Restoration and Creation of Saltmarshes and Other Intertidal Habitats

Professor Alastair Grant

Centre for Ecology, Evolution and Conservation, University of East Anglia

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More than 10 years ago, Dr. Mark Rehfisch and Dr. Phil Atkinson of the British Trust for Ornithology (BTO), Dr. Steve Crooks and myself carried out a review for English Nature of the success (or otherwise) of schemes to create or recreate intertidal habitats such as saltmarshes and mudflats.  The final report of this project is available as an English Nature research report.

Atkinson, P.W., S. Crooks, A. Grant and M. Rehfisch, 2001. The success of creation and restoration schemes in producing intertidal habitat suitable for waterbirds. English Nature Research Report No. 425

This can be downloaded as a three part document: part 1, part 2, part 3. Some discussion of the suitability of created intertidal habitat for birds was published as a paper with the title Can we recreate or restore intertidal habitats for shorebirds and a more detailed study of colonisation of the Tollesbury and Orplands sites by birds was published in the journal Ibis. Please email me to request a reprint.

My post-doc, Hannah Mossman is continuing this work, jointly supervised by Tony Davy in the School of Biological Sciences.  She has carried out detailed ecological surveys of almost all the UK managed retreat sites to assess their success and shown that realignment sites are an imperfect match to natural marshes. Several key species of plant are almost absent on created marshes, and continue to be rare even on sites that were flooded over a century ago. Many sites are waterlogged, and dominated by pioneer species of plants, although the upper parts of some sites are much drier than natural marshes at the same elevation. So one could argue that created saltmarshes do not provide adequate compensation for natural marsh under the terms of either the EU Habitats Directive or the US Clean Water Act. For a brief summary see this BBC News item. Three recent publications on the topic are:

 Davy, A.J., M.J.H. Brown, H. L. Mossman and A, Grant, 2011. Colonisation of a newly developing salt marsh: disentangling independent effects of elevation and redox potential on halophytes.  Journal of Ecology., 99:1350-1357.

 Mossman, H.L., A.J. Davy and A. Grant, 2012. Does managed coastal realignment create saltmarshes with ‘equivalent biological characteristics’ to natural reference sites? Journal of Applied Ecology.

Mossman, H.L., M. J. H. Brown, A. J. Davy and A. Grant, 2011. Constraints on salt marsh development following managed coastal realignment: dispersal limitation or environmental tolerance? Restoration Ecology. 20:65-75


We have also developed methods that enable us to quantify tidal regimes at large numbers of sites simultaneously, and a paper describing these methods was recently published in Estuarine, Coastal and Shelf Science. 

Why all the fuss?

Saltmarshes, mudflats that support significant populations of wading birds, and a number of other natural habits are given a high degree of protection as a result of the provisions of the European Union "Habitats Directive" and "Birds Directive". This imposes a requirement that they should be maintained in "favourable conservation status" or restored to this if they have deteriorated. It also requires that any development which will destroy or damage the habitats or the associated bird populations is only permitted if there are "Imperative Reasons of Over-riding Public Interest" (IROPI). In the rare occasions where such developments are allowed, replacement habitat "with equivalent biological characteristics" must be created to replace that being destroyed. The UK government has been successfully taken to court by NGOs over the implementation of these rules, so the issue is politically quite sensitive.

In consequence, the requirements of these directives are a significant issue in UK planning. For example, their requirements have been a major determinant of where major port developments in South East England have been permitted over the last decade, There have been four proposals to increase container port capacity in south-east England. The first of these was by Associated British Ports (ABP) whose plans to build a container port at Dibden Bay on Southampton Water, were rejected by the UK government on 20th April 2004. A summary of the decision is available from BBC news. The planning inspector concluded that the proposals would damage the integrity of the Solent and Southampton Water Ramsar site and Special Protection Area (SPA). The need to satisfy the requirements of the EU Habitats and Birds directives meant that the proposals included the creation of new intertidal habitats, including a "Mile Long Creek" to substitute for existing habitats that would have been destroyed by the new port. The Inspector concluded that these proposals would reduce the environmental impacts of the development but they "would not be adequate to permit the Secretary of State to meet the requirements of regulation 53 of the Habitats Regulations".The public enquiry on the proposed development opened on 27th November 2001 and closed on 12th December 2002 (see the following BBC News item). This was seen by many as the first major test case for the mitigation/compensation requirements included in the EU Habitats and Birds directives. The conclusions of both the Planning Inspector and the Secretary of State centred on the application of these directives to Dibden. They agreed that there was a need for additional container port facilities in the south east of England, but considered that forseeable national need could be satisfied without the Dibden Bay facility. So the proposals failed to demonstrate "imperative reasons of overriding public interest" and the planned compensatory measures would be inadequate. The proposals therefore failed both tests required by the EU Habitats Directive and its translation into the english Habitats Regulations. When reporting the decision the Transport Minister, Tony McNulty, commented that "one important factor in the making of this decision was the environmental impact of the proposals on internationally protected sites". Further details on the proposals are available from the ABP website, the dedicated web site, New Forest District Council Hampshire County Counciland Southampton City Council. The proposal was opposed by Friends of the Earth, RSPB and English Nature (see background information from early 2001 and their 27th November 20001 press release) amongst others.

Many of the same issues arose with two other proposals to build large container ports in the South East of England:

We also make available here our bibliography of published material on salt marsh restoration and creation, and will add links to other web resources on saltmarsh restoration as time permits.  For further details, email me at: For other information on research opportunities and undergraduate study at the University of East Anglia, please see the Ecology at UEA and The School of Environmental Sciences web pages.

Professor Alastair Grant,

Centre for Ecology, Evolution and Conservation
School of Environmental Sciences
University of East Anglia

26th October 2011

Information on the internet about UK managed retreat sites

Saltmarsh Restoration bibliography

Information on the Tollesbury and Orplands managed retreat sites, Essex, UK

Other managed retreat/saltmarsh creation sites in Essex include:

Abbotts Hall Farm (owned by the Essex Wildlife Trust - see here for more details) and

Northey Island (owned by the National Trust).

Proposals were put out for consultation on the creation of two large managed retreat sites at Wallasea island on the Crouch Estuary and Weymarks near Bradwell on Sea on the Blackwater Estuary. These developments were in compensation for loss of intertidal habitat at Lappel Bank on the Medway Estuary and Fagbury Flats on the Stour/Orwell Estuary. After consultation it was decided to proceed with the Wallasea Island site. The requirement to compensate for these developments results from a ruling from the European Court of Justice in a case brought against the UK government by the RSPB. A web site on this site is maintained by ABPmer and the RSPB have acquired the remaining area of Wallasea island for habitat creation using the title Wild Coast project.

Realignment sites elsewhere in the UK include:

Thorngumbald, also known as Paul Holme Strays on the Humber Estuary (see also);

Brancaster West Marsh on the North Norfolk Coast (see also DEFRA News Release);

Havergate Island in Suffolk and

Nigg Bay on the Cromarty Firth.

A decision has been made to stop attempting to maintain the shingle ridge between Cley and Salthouse on the North Norfolk coast (see Environment Agency press releases from April 2003 and August 2003). In effect this represents a managed realignment of the existing coastline. Original proposals to allow flooding of only part of this area have been abandoned, largely driven by nature conservation considerations (see here for more details).

Other Web resources

The full text of a US National Research Council report Compensating for Wetland Losses Under the Clean Water Act (2001) is available online. This is presents the findings of a committee chaired by Professor Joy Zedler of the University of Wisconsin, Madison, which reviewed the extent to which the goal of No Net Loss of wetlands was being achieved.

The US National Oceans and Atmosphere Administration (NOAA) maitain a web site on the State of the Coast. Of particular interest is their bulletin on restoring coastal habitats.