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The authors are solely responsible for the content of this report. Material included herein does not represent the opinion of the European Community, and the European Community is not responsible for any use that might be made of it.
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It was initially anticipated that the Paull Holme Strays site would ultimately creat 45ha of mudflat and 35ha of salt marsh, i.e 56% mudflat and 44% salt marsh. Estimates for 2007 from an aerial image were 64% mudflat and 36% salt marsh. Estimates from mapping the site gave 46% mudflat and 54% salt marsh in 2010. As the site is still accreting and the vegetation is spreading across the mudflat, the area of mudflat is likely to decrease further in future years, and may ultimately be only a small area opposite the breach where conditions of exposure are more similar to outside.
Besides the general similarity between the areas inside and outside the realignment site, there is still a high degree of spatial variation in community structure within the site, and, due to the low number of species and abundance in the south eastern sector, the realignment site as a whole cannot be considered typical mudflat habitat for this area and the communities are still not considered to be fully developed.
The overall target was to create functioning intertidal habitat and to monitor progress over a 10 year period. Although all parameters monitored are on target to meet criteria set, it is feared that as the site continues to develop in the long term it may not continue to provide 'like for like' direct compensatory habitat. Discussions are ongoing with Natural England to determine what level, if any, of management is required to ensure the site continues to meet its targets and possibly include the habitat within the designated site.
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Paull Holme Strays Managed Realignment
Table of content
- 1. Measure description
- 1a. Measure description
- 1b. Monitoring
- 1c. Monitoring results
- 2. Execution of main effectiveness criteria
- 2a. Effectiveness according to development targets of measure
- 2b. Impact on ecosystem services
- 2c. Degree of synergistic effects and conflicts according to uses
- 3. Additional evaluation criteria in view of EU environmental law
- 3a. Degree of synergistic effects and conflicts according to WFD aims
- 3b. Degree of synergistic effects according to Natura 2000 aims
- 4. Crux of the matter
- 5. Literature
Effectiveness according to development targets of measure
The involvement of an environmental steering group throughout all stages of this scheme was invaluable and through this, the project team was able to identify simple and low cost suggestions and opportunities to maximize the benefits both in the short term, whilst the site was developing, but also in the longer term development and progress of the site. Early landowner liaison and negotiations, along with involvement from local parishes and landowners should be undertaken as early as possible in order to come to agreements at an early stage.Habitat Area
The specific targets for the Paull Holme Strays managed realignment were to create the following habitats:- 45ha of intertidal mudflats (which must support an invertebrate assemblage of similar species, population abundance and biomass to reference sites in the middle estuary)
- 35ha of saltmarsh (which should support a range of species which are representative of the middle and lower saltmarsh communities in the area. Upper saltmarsh should be retained on the remnant flood bank).
Habitat quality
The Paull Holme Strays realignment site comprises a wider northern section and a narrower southern strip. Vegetation has colonised the new mudflat inside the site and except at the highest elevations, very little of the pre-breach vegetation now remains. By 2007, 23 plant species typical of saltmarsh present in this part of the realignment were noted, with all species found outside the realignment also being recorded inside it.It was initially anticipated that the Paull Holme Strays site would ultimately creat 45ha of mudflat and 35ha of salt marsh, i.e 56% mudflat and 44% salt marsh. Estimates for 2007 from an aerial image were 64% mudflat and 36% salt marsh. Estimates from mapping the site gave 46% mudflat and 54% salt marsh in 2010. As the site is still accreting and the vegetation is spreading across the mudflat, the area of mudflat is likely to decrease further in future years, and may ultimately be only a small area opposite the breach where conditions of exposure are more similar to outside.
Benthos
It was reported in 2010 (IECS) that the total number of species found inside the managed realignment site is now comparable to that found outside. A total of 22 species were recorded from the area as a whole with all of them being found inside the site and 19 species being found outside. The mean number of species, Shannon Weiner diversity (H’) and biomass inside the site is now comparable to that one outside, given the significant increase of all parameters since 2004. However, the total abundance still remains much lower inside the site, given that a large increase of this parameter has occurred also outside the site between 2008 and 2010. This increase in abundance (both inside and outside the site) is due to a large increase in the abundance of the sabellid Polychaete Manayunkia aestuarina. Comparison of the two areas excluding M. aestuarina indicates that abundance remains relatively low inside the site.Besides the general similarity between the areas inside and outside the realignment site, there is still a high degree of spatial variation in community structure within the site, and, due to the low number of species and abundance in the south eastern sector, the realignment site as a whole cannot be considered typical mudflat habitat for this area and the communities are still not considered to be fully developed.
Bird Usage
The site has met its initial targets for wader usage in terms of number however, densities remain lower than adjacent areas.General effectiveness
The possible long-term development of the new mudflat into saltmarsh is likely to reduce the available habitat for benthic invertebrates and foraging birds, although additional saltmarsh may provide high tide refuges for birds, as well as roosting and nesting sites.The overall target was to create functioning intertidal habitat and to monitor progress over a 10 year period. Although all parameters monitored are on target to meet criteria set, it is feared that as the site continues to develop in the long term it may not continue to provide 'like for like' direct compensatory habitat. Discussions are ongoing with Natural England to determine what level, if any, of management is required to ensure the site continues to meet its targets and possibly include the habitat within the designated site.