| Natural England |
H |
Habitats (marine) |
H1110 |
Sandbanks which are slightly covered by sea water all the time |
2.5.1 |
2.5.1 Method used - pressures |
pressures_method |
Each site lead was asked to identify the top 2 pressures and the top 2 threats for each sub feature/feature within their SACs. Ranking of threats and pressure was achieved by calculating the count of each threat or pressure for all sites. These counts were then ranked and assigned High, Medium or Low status, depending on the number of counts each pressure/threat received. This method was used as it was the most inclusive method to make sure pressure and threats from all separate sites were considered. |
| Natural England |
H |
Habitats (marine) |
H1110 |
Sandbanks which are slightly covered by sea water all the time |
2.6.1 |
2.6.1 Method used - threats |
threats_method |
Each site lead was asked to identify the top 2 pressures and the top 2 threats for each sub feature/feature within their SACs. Ranking of threats and pressure was achieved by calculating the count of each threat or pressure for all sites. These counts were then ranked and assigned High, Medium or Low status, depending on the number of counts each pressure/threat received. This method was used as it was the most inclusive method to make sure pressure and threats from all separate sites were considered. |
| Natural England |
H |
Habitats (marine) |
H1110 |
Sandbanks which are slightly covered by sea water all the time |
2.7.4 |
2.7.4 Structure and functions - methods used |
structure_and_functions_method |
2. Inside SACs
All marine habitat features within SACs have been assessed at the attribute level for all sub-features by individual site leads. This process made use of all available data and used a combination of the targets within ?favourable condition tables? within existing Regulation 33 / 35 documents and Common standards Monitoring Guidance. Individual attribute level information was aggregated centrally using a series of ?decision rules? with the resulting feature assessments checked by the site leads.
Assumptions applied through this process:
Where Regulation 33 / 35 documents did not include site specific favourable condition tables e.g. Due to additional features being added through the process of moderation, assessments were undertaken using the generic attributes and suitable targets set out within relevant Common Standards Monitoring Guidance. This effectively assumes that these generic attributes describe the key ecological attributes of feature condition at each site sufficiently well to enable them to form a sound basis for feature assessment.
The method of aggregating sub-feature attribute and ?feature wide? attributes to produce site based condition of individual Annex I features assumes the following:
a. General feature attributes identified in the Regulation 33 package favourable condition table apply across each and every individual sub-feature identified for assessment.
B. Where spatial extent data are unavailable for each sub-feature being assessed, the area assigned to each sub-feature is an equal portion of the area identified for the feature (e.g. If there are four sub-features the sub-feature area will be 25% of the total). Where the extent of one or more sub-features within a feature has been quantified, the remaining unallocated area has been shared equally across the remaining sub-features.
B.c. Where data are only available to assess a proportion of the attributes for a feature or sub feature assessments have still been undertaken where at least 50% of the attributes have been able to be assessed. If less than 50% of the attributes were not assessed the whole sub-feature was classed as not-assessed. This introduces a significant assumption that the minority of attributes for which it has not been possible to make an assessment would not overturn the assessment made based on the majority of attributes in any given area. The most obvious example of how this could be incorrect is where a ?not assessed? attribute is in reality unfavourable which following the rational outlined above would lead to the area being declared unfavourable where it may otherwise be considered favourable if this is the conclusion for all assessed attributes.
C.d. Individual attributes were assessed on a proportion basis within defined percentage ranges: 0-5, 6-25, 26-100 provided on the reporting form. In order to arrive at the overall proportion of a sub feature in each reporting category the proportion of favourable / not assessed was determined by ?averaging? across the remaining attributes. However, to ensure that unfavourable areas were not downsized through this averaging the largest proportion unfavourable for any attribute was always carried through into the final assessment. For example if 10ha of seagrass was unfavourable then this amount would not be rescaled.
D.e. Within this weighting process the maximum of each range was used as the basis for the averaging process as this process was considered to more closely reflect the ?most probable? overall condition than using the range mid points, however this is an assumption that is likely to have a minor effect on the overall proportions of features being assigned to each reporting category. Where a local site lead had chosen two ranges, each being 26-100 then this weighting was altered to more accurately reflect the 50:50 ratio that was implied.
E.f. A similar process was used when sub-feature assessment outputs and ?feature wide attribute assessments? were combined to produce overall feature assessments. In this process these two groups of attributes (sub feature and feature wide) were given equal weightings. This has the effect of giving single attributes in either category greater ?weight? in the determining the overall assessments where they are one of only a few attributes in either of these groups. Again this is an assumption which is likely to have a minor effect on the overall proportions of features being assigned to each reporting category. These proportions were also checked by the individual site leads before submission.
3.4. Outside sites
The Water Framework Directive (WFD) Infaunal Quality Index (IQI) tool has been used to assess the condition of Annex I habitats that occur outside of SACs and SSSIs. The IQI is the metric used to assess benthic infauna communities for Good Ecological Status for the WFD.
The IQI cannot replace the benthic invertebrate-orientated attributes used for assessing the condition of Annex I features. However, the nature of the tool means that it takes account of changes in the following benthic attributes sound in favourable condition tables:
? Sediment character (PSA and salinity data is included in the IQI tool for each sample)
? Range and distribution of subtidal sediment communities
? Nutrient enrichment, macroalgal mats
Whilst not directly comparable, the WFD classification is used as a proxy for condition, with:
? Good and high status indicating favourable condition, and
? Moderate, poor and bad indicating unfavourable condition.
The Environment Agency holds a large amount of WFD benthic invertebrate data, already converted to IQI classifications, from Annex I habitats outside of SACs. They also have converted most Natural England subtidal and intertidal sediment surveys into IQI classifications for use in WFD assessment. Therefore, benthic data from post-2006 Natural England and Environment Agency sediment surveys can be used to feed into the IQI for the following Annex I habitats found both inside and outside of SACs:
? Intertidal mud and sandflats
? Large shallow inlets and bays
? Estuaries
? Subtidal sandbanks
How the IQI is calculated for Annex I habitats
? A GIS layer of all the IQI data points used in the 2012 WFD classifications was provided by the EA. Each data point is an individual benthic sample (collected between 2006 and 2011) that has been converted to an IQI status using the metric. Note that some NE intertidal and subtidal sediment surveys may not be in this data set because...
A. The data hasn?t been given to the Environment Agency
b. The sample method used is not compatible with the IQI tool (e.g. Box cores).
C. The IQI only applies to surveys within 1nm (the extent of the WFD).
? JNCC shapefiles of the Estuaries, Subtidal Sandbanks and Large Shallow Inlets & Bays Annex I habitats were overlaid over the IQI layer. For each Annex I habitat, intersecting IQI data points were selected and converted to a separate layer, resulting in 3 layers of IQI data points within polygons of each Annex I habitat. As an example, Plymouth Sound SAC had different data points which overlay each of the Annex I habitat (Fig 3).
? For each set of IQI data point overlying a Annex I polygon, an average IQI was calculated for each year of data available, enabling observations of temporal change. Caution should be observed for surveys with few samples in averaged across the entire SAC. The ?Overall? status is used by the EA for the Water Framework Directive, rather than statuses for individual surveys.
A proxy condition is assigned based on the WFD score ? Favourable or Unfavourable. A confidence in its condition can also be assigned, calculated using the Environment Agency?s VISCOUS tool. This takes the standard error of the data points at a site, and quantifies the uncertainty of the status assessment. The closer a confidence score is to 50% or less highlights which classifications should be treated with an increasing element of caution.
4.5. Data mapping
General comments:
- As a default, when no other GI information to inform area of feature has been available, we have used the figures from the original Standard Data Forms, available on the JNCC website. We are aware that these are likely to be estimates and therefore contain a substantial degree of inaccuracy. |
