Coastal Nature-based Solutions in a changing climate

Overview

Salt marshes are unique coastal habitats that provide numerous ecosystem services including carbon sequestration, coastal protection and eco-tourism via the rich array of flora and fauna that inhabit them. In the UK, many salt marshes are threatened by direct anthropogenic pressures and climate change through sea-level rise, changes in sediment supply and destructive storm surge events.

Although research suggests that future sea-level rise will cause many UK salt marshes to drown later this century because their accretion cannot “keep up” with projected rates of sea-level rise (Horton et al. 2018), changes in sediment supply and sediment redistribution along the coast means many salt marshes will react differently to future sea-level rise (Ladd et al. 2019). As salt marshes typically form above elevations of Mean High Water of Neap tides (Balke et al. 2016), projections of mean sea-level may not linearly translate to increased marsh inundation, especially in estuaries with tidal amplification. Salt marsh restoration and enhancement in the UK as a Nature-based Solution to climate change mitigation and adaptation, includes measures such as managed realignment (I.e., tidal flooding of formerly embanked land) but also direct planting, tidal flat recharge (I.e., sediment nourishment) or installation of breakwaters and permeable groynes. Whereas a lot is known about the immediate effectiveness of such measures, there is a need to investigate their longevity against the backdrop of accelerated sea-level rise.

This project will evaluate the multiple time and space scales of UK salt-marsh response to climate change with a focus on how different nature-based solutions can be implemented in the future as part of a long-term adaptive management strategy.

Methodology

• UK wide re-analysis of UK salt marsh accretion rates compared to recently published sea-level projections by UKCP18 and IPCC 6th Assessment Report (IPCC, 2021).
• Monitoring of tidal marsh inundation duration and frequency using Mini-Buoys (Balke et al. 2021) in saltmarshes with contrasting management/restoration history (e.g. realigned vs. natural marshes).
• Retrieve sediment cores from saltmarshes during fieldwork and undertake laboratory analyses (sediment physical properties, microfossils, chronology development) to constrain the local recent sea-level rise history (e.g. Scotland vs. England).
• Explore the time and spatial scales of saltmarsh growth and recession to evaluate the key drivers of marsh survival across UK saltmarshes.
• Evaluate and model the response of saltmarshes to various interventions via field observations and literature.
• Develop regional adaptive management strategies for UK saltmarshes to implement nature-based solutions under different climate change scenarios.

Project Timeline

Year 1

• Literature review and analysis of UK salt marsh accretion rates compared to IPCC AR6 and/or UKCP18 sea-level projections.
• [Fieldwork] Setting up of Mini Buoys to monitor marsh hydrology and hydrodynamics across seasons (>1year) in contrasting salt marshes in Scotland and Northern England.
• [Fieldwork] Survey modern salt marsh environments at monitoring sites and perform coring across multiple transects to establish estuarine and sea-level history.

Year 2

• Laboratory analysis of core material, and retrieval/analysis of real time monitoring data.
• GIS analysis of marsh expansion and erosion at nested spatial scales in relation to past and predicted sea-level rise. Comparing natural and restored/managed UK sites with other European marshes.
• Draft paper for Journal submission
• Attend national/international conference and present research

Year 3

• Synthesise fieldwork and laboratory findings with desk-based analysis to develop adaptive management strategies.
• Draft thesis chapters

Year 3.5

• Write-up thesis and prepare additional manuscripts for journal submission.
• Engagement with Policy-makers/Stakeholders (e.g. Natural England/Scotland)

Training
& Skills

This project is a collaborative studentship between Durham University and the University of Glasgow. During the project, the successful student will obtain training to develop a range of key skills including data assimilation and statistical analysis, model development and use, and GIS skills. The student will also learn field and laboratory techniques such as microfossil analysis, sediment geotechnical properties and radiometric dating methods. As part of the training support, we have budgeted for the successful candidate to attend the University of Oxford ‘Radiocarbon Dating and Bayesian Chronological Analysis’ workshop.

References & further reading

Horton, B.P., Shennan, I., Bradley, S.L., Cahill, N., Kirwan, M., Kopp, R.E. and Shaw, T.A., 2018. Predicting marsh vulnerability to sea-level rise using Holocene relative sea-level data. Nature communications, 9(1), pp.1-7. (doi: https://doi.org/10.1038/s41467-018-05080-0)
Balke, T. , Vovides, A. , Schwarz, C., Chmura, G. L., Ladd, C. and Basyuni, M. (2021) Monitoring tidal hydrology in coastal wetlands with the Mini Buoy: applications for mangrove restoration. Hydrology and Earth System Sciences, 25, pp. 1229-1244. (doi: 10.5194/hess-25-1229-2021)
Balke, T. , Stock, M., Jensen, K., Bouma, T. J. and Kleyer, M. (2016) A global analysis of the seaward salt marsh extent: the importance of tidal range. Water Resources Research, 52(5), pp. 3775-3786. (doi: 10.1002/2015WR018318)
Ladd, C. J.T. , Duggan-Edwards, M. F., Bouma, T. J., Pagès, J. F. and Skov, M. W. (2019) Sediment supply explains long‐term and large‐scale patterns in salt marsh lateral expansion and erosion. Geophysical Research Letters, 46(20), pp. 11178-11187. (doi: 10.1029/2019GL083315)
UK Climate Projections (2018) https://www.metoffice.gov.uk/research/approach/collaboration/ukcp/index
IPCC, 2021: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press. In Press.

Further Information

If you are interested in the project, please get in touch to discuss your application further:
Sarah Woodroffe
s.a.woodroffe@durham.ac.uk

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