Every year, around June, Karachi's beaches become crowded not just with people but also with hundreds of thousands of seashells spread across the shore in dense, clattering drifts. This year was no exception, sparking online and offline debate about the cause—climate change or a natural spectacle. The science and local fishermen tell a more layered story.
A Prelude to the Monsoon
The phenomenon is not new. A Dawn report dated July 17, 2009, noted large numbers of white and yellow seashells appearing on Clifton Beach overnight. Another Dawn report, dated May 21, 2016, explained that wave action dislodges shellfish, particularly Venus clams (locally known as 'burgar'), from shallow sub-tidal habitats, carrying them onto beaches where they die and leave behind empty shells. The same event was covered by The Express Tribune on May 22, 2016. Both reports linked the phenomenon to the arrival of the monsoon. An Aaj News report dated July 10, 2024, noted that marine experts continue to identify June and July as the recurring seasonal window, though rising pollution levels may contribute to higher marine mortality, leading to larger shell volumes in some years.
Majeed Motani, president of the Pakistan Fisherfolk Forum, with decades of fishing experience, confirmed that the phenomenon is locally known as 'aokar'. Similar seashells appear along several coastal areas, including Ibrahim Hyderi and other Karachi beaches. 'We have been witnessing this phenomenon for decades, particularly during June and July,' he said, explaining that water from deeper parts of the sea rises to the surface and pushes seashells toward the shore, depositing them along the coastline.
What Science Says
Scientific research on the Arabian Sea provides a clearer explanation. When the southwest monsoon arrives around June, strong winds push warm surface water away from the shore, drawing cold water up from the ocean's depths—a process known as upwelling. A study published in the Journal of Sea Research explains that this cold, deep water contains very little oxygen, and when it spreads across the seafloor, it proves fatal for bottom-dwelling creatures such as clams and other shellfish that cannot move quickly enough to escape. Their empty shells are then carried onto beaches by powerful monsoon waves.
A separate paper on the Arabian Sea shelf, published in Deep-Sea Research, found that cold, oxygen-depleted water begins appearing off Karachi as early as June and persists through November—precisely the months when citizens observe the highest concentrations of shells along the coast. Another study stated that the monsoon season coincides with the period when the largest number of marine invertebrates are present in coastal waters near Karachi. In short, shellfish populations are at their peak near the shore just as the harshest ocean conditions arrive, explaining why beaches receive so many shells.
The Anomaly
However, 2026 may be different in at least one respect. Motani told iVerify Pakistan that the number of seashells this year appears higher than usual. Fatima Yamin, a climate change and disaster management expert, highlighted that the Indian National Centre for Ocean Information Services issued a Marine Heatwave Advisory in April, confirming that parts of the Arabian Sea—including coasts of India, Pakistan, and Bangladesh extending towards Oman—are under high alert due to an increase in sea surface temperature anomaly. 'It is yet to be seen if it affects deep waters, but it would impact the continental shelf. This correlates with the accounts of fishermen who have not seen such a large number of marine shell life washed onshore before. Warmer temperatures in the sea surface can also change the oxygen levels, causing marine life to die in water and can cause marine mammals to rise to the surface for oxygen,' she added.
What Happens to the Shells?
Meanwhile, the shells themselves do not go to waste. According to Motani, some people—mostly families living near the sea—collect them as part of their livelihood. The shells are cleaned using chemicals and other methods and then used to make jewellery, photo frames, decorative pieces, flower pots, and other handicrafts sold in the market. Beyond handicrafts, seashells also have broader industrial value increasingly explored by researchers. A study examining sustainable waste management found that seashells can be converted into bio-calcium carbonate through a high-temperature calcination process. When used as a filler in high-density polyethylene (HDPE), a common industrial plastic, the seashell-derived material improved the thermal stability, crystallinity, and tensile strength of the plastic, while only marginally reducing its flexibility.
