Parts of the world's largest mangrove forest are disappearing, taking endangered species like the Bengal tiger with them, British zoologists say.

Rapid deterioration in mangrove health is occurring in the Sundarbans, the largest single block of tidal mangrove forest in the world covering parts of Bangladesh and Indian state of West Bengal, a report by the Zoological Society of London said.

The region is one of the largest reserves for the Bengal tiger, the researchers said.

As human development thrives and global temperature continues to rise, the forest's natural protection from tidal waves and cyclones is being degraded at alarming rates, they said.

"Our results indicate a rapidly retreating coastline that cannot be accounted for by the regular dynamics of the Sundarbans," society scientist Nathalie Pettorelli said. "Degradation is happening fast, weakening this natural shield for India and Bangladesh."

The Sundarbans are home to almost 500 species of reptile, fish, bird and mammals, including the endangered Bengal tiger, researchers said.

"The Sundarbans is a critical tiger habitat; one of only a handful of remaining forests big enough to hold several hundred tigers," Sarah Christie, the society's tiger conservation expert, said. "To lose the Sundarbans would be to move a step closer to the extinction of these majestic animals."