Srijita Bhangi, 11, sits in the waiting room of the jetty boat that connects her island home in Khulna to the mainland Sundarbans, near India's border with Bangladesh.
After spending a few days with her elderly grandparents – an effort to lift her most recent spell of depression – she is travelling back to the school hostel where she has lived since her parents left two years ago to find work in a garment factory 1,000km away, in Tamil Nadu.
Since then she has seen them only once, and the school lodging has effectively become her new home.
"My granddaughter is sad going back to the hostel," admits her frail 72-year-old grandfather, Nripen, who will accompany her on the journey. "Her education has suffered since her parents left. She was in fifth grade in the village school but was demoted (to second grade) in the new school."
As climate change brings sea level rise, growing salinity in water and more dangerous storm surges to the low-lying and already economically depressed Sundarbans region, a rising number of parents are migrating elsewhere in search of work, with mothers increasingly joining fathers away from home, experts say.
Most migrants hope to one day bring their children with them. But poor accommodation near new jobs, language barriers and a lack of childcare mean few children can make the move right away.
That has led to a staggering surge in children left behind in school hostels or with elderly grandparents – and a rising epidemic of childhood depression, malnutrition and vulnerability to child trafficking, local doctors and aid workers say.
They term the left-behind children "new-age orphans".
"The number of children suffering from depression has increased dramatically. We have to treat them for various mental disorders now that were unthinkable even five years ago," said Dr Amitava Choudhury, a medical doctor who has worked in the Sundarbans for 18 years.
Depression has long been common among adults in the region, which has one of the country's highest rates of deliberate self-harm.
Two studies, conducted by researchers from Institute of Psychiatry in Kolkata, published in 2008 and 2013 respectively, found poor "quality of life" – including low incomes and conflicts over forest management – to be the main stressor among adults.
"However, children were never depressive. We hardly found a case. This sudden rise in child depression is alarming," said Dr Pradip Saha, the director of the institute.
Malnutrition among children has also increased substantially because rising temperatures are lowering the number of fish in creeks and ponds, and because worsening floods and hurricanes have reduced cattle herds and left less milk for children to drink, Chowdhury said.
Ageing grandparents also struggle to feed and care for the children, charity workers and other officials said.
"Now protein deficiency is rampant," Chowdhury said. A World Bank survey in 2014 in the region found more than half of children undernourished.
With parents away, child hostels are in huge demand in the region. Most offer residential schooling. But affordability is a major concern among poor villagers.
As a result, many hostels, to keep costs down, provide only basic education and safe shelter.
"We cannot charge high fees for lodging of these children as parents cannot afford it. They often request us to admit the children with a promise of paying the fees later in the year, which never happens," said Anshumas Das, whose Sabuj Sangha charity runs a hostel for 50 left-behind children in Pathar Pratima, a group of Sundarbans islands.
"We just cannot drive the children away, on humanitarian grounds," he said.
In Pathar Pratima, scores of parents have migrated to cities such as Bangalore and New Delhi.
"My mother works as a domestic maid and my father washes cars. I stay here with my aunt," said 13-year-old Sudipto Senapati, in Kedarpur village. "My parents have promised me that I will also shift to Delhi soon. I have been there a few times and I hate living here alone." Often, however, such hopes remain unfulfilled, Das said.
"Parents generally live in shanties, schools are more expensive and cultural alienation is very high," he said.
Another hazard is child trafficking.
"With parents away, young girls and boys are soft targets to lure into trafficking. We could only rescue a tiny fraction of the total number of children trafficked over the past five years," said Dinabandhu Das, secretary of the Joygopalpur Youth Development Centre, an NGO that rescues trafficked children with the help of the police.
The state of West Bengal, where the Sundarbans is located, had the country's highest rate of child trafficking in 2013, with 669 registered cases – a figure considered a gross underestimate as the crime is under-reported, Das said.
Young mothers who migrate in search of work also sometimes fall victim to trafficking and fail to return to their children, he added.
The pressures of migrant work also lead to the breakdown of marriages in some cases, which means one or both parents may fail to return, or single parents fail to earn enough to bring their children to join them.
With the number of children living without parents rising, having more state-run residential schools would be a huge help, said Subhas Acharya, a joint director of the Department of Sundarban Affairs.
He fears the problem will continue to grow as Sundarbans families struggle with climate change and growing population levels and eroding resources.
"The land resource is finite and a population of 4.4 million cannot be sustained within it. Fish stocks have diminished and forest dwelling involves high risks," he said.
But hostels and shelters can never replace the love and care of parents, warned Anshumas Das. "Even if the children live with their grandparents, they feel neglected and depressed. These are the new-age orphans," he said.
Nripen, Srijita's grandfather, agrees. Since his daughter and son-in-law left for work in the garment factory, Srijita has suffered bouts of depression, he said.
"If we die, she will be left entirely to her own devices," he said, walking to the boat that had just arrived. It was time to ferry Srijita to the other side. – Thomson Reuters Foundation