Saltmarsh Monitoring Project 2007-2008
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Saltmarsh Monitoring Project 2007-2008 Contract reference D/C/227 Final Report (2009) Mark McCorry & Tim Ryle A Report for Research Branch, National Parks and Wildlife Service McCorry & Ryle 2009 Acknowledgements Several people have made a significant contribution into this survey and gave us a lot of help along the way. Dr Karen Gaynor and Dr Deirdre Lynn of the Research Branch, NPWS. Many other Research Branch staff who provided information, reports and time including Robert Ovington and Brian Carroll in the GIS Unit. Many regional staff of the NPWS also provided specific information about individual sites. Several members of Dublin Naturalists Field Club, Botanical Society of Britain and Ireland, Coastwatch and Birdwatch Ireland who gave us information about specific sites. Lastly, sincere thanks to all the farmers and land-owners who kindly gave us access to private land around the coast. Saltmarsh Monitoring Project 2007-2008 Summary Report i McCorry & Ryle 2009 Summary The Saltmarsh Monitoring Project (SMP) was designed to meet the monitoring obligations of the EU Habitats Directive with regard to Annex I saltmarsh habitats in Ireland. The initial phase of the survey was carried out in 2006 and involved the survey of 31 sites (McCorry 2007). A monitoring methodology was developed for Irish saltmarsh habitats based on guidelines produced by the JNCC (2004) and the Cmmission of the European Communities (2006). This system is based on vegetation surveys, and assessments of threats and management practices. The current phase of the project mapped and assessed the conservation status of the following Annex I saltmarsh habitats at an additional 100 sites around the coast of Ireland. • Salicornia and other annuals colonising mud and sand (1310), • Atlantic salt meadows (ASM) (Glauco-Puccinellietalia maritimae) (1330), • Mediterranean salt meadows (MSM) (Juncetalia maritimae) (1410), • Mediterranean and thermo-Atlantic halophilous scrubs (Sarcocornetea fruticosi) (1420), Spartina swards were mapped where present but were not assessed at each site surveyed. The current phase of the SMP mapped a total of 1890 ha of Annex I saltmarsh habitat at 100 different sites and carried out 1429 monitoring stops in total (Table i). In combination with the data collected from McCorry (2007) this will provide an excellent resource for the future monitoring of Irish saltmarshes. Unless otherwise stated, all of the results and data presented in this report refer to the 100 sites surveyed in 2007-2008. Table i. Total area of each Annex I saltmarsh habitat and Spartina sward surveyed during 2007-2008 (100 sites), 2006-2008 (131 sites), estimates of total national area of each habitat and the percentage of each habitat surveyed during the two phases of the SMP. Total Surveyed Area (ha) % national area 2007-2008 (100 1 estimated Habitat 2006-2008 2 surveyed by two sites) National Area phases of SMP 1310 67.53 107.7 183 3 59 1330 1,002.81 1,462.35 2,590 56 1410 416.12 584.19 1,000 58 1420 0.358 1.088 1.1 99 Spartina sward 403.16 527.29 1,520 35 Total 1,889.98 2,682.35 5,300 1 Includes Annex I habitats surveyed during 2006 (McCorry 2007) (131 sites). 2 See Section 3.3. 3 Based on a proportion of the total estimated national area of saltmarsh. Achieving Favourable Conservation Status is the overall objective for all Annex I habitat types of European Community interest listed in the Habitats Directive (Commission of the European Communities 2006). It is defined in positive terms, such that a habitat type or species must be prospering and have good prospects of continuing to do so. Monitoring of habitats involves establishing a series of targets that define the desired condition of a habitat attribute, e.g. it is considered desirable that saltmarsh habitats were not overgrazed. Assessment of Saltmarsh Monitoring Project 2007-2008 Summary Report iii McCorry & Ryle 2009 conservation status follows a rule-based approach and involves the evaluation of four parameters – Range, Area (Extent), Structures and Functions, and Future Prospects. The method of assessing conservation status uses a ‘Traffic light’ system, with habitat condition rated as favourable (F), unfavourable-inadequate (UI) or unfavourable-bad (UB). A UB assessment of any of the four parameters assessed results in an overall rating of UB. An assessment of the conservation status of the latter parameters (excluding range) was derived for each habitat at the site level. Changes in area were estimated by examining old maps. Structure and Functions was assessed by collecting data at a representative number of stops across each habitat. A suite of indicators of condition was derived and targets were set for each indicator. A certain number of targets had to be reached for a monitoring stop to pass. The proportion of passes or fails was used to assess the Structure and Functions parameter. Future Prospects were assessed by determining the impact of positive and negative activities at the site. Impacts on Irish saltmarsh habitats (2007-2008) The main impacts noted were identical to those noted in the first phase (McCorry 2007): • grazing by livestock, • Common Cordgrass ( Spartina anglica ) (invasive species), • infilling, reclamation and other impacts related to coastal development. This phase of the SMP found that only 8.3 ha of saltmarsh had been infilled, reclaimed or destroyed by other activities related to coastal development at the 100 sites surveyed, representing a loss of only 0.5% of the overall area of mapped Annex I saltmarsh habitat (ASM & MSM). Some significant destructive damage to saltmarsh was also caused by maintenance works on adjacent seawalls used for coastal defence. Erosion and accretion also affects saltmarsh but both of these are natural processes and saltmarsh will attempt to adjust or reach equilibrium in response to climatic and local changes. In general while there were frequent physical signs of erosion observed at many sites, there was very little evidence of actual measurable saltmarsh loss or saltmarsh retreat during the current monitoring period. There were only 6 sites where erosion was assessed as having an irreparable influence on either ASM or MSM. This was related to the artificial constraint of saltmarsh habitats by landward coastal defences or structures like roads, so there was limited or no capacity for landward retreat at these sites. The methodology did not consider natural erosion as an unfavourable condition. The SMP is a baseline survey so erosional changes may become more apparent through future monitoring surveys Accretion was also noted at many sites (34). Some of these sites are quite dynamic and some of the recent saltmarsh growth may be ephemeral and is likely to be continually re- worked. However, saltmarsh growth at other sites is likely to be part of long term accretion trend. At several sites continued accretion has promoted the development of Spartina swards. Overall gross changes to the lower saltmarsh boundary in the past 100 years were also analysed using GIS by comparing the current extent of saltmarsh to the former extent as indicated by the OSI 2 nd edition 6 inch maps. These data estimates that 17.5 ha of saltmarsh were eroded away at the surveyed sites during this period. However, 255.6 ha of saltmarsh were also newly developed. Sites with saltmarsh growth were more common in the northern Saltmarsh Monitoring Project 2007-2008 Summary Report iiii McCorry & Ryle 2009 half of the country. (This analysis did not consider changes to the upper saltmarsh boundary.) Impacts on Salicornia flats This habitat has a much more limited extent compared to established saltmarsh with only 68 ha mapped, and its site-by-site distribution varied significantly. About 84% of the total area mapped during 2007-2008 was found at only two sites. Most saltmarshes contained < 0.01 ha of this habitat. There were few impacts on Salicornia flats and this is related to its position at the seaward end of the saltmarsh zonation, where there is less pressure from coastal development and much less grazing pressure. The most significant impact was the presence of Common Cordgrass and this invasive species has the capacity to spread into this habitat and reduce its extent in the future. Therefore its future prospects at many sites (18 out of 48) were assessed as unfavourable . Impacts on Atlantic salt meadows (1330) and Mediterranean salt meadows (1410) Atlantic salt meadows (ASM) was the most extensive saltmarsh habitat mapped during the 2007-2008 survey with 1002 ha mapped (forming 53% of the total saltmarsh area) while 416 ha of MSM was also mapped (22%). The main impacts on ASM and MSM were related to unsustainable heavy grazing by livestock, which created low closely cropped swards with areas badly damaged by poaching in the most badly damaged areas. About 58% of the ASM and 70% of the MSM surveyed during the project was grazed by sheep and/or cattle. However, only 3.1% of the ASM and 0.3% of the MSM was assessed as being overgrazed by sheep while 11.9% of ASM and 9% of MSM was being overgrazed by cattle. Cattle generally cause more damage compared to sheep and this is related to poaching damage caused during grazing. This was frequently confined to sections of the saltmarsh where there was increased traffic, such as access points and tracks. The overall impact of grazing by livestock on MSM was generally lower compared to ASM as Sea Rush (Juncus maritimus ) is generally unpalatable and not grazed by sheep or cattle and sheep will generally avoid dense tall vegetation dominated by Sea Rush. The main impact of the spread of Common Cordgrass on the ASM is the transformation of the lower-pioneer saltmarsh community dominated by Common Saltmarsh-grass and/or Sea Purslane, and also containing frequent Glasswort and Annual Sea-blite.