New Delhi, April 24 (PTI): Sundarbans, the world's largest mangrove, faces a threat from global warming and a mere 45 cm rise in the sea level will destroy 75 per cent of the forest spread over 10,000 sq km in West Bengal and Bangladesh, a UN study said.

The forest, listed among the world's natural and cultural sites on UNESCO's World Heritage List, are facing threat due to climate change, said a latest publication, 'Case Studies on Climate change and World Heritage.'

Sundarbans figure in the bio-reserves category in UNESCO's World Heritage List.

Mangroves act as natural buffers against tropical cyclones and also as filtration systems for estuarine and fresh water. They also serve as nurseries for many marine invertebrate species and fish.

Any harm to the mangrove forests will leave India and Bangladesh vulnerable to the effects of disturbances in the Bay of Bengal.

"Further destruction of the Sundarbans mangroves would diminish their critical role as natural buffers against tropical cyclones. The Bay of Bengal is heavily affected by tropical storms, about 10 per cent of the worlds tropical cyclones occur in this area and 17 per cent of these sweep the land in Bangladesh," the report said.

"No matter whether the frequency or intensity of cyclones change in the future due to climatic disturbances, exposure of the region to the devastating effects of storms will increase if the mangroves cannot be conserved successfully," the report added.