Every ecosystem has its fragile balance. That much we have already learnt. Scientists routinely now seek to document the excesses that will lead to imbalance, even where they can do nothing about them. And sometimes, just sometimes, legislation and implementation and eventually protection may follow.

In the far south-west of Bangladesh, Munem Wasif shows us just what these abstract-sounding paradigms mean in practice. Nobody knows certainly why the water levels are changing in the Bay of Bengal, but they are. In a famously low-lying country, more and more people are under threat of catastrophic flooding. Coastal erosion, too, is accelerating, a matter of grave concern in a country where (under the pressure of population) every inch of usable land is at a premium.

Munem Wasif found a region where changes to a single measurable fact – salinity levels in the water table – can be seen to have affected every part of the matrix of balances. Salinity has risen. The old agriculture is no longer possible because the old plants simply can't grow.

Shrimping – a new industry – has grown up, largely for export, using fewer workers and threatening the livelihood of many others. Shrimping in turn exposes more land to salt or brackish water. Farmers are reduced to occasional labour. Established structures of work and the societies centred on work change and break down.

Many people have to venture into the mangrove swamps of the Sundarbans (a national park on the Indian side of the border, but not yet on the Bangladeshi) to fish or to collect roofing materials which used to be available closer to hand. In the Sundarbans they are exposed to a terrifying catalogue of risk, including attack from dog sharks, crocodiles, king cobras and the Bengal tiger. Women (it's always the women) have to go ever farther in search of fresh water. New diseases become frequent, obviously connected to all these changes, but not yet provably so. So it goes on, a kaleidoscope of interconnected shifts, not fully understood, and not half predictable with accuracy.

Munem Wasif has not gone to this blighted region to show us the abstractions of climate-change experts or the theories of macro-economists. Photography deals in the particular, and this project deals in the very particular. Wasif is himself Bangladeshi. Not for him the flak-jacket, the adrenaline rush, and five hours in the red zone. These are his people, although not quite in his part of the country. The accent is different but the language is shared. Wasif in fact rented a motorcycle to complete this commission, and when he tells you the names of the people in the pictures it's because he met them and heard them, and knew them a little.

The pictures, then, are almost by definition subjective. Too much ink has been spilt trying to work out when and whether photographers tell the truth. These pictures are absolutely personal to Wasif, absolutely his expression of his sentiments. But that doesn't stop them being also a remarkable – and true – document of what is happening in the interplay of some of the complex of variables in this corner of Bangladesh.

Photography reads big and small. Wasif shows you Johura Begum's long arm reaching out to her husband as he dies of cancer of the liver, that simple tenderness is the only available healthcare in a village whose population are in desperate need. It's a little tiny truth, certainly. The husband died, the woman lived on, widowed. The photographer was there, he knows. But it is also and at the same time a complex of many metaphors. There are many pictures like this because this scene has been played out so many times all over the world. It's a picture 'about' infrastructure and financing, too, as well as morality and ethics.

In another searing picture, containers of fresh water are dragged on foot in boats through clinging sterile mud. Shajhan Shiraj and his brothers from Gabura, we're told, travel three hours in this kind of way every day. Stunted trees, clear water only in the distance, three men, three boats, and the keel-trail they etch in the mud. It's not just a beautiful picture: the irony of boats travelling so painfully slowly by land with water as their only cargo is unimaginably painful.

There is a powerful crossover in the way pictures work. Read these pictures only as little truths and they will wrench out your heart. Read them as big truths and they will drive you towards planning practical effort for change. You don't need to know that Johura Begum's husband was called Amer Chan to be moved to action by Wasif.

We read about donor fatigue, compassion fatigue. Every viewer of these pictures will have at some point the sense of having seen them before. Salgado in the Sahel, just as shocking, maybe more. Very similar in feel and tonality. But it is not up to the photographers to provide us with new scenes. As long as those scenes are there and look the way they do, photographers will continue to show them to us. Some people will look at Wasif's pictures here and call them derivative, and they'll be right. But it isn't fashion. There is not going to be a new length of trousers this season in the liver cancer business. Photographers can only do so much. If viewers are tired of being harrowed, tired of seeing these scenes one shouldn't have to look at, perhaps we can understand that it's the viewers who need to perk up their ideas, not the photographers. Munem Wasif, for one, is doing his bit. Now it's up to us.

– Francis Hodgson

Head of Photographs, Sotheby's
Chairman of Judges, Prix Pictet
From the essay Munem Wasif: Tiny Truths, Big Truths

Munem Wasif was shortlisted for the Prix Pictet in 2008. As an integral element of the prize, Pictet decided to commission one of the shortlisted artists to record a water-related project. These photographs are the result.

Listen to an exclusive audio interview about this project, plus another short interview about his evolving style as a photographer. Both interviews were recorded in LensCulture's editorial offices.

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