To see the tidal defences and inland channels regulating water and protecting farms and communities is to marvel at the monumental task of transforming 1,500 square miles of wetland into the country's best arable acres. With a habitat and history quite distinct from the rest of the country, we call this huge area the Fens: drained from the early 17th to the mid-19th centuries, at some cost to wildlife, nature and to a distinctive way of life for its people.

For Daniel Defoe, it was ‘all covered in water like a sea … the soak of no less than 13 counties’: a giant sponge absorbing the water flowing into a landscape, once one of Europe's great deltas and ‘most diverse environments’. Today it is interlaced by a network of straightened rivers, parallel channels, small reservoirs, endless long and high embankments, several hundred pumping stations and sluices to hold back water; all this to protect vulnerable and drained farmland, semi-rural communities and, further upstream, Cambridge itself.

Now these flatlands, a food bowl for Britain, often below sea level and leaching carbon into the atmosphere, are degrading as the ground sinks – and the country faces tough choices. Should part of them be returned to a natural state of meadow, marsh, meres (lakes) and meandering rivers – in short, ‘rewetting’, to contain carbon – with the remainder reinforced to protect farmland at a cost of billions over the 21st century? Will the government, when it finally considers the issue, authorize limited funding and make do and mend as best it can? Or are the Fens destined to eventually become a wetland once again, by default if not by design? As we shall see, tentative signs of action are emerging, with a new government task force charged with addressing the challenges in our lowland peatlands – none bigger than the Fens.

One historian who has undertaken a recent detailed study of the area is in no doubt that, even under conservative climate forecasting, sea level rises – perhaps by a third of a metre by 2050 and between 1 and 2.4 metres within 100 years – are likely to lead to the ‘seasonal or permanent inundation of much of the Fens without the construction of sea walls of prohibitive size and expense’.