In the scorching farmlands of south-west Bangladesh, a single coconut tree stands as a barometer of climate change.

Dulal Mondal, 70, a farmer, points halfway up the tree about two feet off the ground to indicate where the waters came the last time the area flooded.

“Next time if heavy rain comes I don’t think water will recede as there is no natural draining or anywhere for it to go,” he says.

Mondal lives in the Jessore district of Bangladesh where increased levels of salt in the water, uneven rainfall and flooding are creating great uncertainty for a whole farming community.

Bangladesh is one of dozens of countries on the frontline of the climate emergency. Here global heating is no theoretical calamity of the future, but a very real, present danger.

By 2050, it is predicted that one in seven people in the country will be displaced by climate breakdown. The sea level is projected to rise by 50cm over this time period and Bangladesh may lose approximately 11% of its land. Deadly storms are usually a question of when, not if.

Here, the climate crisis is so palpable that the debate is not about restricting carbon emissions or preventing global warming but about how to adapt to the change and survive in times of unpredictable weather.

For example, Mondal says that where once his peers would farm mainly rice, now they have taken to fishing. They use floating cages, allowing fish to breed in a secure area. Also, if water levels rise, the cages will too, so flooding is less of an issue.

“About 20 to 30 years ago there would be a minimum of two crops per farming family but now because of waterlogging we have no more than one,” he says. Each cage is owned by one home and yields about 15,000 taka (£135) in additional income for the families a year. It’s also a consistent source of food, which could be vital if natural disaster hits.

“In the last two years there was not too much rain but two years ago we were flooded,” Mondal says. “We worry about the future. If there is heavy rainfall the water could remain logged for a long period of time and we would have to take shelter on main road. We would stay there with our remaining belongings.”

Facebook Twitter Pinterest Bangladeshi farmers near Jessore city speak of the challenges of climate change Photograph: Sarah Marsh/The Guardian

This farming evolution is just one element of a whole range of climate change adaptive practices taking root across southern Bangladesh, an area long prone to cyclones, rising sea levels and drought.

“What’s important is investment in long-term development, to help people adapt to the effects that climate change is having now and help them to not only survive but thrive in their new climate reality,” said Adib Hossain, the head of programmes implementation at Practical Action, one of the charities helping to make changes.

In this part of Bangladesh they have helped introduce effective fertilisers to increase crop growth as well as growing fish in cages and vegetation in sacks or beside rivers – a novel farming technique known as a “dyke garden”.

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The cages are made using cheap materials. Bamboo poles form an outer frame that can float and is covered in netting. They have a top cover to prevent fish jumping and escaping, or being caught by birds. With a capacity of one cubic metre, they hold up to 300 fish at a time. These cages are used for two growing seasons each year.

The fish can be fed on scraps and waste – duckweed, oil cake, kitchen waste, rice bran and snails – and in just a few months they grow to full size.

A woman standing beside Mondal goes down in a small wooden boat and pulls up the mesh cage, within which fish jump up and splutter around. She drops the net and they swim around once more. For the worried farmers in this area, the introduction of these cages has been reassuring, a constant amid a lot of inconsistency.

Facebook Twitter Pinterest Villagers in Jessore district who are using mesh cages for fishing. Photograph: Sarah Marsh

In the nearby district of South Atulia another innovative technique has been employed. Land here is being used for fishing, with pools of water separated by a cracked mud path and spiky vegetation. Omal Biswas, 48, has three daughters and an adopted son. He used to farm rice once a year and during the monsoon he would fish in freshwater. Now he is able to make more money with dyke gardening techniques, growing vegetables around pools of water used for fishing.

Omal has just harvested a crop, he says. They grow bottle gourd, chillis, indian spinach, red amaranth, sponge gourd, ridge gourd and tomatoes. “Before this technology was used I would yield around 20-25,000 taka a year but last year I harvested 120,000 taka through using different varieties of vegetables and growing more in the year.

“Now I can grow vegetables while fishing but I used to rotate the land. I eat the vegetables too,” he adds.

He adds that the additional income helps give them a better quality of life and now he has been able to buy six cows. “The cost of living is rising and the cost of production is increasing so it is a good portion of revenue,” he says.

Practical Action isn’t the only charity supporting farmers. The National Agriculture Technology Program (NATP 2) by the World Bank has also helped people adopt resilient farming methods.

Farmers have deployed ancient agricultural methods such as floating beds, which involve sowing crops onto floating islands made of the fast-growing water hyacinth. Crops such as cucumbers, gourds and eggplants flourish. Beds are raised so as to lie above the reach of tidal surges. In between, trenches serve as pools to farm fish and ducks.

Others have turned to shrimp farming after land was flooded but Practical Action has helped people do this in a more effective way.

Rubina Khatun is one woman who has benefited from this. “The cyclone affected my family. I swam across flood waters with my two sons and took refuge on the road and sheltered in a shop we own for two months. Then we returned to our home,” she says.

Shrimp farming is now a major source of income for her family. The technique used to farm the shrimp more effectively includes using deeper water so the temperature does not change as quickly, and adding a fertiliser made from oil cake, date juice and sugar cane among other things.

Facebook Twitter Pinterest ‘I am not sure what I would do without it now’: Rubina Khatun farming shrimp. Photograph: Sarah Marsh

“I am not sure what I would do without it now,” Khatun says. “But this type of farming is weather dependent. We need rain. If there is less rainfall salinity increases.”

Despite efforts to improve the situation, Bangladesh remains at the mercy of sharp changes in weather patterns. Deep uncertainty persists for millions, even if these newfound techniques are helped to mitigate environmental impact.

“I am worried,” Khatun says. “Too much or too little rain, both are problematic.”

For her, however, the concept of climate change is a world away. “I can feel it in terms of rain but I am not aware of this. I have heard non-government-organisations talking about it but just as a concept. All I know is shrimp farming is a major source of income out of all the ones remaining, so it’s a reassurance.”

This article is part of a series on possible solutions to some of the world’s most stubborn problems. What else should we cover? Email us at theupside@theguardian.com