Do we repair sea defences and protect freshwater habitats, or allow salt water to remain?

Cley marshes, home to the bittern, that could be threatened if its freshwater marshes aren't protected.

The uneasy balance between the vast salt marshes on the north Norfolk coast and the freshwater habitats has been disturbed by the aggressive storm surges which battered our region last month.

The sea tore through the flood defences on the coast, but also ripped open the debate about whether we repair the defences and protect freshwater habitats, or allow the salt water to remain.

Environment Agency boss Paul Leinster told MPs that there would now be discussions with Natural England, and others, as to whether the flood water, which breached defences in Brancaster, Blakeney and Salthouse, will be thwarted.

'The question has to be, do we reinstate those defences and then allow freshwater habitat to re-establish, or allow inter-tidal habitat to establish?' the agency's chief told MPs on Wednesday.

University of East Anglia professor of ecology Alastair Grant, who particularly studies salt marshes, said it was almost inevitable that the sea would break through at some point. Sea level is steadily rising, particularly in East Anglia. The storms had just seen the flooding happen more quickly than expected.

The UK government – through the EA – has to create more salt marshes to replace those being lost to the rising sea to comply with European Union directives.

'In one sense, the surges have created salt marshes that are needed to replace this loss,' said Professor Grant.

'If the breaches aren't repaired then the salt water will stay in and the land will gradually revert to salt marshes, if it is relatively high, or mudflat if it is low down.'

But he said freshwater habitats, 'artificial' but prized by the nature conservationist, would be lost. 'These artificial habitats are actually very important. A lot of money has been spent on building the freshwater marshes, such as Cley, and they are used by birds particularly.'

The bitterns are probably the most high-profile of these species – the Cley marshes are one of the few places in Britain where they breed.

Several species of ducks, warblers, water fowl and water plants could also disappear from the areas affected, he said.

On the flip side, the creation of more salt marshes would be particularly good for Brent geese and wading birds.

But the most visible difference would be the salt marsh plants which might appear, according to the UEA expert.

These could include sea lavender and samphire – the trendy vegetable favoured by top London chefs.

Professor Grant does point out that the areas prone to seawater flooding were originally salt marsh anyway.

'The whole coastline from Salthouse westwards is a series of shingle ridges and sand dunes, which would have originally had salt marshes behind them. They were reclaimed, largely for agricultural use and some of it is grazing marsh,' he said.

In his job he has studied areas that have returned to salt marsh after being flooded either deliberately, or accidently, including sites at Brancaster and Titchwell.

'The work we have done indicates that you often don't get a really high quality salt marsh. There was a big storm surge in 1898 and some areas flooded then still do not look like natural salt marshes, even after 100 years,' he said.

But that does not mean you cannot intervene.

'There are some things that can be done to improve the quality of what you get, such as planting of more interesting species,' he added.

And he also said that agencies could landscape the areas to ensure there were not large waterlogged areas that plants could not grow on.

But what about the lost freshwater environments? That is the crunch, says Professor Grant.

'What needs to happen is some sort of creation of new freshwater habitat. There is not really space to do that on the north Norfolk coast. We may have to go around to the Fens or the Broads to provide for the species and habitats that we are losing.'

So what is the answer?

'We cannot hold back the sea, or at least not without great expense,' he said.

'It makes sense to try if you are protecting many properties, or large areas of land.

'I suppose some would argue that the Cley marshes are irreplaceable, and should be protected at any cost.'

But with sea levels set to continue to rise, repairing flood defences may only be temporary.

Whether or not the Environment Agency and other bodies decide to do this is the big question that will have to be answered in the coming weeks and months.