Bangladesh has been a vulnerable state for much of its short existence. People in this flood-prone country have coped with rising water levels with a combination of innovation, flexibility and resilience – but the extremes the environment is now throwing at them might be beyond anyone’s endurance.

As climate change accelerates, the pressures on rural Bangladeshis mount. Where previously people might have been able to move away for the worst of seasonal flooding, the regularity of waterlogging is making it impossible to farm. Crop varieties cannot cope with the saltwater, and career alternatives are limited.

What, then, can be done for the most vulnerable people; the rural rice farmers of Bangladesh?

Historically, people in Bangladesh had worked around seasonal flooding; farming for part of the year and retreating when water levels rose, or seeking work in the cities as land became unusable.

By the end of the century, however, sea levels are expected to rise along the Bangladesh coastline by up to 1.5m. And that will come with more extreme seasonal fluctuations in sea levels. Disastrous storms and unusually high tides currently occur once each decade, but could become as regular as three to 15 times each year by 2100.

As a result, rural Bangladeshis face a stark choice; change their way or life or seek employment and a home elsewhere.

“The climate is becoming more volatile so we are seeing higher frequency of migration,” says Joyce Chen, an economist at The Ohio State University. “Where in the past we see migration due to annual flooding, or river bank erosion, now we see saltwater intrusion more commonly which affects the environment long term. It makes it harder to grow crops because the land is permanently altered by the saline water.” In the past, he says, people could go to work in the city for a few months while the land was flooded and return when the flood had retreated. Now that is no longer possible. “People realise it is not viable to stay.”

For some, the saltwater offers an opportunity. Where rice might have once grown, shrimp farms are taking over – the saltwater providing the right environment to switch to aquaculture.

“When we look at people converting from agricultural production, households seem to maintain their production pretty well by switching to aquaculture,” says Chen. “They seem pretty resilient. But, the ways they are being resilient now need to be sustainable into the future. How sustainable will aquaculture be? If enough people convert and there is too much saline intrusion that could create new problems and distort the economy in ways people cannot predict.”

The art of re-routing water using earth walls to create artificial islands for farming is perhaps best-known as a Dutch initiative. People in Bangladesh have also taken to building polders, as they are known, to protect their farm land. However, tensions arise when some farmers want to protect their agricultural land, on which they are growing rice, from saltwater intrusion while neighbouring farmers might inundate their land with saltwater in order to start farming shrimp.

“Anecdotes suggest that building sea walls and structures to keep the seawater out may be creating problems more than helping in that it creates conflict,” says Chen. “There are groups that want to allow more saltwater in to convert from agriculture to aquaculture. It benefits those that want to convert but not everyone is doing so. The seawater and levees allow more control which in some cases worsens the salinity problem.”

Chen says there may now be 100,000 people migrating each year due to saltwater flooding, but it is hard to estimate accurately because the changing wider economy is also affecting migration. A strong economy in India attracts workers, too, who often seek construction or agricultural work.

Mobile phones are one way to keep track of where people are moving, Chen has found. There are around 145m Sim card connections in Bangladesh, accounting for 87% of the population, although people change sim cards often and some people keep multiple phones. The high penetration of mobiles in Bangladesh is due to much of the population being reliant on them for banking. Mobile banking allows one person to work in a city as a migrant sending money home. Previously you might have had to wait several months for them to return with cash.

“We see both types of migration going on in Bangladesh – better opportunities in cities attracting workers or, in the case of climate change, they are moving because changes in the environment are making it hard to make ends meet,” says Chen.

As a low-lying country, Bangladesh has always been a vulnerable area to changing sea levels, so adapting and migrating are not unusual demands. Chen says people in Bangladesh are on a good path of economic growth at the moment, but the volatile climate makes it hard to predict whether this growth will continue.

Some Bangladeshis have tried to adapt their crops to the new conditions, but with limited success. “We have heard a little about switching to types of crops that are more saline-tolerant but I don’t think there are that many varieties that exist,” says Chen.

Researchers in China have suggested that they have developed saltwater-resistant strains of rice, but there is little peer-reviewed evidence that these strains are viable, and the water in which the crops were tested contained only 10% the concentration of salt found in seawater.

Migrants moving within Bangladesh are attracted to the larger cities which for the most part are on the coast. Chen warns that this still leaves many people vulnerable to the effects of rising sea levels. Those cities might become uninhabitable with rising tides and could result in many thousands of people needing to find homes elsewhere all at the same time.

Alternatively, some rural Bangladeshis are adapting their homes. “I have heard stories of a lot more people building their houses on stilts, or having retention ponds around farms,” says Chen. “I have heard some stories of schools moving onto boats so they can continue operating after flooding.”

Some migrants seeking work in Bangladesh’s cities find themselves picking through other people’s waste. Children and families can earn money by picking out recyclables. Large quantities of plastic waste, for example, wash into cities in flood water. The labour is hard, and the returns are small, but many workers might be faced with few alternatives.

With few opportunities facing unskilled labourers, finding work when reaching a new city can be hard. One problem facing those responsible for protecting migrant workers in Bangladesh is that those who are most vulnerable are the least able to relocate, Chen warns.

“The most vulnerable people might be stuck in place, says Chen. “People with greater means will be able to move out of vulnerable areas, but those worst affected might be stuck.”

“It will be hard to address the needs of those folks.”

For Chen, the next project involves looking at how migration is affecting the lives of the most vulnerable people in society – children. “There is some evidence that migration due to saline water inundation affects educational outcomes, food insecurity affects health, too,” says Chen.

For many, food insecurities result in a trade-off between personal health and the welfare of their livestock – some of the most valuable assets rural families own. “People talk constantly about how hard it is to get fresh water in Bangladesh – they call it sweet water,” says Chen. “And they have to save the sweet water for their livestock.”

While scientists might develop saltwater-resistant crops in time, and some Bangladeshis will find work in aquaculture, the more immediate concerns of health and safety – of survival – are a big motivator for migrants in Bangladesh. People will go where the water tastes sweetest.