UHI Thesis - pdf download summary Remediation and restoration of ocean exposed cliff-top, in the context of Dounreay (Scotland) nuclear power plant decommissioning Braidwood, David DOCTOR OF PHILOSOPHY (AWARDED BY OU/ABERDEEN) Award date: 2018 Awarding institution: The University of Edinburgh Link URL to thesis in UHI Research Database General rights and useage policy Copyright,IP and moral rights for the publications made accessible in the UHI Research Database are retained by the author, users must recognise and abide by the legal requirements associated with these rights. This copy has been supplied on the understanding that it is copyright material and that no quotation from the thesis may be published without proper acknowledgement, or without prior permission from the author. 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Oct. 2021 Remediation and restoration of ocean exposed cliff-top, in the context of Dounreay (Scotland) nuclear power plant decommissioning David Walter Braidwood BSc (Hons) Conservation and Ecological Management, University of Edinburgh (2007) MSc Biodiversity and Taxonomy of Plants, University of Edinburgh (2010) A thesis presented for the degree of Doctor of Philosophy in Environmental Science at the University of Aberdeen September 2017 Declaration I, David Walter Braidwood, have composed this thesis. All the work included in this thesis I have carried out myself, with the exception of section 1.6 in the introduction, which was written up as a journal paper following discussion with John Coll of Maynooth University, and Roxane Andersen, and was reviewed prior to submission by Mark Taggart, Melanie Smith and Graeme Morgan. Assistance in the lab preparing soil samples for analysis was provided by Anna Eberle (ERI intern). Roxane Andersen (ERI), my director of studies, and supervisors Mark Taggart (ERI), Melanie Smith (Inverness College UHI), and Graeme Morgan (DSRL), have helped supervise the design, data analysis and writing of the thesis. Feedback from them has been incorporated. All quotations within this thesis are distinguished by quotation marks, and sources of information have been acknowledged. This thesis, or any part thereof, has not been accepted in any previous application for a degree. David W. Braidwood September 2017 1 ‘Restoration ecology is an expensive self-indulgence for the upper classes, a New Age substitute for psychiatry. It distracts intelligent and persuasive people from systematic initiatives’ Kirby (1994) ‘Unless someone like you cares a whole awful lot, Nothing is going to get better. It’s not’ The Lorax, Dr.Seuss (1971) Acknowledgements Many thanks are owed to my Director of Studies, Roxane Andersen, for the help, support and feedback she has provided over the course of the past few years. It has not always been an easy time, but her willingness to help, take time to explain things (often again…and again), and to help keep me on the right track, have been immensely appreciated. Other supervisors also deserve thanks: Mark Taggart, for much needed assistance in the labs – in both discussing and training. Melanie Smith for time at the start discussing options of which direction to head in, and offering continued advice. Finally Graeme Morgan, at DSRL, for providing the assistance and support on the industry side. Others at Dounreay who have helped include Lindsay Henderson, helping at the start, and Mark Kime, there until the end! Thanks too for funding from DSRL. Thanks to those who willingly let me on to their land to sample and survey – I appreciated the warm sunny weather I got virtually every survey day in 2014, and to Nick Littlewood for help with invertebrate identification in 2016. Thanks to those ERI staff and students who assisted, especially Dagmar ‘Dasha’ Svobodova, Mona Larssen and Colin McKenzie for help in the labs, Paul Gaffney (for taking a break from washing tubes to help me with the AQ2 and R), and Andrew French (for taking a break from GIS and R to help me with the ICP – and then to provide help with GIS and R). Appreciated, too, are the rest of ERI, for other help, chats, cups of tea, a biscuit and a crossword here and there, and in particular Audrey, always happy to help as needed. A massive thanks go to my parents, Brian and Sonia, who instilled in me an interest in, and wonder of, the natural world from a young age. Thanks to my boys - Arthur, Forrest, Rufus and Hunter – thanks for dragging me outside for walks, camping and fun. Last, but not least, the biggest ‘Thank you’ goes to my wife, Bronagh. Thanks B! Dedicated to two inspirational and charismatic people who sadly are no longer around at this end of the PhD: my father, Brian Braidwood, and my aunt Jane (née Williams) Braidwood. You are both much missed. 2 Abstract Restoration ecology continues to become ever more relevant as legislation demands we prevent biodiversity losses. Post-industrial restoration sites pose a number of additional challenges, including balancing ecological need with logistical and financial constraints. In the North of Scotland, one such site is the Dounreay Nuclear Power Plant, now undergoing decommissioning. The intention is to restore cliff-top habitat with native vegetation, blending in with its surroundings and necessitating minimal maintenance. The overall objective of this PhD research was to help develop a plan for the restoration of the site. A key challenge in this particular case was the residual low level radioactivity at depth in some areas, and a restoration layer is required to prevent contamination of bioreceptors at the surface, however, topsoil availability is limited. The cliff top site, and exposure to salt spray driven by strong winds, meant the identification of suitable vegetation communities for different areas could be crucial to its success. Vegetation and soil surveys across nine reference sites along the North coast of Scotland identified five non-peat vegetation communities suitable for Dounreay’s restoration. To test what combination of substrates and topsoils would support better germination a controlled experiment in a growth chamber, followed by an in situ vegetation trial plot experiment, was carried out. Vegetation germinated without topsoil on fine grade crushed rocks, though cover, richness, diversity and biomass were all lower in treatments without topsoil than where topsoil was present, mostly due to lower soil moisture and nutrient levels. The level of cover continued to increase throughout the three years of the trial plots when topsoil was absent, and in time levels for these variables may become equal. Invertebrate richness and diversity within the trial plots were compared with neighbouring reference sites. Our results suggest that a functional invertebrate community was rapidly restored to the tested treatments. The exclosure of part of the site for up to 300 years means that the site will be left to develop for a long time without further human intervention: therefore, the effects of climate change should to be taken in to account in the selection of species to include in the restoration. A search through herbarium specimens revealed no loss of those species from the north of Scotland in the past ca. 150 years, despite changes in regional temperatures. Projected changes in temperature during the coming 50 years show a dramatic shift in space likely to be occupied by species found there now. 3 This prompted the development of a novel concept: that of utilising restoration sites as “protorefuges” or “protorefugia”, i.e. restoration sites where threatened species at the leading edge of climate change can be translocated ahead of the climate changing. There, they would be joined by individuals of the wider population naturally dispersed as the climate shifts. Overall, these results enabled the development of a refined restoration plan for Dounreay, which takes into account the particular setting, constraints and timelines involved. With the decommissioning of an increasing number of nuclear sites across Britain and Europe taking place in the coming years, this research should be developed further. In particular our novel concept of protorefugia could even be put into practice, benefiting both restoration and conservation. 4 Thesis Contents Declaration .................................................................................................................................... 1 Acknowledgements ...................................................................................................................... 2 Abstract .......................................................................................................................................... 3 Thesis Contents ...........................................................................................................................