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Island Biodiversity


The Convention on Biodiversity was ratified in 1994 by the Government of Sri Lanka and the Biodiversity Secretariat of the Ministry of Environment is the focal point. Therefore, many programmes are conducted each year towards the conservation of biodiversity in Sri Lanka. Another important activity is the commemoration of International Day. The theme this year is “ Island Biodiversity”.

Islands and their surrounding near-shore marine areas constitute unique ecosystems often comprising many plant and animal species that are endemic—found nowhere else on Earth. The legacy of a unique evolutionary history, these ecosystems are irreplaceable treasures. They are also key to the livelihood, economy, well-being and cultural identity of 600 million islanders—one-tenth of world population. Island species are also unique in their vulnerability: of the 724 recorded animal extinctions in the last 400 years, about half were island species. Over the past century, island biodiversity has been subject to intense pressure from invasive alien species, habitat change and over-exploitation, and, increasingly, from climate change and pollution. This pressure is also keenly felt by island economies. Among the most vulnerable of the developing countries, small island developing States (SIDS) depend on the conservation and sustainable use of island biodiversity for their sustainable development. Despite the fact that there is no clear definition of SIDS excepting outlines which state that a) it has to be a Least Developing Country (LDC); b) economic vulnerability, c) less than 1.5 million population and d) at least 0.02% share of World Trade threshold. Islands such as Seyshelles, Maldives and the Andamans are SIDS whereas Madagascar and Sri Lanka do not fall into that category.


 Over time, this isolation exerts unique evolutionary forces that result in the development of a distinct genetic reservoir and the emergence of highly specialized species with  entirely new characteristics. Islands harbour higher concentrations of endemic species than do continents,  and the number and proportion of endemics rises with increasing  isolation, island size and topographic variety. For example, over 90% of Hawaiian island species are endemic. In Mauritius, some 50% of all higher plants, mammals, birds, reptiles  and amphibians are endemic, and the Seychelles has the highest level of amphibian endemism in the world. Madagascar is home to more than 8000 endemic species, making it the  nation with the highest number of endemic species in sub-Saharan Africa.

Principal threats to Island Biodiversity

  1. Invasive alien species are among the primary threats to biodiversity on most islands and cause serious ecological and economic damage and high social costs. Because island species are small, highly specialized and defenceless against potential predators and competitors, islands are particularly susceptible to the effects of invaders.
  2. Tourism is a principal economic activity in a large majority of islands.  However, when development is uncontrolled, it can be a major cause of ecosystem degradation and destruction through i) destruction of habitats for the development of infrastructure; ii) transportation facilitating the introduction of invasive alien species; iii) degradation of habitats from an increased quantity of waste generated; iv) damage of habitats as a result of recreational activities. 
  3. Climate change and variability The most significant impacts of climate change are sea-level and sea-surface temperature rise. Sea-level rise will cause increased salinity, increase shortage of freshwater supply and loss of agricultural land. The rise in sea temperature causes coral bleaching  which negatively affects fishes sea creatures whose survival depends on reefs. As a result, the food security and economies of islands, which are largely dependent on marine ecosystems, will be negatively affected.

  4. Natural disasters Islands suffer from natural disasters, such as cyclones, storm surges, volcanic eruptions, earthquakes, forest fires, landslides, extended droughts and extensive floods. These events and their aftermath cause wildlife mortality, as a result of the disappearance of food, the stress-induced failure to breed and the degradation of habitats. 

  5. Overexploitation and unsustainable uses Overexploitation of resources, by over-fishing, over-hunting, overgrazing and over-harvesting, is a major cause of biodiversity loss in island ecosystems.

  6. Pollution and waste disposal An increase in pollution from liquid and solid waste, as well as from agrochemicals, is causing degradation of river, sub-surface and coastal water quality. The fertilizers, pesticides and herbicides required to maintain high crop yields are washed off fields and transported in waterways, contaminating aquifers and reservoirs that provide freshwater supplies, and affecting the biology of sensitive riverine and coastal ecosystems.

Sri Lanka and its Island Biodiversity 

Sri Lanka separated from the Indian mainland during the late Miocene followed by several sea level changes revealing land bridges. During this time fauna travelled to and fro from the Indian mainland.

In the course of events, the elevation of the Himalayan mountain range, the separation of parts of Asia from the mainland to form large islands such as Sri Lanka, Sumatra, and Borneo etc occurred.

The evolution of modern man in Africa and his dispersal/ migration to other countries; the extinction of certain animals due to hunting, the production of stone tools (evolution of technology), the development of human settlements and domestication of both flora and fauna occurred during the Pleistocene. Fossils of many extinct mega fauna such as the Rhinoceros, Hippopotamus, Elephants, Lions and Tigers have been discovered in the Ratnapura Fossil beds of the Pleistocene period. While extinctions resulted in the loss of many such fauna some species such as the Acavus land snail, Panthera, Melanochelys Canarium species are extant even today. During the Pleistocene ice ages, Sri Lanka was intermittently connected to mainland India until sea level rise created the present disruption ors separation approximately 10,000 years ago. Thereafter, species became isolated and with restricted dispersal, speciation occurred resulting in many new endemic flora and fauna. The topography and climate also contributed to a large extent towards the high endemicity of the island.

Today, Sri Lanka and the Western-Ghats together is considered as a biodiversity “hotspot” because they are construed as forming “a community of species that fits together as a biogeographic unit”. However, recent genetic studies of amphibians and fish have revealed that the Sri Lankan fauna is derived from an evolutionarily diverse faunal stock from the Indian mainland and maintains a unique biodiversity.

The high rate of endemism of the island is given in the table below, in accordance with the National Red List 2012.  



Total Species
















  Freshwater fish






  Freshwater crabs



There are many islands around the coastline of Sri Lanka . A majority of the islands are situated on the North- West side of Sri Lanka. Many of these islands have not been recorded nor have some of them been studied. Furthermore, the riverine system too contains many islands.

A brief description of some of the islands and their biodiversity is as follows;

Mannar is the largest island in Sri Lanka. . It is linked to the main island of Sri Lanka by a causeway. It has an area of about 50 square kilometres, mainly covered with vegetation and sand. Adam's Bridge is a chain of limestone shoals, between Pamban Island, also known as Rameswaram Island, off the southeastern coast of Tamil Nadu, India, and Mannar Island, off the northwestern coast of Sri Lanka. Geological evidence suggests that this bridge is a former land connection between India and Sri Lanka. Located on the southeastern tip of the subcontinent, the Gulf of Mannar is known to harbour over 3,600 species of flora and fauna, making it one of the richest coastal regions in Asia. 117 hard coral species have been recorded in the Gulf of Mannar. However, the combined effects of 47 villages, with a total population of around 50,000 has meant that overharvesting of marine species has become a problem. Fish catches have declined, as have pearl oyster, gorgonian coral, and acorn worm populations. Local fishermen rely on the reef to feed their families, but destructive fishing methods combined with the stress of pollution and coral mining have meant both nearshore and offshore catches have decreased. Endangered species include dolphins, dugongs, sea turtles, whales and sea cucumbers. Gulf of Mannar Marine National Park was declared in 1986 and  the park and its 10 km buffer zone were declared a Biosphere Reserve in 1989.

Kalpitiya is located in Puttalam district, North Western province of Sri Lanka. It is known for its serene beauty. It consists of 14 islands. It has a total area of 16.73 km2. The people of Kalpitiya are mostly fishermen. It is now developing as an attractive tourist destination. It is a marine sanctuary with a diversity of habitats ranging from bar reefs, flat coastal plains, saltpans, mangroves swamps, salt marshes and vast sand dune beaches. It provides nursing grounds for many species of fish and crustaceans. The coastal waters are also home to spinner, bottlenose and Indo-Pacific humpback dolphins, whales, sea turtles, and even the illusive dugong that are of great appeal to potential tourists.

Pigeon Island National Park is one of the two marine national parks of Sri Lanka. The national park is situated 1 km off the coast of Nilaveli, a coastal town in Eastern Province, encompassing a total area of 471.429 hectares. The island's name derives from the Rock Pigeon which has colonized it. The national park contains some of the best remaining coral reefs of Sri Lanka. Pigeon Island was designated as a sanctuary in 1963. In 2003 it was redesignated as a national park.


Delft island also known as Neduntheevu is the second largest island that occurs in the territorial waters of Sri Lanka. It is located in the Palk Strait, 10 km off the mainland. The maximum length of the island is 8km and its width is 6km. Its current population consists of 4800 individuals. According to the chronicles, during the early Anuradhapura period, there were a number of Buddhist temples on Delft Island, that were occupied by thousands of Buddhist priests (Bikkhus) that lived in the islands surrounding Nagadeepa (present Jaffna peninsula). The island features tropical semi-arid vegetation, dominated by palmyrah palms, coconut palms, dry shrubs and grasses. There is also a giant baobab (Adansonia digitata) tree on the island, which is a local landmark. A total of 146 faunal species including ten dragonfly species, 15 butterfly species, one amphibian species, eight reptile species, 101 bird species and 11 mammal species, have been recorded from Delft Island. This included one species - Appias galane (Lesser albatross) - that is endemic to Sri Lanka. The faunal assemblage of Delft Island includes 37 migratory bird species. (IUCN).  

Nagadvipaya also known as Nainativu is a small but notable island off the coast of the Jaffna Peninsula. It was believed that a tribe of people called ‘Nagas’ lived on the island. The Mahavamsa notable quotes that out of the 12 sites visited by Lord Buddha in Sri Lanka the second visit to Sri Lanka was to Nagadvipaya to settle a dispute amongst the Naga Kings over the ownership of a jeweled gold plate which is said to be placed in the The Ancient Nagadveepa Vihara.

Maduganga Estuarine Lagoon is situated in the south of Colombo. The lagoon contains about 15 small islands largest of which is Maduwa with an extent of 39 ha. The Maduganga is rich in biodiversity and contains 11 species of True mangroves. The only site which contains Lumnitzera littorea (Rathamilla) is Maduganga. It also contains 248 species of vertebrates as well. Currently boat excursions are held for people visiting the islands. New tourism plans pose a threat if unmanaged to this sensitive ecosystem.

What you can do to conserve Island Biodiversity

  1. Prevent destruction of natural sand dunes in the coastal region.
  2. Prevent destruction of mangroves and coastal species.
  3. Prevent polluting coastal waters.
  4. Prevent development activities in reservation area of coastal and riverine systems.
Last Updated on Wednesday, 30 April 2014 13:00