Lowland raised bogs

Context

Bogs are wetlands that support vegetation that is usually peat-forming and which receive mineral nutrients principally from precipitation rather than ground water.  This is referred to as ombrotrophic (rain-fed) mire.  Two major bog types are identified, namely raised bog and blanket bog.  These two types, are for the most part, fairly distinctive, but they are extremes of what can be considered an ecological continuum and intermediate (or mixed) types occur. 
 
The vegetation of bogs which have not been modified by surface drying and aeration or heavy grazing is dominated by acidophilous species, such as bog-mosses Sphagnum spp., cottongrass Eriophorum spp. and cross-leaved heath Erica tetralix.  The water-table on these types of bogs is usually at or just below the surface.
 
Raised bogs are elevated deposits of peat in the lowlands.  They are divided into active bogs, in which the peat is still being added to, and degraded bogs in which peat formation is at least temporarily at a standstill.  The difference is reflected in the Natura 2000 features: 'active raised bog' and 'degraded bog still capable of natural regeneration'.  The Natura 2000 feature 'depressions in peat substrates (Rhynchosporion)' may also be found on lowland raised bog. 
 
In lowland areas with predominantly acid substrata there are examples of valley and basin mires that receive acid surface seepage, which gives rise to vegetation similar to that of bogs.  However, these types are covered in the Fens and marshes reporting category.
 
SSSIs can be notified if they qualify under criteria outlined in Section 4 of Chapter 8 Bogs 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 19% 22% 21%
Main monitoring coverage E, S, W, NI E, S, NI  
Reported assessments 79 120 199
Completeness of assessments 81% unknown  
Distribution of features     UK
 

Number of assessments reported by country and site type

Country SAC SSSI/ASSI
England 17 38
Scotland 41 63
Wales 9 0
Northern Ireland 12 19
United Kingdom 79 120
 

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
Active raised bogs Active raised bogs 44 55 80%
Degraded raised bogs still capable of natural regeneration Degraded raised bog 32 37 86%
Depressions on peat substrates of the Rhynchosporion Depressions on peat substrates 3 3 100%
Transition mires and quaking bogs Very wet mires often identified by an unstable 'quaking' surface 0 3 0%
 
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
Active raised bogs Active raised bogs 2
Bogs Bogs 38
Estuarine raised bog Estuarine raised bog 2
Intermediate raised bog Intermediate bog 3
Raised bogs Raised bogs 75
 
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

Only a fifth (21%) of lowland raised bogs reported are in favourable condition.  This is well below the average for terrestrial habitats, all habitats, or all features combined.  The proportion of features on A/SSSIs and SAC sites reported in favourable condition is similar, with 22% and 19% respectively.  More of the unfavourable SAC features reported are recovering (52%) than on A/SSSIs (35%).  This no doubtreflects the additional resources aimed at achieving favourable condition on Natura 2000 sites.  No lowland raised bogs in England are in favourable condition, but 44% are unfavourable-recovering.
 
The main causes of unfavourable condition are water management (presumably, drainage) and lack of remedial management (neglect).  It is important to recognise that water management (drainage) affects bog condition when carried out within the designated site and around its borders within a marginal area known as the hydrological protection zone.  Other important causes include invasive species (e.g. birch Betula spp.) and under-grazing.  Development carried out under planning permission may have been under-recorded, as it should include commercial peat extraction.  It may be that the activity is split between this category and extraction/removal.  Peat extraction is still a cause of unfavourable condition on about 750 ha of lowland bog in England; most of this is on two pSAC sites.
 
Air pollution is only cited in a few cases.  This is likely to be an under-estimate, as most surveyors would attribute the effects of it to other causes, such as drainage.  Critical loads of sulphur are still being exceeded for some lowland raised bogs, and are predicted to do so at least to 2010.  Dry deposition of ammonia is still very high in most parts of England, Wales and Northern Ireland.  Bisulphite has an inhibitory effect on some Sphagnum moss species, and deposition of nitrogen encourages rank competitors such as the purple-moor grass Molinia caerulea.