Many scientists believe the only long-term solution is for most of the Sundarbans population to leave. That may be not only necessary but environmentally beneficial, giving shorn mangrove forests a chance to regrow and capture river sediment in their tangled, saltwater-tolerant roots.
"The chance of a mass migration, to my mind, is actually pretty high. India is not recognizing it for whatever reason," said Anurag Danda, who leads the World Wildlife Fund's climate change adaptation program in the Sundarbans. "It's a crisis waiting to happen. We are just one event away from seeing large-scale displacement and turning a large number of people into destitutes."
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West Bengal is no stranger to mass migration. Kolkata, its capital, has been overrun three times by panicked masses fleeing violence or starvation: during a 1943 famine, the 1947 partition and the 1971 war that created today's Bangladesh.
India, however, has no official plan either to help relocate Sundarbans residents or to protect the region from further ecological decline.
"We need international help. We need national help. We need the help of the people all over the world. We are very late" in addressing the problem, said West Bengal state's minister for emergencies and disaster management, Janab Javed Ahmed Khan. He said West Bengal must work urgently with the Indian and Bangladeshi governments to take action.
Bangladesh is supporting scientists "trying to find out whether it's possible to protect the Sundarbans," said Taibur Rahman, of the Bangladesh government's planning commission. "But we are already experiencing the effects of climate change. The people of the Sundarbans are resilient and have long lived with hardship, but many now are leaving. And we are not yet prepared."
A network of concrete dykes and barriers, like those protecting the Netherlands, offers limited protection to some of the islands in Bangladesh's portion of the Sundarbans. The World Bank is now spending some $200 million to improve those barriers.
Experts worry that politicians will ignore the problem or continue to make traditional promises to build roads, schools and hospital clinics. This could entice more people to the region just when everyone should be moving out.
"We have 15 years ... that's the rough time frame I give for sea level rise to become very difficult and population pressure to become almost unmanageable," said Jayanta Bandopadhyay, an engineer and science professor at Jawaharlal Nehru University in New Delhi who has studied the region for years.
Bandopadhyay and other experts say India and Bangladesh should be creating jobs, offering skills training, freeing lands and making urbanization attractive so people will feel empowered to leave.
Even if India musters that kind of political will, planning and funds, persuading people to move will not be easy.
Most families have been living here since the early 1800s, when the British East India Company - which then governed India, Pakistan and Bangladesh for the British Empire - removed huge mangrove forests to allow people to live on and profit from the fertile agricultural land.
Even those who are aware of the threat of rising seas don't want to leave.
"You cannot fight with water," said Sorojit Majhi, a 36-year-old father of four young girls living in a hut crouched behind a crumbling mud embankment. Majhi's ancestral land has also been swallowed by the sea. He admits he's sometimes angry, other times depressed.
"We are scared, but where can we go?" he said. "We cannot fly away like a bird."