research, K. Nawarat, J. Reyns, M.I. Vousdoukas, and their team have used a combination of satellite imagery and geospatial datasets to provide the most comprehensive global assessment of coastal hardening to date. Their findings are a wake-up call, showing that one-third of the world’s sandy coastline is already hardened with seawalls, rock armour, and other artificial structures. This trend, they argue, is not just a localized problem but a global threat that will accelerate with rising sea levels.
The core of the problem lies in a phenomenon known as “coastal squeeze.” Sandy beaches are dynamic systems, and in a natural state, they retreat inland as sea levels rise. This natural migration allows them to maintain their existence and protective function. Coastal hardening, however, acts like a wall, preventing this natural movement. As the sea level rises and waves continue to push, the beach is squeezed against the hardened structure, eventually leading to its complete loss. It’s a tragic irony: the very structures meant to protect our coastlines are the ones causing their demise.
The study projects that this coastal squeeze will lead to a significant loss of sandy beaches worldwide. Under a high-emissions scenario (SSP5-8.5), the world could lose up to 26% of its sandy coastline—an astonishing 52,100 kilometers—by the end of the century. Even in a more moderate scenario (SSP2-4.5), the loss is still projected to be substantial, at 21% or approximately 42,080 kilometers. These figures are not just statistics; they represent the loss of habitats, tourist economies, and natural storm protection for countless communities.
The researchers also pinpointed the most vulnerable regions. Currently, the Bay of Bengal, Western and Central Europe, the Mediterranean, Western North America, and East Asia have the highest rates of coastal hardening. Looking ahead, the projected severe losses are concentrated in Eastern North America, Northern South America, the Mediterranean, the Bay of Bengal, Western Africa, and South-east Asia. Interestingly, the study found that the majority of these severe losses are projected to occur in high and upper-middle-income countries, highlighting a global issue that transcends traditional economic divides.
The above image shows the percentage of sandy coasts with human-made structures across different regions, along with the probability distribution of the distances between the shoreline and these structures. The blue box represents the 5th–95th percentile range, the red vertical line shows the median values, and the black whiskers on each side of the blue box extend to the minimum and maximum values, with all results based on data from GISA-10m and OpenStreetMap.
This research isn’t just a grim prediction; it’s a critical piece of information that should inform coastal management strategies for decades to come. It underscores the urgent need to reconsider our approach to coastal protection. Instead of relying on hard, static structures, we must explore more sustainable, nature-based solutions that work with, rather than against, the natural dynamics of our coastlines. The future of our sandy beaches depends on it.
Reference
Nawarat, K., Reyns, J., Vousdoukas, M.I. et al. Coastal hardening and what it means for the world’s sandy beaches. Nat Commun 15, 10626 (2024). https://doi.org/10.1038/s41467-024-54952-1
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