A 1.7 m marine sediment core was extracted from the Ek Way Nal underwater site to evaluate the impact of sea-level rise on the site. The location of the core was a narrow strip of land covered by living red mangroves (Rhizophora mangle) that bisects Ek Way Nal. If the site continued under the strip of land, then the core would have cultural material. Alternatively, the strip of land may have been present when the site was occupied. Loss-on ignition and microscopic sorting of sediment from the core were carried out to evaluate if the sediment was red mangrove peat—a proxy for sea-level rise and if the cultural material was present at depths similar to those at underwater portions of the site.

The erosion of coastal archaeological sites is a worldwide heritage crisis. However, regional variability in the archaeological record and the natural environment necessitates localized consideration of the erosion of archaeological sites to facilitate informed research prioritization decisions about coastal cultural resources. In this article, we present and compare the results of recent coastal survey programs from southern Nova Scotia and far northeastern Maine to earlier ones to ascertain the extent of erosion since the mid-twentieth century. We then situate regional erosion in culture-historical terms via a case study from archaeological sites at Sipp Bay, Maine, from which materials were collected and tested in the early to mid-twentieth century. We compare the results of that work to our recent excavations. Finally, we model future sea-level rise scenarios to estimate future site destruction and compare these models between regions. Together, these data illustrate patterns in site preservation for geoarchaeological examination, provide insight into erosion-driven biases in the extant archaeological record, and offer information to guide research prioritization.

It is often inferred that rising sea levels will result in widespread coastal recession. Erosion appeared prevalent in a worldwide compilation of evidence derived from maps and aerial photographs undertaken in the 1980s by the Commission on the Coastal Environment. Eric Bird, chair of the commission, inferred that >70% of sandy coastlines had retreated, a generalisation that has been widely cited. We reconsider these findings in respect of subsequent advances in shoreline mapping, including greater precision possible using geographical information systems and more frequent remote sensing imagery with increased spatial, spectral and temporal resolution. Satellite-derived shorelines now enable broad global and regional generalisations about shoreline position. Beaches fluctuate over a range of timescales, meaning that trends in their position are highly dependent on techniques and temporal scales adopted for monitoring. Recent global- and regional-scale shoreline assessments indicate that many sandy shorelines have been stable, and that detectable retreat has occurred on fewer beaches than previously inferred. Accretion is apparent on some coasts, particularly where engineering interventions protect or have reclaimed land. There is considerable variability in the behaviour of monitored beaches, and it is not yet possible to decipher a response to the gradual centimetre-scale rise in sea level of recent decades. Instead, we re-emphasise the several other factors that were considered to contribute to recession by the Commission, many of which relate to a change in sediment budget. To provide insights into future coastline behaviour, a better understanding of the multiple drivers on individual beaches is needed to discriminate between erosional events and longer-term trends in shoreline position.

This foreword introduces the inaugural International and Comparative Law Quarterly (ICLQ) Forum, a new initiative designed to provide in-depth analysis of a particular field of law within the ICLQ’s sphere of interest. The first Forum focuses on the law of the sea, a subject with which the journal has been closely associated since its inception. The choice of theme reflects both the ICLQ’s historic contributions to maritime scholarship and the renewed urgency of ocean-related legal challenges. The collected contributions examine contemporary developments, including the implementation of the Agreement on Marine Biological Diversity of Areas Beyond National Jurisdiction, climate change and sea-level rise, maritime security, fisheries governance and human rights at sea. Together, they assess the continuing vitality of the United Nations Convention on the Law of the Sea as a ‘living treaty’ and interrogate its capacity to respond to shifting geopolitical, environmental and technological realities. Beyond charting doctrinal evolution, the Forum highlights the law of the sea’s systemic significance for the development of international law more broadly. It invites reflection on whether the traditional State-centric framework can sustain effective ocean governance in the face of accelerating global pressures.

This article contends that anthropogenic sea-level rise seriously undermines the exercise of self-determination by peoples living in Small Island Developing States (SIDS). Moreover, it argues that the effects of this would be severely exacerbated if the international community were to reject the possibility of statehood enduring notwithstanding total submergence, the complete loss of inhabitable land or the mass exodus of extant populations. In support of the claims made by several SIDS themselves, this article provides an analysis focused upon the relationship between the law of State continuity, on the one hand, and the peremptory norm of self-determination on the other. Ultimately, this analysis advances an understanding of State continuity and sea-level rise that favours existential resilience, making any future losses of statehood contingent upon voluntary dissolution by affected States.

Climate change resulting from human activity is causing sea-levels to rise. Rising sea-levels pose an existential threat to small islands. Some have argued that this might result in islands losing their status as ‘islands’ and, at the same time, their maritime areas. The present article disagrees. In order to qualify as an ‘island’, a coastal feature must be ‘a naturally formed area of land, surrounded by water, which is above water at high tide’: Article 121(1) of the United Nations Convention on the Law of the Sea (UNCLOS). A feature that meets these requirements is, according to Article 121(2), entitled to a territorial sea, an exclusive economic zone and a continental shelf. Article 121(3) provides that rocks which cannot sustain human habitation or an economic life of their own have no exclusive economic zone or continental shelf. The words ‘naturally formed area of land’, as well as broader considerations, suggest that the status of a feature is determined on the basis of its natural condition—not changes generated by human activity. Just as construction through human artifice cannot elevate a coastal feature into an island, man-made climate change which causes sea-level rise cannot turn an island into something other than what is described in Article 121(1).

According to the Intergovernmental Panel on Climate Change’s Sixth Assessment Report, sea-level rise will continue for thousands of years. Many small island States and low-lying coastal States are already experiencing sea-level rise together with landward regression of coastal areas. This raises several legal questions, such as whether States are obligated to revise existing baselines, outer limits of maritime zones and charts. This article examines the legal lacunae in the United Nations Convention on the Law of the Sea (UNCLOS) concerning the legal consequences of sea-level rise on baselines and maritime boundaries, including islands and archipelagos. It provides an overview of the work of the International Law Commission on sea-level rise in relation to international law. It traces the evolution of States’ views within the Sixth Committee between 2018 and 2024 and the UN, as well as the recent Advisory Opinions on climate change of the International Tribunal for the Law of the Sea and the International Court of Justice. It concludes by noting how the legal lacunae in UNCLOS have been clarified, leaving to be determined the next steps in implementing the convergence of States’ interpretations of UNCLOS and customary international law in favour of preservation of baselines and maritime boundaries despite the physical effects of sea-level rise on coastlines.

The long-term development of coral reef frameworks and the net vertical accretion of reefs fundamentally underpins the provisioning of most reef-related ecosystem services. One area of particular concern at present is how rates of reef accretion are changing under ecological decline and what the consequences of this may be for the capacity of reefs to keep pace with near-future sea-level rise (SLR). This may have major implications for the capacity of reefs to maintain their coastal protective functions and to support reef island stability. Both are issues relevant to understanding future tropical coastal risk. Long-term (millennial timescale) rates of reef accretion are relatively well constrained, including through past periods of sea-level fluctuations. However, widespread and persistent ecological degradation of coral communities has caused many reefs to diverge significantly from their past accretion trajectories. This renders historical analogues increasingly unreliable for projecting future accretion potential. Addressing this necessitates a reorientation towards considering reef accretion rates across shorter (ecological to geomorphic) timescales, i.e., over years to multi-decades. This is essential if we are to better constrain contemporary reef accretion rate and SLR interactions at timescales relevant to predicting emerging coastal risks and understanding future implications for reef-derived benefits. Here, we review existing approaches for quantifying vertical reef accretion rates of modern reefs. These methods span data recovered from fossil outcrops or core-derived records, the conversion of carbonate budget data, direct in situ measurements and emerging remote sensing and image-based techniques. The review explores the advantages and limitations of these different approaches and outlines options for developing an integrated framework to link past, present and future reef accretion potential.

Addressing sea-level rise and coastal flooding requires adaptation strategies tailored to specific coastal environments. However, a lack of detailed geomorphological data on global coasts impedes effective strategy development. This research maps seven coastal environments worldwide, and for each environment analyzes the effect of coastal changes on coastal populations by including sea-level change, extreme sea-level events with varying return periods and population growth from 1950 to 2050. It identifies the historical exposure of low-lying deltaic and estuarine flood areas (>48% of total population) and reveals that flood exposure will significantly increase for barrier islands and strandplains by 2050 (with over a 40% rise in exposure), particularly along African coastlines. Population growth emerges as the primary factor behind the increased exposure. While sea-level rise is projected to contribute between 26% and 65% of the increased inundated area by 2050 compared to a 10-year extreme sea-level event, varying by coastal environment. The findings highlight the critical need for mitigation measures that account for the distinct responses of different coastal types to sea-level rise, posing various risks over varying timescales.

While adapting to future sea-level rise (SLR) and its hazards and impacts is a multidisciplinary challenge, the interaction of scientists across different research fields, and with practitioners, is limited. To stimulate collaboration and develop a common research agenda, a workshop held in June 2024 gathered 22 scientists and policymakers working in the Netherlands. Participants discussed the interacting uncertainties across three different research fields: sea-level projections, hazards and impacts, and adaptation. Here, we present our view on the most important uncertainties within each field and the feasibility of managing and reducing those uncertainties. We find that enhanced collaboration is urgently needed to prioritize uncertainty reductions, manage expectations and increase the relevance of science to adaptation planning. Furthermore, we argue that in the coming decades, significant uncertainties will remain or newly arise in each research field and that rapidly accelerating SLR will remain a possibility. Therefore, we recommend investigating the extent to which early warning systems can help policymakers as a tool to make timely decisions under remaining uncertainties, in both the Netherlands and other coastal areas. Crucially, this will require viewing SLR, its hazards and impacts, and adaptation as a whole.

We examined a zooarchaeological assemblage from Badger Island, a 12.4 km2 landbridge island in the Furneaux Group, Bass Strait, south-eastern Australia. The accumulation consisted of Pleistocene and Holocene strata that were rich in mammal remains. Small mammal remains were accumulated by owls, whereas large mammal remains were accumulated by people and/or autochthonous mortality. The Pleistocene fauna was dominated by grassland mammals, particularly Mastacomys fuscus (Broad-toothed Rat), but these gradually declined and were largely replaced by forest–woodland dwelling mammals in the Holocene. The same pattern of faunal change has been observed on the large main island of Tasmania (∼65,000 km2), suggesting changes observed at Beeton Rockshelter are representative of the region. Because all of the Furneaux Group Islands were united as one landmass in the past, the fossil fauna observed in Beeton Rockshelter is relevant to conservation-oriented mammal-restoration initiatives, which are being considered throughout the entire Furneaux Group.

With coastal populations rising at three times the global average, sustainable ways of safeguarding human needs around access and use of the coast alongside lasting ecosystem health of coastal environments must be developed. At the same time, human populations are facing the challenge of managing coastal access on the back of a legacy of human interventions that have already altered – and have often had unintended or unforeseen impacts on – the coastal system and its functioning.

We chart the history of the evolution of North Bull Island in Dublin Bay as an example of major unforeseen sedimentation in a coastal estuarine bay following the construction of river mouth training walls. We investigate the impact of a constructed causeway on the evolved ‘naturescape’ by comparing accretion and elevation change on the mid-marsh either side of the access road over a 32-month period (autumn 2021 to summer 2024) and measuring water levels either side of the causeway on six spring tides on consecutive days characterised by varying meteorological conditions in early September 2023. The results allow us to consider the potential implications a lack of physical connectivity may cause for the future of the two artificially separated back-barrier lagoon environments.

In the next 30 to 50 years, rising sea levels caused by global warming will subsume low-lying islands in the Pacific Ocean. Inhabitants will have to relocate, but there are few choices. Among nations (with the exception of Fiji and New Zealand) there is little preparation for the inevitable migration of Pacific Islanders. Which nations should commit to the processes of equitable relocation? The following article will address this question through historical context and colonial occupation; current legal debates surrounding climate change and maritime migration; and the potential rights of “deterritorialized” states, such as retention of exclusive economic zones. Historical context includes an examination of U.S. insular territories in the Pacific and the continued exercise of presidential authority over island possessions.

The capacity of river mouths to reduce storm surge water levels upstream, referred to as along-estuary attenuation, has been assessed by several studies. The coastal protection function of semi-enclosed water bodies such as lagoons and channels with narrow inlets remains less explored and generalization is hampered by differences in morphology and hydrodynamic forcing. Here we use a hydrodynamic model to investigate surge attenuation along a microtidal channel with a narrow inlet at the Baltic Sea coast of Germany called The Schlei. We quantify the importance of wind and the contribution of the barrier spit system, which is constricting the inlet, to the reduction of water levels at the landward end of the channel. In addition, we explore the role of dikes in the region for the reduction of peak water levels and coastal flooding. We find effective along-channel attenuation inside The Schlei in its current state, which is mostly a result of the channel’s narrows. However, reduction rates decrease under simplified sea-level rise scenarios. Furthermore, along-channel attenuation is highly variable and can change to substantial amplification depending on hydrometeorological forcing. The barrier spit contributes to along-channel attenuation whereas the effect of existing dikes (or their removal) for along-channel attenuation is negligible.

Tidal flooding occurs when coastal water levels exceed impact-based flood thresholds due to tides alone, under average weather conditions. Transitions to tidal flood regimes are already underway for nuisance flood severities in harbours and bays and expected for higher severities in coming decades. In the first such regional assessment, we show that the same transition to tidally forced floods can also be expected to occur in Australian estuaries with less than 0.1 m further sea-level rise. Flood thresholds that historically used to only be exceeded under the combined effects of riverine (freshwater) and coastal (salt water) influences will then occur due to high tides alone. Once this tidal flooding emerges, it is projected to become chronic within two decades. Locations most at-risk of the emergence of tidal flooding and subsequent establishment of chronic flood regimes are those just inside estuary entrances. These locations are exemplified by low freeboard, the vertical distance between a flood threshold and a typical high tide level. We use a freeboard-based analysis to estimate the sea-level rise required for impacts associated with official flood thresholds to occur due to tides alone. The resultant tide-only flood frequency estimates provide a lower bound for future flood rates.

Sedentary occupation of the southern Levantine coast spans from the Pre-Pottery Neolithic C to the Early Bronze Age Ib phase (c. 7000–3100 BC). Sites dating to the Early Pottery Neolithic (c. 6400–5500 BC) are scarce, however, potentially reflecting the effects of the 8.2ka climatic event. Here, the authors present the investigations at the submerged site of Habonim North off the Carmel Coast. Typological and radiocarbon dating indicate an Early Pottery Neolithic occupation and evidence for continuity of subsistence and economic strategies with both earlier and later Neolithic cultures. The results indicate the resilience of coastal communities in the face of significant climatic uncertainty and contribute to understanding human responses to environmental change.

Climate change-induced sea level rise has exacerbated coastal change putting millions of people at risk from coastal hazards, such as flooding and coastal erosion. Nature-based solutions have been recognised as an opportunity to simultaneously address the coastal hazard risks and achieve biodiversity goals. While such solutions are included in climate adaptation strategies, “hard” engineered solutions are still often preferred by those implementing the schemes. We sought to explore the diverse perspectives on UK coastal flood risk management among interested and/or affected groups by utilising the Q-methodology. We identified five perspectives: (1) The Pro-Green Practitioners; (2) The Future-Planning Relocators; (3) The Case-by-Case Thinkers; (4) The Cautious Practitioners and (5) The Climate Change Concerned. All five perspectives strongly valued the co-benefits of nature-based solutions and their role in coastal risk reduction. None of the perspectives prioritised hard-engineered solutions as the primary flood protection strategy in the UK, though they recognised their role in protecting essential infrastructure. The main disagreements between perspectives were (1) on the need for relocation strategies, and (2) whether nature-based solutions could cause social inequalities. The Q-methodology does not identify how prevalent such perspectives are, thus further research is needed to assess the social acceptance of nature-based solutions.

Major technological advances have made measurements of coastal subsidence more sophisticated, but these advances have not always been matched by a thorough examination of what is actually being measured. Here we draw attention to the widespread confusion about key concepts in the coastal subsidence literature, much of which revolves around the interplay between sediment accretion, vertical land motion and surface-elevation change. We attempt to reconcile this by drawing on well-established concepts from the tectonics community. A consensus on these issues by means of a common language can help bridge the gap between disparate disciplines (ranging from geophysics to ecology) that are critical in the quest for meaningful projections of future relative sea-level rise.