Condition of intertidal saltmarsh communities in coastal waters determined using Water Environment Regulations methods.
The targets covering the area of intertidal saltmarsh communities at an acceptable condition has largely been achieved in the Celtic Sea UK Marine Strategy sub-region but not for the Greater North Sea, although achievement of the target varies between constituent Regional Seas. Data coverage is limited and there is low confidence in the assessment results.
Background
UK Target on intertidal saltmarsh quality
This indicator is used to assess progress against the Water Environment Regulations (WER) ecological status boundaries and areas of unacceptable impact, which are components of the sediment habitats targets, set in the UK Marine Strategy Part One (Defra, 2019).
Key pressures and impacts
The WER saltmarsh indicator is designed primarily to detect impacts from hydromorphological pressures arising from activities such as sediment transport, navigation, and flood protection, and to a lesser extent, increased nutrient concentrations (eutrophication).
Risk assessment information used in the UKMS assessments was derived by the UK WER monitoring authorities to support the Cycle One River Basin Management Plan (RBMP) classifications by identifying pressures considered likely to cause water bodies to fail to achieve their WER environmental objectives. These identified 83 of the 467 coastal water bodies as ‘At risk’ or ‘Probably at risk’ of failing to meet their objectives due to hydromorphological pressures.
Measures taken to address the impacts
Measures to protect benthic habitats are set out in the UK Marine Strategy Part Three. These include those related to the Habitats Regulations (HR), WER RBMPs, Urban Wastewater Treatment Regulations, Nitrate Pollution Prevention Regulations, OSPAR measures on species and habitats, Marine Spatial Planning, land management schemes, catchment sensitive farming and European Marine Site management schemes.
Monitoring, assessment and regional cooperation
Areas that have been assessed
Progress against the UK target was assessed for the Celtic Sea UK Marine Strategy sub-region and Greater North Sea UK Marine Strategy sub-region and their constituent UK Regional Seas set out in Charting Progress 2 (CP2) (UKMMAS, 2010). These areas were assessed in the 2018 UK Marine Strategy assessments.
Monitoring and assessment methods
Routine monitoring of saltmarsh is undertaken for WER, HR and Site of Special Scientific Interest site assessment. The WER saltmarsh indicator is a multi-metric index based on saltmarsh extent (as proportion of the intertidal, proportion of historic extent and change over multiple periods), proportions of zones present, area covered by the dominant zone and taxa number as a proportion of a historic reference. These measurements are combined to derive an Ecological Quality Ratio (EQR). Newly created marsh is not included in the assessment, as these are still developing, and not part of the surveillance programme which focuses on the long-term baseline monitoring.
Assessment thresholds
The indicator quality threshold is defined as the boundary for WER Good Ecological Status (EQR ≥0.60) or Good Ecological Potential (GEP) for Heavily Modified Water Bodies (HMWBs). The UK Marine Strategy assessment target is met where the assessed surface area achieving the quality threshold meets the extent threshold of 95%.
Regional cooperation
WER saltmarsh indicator assessments are included within OSPAR Quality Status Report benthic habitat community condition assessments. The boundary for Good Ecological Status could not be intercalibrated with that of other North-East Atlantic Member States.
Further information
The Water Environment Regulations intertidal saltmarsh indicator is a multi-metric indicator derived from the following measurements of the saltmarsh communities within a water body:
Saltmarsh extent as a proportion of “historic saltmarsh”: Current extent is mapped by digitising areas of saltmarsh from aerial imagery. The extent area is measured as a proportion of historic saltmarsh area. Historic saltmarsh area is derived from historic maps and from an estimate of land claim using LiDaR (Light Detection and Ranging) measurements.
Saltmarsh extent as a proportion of the intertidal area: The extent is measured as a proportion of the intertidal area which has been derived from the OS landline series.
Change in saltmarsh extent over two or more time periods: Recent change is measured by comparing the current extent with a recent baseline extent.
Proportion of saltmarsh zones present: The tool assumes that an area of saltmarsh can have up to five functional zones (in England and Wales). The number of zones as a proportion of the maximum five is measured for each water body.
Proportion of saltmarsh area covered by the dominant zone: The tool assumes that no one zone should strongly dominate the others. The most dominant zone area is measured as a proportion of the overall areal cover.
Taxa as a proportion of a historical reference value or as a proportion of 15 taxa: Where the National Biodiversity Network (NBN) provides suitable historic data the total number of present taxa is compared to the total number of historically recorded taxa. Where NBN data is not available a value of 15 taxa is used.
Values of these six metrics were calculated to determine what these would be for undisturbed waters (reference conditions). The observed results are then compared with the reference condition values and combined to calculate the EQR which operates between zero and one. EQR values close to one indicate angiosperm communities are close to their natural state; those near to zero indicate a high level of pollution or disturbance. The EQR is used to categorise the water body into one of the five Ecological Quality Status classes as required by the WER:
High status: ≥ 0.8
Good status: 0.6 ≤ 0.8
Moderate status: 0.4 ≤ 0.6
Poor status: 0.2 ≤ 0.4
Bad status: <0.2
Further details on the WER intertidal saltmarsh indicator are available at the WER UK Technical Advisory Group (UKTAG) website:
Assessment method
Baseline setting
The WER saltmarsh indicator reference conditions have been used for the UK Marine Strategy baseline. Reference conditions are based on i) zero loss in extent relative to historic data, ii) full coverage of the available intertidal habitat, iii) no reduction in extent relative to recent data, iv) the presence of five saltmarsh zones, v) the maximum number of zones for the biogeographical area and vi) the number of taxa in historic data (or 15 taxa, if no historic data). This complies with the approaches to setting baselines for UK Marine Strategy as outlined by the OSPAR Intersessional Correspondence Group on Biodiversity Assessment and Monitoring (ICG COBAM) (OSPAR Commission, 2012) as:
-
a state in which the anthropogenic influences on species and habitats are considered to be negligible.
-
a state in the past, based on a time-series dataset for a specific species or habitat, selecting the period in the dataset which is considered to reflect least impacted conditions.
Quality and extent target
The target of Good Ecological Status or GEP (where mitigation measures against the modification features are considered sufficient for HMWBs) as defined for the WER is being applied as the indicator quality threshold for the UK Marine Strategy assessments. The extent target is met where ≥95% of the surface area of the assessed saltmarsh communities within a UK Regional Sea meet the quality threshold. Saltmarsh beds are priority habitats within the UK Biodiversity Action Plan (BAP), so this target conforms to those relating to the assessed surface area achieving an acceptable condition recommended by UKTAG (2007) for High Ecological Status and the Habitats Regulations target for Favourable Condition.
The qualitative and quantitative targets may be reviewed and revised in future assessment cycles.
Aggregation approach
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Saltmarsh WER classification results for coastal water bodies from the 2021 Cycle Three RBMPs were collated at the survey level from the UK WER monitoring authorities. The percentage cover of assessed saltmarsh beds at each WER ecological status class were calculated within each UK Regional Sea. The assessments use data derived WER classification results for use in the WER Cycle Three RBMP and exclude those rolled forwards from previous classifications. Please note: UK Marine Strategy assessments are based on the data and processes used for the WER water body classifications within the RBMP assessments and exclude changes to the classifications as a result of subsequent investigations.
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Saltmarsh beds categorised as ‘Bad’, ‘Poor’ or ‘Moderate’ ecological status under WER were categorised as being below the indicator quality target, with those at ‘Good’ or ‘High’ ecological status categorised as being above the indicator quality target.
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The final UK Regional Sea assessment is calculated as the total extent of saltmarsh within all classified water bodies which meets the indicator quality target as a percentage of the maximum recorded saltmarsh extent (based on either historic or recent data). The overall indicator target is achieved when the extent of classified saltmarsh meeting the quality target is 95% of all classified saltmarsh beds within a UK Regional Sea.
Please note: the method for setting the saltmarsh indicator baseline has been updated from the use of the historical saltmarsh extent in the 2018 assessments to the use of the maximum recorded saltmarsh extent in the current assessment.
Confidence assessment
The approach to determining confidence in the UK Regional Sea assessments is based on the extent to which the indicator and associated assessments fulfil certain criteria which impact the extent to which the assessment represents the available habitat relevant to the indicator, the extent to which the indicator can identify the overall effect of the relevant pressures and the confidence in the assessment result being above/below the indicator target. The confidence assessment method was developed for the 2018 Marine Strategy assessments. Confidence thresholds were arbitrarily set based on an equal division of the range of values for each criterion. Details of the criteria are provided in Table 1.
Table 1: Confidence assessment criteria for the UK Regional Sea WER saltmarsh indicator assessments.
|
UK Regional Sea confidence assessment criteria |
Low |
Medium |
High |
|
Spatial coverage of classification data
This criterion indicates the extent to which WER water bodies (WBs) within a UK Regional Sea are classified by the indicator. High proportion of WBs classified within a UK Regional Sea corresponds to high confidence in the UK Marine Strategy assessment. |
<33.3% of WER water bodies (WBs) assessed |
33.3% - 66.6% of WBs assessed |
>66.6% of WBs assessed |
|
Spatial coverage of pressures
This criterion provides a measure of the extent to which the classified WER WBs correspond to the presence of relevant pressures (as determined through the WER risk assessments), indicating the potential of the WER classifications to detect the associated impacts of such pressures. High coverage of the areas exposed to pressure (i.e. those considered at risk of failing to achieve GES under WER) by the WER water body classifications corresponds to high confidence within the UK Regional Sea scale Marine Strategy assessment. |
<33.3% of At Risk/Probably At Risk WBs assessed |
33.3% - 66.6% of At Risk/Probably At Risk WBs assessed |
>66.6% of At Risk/Probably At Risk WBs assessed |
|
Indicator level agreement (Cohen's Kappa) between assessment results and pressure from Risk Assessments
Cohen’s Kappa agreement provides an indication of the extent to which the indicator WER classifications correspond to the risk assessments at the water body level. Agreement between water bodies categorised as ‘At Risk’ or ‘Probably At Risk’ and those at less than Good Ecological Status is calculated using all water body data. High confidence in the UK Marine Strategy assessments corresponds to high agreement between the indicator classifications and risk assessment results. Low correspondence may be indicative of either low sensitivity of the indicator to the pressure or indicative of a low correspondence between the risk assessment results and the true extent of the pressure (further investigation recommended). |
<0.333 |
0.333 - 0.666 |
>0.666 |
|
Variability of assessment results
This criterion is a measure of the variability of the different WER water body classifications within a UK Regional Sea scale UK Marine Strategy assessment. Low variability in the WER classifications corresponds with high confidence in the assessment. |
<66.6% of assessment units (saltmarsh bed extent) within same WER status |
66.6% - 83.3% of assessment unit (saltmarsh bed extent) at same status |
>83.3% of assessment units (saltmarsh bed extent) at same status |
|
Proximity of observed extent to extent threshold
This criterion is a measure of the magnitude of the difference between the observed extent meeting the quality target and the extent threshold. Large differences between the observed extent meeting the quality target and the extent threshold corresponds to high confidence in the UK Regional Sea scale UK Marine Strategy assessment. |
BAP Priority habitats: assessment within 1.66% of target |
BAP Priority habitats: assessment within 1.66% - 3.33% of target |
BAP Priority habitats: assessment >3.33% of target |
The overall confidence assessment is based on the lowest extent to which the criteria are fulfilled (one-out-all-out).
Deviations by WER Monitoring Authorities
Saltmarsh data was collected for use in the WER Cycle Three RBMP classifications by the Environment Agency (EA) of England and Natural Resources Wales (NRW) only. Both monitoring authorities applied the assessment methods as described within the UKTAG method statement.
Results
Results and progress towards achieving the relevant UK target
Latest findings
Status assessment
Assessments are based on aggregated coastal water body classifications derived for the 2021 Cycle Three UK RBMPs. The results of the aggregated intertidal saltmarsh indicator assessment for the UK Marine Strategy sub-regions and UK Regional Seas presented in Table 2 and Figure 1.
Table 2: Proportion of total saltmarsh extent meeting the indicator quality threshold with corresponding assessment result and confidence for each UK Regional Sea and corresponding Marine Strategy sub-region summary.
| UK MS sub-region | Extent meeting quality threshold (EQR ≥ 0.6) | Extent threshold met (≥ 95%) | Assessment summary | Regional Sea | Extent meeting quality threshold (EQR ≥0.6) | Extent threshold met (≥ 95%) | Confidence |
| Greater North Sea | 16.2 % | ❌ | Target not met for the sub-region (low confidence). | 1. Northern North Sea* | 100.0 % | ✅ | Low |
| 2. Southern North Sea | 10.4 % | ❌ | Low | ||||
| 3. Eastern English Channel | 0.0 % | ❌ | Low | ||||
| Celtic Sea | 100.0 % | ✅ | Target met for the sub-region (low confidence). | 4. Western Channel and Celtic Seas | 100.0 % | ✅ | Low |
| 5. Irish Sea | No data | - | - | ||||
| 6. Minches and Western Scotland | No data | - | - | ||||
| 7. Scottish Continental Shelf | No data | - | - | ||||
| 8. Atlantic North-West Approaches, Rockall Trough and Faeroe/Shetland Channel | Suitable habitat absent | - | - | ||||
| 9. Shared waters between N Ireland and Rep of Ireland | No data | - | - |
The overall indicator target may not have been achieved for the Greater North Sea UK Marine Strategy sub-region-Region, with a high proportion of its assessed area failing to meet the indicator quality target. Whilst the indicator quality threshold has been met for all contributing water bodies in the Northern North Sea, the results indicate that the extent of assessed saltmarsh failing to achieve the quality threshold for the Southern North Sea and Eastern English Channel UK Regional Seas results in the likely failure in meeting the target for UK Marine Strategy sub-region. In the Southern North Sea and Eastern English Channel UK Regional Seas, the majority of water bodies assessed as below the quality target are within water bodies categorised as a ‘Heavily Modified Water Body’ (HMWB) for morphological alteration pressures. None of the WER water bodies have sufficient mitigation measures in place to meet the target of GEP.
The overall target has largely been achieved within the Celtic Seas UK Marine Strategy sub-region, with all assessed areas within its constituent UK Regional Sea (Western Channel and Celtic Seas) meeting the quality target. The remaining five UK Regional Seas have not been assessed due to either an absence of intertidal habitat or an absence of WER classification data.
The confidence for WER saltmarsh indicator assessments has been categorised as low for all UK Regional Seas, primarily due to the low spatial coverage of the WER assessments, and the low proportion of water bodies categorised as being ‘At Risk’ or ‘Probably At Risk’ from morphological alteration and/or diffuse source pollution pressures from the WER Risk Assessments that were classified under WER.
Findings from the 2012 and 2018 UK assessments
This indicator was not considered as part of the 2012 Initial Assessment. The 2018 UK assessment concluded that the targets covering the condition of intertidal saltmarsh communities had been achieved in the Celtic Seas but not for the Greater North Sea UK Marine Strategy sub-regions. The assessment results were assigned low confidence.
The detailed 2018 assessment is available via the UK Marine Monitoring & Assessment Strategy (UKMMAS) Marine Online Assessment Tool:
Trend assessment
The aggregated WER results were not considered as part of the 2012 Initial Assessment.
The saltmarsh assessment results remain unchanged between the 2018 and current assessment, with the overall indicator target continuing to be largely achieved for the Celtic Seas sub-region and not met for the Greater North Sea sub-region. Data availability has reduced slightly, with the number of water body assessments decreasing from eight in the 2018 assessments to seven in the current assessments. The assigned confidence remains low for both sub-regions and all Regional Seas between the two assessments.
Figure 1: UK Regional Seas with corresponding assessment results indicating locations of coastal water bodies used for RBMP Cycle Three WER saltmarsh classifications with corresponding ecological status.
Further information
The assessment is based on aggregated results from the classifications derived for the UK Cycle Three RBMPs. The method is based on the intertidal saltmarsh assemblages and considered responsive to hydromorphological and nutrient enrichment pressures from inshore activities.
The indicator determines the impact to the ecological quality of saltmarsh communities of intertidal habitats by combining measures of saltmarsh extent (current extent as a proportion of the intertidal, proportion of historic extent and extent change), proportions of zones present, extent of the dominant zone as a proportion of the total extent and the number of observed saltmarsh taxa as a proportion of a historic reference. The metrics are combined within an EQR, with weightings set within the tool to most suitably correspond to changes within saltmarsh communities resulting from anthropogenic pressures. Metrics are calculated at the level of WER water body using data collected within a six-year period. The water body assessments indicate the extent to which the entire saltmarsh community deviates from reference conditions and relates this to the boundary between Moderate and Good Ecological Status (EQR ≥0.60) to identify whether the water body has achieved the target of Good Ecological Status. The extent target is met where ≥95% (priority habitat threshold) of the assessed surface area meets the quality target of Good or High Ecological Status or GEP.
A summary of the data used for each UK Marine Strategy sub-region and Regional Sea WER saltmarsh indicator assessment is provided in Table 3. Individual WER water body information with associated Third Cycle RBMP saltmarsh classification results is provided in Table 4.
Table 3: Summary of the data used for the UK Marine Strategy WER saltmarsh indicator Regional Sea assessments.
|
Regional Sea |
Regional Sea |
Total area (sq km) |
RS Total WB area (sq km) |
Assessed WB Count |
Assessed WB Area (Km2) |
Assessed Area (% of total) |
Assessed HMWBs |
Assessed 'At Risk' WER WBs (Morph) |
Assessed 'At Risk' WER WBs (Diffuse) |
|
Greater North Sea |
1. Northern North Sea |
181,551.6 |
8,164.8 |
2 |
100.6 |
1.2 |
0 |
0 |
1 |
|
Greater North Sea |
2. Southern North Sea |
61,882.1 |
3,190.7 |
3 |
799 |
25 |
2 |
3 |
1 |
|
Greater North Sea |
3. Eastern English Channel |
21,970.8 |
1,903.5 |
1 |
259.6 |
13.6 |
1 |
1 |
1 |
|
Celtic Sea |
4. Western Channel and Celtic Seas |
93,959.8 |
5,086.4 |
2 |
112.7 |
2.2 |
0 |
1 |
1 |
Table 4: Summary of WER water body pressure information and WER saltmarsh indicator classification results aggregated to the UK Regional Sea UK Marine Strategy assessments. *Assessed against WER target of Good Ecological Potential (GEP).
|
Regional Sea |
Agency |
Water body name |
HMWB |
At Risk/ Probably At Risk from Diffuse Source Pollution pressure |
At Risk/ Probably At Risk from Morphological alteration pressures |
Saltmarsh Baseline Extent (Ha) |
Saltmarsh Current Extent (Ha) |
Water body EQR |
WER status |
|
1. Northern North Sea |
EA |
Farne Islands to Newton Haven |
No |
No |
No |
30.1 |
30.1 |
0.65 |
Good |
|
1. Northern North Sea |
EA |
Holy Island & Budle Bay |
No |
Yes |
No |
246.9 |
246.9 |
0.75 |
Good |
|
2. Southern North Sea |
EA |
Lincolnshire |
Yes |
No |
Yes |
589.3 |
589.3 |
0.56 |
Moderate* |
|
2. Southern North Sea |
EA |
Norfolk North |
Yes |
Yes |
Yes |
585.8 |
332.7 |
0.62 |
Good* |
|
2. Southern North Sea |
EA |
Wash Outer |
No |
No |
Yes |
2031.0 |
1321.1 |
0.54 |
Moderate |
|
3. Eastern English Channel |
EA |
Solent |
Yes |
Yes |
Yes |
288.5 |
124.6 |
0.48 |
Moderate* |
|
4. Western Channel and Celtic Seas |
NRW |
Burry Inlet Outer |
No |
No |
No |
1211.2 |
1211.2 |
0.79 |
Good |
|
4. Western Channel and Celtic Seas |
NRW |
Milford Haven Outer |
No |
Yes |
Yes |
38.9 |
38.9 |
0.79 |
Good |
The UK WER risk assessments identified a total of 19% (90 of the 467 assessed) of coastal water bodies are ‘At Risk’ or ‘Probably at Risk’ of failing to meet their environmental objectives due to morphological alterations and/or diffuse source pollution (including nutrient enrichment) pressures. The WER risk assessments for England and Wales have not been updated between the 2018 and current assessments so variations in pressures influential to saltmarsh status cannot be evaluated.
Detailed assessment results for each UK Marine Strategy sub-region are presented for each of their component UK Regional Sea. The UK Marine Strategy Sub-Regions comprise of their component UK Regional Seas as follows:
Greater North Sea UK Marine Strategy sub-region:
1. Northern North Sea
2. Southern North Sea
3. Eastern English Channel
Celtic Sea UK Marine Strategy sub-region:
4. Western Channel and Celtic Seas
5. Irish Sea
6. Minches and Western Scotland
7. Scottish Continental Shelf
8. Atlantic North-West Approaches, Rockall Trough and Faeroe/Shetland Channel
9. Shared waters between N Ireland and Rep of Ireland
Northern North Sea
The overall risk of the Northern North Sea failing to meet the target for saltmarsh can be considered as low. All WER assessments within the Northern North Sea indicate that saltmarsh communities are above the indicator quality target, with both assessed water bodies being classified as WER Good Ecological Status (Figure 2). The quality threshold has been achieved for 100% of the assessed surface area for the Northern North Sea, therefore achieving the 95% extent target for the Regional Sea.
Figure 2: Outline of the Northern North Sea Regional Sea inshore indicating saltmarsh UK Marine Strategy assessment result and location and ecological status of the corresponding WER water bodies.
The corresponding WER risk assessments categorise one water body as ‘At Risk’ or ‘Probably At Risk’ of failing to achieve the indicator quality target as a result of morphological alterations and/or diffuse source pollution pressures, with the other water body being ‘Not At Risk’ or ‘’Probably Not At Risk’ of failing. However, the Northern North Sea regional sea intersects with a total of 72 water bodies, with eight of these considered 'At Risk' from morphological alterations and/or diffuse source pollution pressures that have not been assessed with the saltmarsh indicator.
When considering indicator quality targets for HMWBs (WER GEP), none of the water bodies assessed as below the indicator quality target are categorised as HMWBs. Meeting a target of WER GEP is therefore not considered.
The overall confidence in the Northern North Sea regional sea saltmarsh assessment is categorised as low. This is primarily based on the low spatial coverage of the assessment data (two out of 72 water bodies within the region), the low spatial coverage of 'At Risk' or 'Probably At Risk' water bodies in terms of morphological alterations and/or diffuse source pollution pressures (one out of nine water bodies within the region) and the close proximity of the assessment results to the indicator target. The confidence in the assessment is also reduced by the low correspondence between the saltmarsh indicator and morphological alterations and/or diffuse source pollution pressures Risk Assessment results (Kappa agreement of 0.333).
Southern North Sea
The overall risk of the Southern North Sea failing to meet the target for saltmarsh can be considered as high. The majority of WER assessments within the Southern North Sea indicate that saltmarsh communities are below the indicator quality target, with water bodies predominantly being at WER Moderate Ecological Status (two of the three water bodies) with a single water body achieving WER Good Ecological Status (Figure 3). The quality threshold has been achieved for 10.38% of the assessed surface area for the Southern North Sea, therefore failing to meet the 95% extent target for the Regional Sea.
Figure 3: Outline of the Southern North Sea Regional Sea inshore indicating saltmarsh UK Marine Strategy assessment result and location and ecological status of the corresponding WER water bodies.
The WER risk assessments categorise all three water bodies within the Southern North Sea as ‘At Risk’ or ‘Probably At Risk’ of failing to achieve the indicator quality target as a result of morphological alterations and/or diffuse source pollution pressures. The Southern North Sea regional sea intersects with a total of 14 water bodies, with ten categorised as 'At Risk' from morphological alterations and/or diffuse source pollution pressures which have not been assessed with the saltmarsh indicator.
When considering indicator quality targets for HMWBs (WER GEP), one of the water bodies assessed (Lincolnshire) as below the indicator quality target is categorised as a HMWB. In this case, the target of ‘Good Ecological Potential’ has also not been attained for this water body.
The overall confidence in the Southern North Sea regional sea saltmarsh assessment is categorised as low, as a result of the low spatial coverage of the assessment data (three out of 14 water bodies within the region) and the low spatial coverage of 'At Risk' or 'Probably At Risk' water bodies in terms of morphological alterations and/or diffuse source pollution pressures (three out of 13 water bodies within the region). Assessment confidence is also reduced by the low correspondence between the saltmarsh indicator and morphological alterations and/or diffuse source pollution pressure Risk Assessment results (Kappa agreement of 0.333) and the moderate degree of variability in WER water body status within the Southern North Sea regional sea.
Eastern English Channel
The overall risk of the Eastern English Channel failing to meet the target for saltmarsh can be considered as high. A single water body (Solent) within the Eastern English Channel assessed with the saltmarsh indicator was classified as WER Moderate Ecological Potential (Figure 4). The water body was categorised as a HMWB, failing to achieve ‘Good Ecological Potential’ due to insufficient mitigation measures within the water body. The full extent of the assessed surface area of the Eastern English Channel has therefore failed to achieve the quality target with the 95% extent target failing to have been met for the Regional Sea.
Figure 4: Outline of the Eastern English Channel Regional Sea inshore indicating saltmarsh UK Marine Strategy assessment result and location and ecological status of the corresponding WER water bodies.
The single water body assessed within the Eastern English Channel is categorised as ‘At Risk’ or ‘Probably At Risk’ of failing to achieve the indicator quality target as a result of morphological alterations and/or diffuse source pollution pressures. The Eastern English Channel regional sea intersects with a total of 11 water bodies, with 10 of these water bodies considered 'At Risk' from morphological alterations and/or diffuse source pollution pressures which have not been assessed with the saltmarsh indicator.
The overall confidence in the Eastern English Channel regional sea saltmarsh assessment is categorised as low. This is primarily based on the low spatial coverage of the assessment data (one out of 11 water bodies within the region), the low spatial coverage of 'At Risk' or 'Probably At Risk' water bodies in terms of morphological alterations and/or diffuse source pollution pressures (one out of 11 water bodies within the region). The confidence in the assessment is also reduced by the low correspondence between the saltmarsh indicator and morphological alterations and/or diffuse source pollution pressure Risk Assessment results (Kappa agreement of 0.333).
Western Channel and Celtic Seas
The overall risk of the Western Channel and Celtic Seas failing to meet the target for saltmarsh can be considered as low. The two assessed water bodies within the Western Channel and Celtic Seas were classified as WER Good Ecological Status, indicating that saltmarsh communities are above the indicator quality target within the Regional Sea (Figure 5). The quality threshold has therefore been achieved for 100% of the assessed surface area, meeting the 95% extent target for the Western Channel and Celtic Seas Regional Sea.
Figure 5: Outline of the Western Channel and Celtic Seas Regional Sea inshore indicating saltmarsh UK Marine Strategy assessment result and location and ecological status of the corresponding WER water bodies.
One water body was categorised as ‘At Risk’ or ‘Probably At Risk’ of failing to achieve the indicator quality target as a result of morphological alterations and/or diffuse source pollution pressures within the WER Risk Assessments, with the remaining water body being ‘Not At Risk’ or ‘’Probably Not At Risk’ of failing. The Western Channel and Celtic Seas regional sea intersects with a total of 25 water bodies, with 14 of these water bodies categorised as 'At Risk' from morphological alterations and/or diffuse source pollution pressures which have not been assessed with the saltmarsh indicator.
The overall confidence in the Western Channel and Celtic Seas regional sea saltmarsh assessment is categorised as low. This is primarily based on the low spatial coverage of the assessment data (two out of 25 water bodies within the region), the low spatial coverage of 'At Risk' or 'Probably At Risk' water bodies in terms of morphological alterations and/or diffuse source pollution pressures (one out of 15 water bodies within the region) and the close proximity of the assessment results to the indicator target. The confidence in the assessment is also reduced by the low correspondence between the saltmarsh indicator and morphological alterations and/or diffuse source pollution pressures Risk Assessment results (Kappa agreement of 0.333).
Conclusions
The target for the saltmarsh communities has been largely met for the Celtic Seas UK Marine Strategy sub-region but has not been met for considerable areas of the Greater North Sea UK Marine Strategy sub-region. Confidence in the assessment is low for both sub-regions.
The indicator target has been met for two of the four assessed UK Regional Seas. In the remaining two, considerable areas of assessed saltmarsh have not achieved the quality threshold. The hydromorphological pressures which impact the saltmarsh communities have a relatively localised effect, operating over relatively small spatial scales. The indicator results are therefore likely to be of limited relevance to UK Marine Strategy sub-region and Regional Sea scale assessments, although effects of larger scale pressures such as eustatic sea level change should be considered.
Reduction in the quality of saltmarsh communities may be occurring within the Southern North Sea and Eastern English Channel, potentially accountable to hydromorphological pressures within HMWBs. Sufficient mitigation measures are in place for only one HMWB within the Southern North Sea with further mitigation measures required if WER GEP is to contribute to meeting UK Marine Strategy targets in these UK Regional Seas. The results reflect overall achievement of targets within the assessment period and are unable to provide directional trends.
The results are based on a low number of surveys with additional data required to confirm the failures with detailed investigation of the saltmarsh communities and corresponding pressures being required before any reasons for failures can be confirmed.
The results may inform data collection and research requirements to improve confidence and accuracy of future assessments.
Knowledge gaps
The knowledge gaps accompanying the assessments include the following:
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The assessments represent a small proportion of the overall UK coastline with WER assessments provided for eight out of 467 coastal water bodies. The natural conditions required for saltmarsh beds to exist limits their occurrence in coastal water bodies.
-
Saltmarsh classifications were not undertaken for WER for Scotland and Northern Ireland for RBMP Cycle Three.
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A comprehensive dataset of the full Available Intertidal Habitat for saltmarsh is not yet available.
-
The tool does not account for accreting or drowning shores.
-
The saltmarsh indicator is not calibrated for different grazing pressures.
-
Rare species are not specifically targeted during WER surveys and have equal weighting to common species within the saltmarsh indicator.
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It is recommended that the results of WER investigations are considered in future assessments.
References
Defra (2019). Marine Strategy Part One: UK Updated Assessment and Good Environmental Status. 23 October 2019. Accessed 10 July 2025. https://www.gov.uk/government/publications/marine-strategy-part-one-uk-updated-assessment-and-good-environmental-status.
Authors
Graham Phillips1
1Environment Agency
Assessment metadata
| Assessment Type | UK Marine Strategy Assessment Part 1 (2024) |
|---|---|
Benthic habitats | |
| Point of contact email | marinestrategy@defra.gov.uk |
| Metadata date | Tuesday, July 1, 2025 |
| Title | Condition of intertidal saltmarsh communities in coastal waters determined using Water Environment Regulations methods. |
| Resource abstract | |
| Linkage | Water Framework Directive Cycle 3 River Basin Management Plans: England: Northern Ireland: Scotland: Wales: English language version: https://naturalresources.wales/evidence-and-data/research-and-reports/water-reports/river-basin-management-plans/river-basin-management-plans-published/?lang=en |
| Conditions applying to access and use | © Crown copyright, licenced under the Open Government Licence (OGL). |
| Assessment Lineage | |
| Dataset metadata | Please contact marinestrategy@defra.gov.uk |
| Dataset DOI | Please contact marinestrategy@defra.gov.uk |
The Metadata are “data about the content, quality, condition, and other characteristics of data” (FGDC Content Standard for Digital Geospatial Metadata Workbook, Ver 2.0, May 1, 2000).
Metadata definitions
Assessment Lineage - description of data sets and method used to obtain the results of the assessment
Dataset – The datasets included in the assessment should be accessible, and reflect the exact copies or versions of the data used in the assessment. This means that if extracts from existing data were modified, filtered, or otherwise altered, then the modified data should be separately accessible, and described by metadata (acknowledging the originators of the raw data).
Dataset metadata – information on the data sources and characteristics of data sets used in the assessment (MEDIN and INSPIRE compliance).
Digital Object Identifier (DOI) – a persistent identifier to provide a link to a dataset (or other resource) on digital networks. Please note that persistent identifiers can be created/minted, even if a dataset is not directly available online.
Indicator assessment metadata – data and information about the content, quality, condition, and other characteristics of an indicator assessment.
MEDIN discovery metadata - a list of standardized information that accompanies a marine dataset and allows other people to find out what the dataset contains, where it was collected and how they can get hold of it.