Wildlife Regions of India : Coastal & Island Ecosystems

India’s Coastal and Island Ecosystems encompass a staggering diversity of marine and littoral habitats, stretching along a 7,500-kilometre mainland coastline and extending deep into the Bay of Bengal and the Arabian Sea to include the remote Andaman, Nicobar, and Lakshadweep archipelagos. Geologically diverse, this region features immense river deltas, shallow continental shelves, ancient coral atolls, and rugged volcanic islands. The climate is predominantly tropical marine, characterized by high humidity, intense monsoonal rains, and significant cyclonic disturbances that naturally shape the coastal topography. These dynamic forces sustain a highly productive array of ecosystems, including vast tidal mudflats, dense mangrove estuaries, sprawling seagrass meadows, and complex fringing and atoll coral reefs. The biodiversity of this region is globally exceptional, supporting marine megafauna such as the Dugong, cetaceans, and multiple species of nesting sea turtles, alongside apex terrestrial predators uniquely adapted to estuarine life. Ecologically, these coastal and marine landscapes are indispensable; they function as monumental blue-carbon sinks, crucial nurseries for global fisheries, and indispensable natural buffers against coastal erosion and catastrophic storm surges. However, they face existential conservation challenges. Rapidly accelerating climate change is driving sea-level rise, ocean acidification, and devastating coral bleaching events. Furthermore, aggressive coastal development, unregulated aquaculture, overfishing, and massive plastic pollution severely threaten the integrity of these marine habitats. Biosphere Reserves located in these littoral and oceanic frontiers are critically vital. They safeguard irreplaceable marine genetic resources, protect highly localized endemic island species, promote the recovery of degraded reef systems, and ensure the sustainable livelihoods of traditional coastal and indigenous communities whose survival is inextricably bound to the health of the ocean.

Sundarbans Biosphere Reserve

Located in the vast Ganges-Brahmaputra-Meghna delta of West Bengal, the Sundarbans Biosphere Reserve is a globally unique, tidally dynamic landscape resting barely above sea level. The climate is tropical and highly humid, heavily influenced by intense monsoon precipitation and frequent cyclonic storms from the Bay of Bengal. This estuarine environment is dominated by the world’s largest contiguous mangrove forest, intricately dissected by a labyrinth of tidal rivers such as the Matla, Bidya, and Gosaba, alongside vast mudflats and salt marshes. The floral diversity is characterized by specialized halophytes, notably the regionally endemic Sundari (Heritiera fomes) tree. Uniquely, it is the only mangrove ecosystem on Earth harboring the Bengal Tiger, which leads a remarkably adaptable amphibious lifestyle here. The rich fauna includes the Estuarine Crocodile, Water Monitor Lizard, Ganges River Dolphin, and the critically endangered Northern River Terrapin. Avian life is prolific, featuring the Masked Finfoot and Mangrove Pitta. Deeply integrated with marginalized fishing and honey-collecting communities, the reserve provides an indispensable coastal defense against storm surges. Recognized by UNESCO in 2001, the Sundarbans is of paramount ecological importance as a massive blue-carbon sink, a critical nursery for marine fisheries, and an irreplaceable sanctuary for specialized deltaic biodiversity facing severe threats from rising sea levels.

Landscape Connectivity

The Sundarbans Biosphere Reserve forms the Indian half of a colossal, transboundary deltaic ecosystem that continues seamlessly into Bangladesh, constituting the largest continuous mangrove block on the planet. Its core comprises the Sundarbans National Park, which is concurrently designated as a Tiger Reserve, a UNESCO World Heritage Site, and a Ramsar Site. This core is heavily buffered by the Sajnekhali, Lothian Island, and Haliday Island Wildlife Sanctuaries. Unlike terrestrial reserves, ecological connectivity here is defined by complex hydrological networks and shifting tidal fluxes rather than forested ridges. These interconnected waterways facilitate the unrestricted movement of aquatic megafauna, such as dolphins and estuarine crocodiles, while the unbroken mangrove canopy supports crucial tiger dispersal across the delta. Internationally, maintaining absolute ecological continuity with the Sundarbans Reserve Forest in Bangladesh is absolutely essential for preserving the genetic viability of the entire tiger population and ensuring the overarching hydro-dynamics of the delta against encroaching climate impacts.

Gulf of Mannar Biosphere Reserve

Situated along the southeastern Coromandel Coast of Tamil Nadu, extending outwards into the Laccadive Sea, the Gulf of Mannar Biosphere Reserve is India’s premier marine protected area. Encompassing a chain of 21 uninhabited coral islands and their surrounding shallow coastal waters, the landscape is defined by a tropical maritime climate. The reserve boasts a highly complex mosaic of productive marine ecosystems, prominently featuring extensive fringing coral reefs, massive seagrass meadows, sprawling algal beds, and coastal mangrove forests. This nutrient-rich environment supports an astonishing marine biodiversity, serving as the most critical Indian sanctuary for the globally vulnerable Dugong (Sea Cow). The vibrant coral reefs harbor diverse marine fauna, including Green Sea Turtles, Olive Ridleys, Spinner Dolphins, and over a hundred species of hard corals. It is also uniquely known for supporting rare evolutionary lineages like the acorn worm (Balanoglossus). The reserve is deeply intertwined with the livelihoods of traditional Marakkayar fishing communities who rely on its marine productivity. Inducted into the UNESCO MAB network in 2001, the Gulf of Mannar is of profound conservation importance for protecting vital marine nurseries, restoring degraded coral reefs, and mitigating the catastrophic impacts of destructive fishing practices and localized ocean acidification.

Landscape Connectivity

The Gulf of Mannar Biosphere Reserve functions as a critical seascape corridor within the broader Indo-Pacific marine realm, securing vital oceanographic linkages between the Bay of Bengal and the Arabian Sea. The core of the reserve is the Gulf of Mannar Marine National Park, which fiercely protects the 21 islands and their immediate fringing reefs. Ecologically, this seascape is intrinsically connected to the adjacent Palk Bay to the north, facilitating the vital migration of Dugongs, sea turtles, and pelagic fish species across the shallow continental shelf. Furthermore, the coastal mangrove patches maintain crucial terrestrial-marine linkages with the estuaries of the Thamirabarani River, functioning as essential nutrient filters and nurseries for nearshore fisheries. Protecting this unbroken marine connectivity is imperative to ensure the resilience of the coral reef ecosystems against localized bleaching events and to safeguard the historic migratory routes of endangered marine megafauna.

Great Nicobar Biosphere Reserve

Located in the Andaman and Nicobar archipelago at the southernmost tip of Indian territory, the Great Nicobar Biosphere Reserve is a deeply isolated, ecologically pristine island landscape in the eastern Indian Ocean. Reaching an altitude of 642 meters at Mount Thullier, the island experiences a perhumid equatorial climate with almost year-round heavy rainfall. This isolated environment sustains lush, unfragmented ecosystems, transitioning from coastal mangrove and littoral forests to incredibly dense tropical evergreen rainforests inland, bordered by vibrant fringing coral reefs offshore. The region’s profound geological isolation has resulted in remarkable faunal endemism, serving as the exclusive habitat for the Nicobar Megapode, Nicobar Tree Shrew, and the Great Nicobar Crested Serpent Eagle. The terrestrial and marine interfaces support the Saltwater Crocodile, Reticulated Python, Robber Crab, and critical nesting beaches for Leatherback Sea Turtles. The island is the ancestral, strictly protected homeland of the indigenous Shompen hunter-gatherers and the coastal Nicobarese tribes. Inducted into the UNESCO MAB network in 2013, Great Nicobar is scientifically invaluable as an undisturbed evolutionary laboratory, a sanctuary for highly restricted equatorial endemics, and a fragile ecosystem currently facing severe threats from proposed mega-infrastructure and maritime development projects.

Landscape Connectivity

The Great Nicobar Biosphere Reserve operates as an isolated oceanic refugium, where landscape connectivity is defined by internal ecological contiguity rather than physical links to other terrestrial landmasses. The biosphere’s core is robustly established by the Campbell Bay National Park in the north and the Galathea National Park in the south. These two core areas are linked by a vital, unbroken forested corridor that facilitates the movement of endemic avifauna and terrestrial reptiles across the island’s mountainous interior. The pristine Galathea Bay functions as an indispensable marine-terrestrial interface, providing the most critical nesting beaches in the entire northern Indian Ocean for globally endangered Leatherback Sea Turtles. Oceanographically, the reserve is connected via the Andaman Sea currents to the wider Indo-Malayan archipelago, influencing the dispersal of coral larvae and pelagic marine species. Maintaining the absolute internal contiguity of this island is imperative, as any major linear infrastructure bisecting the forests would permanently sever its highly fragile evolutionary web.

Regional Summary Table: Coastal & Island Ecosystems