An Elevated Seabed

Neduntheevu, or Delft Island, is a flat, oval landmass of about 50 square kilometers in the Palk Strait. Geologically, it is an uplifted section of the seabed, composed primarily of coralline material, limestone, and other marine deposits from the Eocene, Miocene, and Pliocene eras. The island has a low relief, mostly under 5 meters above sea level, and lacks any rivers or lakes. Its freshwater comes from rainfall collected in natural depressions. The soil is thin, sandy, and coarse, overlying the coral bedrock. These soils, identified as Solodized Solonetz and Grumusols, are highly salinized.

The climate is semi-arid, with an average annual rainfall around 500 mm. A long dry season lasts from February to September, followed by a wet season from October to January. This environment, combined with the porous coral-based geology, creates hypersaline conditions in the island's salt marshes and tidal flats. These extreme conditions limit the types of vegetation that can survive, making the island a natural laboratory for studying plant adaptations to salinity. The island's flora is classified as belonging to the AI floristic zone, typical of Sri Lanka's coastal and marine belts.

Life in the Salt

The most specialized vegetation on Neduntheevu is found in its salt marshes. These areas are dominated by halophytes—plants adapted to live in saline environments. The family Chenopodiaceae is well-represented, with species such as Suaeda maritima, Suaeda monoica, and Salicornia brachiata being true saltmarsh plants. These succulent plants have evolved mechanisms to cope with high salt concentrations in the soil and water. Other common halophytes include Sesuvium portulacastrum, known locally as "Vankiruvilai".

The island's biodiversity is important for its resilience. A 2011 survey documented 203 species of flowering medicinal plants. This includes one endemic species, Vernonia zeylanica. Vast stretches of Aloe vera grow wild in the sandy areas. The unique ecosystem also supports a diverse range of fauna. Surveys have recorded 101 bird species (37 of which are migratory), 11 mammal species, 8 reptile species, and 15 butterfly species. The salt pans and lagoons provide important habitats for these animals, particularly visiting waterbirds like ducks, storks, and spoonbills.

Practical Information

Opening Hours

The island is accessible year-round, but ferry schedules dictate visit times. A day trip is common, with a morning ferry arrival and an afternoon departure.

Admission

The ferry service operated by the Sri Lankan Navy is often free of charge, though this can change. Priority is given to island residents.

Accessibility

The terrain is flat but rugged, with dirt roads and coral-strewn plains. Getting around typically requires hiring a local tuk-tuk or a small lorry. The ferry ride from the mainland can be rough.

Island of Salt-Loving Plants

An Elevated Seabed

Life in the Salt

💡Fun Facts

References

There's more in the app

Practical Information

Island of Salt-Loving Plants

An Elevated Seabed

Life in the Salt

💡Fun Facts

References

There's more in the app

Practical Information

Nearby curiosities

Nearby curiosities