Decline of horseshoe crab populations in Odisha: A study on coastal erosion and human impact

Bhubaneswar: A collaborative study by researchers from India, the US, and Brazil has unveiled the complex factors contributing to the decline of horseshoe crab populations along the Odisha coast. The study, published in the ‘Journal of Coastal Conservation’, highlights the interplay between coastal erosion, rise in sea level, and human activities such as construction, habitat disruption, and pollution.

Horseshoe crabs are ancient arthropods predating dinosaurs and have survived multiple global cataclysms. Their unique blue blood, rich in amebocytes, is crucial for medical testing to detect bacterial contamination in vaccines and surgical implants. Ironically, this trait, which saved countless lives during the Covid-19 pandemic, now contributes to their overexploitation and decline, said the researchers.


The research team, comprising members from Fakir Mohan University, Utkal University, Central University of Punjab, University of South Alabama, and Federal University of Paraiba, Brazil found that between 1990 and 2020, the average rate of shoreline retreat was 1.34 metres per year, with some areas eroding by more than three meters annually.

“The Balasore coastline is eroding at an alarming rate, particularly near estuarine zones like Chandipur and Balaramgadi. Cyclonic storm surges and human interference have transformed these once-thriving horseshoe crab habitats into high-risk erosion zones,” said lead author Manoranjan Mishra, a geography professor at Fakir Mohan University.

Over the past two decades, rapid growth in coastal settlements, aquaculture ponds, and small-scale industries in Balasore has exacerbated the situation. “Unregulated construction, sand mining, and pollution have weakened the coast’s natural defenses,” noted Bisnu Prasad Dash from the Horseshoe Crab Research Centre at Fakir Mohan University.

The study found that nesting beaches are being encroached upon by expanding fishing communities and tourism infrastructure. In some areas, crab nesting grounds have been converted into shrimp farms or used as dumping sites for construction debris.

“Villagers often don’t realise the ecological importance of these animals. We have observed a decline in population density at several traditional nesting sites, including Dublagadi and Bichitrapur,” said Pritam Chand, a co-author from the Central University of Punjab.

The research highlights that sea-level rise rates in the northern Bay of Bengal, around 2.7 mm per year, are among the highest globally. Combined with repeated storm surges, this accelerates beach erosion and salinity intrusion. “Post-cyclone sediment displacement significantly alters breeding sites. Each major storm effectively redraws the map of coastal habitats,” noted Debdeep Bhattacharyya, a GIS specialist and co-author.

When erosion wipes out farmland or mangroves, co-author Rajkumar Guria said, people move closer to the shore for income through sand mining or tourism, further degrading habitats of this species.