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Coastal futures: New framings, many questions, some ways forward

Published online by Cambridge University Press:  04 July 2023

Tom Spencer*
Affiliation:
Department of Geography, University of Cambridge, Cambridge, UK
Janine Adams
Affiliation:
Institute for Coastal and Marine Research, Nelson Mandela University, Gqeberha, South Africa
Martin Le Tissier
Affiliation:
Coastal Matters Ltd, Newcastle upon Tyne, UK
A. Brad Murray
Affiliation:
Division of Earth and Climate Sciences, Nicholas School of the Environment, Duke University, Durham, NC, USA
Kristen Splinter
Affiliation:
Water Research Laboratory, School of Civil and Environmental Engineering, UNSW Sydney, Sydney, NSW, Australia
*
Corresponding author: Tom Spencer; Email: [email protected]
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Abstract

Although coasts are frequently seen as at the frontline of near-future environmental risk, there is more to the understanding of the future of coastal environments than a simple interaction between increasing hazards (particularly related to global sea level rise) and increasing exposure and vulnerability of coastal populations. The environment is both multi-hazard and regionally differentiated, and coastal populations, in what should be seen as a coupled social–ecological–physical system, are both affected by, and themselves modify, the impact of coastal dynamics. As the coupled dance between human decisions and coastal environmental change unfolds over the coming decades, transdisciplinary approaches will be required to come to better decisions on identifying and following sustainable coastal management pathways, including the promotion of innovative restoration activities. Inputs from indigenous knowledge systems and local communities will be particularly important as these stakeholders are crucial actors in the implementation of ecosystem-based mitigation and adaptation strategies.

Type
Perspective
Creative Commons
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Copyright
© The Author(s), 2023. Published by Cambridge University Press

Impact statement

Coasts are shaped by both processes of natural change and changes in patterns of use of space and resources by societies. Coasts are particularly sensitive to global change and continuously respond to these changes, often in ways that lead to new threats, or exacerbate existing threats, to the very supply of goods, services and space that make them so attractive to societies. Transformations for sustainable development at the coast present both a considerable set of challenges and opportunities. We argue that understanding the future of coastal environments requires a much wider, and more sophisticated, framing than simply considering the impacts of global sea level rise on rapidly growing coastal populations. In essence, the globalised view needs to be extended into arguments that stress: the importance of place-and people-based biophysical systems and social contexts; the need for technical innovation in restoring and rehabilitating degraded coastal environments; and the identification of just and equitable adaptive response pathways towards better, more robust coastal futures.

Introduction

Across polar, temperate and tropical regions, coastal zones collectively define a critical interface of the global ocean–atmosphere system. Arguably among the most transformed landscapes on Earth, coasts consist of sensitive social–ecological–physical systems, deeply embedded in many of the UN sustainable development goals (SDGs). While the oceans clearly relate to SDG 14 (life below water), coastal environments also play key roles in the eradication of poverty (SDG1); the ending of hunger and the sustainability of agriculture (SDG2); the provision of affordable and clean energy (SDG 7); the adaptation of coastal cities and communities to environmental change (SDG 11); the good use of resources, including food security (SDG 12); responses to climate change (SDG 13); and the promotion of just and equitable societies, including the maintenance of sovereign boundaries, under ever-changing coastal landscapes (SDG 16). Yet whilst coasts are placed high on the ladder of planetary environmental concerns (e.g., Oppenheimer et al., Reference Oppenheimer, Glavovic, Hinkel, van de Wal, Magnan, Abd-Elgawad, Cai, Cifuentes-Jara, DeConto, Ghosh, Hay, Isla, Marzeion, Meyssignac and Sebesvari2019), this positioning is often framed in terms of the single, coupled interaction of, on the one hand, the hazard of global mean sea level (GMSL) rise and, on the other hand, of the exposure and vulnerability that comes from the rapid growth of coastal populations (both resident and transient from tourism) and accompanying infrastructure. GMSL is projected to rise between 0.38 [range: 0.28–0.55] m (SSP1–1.9) and 0.77 [range: 0.63–1.01] m (SSP5–8.5) by 2,100 relative to 1986–2005 under low and high emissions scenarios, respectively. However, greater GMSL rise could be caused by the earlier-than-projected disintegration of marine ice shelves, the abrupt, widespread onset of marine ice sheet and ice cliff instability around Antarctica, and faster-than-projected changes in the surface mass balance and discharge from the Greenland Ice Sheet (Fox-Kemper et al., Reference Fox-Kemper, Hewitt, Xiao, Aðalgeirsdóttir, Drijfhout, Edwards, Golledge, Hemer, Kopp, Krinner, Mix, Notz, Nowicki, Nurhati, Ruiz, Sallée, Slangen, Yu, Masson-Delmotte, Zhai, Pirani and Zhou2021; Slangen et al., Reference Slangen, Palmer, Camargo, Church, Edwards, Hermans, Hewitt, Garner, Gregory, Kopp, Santos and van de Wal2023). Presently (2023), 2.15 billion people live in the near-coastal zone and 898 million in the low-elevation coastal zone globally. These numbers could increase to 2.9 billion and 1.2billion, respectively over the 21st century, depending on adopted socioeconomic scenarios (Reimann et al., Reference Reimann, Vafeidis and Honsel2023). Of the 37 megacities (populations in excess of 10 M), 62% can be considered ‘coastal’ (Barragan and de Andres, Reference Barragan and de Andres2015).

Modern developed coasts constitute a fundamentally new type of system, one with characteristics that result from tight couplings between human and natural coastal dynamics (e.g., McNamara et al., Reference McNamara, Lazarus and Goldstein2023), in places creating totally new, artificial coastal land areas (e.g., Sengupta et al., Reference Sengupta, Choi, Tian, Brown, Meadows, Hackney, Banerjee, Li and Zhou2023). The common framing that sees causality running from the physical environment to its social impacts often results in human influence forming the final section of an academic paper or the last chapter in a coastal textbook. But rather than ‘natural systems with humans disturbing them’ one can tell a more compelling alternative story, one of ‘human systems, entwined with natural systems embedded within them’. On some coasts, recent settlers have arrived with little, or no, knowledge of the coastal environment and the potential flood hazards they may face whereas elsewhere there may be deep knowledge from long histories of interaction with their natural surroundings. Climate adaptation strategies need to be fitted to the communities at risk, including, where they can, the incorporation of indigenous knowledge and values (David-Chavez and Gavin, Reference David-Chavez and Gavin2018; Proulx et al., Reference Proulx, Ross, Macdonald, Fitzsimmons and Smit2021). More broadly, there will be a need to move beyond solely technocentric thinking at the coast, including considerations of the role and juxtaposition of the arts and humanities with the natural sciences.

It follows, therefore, that transformations for sustainable development at the coast present both a considerable challenge and a particular opportunity. We argue that understanding the future of coastal environments requires a much wider, and more sophisticated, framing than simply considering the impact of GMSL on a coastal population metric. In essence, the often globalised view needs to be extended into arguments that stress the importance of location-and people-based biophysical systems and social contexts, including the range of possible just and equitable adaptive responses to change (in the broadest sense).

Coastal dynamics beyond the single metric of global sea-level rise

Quite different from a simple global signal, there are many different regional rates of relative sea-level (RSL) rise; some regions exhibited rates of RSL change five times the global mean between 1993 and 2003 (Bindoff et al., Reference Bindoff, Willebrand, Artale, Cazenave, Gregory, Gulev, Hanawa, Le Quéré, Levitus, Nojiri, Shum, Talley, Unnikrishnan, Solomon, Qin, Manning, Chen, Marquis, Averyt, Tignor and Miller2007). Inter-annual RSL variability is also likely to be significant, into decimetres in places, in the near future (e.g., Palmer et al., Reference Palmer, Gregory, Bagge, Calvert, Hagedoorn, Howard, Klemann, Lowe, Roberts, Slangen and Spada2020) and it may take decades for the signal of anthropogenically forced RSL change to be clearly detectable (Lyu et al., Reference Lyu, Zhang, Church, Slangen and Hu2014) and influence shorelines (D’Anna et al., Reference D’Anna, Idier, Castelle, Rohmer, Cagigal and Mendez2022). Micro-tidal coasts are likely to be more vulnerable to global change, with the effects being seen earlier, because the sea level rise signal becomes a larger proportion of the total water level (tide plus sea level rise) signal (Ponte et al., Reference Ponte, Carson, Cirano, Domingues, Jevrejeva, Marcos, Mitchum, van de Wal, Woodworth, Ablain, Ardhuin, Ballu, Becker, Benveniste, Birol, Bradshaw, Cazenave, De Mey-Frémaux, Durand, Ezer, Fu, Fukumori, Gordon, Gravelle, Griffies, Han, Hibbert, Hughes, Idier, Kourafalou, Little, Matthews, Melet, Merrifield, Meyssignac, Minobe, Penduff, Picot, Piecuch, Ray, Rickards, Santamaría-Gómez, Stammer, Staneva, Testut, Thompson, Thompson, Vignudelli, Williams, SDP, Wöppelmann, Zanna and Zhang2019). Furthermore, coastal change is driven not only by these slow onset, chronic dynamics (sea level rise and additionally ocean warming and ocean acidification) but also by acute shocks, from tropical and extratropical storms, associated storm surges, marine heat waves, coastal catchment wildfires, and freshwater flood inputs (e.g., Kirezci et al., Reference Kirezci, Young, Ranasinghe, Muis, Nicholls, Lincke and Hinkel2020; Warrick et al., Reference Warrick, East and Dow2023). All these impacts show high regional variability; thus, for example, while coasts on the western margins of the Pacific basin sit within the tropical cyclone belt and are at risk from storm surges, low-lying islands in more equatorial and eastern Pacific Ocean locations experience flooding from the combination of distant-source swell waves, king tides and sea level rise (e.g., Tuvalu and Kiribati: Hoeke et al., Reference Hoeke, Damlamian, Aucan and Wandres2021). Recent ‘heat domes’, catastrophic fluvial flooding, extensive droughts and large-scale coral bleaching events suggest that the climate change signal may well be first seen in these, until now rare, extreme events, with shortening recurrence intervals between them (Seneviratne et al., Reference Seneviratne, Zhang, Adnan, Badi, Dereczynski, Di Luca, Ghosh, Iskandar, Kossin, Lewis, Otto, Pinto, Satoh, Vicente-Serrano, Wehner, Zhou, Masson-Delmotte, Zhai, Pirani, Connors, Péan, Berger, Caud, Chen, Goldfarb, Gomis, Huang, Leitzell, Lonnoy, Matthews, Maycock, Waterfield, Yelekçi, Yu and Zhou2021). And compound extreme events (e.g., storm surge high water levels accompanied by freshwater runoff from heavy rains, or a sequence of tropical hurricanes making landfall) add further complexity to system response (Zscheischler et al., Reference Zscheischler, Westra, van den Hurk, Seneviratne, Ward, Pitman, AghaKouchak, Leonard, Wahl and Zhang2018). Concentrating solely on sea level rise drives a focus on a ‘future problem’ of slow vertical system response and neglects the other processes that shape our coastlines. These include settings where longshore processes, and thus lateral system response, as well as shorter-term processes, such as storms, are often dominant (e.g., for the under-assessment of extreme water levels compared to the focus on sea level rise see Wahl et al., Reference Wahl, Haigh, Nicholls, Arns, Dangendorf, Hinkel and Slangen2017). Furthermore, a sea level rise focus underplays those critical controls on system health that are only weakly linked to climate change, such as changes in fluvial and/or marine sediment supply.

Coastal systems as integrated biophysical systems

A significant proportion of coastal systems are vegetated (tidal wetlands, sand dunes, coastal cliffs) or are located behind biosedimentary systems (coral reefs, seagrass-floored lagoons) in inter-connected coastal ‘seascapes’ (Ogden et al., Reference Ogden, Nagelkerken, McIvor and Bortone2014). Knowledge about the entrainment, transport and deposition of coastal sediments and the nature of, and controls on, coastal ecology are well established, although research often reflects the ease of access (e.g., locations near field stations and institutions in developed economies, often in the summer months). Furthermore, physical science typically concentrates on monitoring (which prioritises the temporal element) whereas biological science largely focuses on sampling (which favours the spatial element). In addition, understanding the processes that shape and reshape coastal biophysical environments requires addressing the couplings between ecological and physical processes, in contrast to studying them separately (e.g., D’Alpaos, Reference D’Alpaos2011; Durán Vinent and Moore, Reference Durán Vinent and Moore2015). On many coasts, therefore, there is an urgent need to merge these different perspectives across disciplines and address coastal dynamics as an integrated biophysical system (Solan et al., Reference Solan, Spencer, Paterson, Unsworth, Christie, Blight, Brown, Brooks, Lichtman, Wei, Li, Thorne, Leyland, Godbold, Thompson, Williams, Plater, Moller and Amoudry2023). And as satellites open up the possibility of large spatial and temporal scale monitoring of a variety of coastal processes and ecosystem health monitoring, more holistic observational approaches become possible (e.g., Blount et al., Reference Blount, Carrasco, Cristina and Silvestri2022; Vitousek et al., Reference Vitousek, Buscombe, Vos, Barnard, Ritchie and Warrick2023). These new theoretical and observational approaches are particularly important given the growing interest in non-structurally engineered responses to coastal erosion and shoreline retreat (Van Zelst et al., Reference van Zelst, Dijkstra, van Wesenbeeck, Eilander, Morris, Winsemius, Ward and de Vries2021; Wedding et al., Reference Wedding, Reiter, Moritsch, Hartge, Reiblich, Gourlie and Guerry2022). Nature-based coastal protection offers the promise of long-term sustainability as, with adequate sediment supply, coasts have the potential to respond to environmental forcing, including the tracking of rising sea levels (Spalding et al., Reference Spalding, McIvor, Beck, Koch, Möller, Reed, Rubinoff, Spencer, Tolhurst, Wamsley, van Wesenbeeck, Wolanski and Woodroffe2014). However, nature-based approaches to enhancing resilience in the near future can in some cases reduce resilience over decadal timescales. Thus, for example, building artificially high barrier island dunes reduces storm overwash in the short term but promotes narrower and lower islands in the long term, so that when dunes are overtopped, sediment redistributions – and impacts on island infrastructure – are more immediate and severe (Magliocca et al., Reference Magliocca, McNamara and Murray2011). Understanding, and thus aiding, the trajectory of a coastal ecosystem’s ability to adapt and maintain functionality is fundamental to the long-term maintenance of natural capital and the delivery of ecosystem services. But what exactly do we know about the design rules and implementation practices to successfully work with natural processes in coastal risk management? (e.g., Orton et al. (Reference Orton, Ralston, van Prooijen, Secor, Ganju, Chen, Fernald, Brooks and Marcell2023) on the knowledge gaps behind the construction and operation of gated storm surge barriers). And given that risks and habitability (e.g., Horton et al., Reference Horton, Sherbinin, de Wrathall and Oppenheimer2021), over decadal timescales, change as the landscapes and ecosystems change, what practises will enable long-term, mutual resilience of coastal landscapes, ecosystems, and societies?

Coasts in the Anthropocene

On developed coasts, physical and ecological processes clearly impact human communities; the very processes that create and maintain coastal environments, including sea-level rise, storms, and ecological change, often represent hazards for people, structures and infrastructure. On the other hand, human decisions and actions have resulted in the removal, degradation and fragmentation of coastal environments and have lessened the ability of these systems to adapt to climate change and act as natural protective barriers for coastal populations (Simkin et al., Reference Simkin, Seto, McDonald and Jetz2022; De Dominicis et al., Reference De Dominicis, Wolf, van Hespen, Zheng and Hu2023). These impacts are not new; there have been centuries of modification, degradation and loss from the anthropogenic activities of land conversion (for agriculture, aquaculture, industry, housing and infrastructure) and misuse (dredging and canalisation, waste disposal and pollution) although one might argue that the scale of human impact – and its consequences – has greatly increased in the last 100 years. Thus, economic damages to coastal assets from tropical cyclones at 2100 are projected to increase by >300% on present values due solely to coastal development, a much larger effect than that projected for climate change impacts, even under high-end climate warming scenarios (Gettelman et al., Reference Gettelman, Bresch, Chen, Truesdale and Bacmeister2018).

It is clear that to understand how this complex socio-ecological-physical system works at the coast, and how it might evolve over decades as the coupled dance between human decisions and coastal environmental change unfolds, will require transdisciplinary approaches. Deep collaborations among stakeholders, practitioners, and researchers from a wide range of physical, biological and social sciences will be needed. Forging new, transdisciplinary science will produce the understandings that will inform decision-making, allowing communities and societies to evaluate the long-term outcomes of decisions with which they are faced, both now and to mid-century.

Transdisciplinary approaches will also be necessary to inform innovative restoration activities. Anthropogenic pressures are driving coastal ecosystem loss and coastal squeeze. However, restoration research is growing and there are important lessons to be learnt from those activities which analyse the ecological and social effects of restoration activities. A socio-environmental approach addresses the gap between governance, implementation and social commitment and allows for transfer of knowledge across the science-policy-practice continuum. Innovative approaches for water quality improvement, for hydrological reconnection and for restoring ecosystem services and societal benefits are priority areas for investigation. Inputs from indigenous knowledge systems and local communities are particularly important as these stakeholders are crucial actors in the implementation of ecosystem-based mitigation and adaptation strategies (Porri et al., Reference Porri, McConnachie, van der Walt, Wynberg and Pattrick2023).

For sustainable coastal futures the management, development, and use of the coast’s resources requires critical and reflective research across all disciplines to realise transformations to prevailing practices, institutional structures and processes, including consideration of the inter-connected ethical, cultural, political, social, economic, institutional, technological and behavioural dimensions of coastal development. There are many gaps in our knowledge and understanding about how to transform prevailing coastal thinking and practices. How can formal and informal coastal governance structures and processes be aligned to foster resilience, adaptive capacity and sustainability? What does experience in different coastal contexts reveal about limits, barriers and opportunities? What can be done to support and empower coastal communities that are most at risk in this era of global change – the exposed and vulnerable communities in low-lying deltaic regions (Shaw et al., Reference Shaw, Luo, Cheong, Abdul Halim, Chaturvedi, Hashizume, Insarov, Ishikawa, Jafari, Kitoh, Pulhin, Singh, Vasant, Zhang, Pörtner, Roberts, Tignor, Poloczanska, Mintenbeck, Alegría, Craig, Langsdorf, Löschke, Möller, Okem and Rama2022); sea level atoll islands (Duvat et al., Reference Duvat, Magnan, Perry, Spencer, Bell, Wabnitz, Webb, White, McInnes, Gattuso, Graham, Nunn and Le Cozannet2021; Cooley et al., Reference Cooley, Schoeman, Bopp, Boyd, Donner, Ghebrehiwet, Ito, Kiessling, Martinetto, Ojea, M-F, Rost, Skern-Mauritzen, Pörtner, Roberts, Tignor, Poloczanska, Mintenbeck, Alegría, Craig, Langsdorf, Löschke, Möller, Okem and Rama2022); and the circum-arctic region (Ford et al., Reference Ford, Pearce, Canosa and Harper2021)? How can conflicting beliefs, worldviews and practices be reconciled? What can be done to align interests and coastal equity and sustainability prospects across sectoral, institutional, geographic and temporal scales? What can be learned from past transformative coastal change? Such questions necessitate reframing how we understand and take actions in pursuit of ‘human progress’ with vitally important implications for how we reconcile individual, group and societal interests, rights and responsibilities within and between generations.

Conclusions

Finally, whilst we recognise that the goal of environmental sustainability is laudable in principle, what is it that can be sustained if all around is changing rapidly and continuously towards an unpredictable future? We argue that the goal of achieving sustainability should be replaced by a strategy of eliminating manifestly unsustainable practices. This is challenging when there are considerable legacy issues on many coasts (including, e.g., the decommissioning of ageing nuclear power stations and identifying and remediating coastal landfill sites). But we call on all academic, policy and governance communities to provide the underpinning principles and understandings, both quantitative and qualitative, that will allow societies to properly identify sensible trajectories and thus proactively steer themselves towards better coastal futures.

Open peer review

To view the open peer review materials for this article, please visit http://doi.org/10.1017/cft.2023.22.

Data availability statement

Data availability is not applicable to this article as no new data were created or analysed in this study.

Author contribution

All authors contributed to the conception and design of the paper, initial drafting and subsequent revisions.

Competing interest

The authors declare none.

References

Barragan, JM and de Andres, M (2015) Analysis and trends of the world’s coastal cities and agglomerations. Ocean & Coastal Management 114, 1120.CrossRefGoogle Scholar
Bindoff, NL, Willebrand, J, Artale, V, Cazenave, A, Gregory, J, Gulev, S, Hanawa, K, Le Quéré, C, Levitus, S, Nojiri, Y, Shum, CK, Talley, LD and Unnikrishnan, A (2007) Observations: Oceanic climate change and sea level. In Solomon, S, Qin, D, Manning, M, Chen, Z, Marquis, M, Averyt, KB, Tignor, M and Miller, HL (eds.), Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge: Cambridge University Press, pp. 386432.Google Scholar
Blount, TR, Carrasco, AR, Cristina, S and Silvestri, S (2022) Exploring open-source multispectral satellite remote sensing as a tool to map long-term evolution of salt marsh shorelines. Estuarine, Coastal and Shelf Science 266, 107664. https://doi.org/10.1016/j.ecss.2021.107664.CrossRefGoogle Scholar
Cooley, S, Schoeman, D, Bopp, L, Boyd, P, Donner, S, Ghebrehiwet, DY, Ito, S-I, Kiessling, W, Martinetto, P, Ojea, E, M-F, Racault, Rost, B, and Skern-Mauritzen, M (2022) Oceans and coastal ecosystems and their services. In Pörtner, H-O, Roberts, DC, Tignor, M, Poloczanska, ES, Mintenbeck, K, Alegría, A, Craig, M, Langsdorf, S, Löschke, S, Möller, V, Okem, A and Rama, B (eds.), Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge: Cambridge University Press, pp. 379550. http://doi.org/10.1017/9781009325844.005.Google Scholar
D’Alpaos, A (2011) The mutual influence of biotic and abiotic components on the long-term ecomorphodynamic evolution of salt-marsh ecosystems. Geomorphology 126, 269278. https://doi.org/10.1016/j.geomorph.2010.04.027.CrossRefGoogle Scholar
D’Anna, M, Idier, D, Castelle, B, Rohmer, J, Cagigal, L and Mendez, FJ (2022) Effects of stochastic wave forcing on probabilistic equilibrium shoreline response across the 21st century including sea-level rise. Coastal Engineering 175, 104149. https://doi.org/10.1016/j.coastaleng.2022.104149.CrossRefGoogle Scholar
David-Chavez, DM and Gavin, MC (2018) A global assessment of indigenous community engagement in climate research. Environmental Research Letters 13, 123005. http://doi.org/10.1088/1748-9326/aaf300.CrossRefGoogle Scholar
De Dominicis, M, Wolf, J, van Hespen, R, Zheng, P and Hu, Z (2023) Mangrove forests can be an effective coastal defence in the Pearl River Delta, China. Communications Earth & Environment 4, 13. https://doi.org/10.1038/s43247-022-00672-7.CrossRefGoogle Scholar
Durán Vinent, O and Moore, L (2015) Barrier island bistability induced by biophysical interactions. Nature Climate Change 5, 158162. https://doi.org/10.1038/nclimate2474.CrossRefGoogle Scholar
Duvat, VKE, Magnan, AK, Perry, CT, Spencer, T, Bell, JD, Wabnitz, C, Webb, AP, White, I, McInnes, KL, Gattuso, J-P, Graham, NAJ, Nunn, PD and Le Cozannet, G (2021) Risks to future atoll habitability from climate-driven environmental changes. WIREs Climate Change 2021, 3700. https://doi.org/10.1002/wcc.700.Google Scholar
Ford, JD, Pearce, T, Canosa, IV and Harper, S (2021) The rapidly changing Arctic and its societal implications. WIREs Climate Change 12, e735. https://doi.org/10.1002/wcc.735.CrossRefGoogle Scholar
Fox-Kemper, B, Hewitt, HT, Xiao, C, Aðalgeirsdóttir, G, Drijfhout, SS, Edwards, TL, Golledge, NR, Hemer, M, Kopp, RE, Krinner, G, Mix, A, Notz, D, Nowicki, S, Nurhati, IS, Ruiz, L, Sallée, J-B, Slangen, ABA and Yu, Y (2021) Ocean, cryosphere, and sea-level change. In Masson-Delmotte, V, Zhai, P, Pirani, A and Zhou, B (eds.), Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge: Cambridge University Press, pp. 12111362.Google Scholar
Gettelman, A, Bresch, DN, Chen, C-C, Truesdale, JE and Bacmeister, JT (2018) Projections of future tropical cyclone damage with a high-resolution global climate model. Climatic Change 146, 575585. https://doi.org/10.1007/s10584-017-1902-7.CrossRefGoogle Scholar
Hoeke, RK, Damlamian, H, Aucan, J and Wandres, M (2021) Severe flooding in the atoll nations of Tuvalu and Kiribati triggered by a distant tropical cyclone pam. Frontiers in Marine Science 7, 539646. https://doi.org/10.3389/fmars.2020.539646.CrossRefGoogle Scholar
Horton, RM, Sherbinin, A, de Wrathall, D and Oppenheimer, M (2021) Assessing human habitability and migration. Science 372, 12791283. https://doi.org/10.1126/science.abi8603.CrossRefGoogle ScholarPubMed
Kirezci, E, Young, IR, Ranasinghe, R, Muis, S, Nicholls, RJ, Lincke, D and Hinkel, J (2020) Projections of global-scale extreme sea levels and resulting episodic coastal flooding over the 21st century. Scientific Reports 10, 11629. https://doi.org/10.1038/s41598-020-67736-6.CrossRefGoogle ScholarPubMed
Lyu, K, Zhang, X, Church, J, Slangen, ABA and Hu, J (2014) Time of emergence for regional sea-level change. Nature Climate Change 4, 10061010. https://doi.org/10.1038/nclimate2397.CrossRefGoogle Scholar
Magliocca, NR, McNamara, D and Murray, AB (2011) Long-term, large-scale effects of artificial dune construction along a barrier island coastline. Journal of Coastal Research 27, 918930.CrossRefGoogle Scholar
McNamara, DE, Lazarus, ED and Goldstein, EB (2023) Human–coastal coupled systems: Ten questions. Cambridge Prisms: Coastal Futures 1, 18. https://doi.org/10.1017/cft.2023.8.Google Scholar
Ogden, JC, Nagelkerken, I and McIvor, CC (2014) Connectivity in the tropical coastal seascape. Implications for marine spatial planning and resource management. In Bortone, SA (ed.) Interrelationships between Corals and Fisheries. Boca Raton, FL: CRC Press, pp. 253273.Google Scholar
Oppenheimer, M, Glavovic, B, Hinkel, J, van de Wal, R, Magnan, AK, Abd-Elgawad, A, Cai, R, Cifuentes-Jara, M, DeConto, RM, Ghosh, T, Hay, J, Isla, F, Marzeion, B, Meyssignac, B and Sebesvari, Z (2019) Chapter 4: Sea level rise and implications for low lying islands, coasts and communities. In IPCC Special Report on the Ocean and Cryosphere in a Changing Climate. Cambridge: Cambridge University Press, pp. 321445.Google Scholar
Orton, P, Ralston, D, van Prooijen, B, Secor, D, Ganju, N, Chen, Z, Fernald, S, Brooks, B and Marcell, K (2023) Increased utilization of storm surge barriers: A research agenda on estuary impacts. Earth’s Future 11, e2022EF002991. https://doi.org/10.1029/2022EF002991.CrossRefGoogle Scholar
Palmer, MD, Gregory, JM, Bagge, M, Calvert, D, Hagedoorn, JM, Howard, T, Klemann, V, Lowe, JA, Roberts, CD, Slangen, ABA and Spada, G (2020) Exploring the drivers of global and regional sea-level change over the 21st century and beyond. Earths Future 8, e2019EF001413.CrossRefGoogle Scholar
Ponte, RM, Carson, M, Cirano, M, Domingues, CM, Jevrejeva, S, Marcos, M, Mitchum, G, van de Wal, RSW, Woodworth, PL, Ablain, M, Ardhuin, F, Ballu, V, Becker, M, Benveniste, J, Birol, F, Bradshaw, E, Cazenave, A, De Mey-Frémaux, P, Durand, F, Ezer, T, Fu, L-L, Fukumori, I, Gordon, K, Gravelle, M, Griffies, SM, Han, W, Hibbert, A, Hughes, CW, Idier, D, Kourafalou, VH, Little, CM, Matthews, A, Melet, A, Merrifield, M, Meyssignac, B, Minobe, S, Penduff, T, Picot, N, Piecuch, C, Ray, RD, Rickards, L, Santamaría-Gómez, A, Stammer, D, Staneva, J, Testut, L, Thompson, K, Thompson, P, Vignudelli, S, Williams, J, SDP, Williams, Wöppelmann, G, Zanna, L and Zhang, X (2019) Towards comprehensive observing and modelling systems for monitoring and predicting regional to coastal sea level. Frontiers in Marine Science 6, 437. http://doi:10.3389/fmars.2019.00437.CrossRefGoogle Scholar
Porri, F, McConnachie, B, van der Walt, K-A, Wynberg, R and Pattrick, P (2023) Eco-creative nature-based solutions to transform urban coastlines, local coastal communities and enhance biodiversity through the lens of scientific and indigenous knowledge. Cambridge Prisms: Coastal Futures 1, 114. https://doi.org/10.1017/cft.2022.10.Google Scholar
Proulx, MJ, Ross, L, Macdonald, C, Fitzsimmons, S and Smit, M (2021) Indigenous traditional ecological knowledge and ocean observing: A review of successful partnerships. Frontiers in Marine Science 8, 117. https://doi.org/10.3389/fmars.2021.703938.CrossRefGoogle Scholar
Reimann, L, Vafeidis, AT and Honsel, LE (2023) Population development as a driver of coastal risk: Current trends and future pathways. Cambridge Prisms: Coastal Futures 1, 112. https://doi.org/10.1017/cft.2023.3.Google Scholar
Seneviratne, SI, Zhang, X, Adnan, M, Badi, W, Dereczynski, C, Di Luca, A, Ghosh, S, Iskandar, I, Kossin, J, Lewis, S, Otto, F, Pinto, I, Satoh, M, Vicente-Serrano, SM, Wehner, M and Zhou, B (2021) Weather and climate extreme events in a changing climate. In Masson-Delmotte, V, Zhai, P, Pirani, A, Connors, SL, Péan, C, Berger, S, Caud, N, Chen, Y, Goldfarb, L, Gomis, MI, Huang, M, Leitzell, K, Lonnoy, E, Matthews, JBR, Maycock, TK, Waterfield, T, Yelekçi, O, Yu, R and Zhou, B (eds.), Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge: Cambridge University Press, pp. 15131766. https://doi.org/10.1017/9781009157896.013.Google Scholar
Sengupta, D, Choi, YR, Tian, B, Brown, S, Meadows, M, Hackney, CR, Banerjee, A, Li, Y and Zhou, Y (2023) Mapping 21st century global coastal land reclamation. Earth’s Future 11, e2022EF002927. https://doi.org/10.1029/2022EF002927.CrossRefGoogle Scholar
Shaw, R, Luo, Y, Cheong, TS, Abdul Halim, S, Chaturvedi, S, Hashizume, M, Insarov, GE, Ishikawa, Y, Jafari, M, Kitoh, A, Pulhin, J, Singh, C, Vasant, K and Zhang, Z (2022) Asia. In Pörtner, H-O, Roberts, DC, Tignor, M, Poloczanska, ES, Mintenbeck, K, Alegría, A, Craig, M, Langsdorf, S, Löschke, S, Möller, V, Okem, A and Rama, B (eds.), Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge: Cambridge University Press, pp. 14571579. http://doi.org/10.1017/9781009325844.012.Google Scholar
Simkin, RD, Seto, KC, McDonald, RI and Jetz, W (2022) Biodiversity impacts and conservation implications of urban land expansion projected to 2050. Proceedings of the National Academy of Sciences USA 119, e2117297119. https://doi.org/10.1073/pnas.2117297119.CrossRefGoogle ScholarPubMed
Slangen, ABA, Palmer, MD, Camargo, CML, Church, JA, Edwards, TL, Hermans, THJ, Hewitt, HT, Garner, GG, Gregory, JM, Kopp, RE, Santos, VM and van de Wal, RSW (2023) The evolution of 21st century sea-level projections from IPCC AR5 to AR6 and beyond. Cambridge Prisms: Coastal Futures 1, 113. https://doi.org/10.1017/cft.2022.8.Google Scholar
Solan, M, Spencer, T, Paterson, DM, Unsworth, CA, Christie, EK, Blight, AJ, Brown, J, Brooks, H, Lichtman, ID, Wei, X, Li, X, Thorne, P, Leyland, J, Godbold, JA, Thompson, C, Williams, ME, Plater, A, Moller, I and Amoudry, LO (2023) Biological-physical interactions are fundamental to understanding and managing coastal dynamics. Royal Society Open Science 10, 230155. https://doi.org/10.1098/rsos.230155.CrossRefGoogle ScholarPubMed
Spalding, MD, McIvor, AL, Beck, MW, Koch, EW, Möller, I, Reed, DJ, Rubinoff, P, Spencer, T, Tolhurst, TJ, Wamsley, TV, van Wesenbeeck, BK, Wolanski, E and Woodroffe, CD (2014) Coastal ecosystems: A critical element of risk reduction. Conservation Letters 7, 293301. https://doi.org/10.1111/conl.12074.CrossRefGoogle Scholar
van Zelst, VTM, Dijkstra, JT, van Wesenbeeck, BK, Eilander, D, Morris, EP, Winsemius, HC, Ward, PJ and de Vries, MB (2021) Cutting the costs of coastal protection by integrating vegetation in flood defences. Nature Communications 12, 6533. https://doi.org/10.1038/s41467-021-26887-4.CrossRefGoogle ScholarPubMed
Vitousek, S, Buscombe, D, Vos, K, Barnard, PL, Ritchie, AC and Warrick, JA (2023) The future of coastal monitoring through satellite remote sensing. Cambridge Prisms: Coastal Futures 1, 118. https://doi.org/10.1017/cft.2022.4.Google Scholar
Wahl, T, Haigh, ID, Nicholls, RJ, Arns, A, Dangendorf, S, Hinkel, J and Slangen, ABA (2017) Understanding extreme sea levels for broad-scale coastal impact and adaptation analysis. Nature Communications 8, 16075. https://doi.org/10.1038/ncomms16075.CrossRefGoogle ScholarPubMed
Warrick, JA, East, AE and Dow, H (2023) Fires, floods and other extreme events – How watershed processes under climate change will shape our coastlines. Cambridge Prisms: Coastal Futures 1, 112. https://doi.org/10.1017/cft.2022.1.Google Scholar
Wedding, LM, Reiter, S, Moritsch, M, Hartge, E, Reiblich, J, Gourlie, D and Guerry, A (2022) Embedding the value of coastal ecosystem services into climate change adaptation planning. PeerJ 10, e13463. https://doi.org/10.7717/peerj.13463.CrossRefGoogle ScholarPubMed
Zscheischler, J, Westra, S, van den Hurk, BJJM, Seneviratne, SI, Ward, PJ, Pitman, A, AghaKouchak, BDM, Leonard, M, Wahl, T and Zhang, X (2018) Future climate risk from compound events. Nature Climate Change 8, 469477. https://doi.org/10.1038/s41558-018-0156-3.CrossRefGoogle Scholar

Author comment: Coastal futures: New framings, many questions, some ways forward — R0/PR1

Comments

Dear Coastal Futures,

Coasts are shaped by both processes of natural change and changes in patterns of use of space and resources by societies. Coasts are particularly sensitive to global change and continuously respond to these changes, often in ways that lead to new threats, or exacerbate existing threats, to the very supply of goods, services and space that make them so attractive to societies. Transformations for sustainable development at the coast present both a considerable set of challenges and opportunities. We argue that understanding the future of coastal environments requires a much wider, and more sophisticated, framing than simply considering the impacts of global sea level rise on rapidly growing coastal populations. In essence, the globalized view needs to be extended into arguments that stress: the importance of place-and people-based biophysical systems and social contexts; the need for technical innovation in restoring and rehabilitating degraded coastal environments; and the identification of just and equitable adaptive response pathways towards better, more robust coastal futures.

Yours sincerely,

Professor Tom Spencer

on behalf of all authors (Spencer. Adams, LeTissier, Murray and Splinter)

Review: Coastal futures: New framings, many questions, some ways forward — R0/PR2

Conflict of interest statement

Reviewer declares none.

Comments

Thank you for inviting me to review this Perspective piece by the Editor-in-Chief and Senior Editors. This is a well written piece and I have no major concerns. Some of the key messages that the authors could be stronger so that there is a clearer argument throughout, as it is more a statement of facts, rather than a visionary strength or weakness of a scientific theory or hypothesis. Other aspects to be considered include:

Line 64 – ‘endangered’ I’m not sure whether I would use this word. A landscape (unless biological) is not going to die off!

Line 67-70. Please consider SDG 1 and/or 2 – zero poverty and no hunger. Mega deltas are major food basins affected by salinity and sea-level rise. See https://doi.org/10.1016/j.jenvman.2020.111736

Line 92 – I agree with you here. It also involves legislation and regulations that were targeted for inland areas, or those inland knowing that the coast will affect them through migration or access (tourism).

Line 118 – I agree here with the fact that SLR has been pushed as the main driver of change. Population and development is a lot greater, and has been for a long time. It’s harder to consider due to the human element, The first is not appropriate to cite, but see: https://in.pinterest.com/pin/470766967272221885/ or read here https://doi.org/10.1029/2022EF002927 You could also mention here changing extremes and their growing importance in impact assessments as they have traditionally been overlooked in this area (e.g. https://doi.org/10.1038/ncomms16075). Also how the coast is used as a means of resources / employment in developing nations that are projected to rapidly expand. There are lots of issues here, e.g. sandy mining that could be explored, as this is a key feature of future coastlines.

Line 136 – I agree with this point too on merging on systems, as we all like to think in silos.

Line 178 – This is particularly so where there are legal obligations, such as with coastal squeeze and the resulting loss of habitats.

Review: Coastal futures: New framings, many questions, some ways forward — R0/PR3

Conflict of interest statement

Multiple contacts with the authors on scientific topics and editoral projects - no common project with them.

Comments

This article proposes that the current framing coastal research is too limited in scope to fully embrace the problem of sustainable development in coastal areas, as it often focuses on assessing sea-level rise impacts and stakes at risks, without considering the broader aim of ensuring sustainability in the long term or identifying sustainable coastal management pathways and achieve SDGs in coastal areas. The paper proposes transdisciplinary research to address this. The paper is short, concise and well written, which is excellent. In my view it completes and extends the perspectives ot previous authors in a usefull and timely way, e.g. Brown et al (https://www.nature.com/articles/nclimate2344), and therefore can be an excellent contribution for researchers and practitionners.

I think that this paper is relevant and fully in scope to coastal futures and I have minor comments.

Two general minor comments:

- In the worst case, the perspectives for sustainable development pathway may be very limited and the habitability of coastal zones may be questioned. Examples could be low-lying megadeltas affected by reduced sediments inputs and at risks of cyclones or storms, or small islands. May be this specific case would deserve a note. This question of habitability is assessed in the chapter 15 of the IPCC for small islands https://www.ipcc.ch/report/ar6/wg2/downloads/report/IPCC_AR6_WGII_Chapter15.pdf

- If the authors can include a conceptual figure in their paper, illustrating their key idea (how the new framings and proposed way forwards can address the challenge of sustainable development in coastal areas), this would be potentially usefull.

Page 3 line 76 : I would suggest to add uncertainties around these median values of sea-level projections and eventually mention that larger sea levels outcomes can not be excluded in case of Antarctica ice-sheets collapse. All arguments on these aspects are presented in Fox-Kemper et al 2021, which the author cite.

Page 3 line 89: the argument is excellent but I find the introduction of indigenous knowledge here a bit abrupt. Indigenous knowledge is defined in the IPCC glossary (WGII 2022) as “The understandings, skills and philosophies developed by societies with long histories of interaction with their natural surroundings”. In many cases there are coastal communities who have settled in coastal zones recently, without much knowledge on this coastal area and without actually considering coastal hazards such as flooding or other coastal conservation issues. May be there is a point to be made on coastal communities in general before explaining how this view integrates indigeneous knowledge?

Page 3 line 115: again I fully agree with the argument but I think the role of extreme events will be different depending on the region. For example, in some tropical regions such as eastern Polynesia or Guyana, cyclones are rare or never happen, and sea level rise may actually first materialize in the form of new or more frequent and more intense chronic flooding events (superimposition of high tides and sea level rise, eventually compound with swells or rainfall). E.g. Moftakhari et al. https://doi.org/10.1029/2018WR022828 - may be a bit of nuance here is needed. Note also that this paper can be useful to support the statement that indirect and cascading impacts of sea level rise are potentially very important, yet there is a research gap in this area

Line 145-148: I think that the example of Magliocca et al is well chosen, but the problem is that you need to read the abstract to understand how the reconstruction and maintenance of dunes can compromise resilience in the long term. Just a bit of reformulation is probably sufficient here.

Line 152: again I think it is an excellent point – here a recent perspective by Orton et al. also supporting this statement in the context of the likely increase of storm surges barriers constructions in estuaries worldwide https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2022EF002991

Line 192: I suggest considering adding the environmental dimension here (e.g., ecosystem conservation, ecosystem services management…)

Line 211 and 212: eliminating unsustainable strategies is certainly a sound objective, but I am not sure it is sufficient to guarantee sustainability. In my view there is a legacy from past decisions that require additional innovations to move some coastal systems into a sustainable state. For example, coastal nuclear plants, landfills or polluted soils exist already and will need to be managed.

Typos:

- Line 81 – revision mode activated

I hope that this review is useful

Gonéri Le Cozannet, 01/06/2023

Recommendation: Coastal futures: New framings, many questions, some ways forward — R0/PR4

Comments

Both reviewers agree that this perspective piece is well written and clearly within scope of Coastal Futures, although one notes that the overall argument could be strengthened. I support the reviewrs‘ recommendation of publication after minor revisions. Most of the suggestions should be relatively easy to address; I leave it to the authors’ judgement regarding an appropriate balance between including additional content (or nuance) and keeping the overall perspective piece clear and concise. The suggestion to include a conceptual figure may be rather more challenging to address, although I agree with the reviewer that this would further add to the quality and impact of the article.

Decision: Coastal futures: New framings, many questions, some ways forward — R0/PR5

Comments

No accompanying comment.

Author comment: Coastal futures: New framings, many questions, some ways forward — R1/PR6

Comments

No accompanying comment.

Review: Coastal futures: New framings, many questions, some ways forward — R1/PR7

Conflict of interest statement

Reviewer declares none.

Comments

Many thanks for answering the reviewers' comments and providing an easy to read response. All but one have been answered satisfactory. In response to your addition text below, please can you add a supporting reference. Thank you. I look forward to seeing your work published.

R2: Page 3 line 89: the argument is excellent but I find the introduction of indigenous knowledge here a bit abrupt. Indigenous knowledge is defined in the IPCC glossary (WGII 2022) as “The understandings, skills and philosophies developed by societies with long histories of interaction with their natural surroundings”. In many cases there are coastal communities who have settled in coastal zones recently, without much knowledge on this coastal area and without actually considering coastal hazards such as flooding or other coastal conservation issues. May be there is a point to be made on coastal communities in general before explaining how this view integrates indigeneous knowledge?

Response: We adjust our text as follows:

‘On some coasts, recent settlers have arrived with little, or no, knowledge of the coastal environment and the potential flood hazards they may face whereas elsewhere there may be deep knowledge from long histories of interaction with their natural surroundings. Climate adaptation strategies need to be fitted to the communities at risk, including, where they can, indigenous knowledge and values. More broadly, there will be a need to move beyond solely technocentric thinking at the coast, including a consideration of the role and juxtaposition of the arts and humanities with the natural sciences.

Recommendation: Coastal futures: New framings, many questions, some ways forward — R1/PR8

Comments

My thanks to the authors for their revisions and clear responses to the previous review comments. One of the reviewers has noted that the revised text around Page 3 Line 89 (on indigenous knowledge and knowledge of hazards within coastal communities) should be supported by one or more references. I believe that this is a reasonable request, and encourage the authors to include at least one supporting reference to the revised text. After this (very) minor revision, I would be happy to accept the paper without requiring additional reviewer comments.

Decision: Coastal futures: New framings, many questions, some ways forward — R1/PR9

Comments

No accompanying comment.

Author comment: Coastal futures: New framings, many questions, some ways forward — R2/PR10

Comments

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Recommendation: Coastal futures: New framings, many questions, some ways forward — R2/PR11

Comments

No accompanying comment.

Decision: Coastal futures: New framings, many questions, some ways forward — R2/PR12

Comments

No accompanying comment.