Intertidal sands and muds

Context

This reporting category includes littoral (intertidal) sediment habitats which are widespread around the UK, forming features such as beaches, sand banks, and intertidal mudflats.  A large proportion of this habitat occurs in estuaries and inlets where it can cover extensive areas.  Notable examples are the Wash, Burry Inlet, Morecambe Bay, the Solway, Moray and Cromarty Firths, and Strangford Lough.  Significant but smaller areas of littoral sediment also occur at the head of inlets and sea lochs.  Beaches, which tend to be composed of sandier material, develop in more exposed situations and are also widely distributed.  Sand flats are more common in northern and western parts of the country and finer-grained flats are more common in southern and eastern areas.  Muddy sediments usually occur in sheltered areas, especially estuaries.
 
The marine communities found in areas of littoral sediment vary depending on the sediment type, sediment mobility, and salinity of the overlying water.  Mobile gravels and sands, for example, tend to be highly impoverished, whereas sheltered areas with mixed sediments can support very rich communities.  There is also a zonation of species down the shore which principally reflects the degree of immersion by the tide.  In general, tidal flats are low in species diversity, but they often support very dense populations of invertebrates.  The overall biomass of the area can, therefore, be extremely high.
 
The high biomass of intertidal communities on mudflats can support large numbers of waders and wintering waterfowl, including substantial proportions of the total world populations of the barnacle goose Branta leucopsis, and brent goose Branta bernicla, which feed on the eelgrass beds Zostera spp. in the littoral fringe and shallow sublittoral areas.  There are also internationally important numbers of ruddy turnstone Arenaria interpres, knot Calidris canutus and common redshank Tringa totanus which feed on invertebrates when the sediment shores are exposed by the tide.  Offshore intertidal sand banks around the Wash, north Norfolk coast and the sheltered shores of Orkney, are some of the locations used as haul-out sites by common seals Phoca vitulina.
 
SSSIs can be notified if they qualify under criteria outlined in the intertidal marine habitats and saline lagoons chapter and Section 10 of Chapter 1 Coastlands of the Guidelines for Selection of Biological SSSIs.  In Northern Ireland, ASSIs are selected on a very similar basis – the Guidelines for the Selection of Biological ASSIs in Northern Ireland is an addendum to the SSSI guidelines rather than an alternative 
 

Summary statistics

  SAC A/SSSI Total
Favourable condition 63% 70% 69%
Main monitoring coverage E, S E  
Reported assessments 16 132 148
Completeness of assessments 55% unknown  
Distribution of features     UK
 

Number of assessments reported by country and site type

Country SAC SSSI/ASSI
England 12 122
Scotland 4 9
Wales 0 0
Northern Ireland 0 1
United Kingdom 16 132
 

Natura features

List of Natura 2000 interest features within this reporting category

Interest feature name  
Formal name Informal name No. of assessments reported Total no. of features % assessed
Mudflats and sandflats not covered by seawater at low tide Intertidal mudflats and sandflats 16 29 55%
 
Natura 2000 comprises Special Protection Areas (under the Birds Directive) and Special Areas for Conservation (under the Habitats and Species Directive). The list presented here includes all of the qualifying interest features under these Directives, and shows the proportion of these features for which a condition assessment has been made.
 

SSSI features

List of SSSI and ASSI interest features in this reporting category

Interest feature name  
Formal name Informal name No. of assessments reported
Eel grass bed Eel grass bed 1
Intertidal Sands and Muds 9
Littoral sediment Littoral sediment 113
Mudflat Mudflat 5
Sandflat Sandflat 3
Subtidal Sandbanks which are slightly covered by sea water all the time 1
 
This list has not been fully standardised at a UK level yet. It is intended to show the principal constituent "feature types" for this reporting category.
 

Maps - distribution

UK distibution of reported interest features

Distribution of reported interest features.

Map showing the locations of the 10km squares in which at least one condition assessment has been reported. It does not show features that have not yet been assessed.

 

Maps - Natura

Distribution of SAC features showing assessments of favourability Condition of SAC features, with those currently reported as unfavourable-recovering shown as favourable
Current condition of SAC features
Distribution of SAC features showing assessments of favourability (where unfavourable-recovering is counted as unfavourable).
Condition of SAC features, with those currently reported as unfavourable-recovering shown as favourable
The implication of the unfavourable-recovering condition assessments is that at some point in the future these features should become favourable. This map shows the effect of that recovery by counting the favourable and unfavourable-recovering assessments together.

 

IMPORTANT NOTE: we do not have information on the timescale of the predicted recovery, which may be influenced by many past, natural and human related factors. A sustained sympathetic management regime is more likely to result in favourable condition being attained.

Key: Proportion of assessed features on 10km squares that are favourable:

Natura map legend - Key: proportion of assessed features on 10km squares that are favourable

 

Details of how these maps were produced

 

Maps - SSSI

Current condition of SSSI/ASSI features Condition of SSSI/ASSI features, with those currently reported as unfavourable-recovering shown as favourable
Current condition of SSSI/ASSI features
Distribution of SSSI/ASSI features showing assessments of favourability (where unfavourable-recovering is counted as unfavourable).
Condition of SSSI/ASSI features, with those currently reported as unfavourable-recovering shown as favourable
The implication of the unfavourable-recovering condition assessments is that at some point in the future these features should become favourable. This map shows the effect of that recovery by counting the favourable and unfavourable-recovering assessments together.

 

IMPORTANT NOTE: we do not have information on the timescale of the predicted recovery, which may be influenced by many past, natural and human related factors. A sustained sympathetic management regime is more likely to result in favourable condition being attained.

Key: Proportion of assessed features on 10km squares that are favourable:

SSSI map legend - Proportion of assessed features on 10km squares that are favourable

 

Details of how these maps were produced

 

Condition summary

Reporting category condition summary on Natura 2000 sites and SSSI

This lists the 10 different condition assessments and presents a bar chart showing the number of features within the SSSI series and the Natura 2000 series (either SPA for bird features or SAC for features other than birds). Note that for Natura 2000 we are able to estimate the number of features that have not been assessed during the 6 year reporting period - we are unable to do this for SSSI/ASSI because we do not have an overall list of notified interest features for these designations.

 

NB favourable unclassified and unfavourable unclassified have been used in this first six year cycle to get around difficulties in identifying trends in condition as common standards monitoring is implemented. It is expected that these categories will not be used for subsequent assessments of a feature.

 

Condition assessment - Natura 2000 features

The number and proportion of assessments for Natura 2000 (SAC and SPA) interest features falling into each of the condition categories
The number and proportion of assessments for Natura 2000 (SAC and SPA) interest features falling into each of the condition categories. Note that the �unfavourable� category includes all reports of unfavourable condition except �unfavourable recovering� which is shown as a separate segment.
 

Condition assessment - SSSI features

The number and proportion of assessments for SSSI/ASSI interest features falling into each of the condition categories
The number and proportion of assessments for SSSI/ASSI interest features falling into each of the condition categories. Note that the �unfavourable� category includes all reports of unfavourable condition except �unfavourable recovering� which is shown as a separate segment.
 

Adverse activities

The number of interest features where an activity has been reported as being implicated in the "unfavourable" condition of a feature
The number of interest features where an activity has been reported as being implicated in the "unfavourable" condition of a feature. More than one adverse activity may be reported for each feature.
 

Management measures

The measures summary bar chart lists the management measures relevant to the reporting category
For each "measure" the chart shows the number of interest features where that measure has been taken on a site to improve or maintain the condition of an interest feature. More than one measure may be reported for each feature assessed.
 

Interpretation

 
69% of intertidal sand and mud features reported are in favourable condition.  This is above average for marine and coastal features, for all habitat features, and for all features considered together.  70% of the A/SSSI features reported are in favourable condition and 7% are unfavourable-recovering.  63% of the SAC features reported are in favourable condition with 6% unfavourable-recovering.  The sole eelgrass feature that has been reported is in favourable condition.
 
Detrimental activities identified for features in unfavourable condition include lack of remedial management, coastal squeeze, inappropriate management, sea fisheries, over- and under-grazing and water quality problems.  Water quality also affects the habitat in the intertidal zone. 
 
Pollution arises from point sources, such as sewage treatment outfalls, or diffuse sources such as agricultural run-off.  This is in part being addressed through a review of consents for discharges being carried out and for plans to increase tertiary treatment in waste water treatment plants.  Recent work indicates water quality may be more important for the condition of mudflats than hitherto recognised, and links between condition assessments and water quality issues needs to be strengthened. 
 
Coastal squeeze occurs when sea defences prevent vegetation migrating landwards in response to sea-level rise.  The result is a loss of shoreline habitats.  Coastal squeeze is being addressed in England through shoreline management plans, estuary strategies and through other mechanisms such as high level biodiversity targets within the Environment Agency.  However, much of this has a long lead-in time and outcomes will be constrained by strategic considerations outwith the control of the country conservation agencies.