In a dimly lit hut made of mud and straw, a shaft of sunlight slices through a hole in the ceiling and lands on a bag of rice. Debendra Tarek, 80, pulls out a handful of the rough brown grains and holds them up to the beam of light.

His bare chest is sunken, and his eyes glow deep in their sockets. "This resists the saltwater," the village elder explains through an interpreter. This variety of rice, he says, allows his family to remain here on Ghoramara, the island where they were born.

Ghoramara is one of thousands of islands that make up the largest mangrove forest in the world. It is part of the Sundarbans — a delta on India's eastern border with Bangladesh, where three major rivers empty into the Bay of Bengal. This is tidal country, where land disappears and reappears as waters rise and fall each day. Lately, noncyclical change is reshaping this landscape in unfamiliar ways. Rising waters tear chunks out of the landscape. Islands disappear and don't return.

Ghoramara has lost half its land mass since 1969, according to researchers at Jadavpur University in Kolkata, India. Sugata Hazra runs the university's School of Oceanography Studies. Hazra says the island has shrunk from 8.5 square kilometers in 1969 to just 4.3 kilometers in 2014. Ghoramara used to be home to 40,000 people. Today, most have been forced to leave. They've become climate refugees. Tarek and his family are among the 3,500 people who remain.

Many of the 4 million people who live in the Sundarbans are poor subsistence farmers like Tarek. Rice is the staple crop, and growing it requires abundant fresh water. In a rice paddy, the brackish water that surrounds these islands can be devastating. "When floodwater would enter the fields, it would destroy the entire crop," Tarek tells me. It might be three to five years until a rice paddy can be planted again.

In Kolkata, about 60 miles north of Ghoramara, Asish Ghosh understands that climate change could cause rice paddies to flood with saltwater more frequently, making Tarek's problems worse. And he believes he can help. Ghosh is the founder of an environmental organization called ENDEV, The Society for Environment and Development.

"We used to grow 6,000 varieties of rice" in the Indian state of West Bengal, Ghosh says. "That is an incredible figure." The problem is, 90 percent of those varieties have disappeared. Farmers no longer grow them, and nobody has saved the seeds. Still, Ghosh figured that some of the 600 remaining varieties must be salt-resistant.

His team called research facilities and universities, asking for the names of salt-resistant rice varieties. They collected six names — but no samples. "Where are you going to get them?" Ghosh recalls one researcher asking. "He laughed at me over the phone."

The hunt was on. "I was searching like a madman, writing emails to all possible places. To the national plant center, the national rice collection center," says Ghosh. "Then I called up an NGO in the Sundarbans I'd been working with. They searched out the oldest man they could find and asked whether he had any of these varieties."

After six months of scouring villages and research institutions, Ghosh procured seeds for five of the six salt-resistant rice varieties. (It still bothers him that he can't find the sixth.) In 2011, he gave small samples of the rice to farmers in the Sundarbans, along with careful instructions: "Grow these for seeds. Don't eat the rice. Save it."

There are places in the world where farmers have raised hardier crops thanks to technological innovation, gene-splicing or other advanced scientific practices. This is not that kind of story. "I am reviving traditional knowledge," says Ghosh.

Five years into the program, Ghosh says "countless" farmers in the Sundarbans are now planting salt-resistant rice. He has been recognized by the Nature Conservancy and other international organizations. And countries far from India have picked up the idea. Ghosh says he has presented at conferences with researchers who are planting salt-resistant rice native to Tanzania, and he's met scientists who have re-established salt-resistant potatoes in flood-prone parts of coastal Pakistan.

This is not a long-term solution for the islands most affected by climate change. But salt-resistant rice can provide a buffer for some of the most vulnerable people who might otherwise be ruined.

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