Climate change has been recognised as a major concern in coastal hotspots exposed to multiple climate hazards under regionally specific characteristics of vulnerability. We review the emerging research and current trends in the academic literature on coastal climate risk and adaptation from a human security perspective. The ecological and socioeconomic developments are analysed for key risk areas, including coastal infrastructure; water, food and fisheries; health; human mobility; and conflict, taking the different geographical contexts of coastal areas in islands, megacities and deltas into consideration. Compounding and cascading interactions require integrative research and policy approaches to address the growing complexity. Governance mechanisms focus on coastal management and adaptation, nature-based solutions and community-based adaptation, considering their synergies and trade-offs. This perspective allows for a holistic view on climate risks to human security and vicious circles of societal instability in coastal systems and the interconnectedness of different risk dimensions and systems necessary for sustainable and transformative adaptation solutions for the most affected coastal hotspots.

This article deals with the sea level rise phenomenon caused by the climate change process and its impact on the statehood of so-called disappearing island states as well as on the consequent factual and legal status of their populations. In classical international law doctrine, the loss of a state’s territory will lead to the extinction of statehood and, consequently, the loss of that state’s international legal personality, and possibly also to the statelessness of its nationals. This article proposes an alternative solution based on the transformation of disappearing island states into new non-territorial subjects of international law — “climate deterritorialized nations” — as successors to disappeared inundated states.

This article is a rejoinder to Dr. Massimo Lando’s ‘Stability of maritime boundaries and the challenge of geographical change’ which proposes that positive international law offers no legal basis for the delimitation of fluctuating boundaries and discusses the many complexities involved in the delimitation and management of such boundaries. This rejoinder delves deeper into the main point of contention: the legal basis for fluctuating boundaries. It argues that coastal states have an inherent entitlement to a territorial sea and that Article 15 of The United Nations Convention on the Law of the Sea (UNCLOS) entails a default rule for the establishment of provisional fluctuating boundaries. This limit is not necessarily a strict median line because it may be adjusted by reference to special circumstances. Furthermore, the lack of explicit reference to provisional arrangements in UNCLOS Article 15 should not be read as an indication that there are no provisional boundaries in the absence of boundary agreements.

This article further argues that there are judicial precedents for fluctuating boundary-segments. The Nicaragua v. Honduras decision left a segment of the territorial sea un-delimited, resulting in a partially fluctuating boundary, until otherwise agreed. Moreover, the International Court of Justice (ICJ) explicitly established a mobile boundary-segment in Costa Rica v. Nicaragua but as highlighted by Dr. Lando, this was done with the permission of the parties. Much depends on the claims brought by disputing parties and their stance on fluctuating boundaries but this decision demonstrated the ICJ’s willingness to employ fluctuating boundaries in response to coastal instability.

Geographical phenomena impacting the shape of coastlines may have implications for the stability of maritime boundaries delimited by agreement or judicial process. Sea level rise resulting from human-caused climate change has recently arisen as an additional phenomenon compelling the re-assessment of the stability of maritime boundaries over time. In a recent article published in this Journal, Dr. Snjólaug Árnadóttir has argued that a solution to the challenges of coastline change could be for maritime boundaries to fluctuate following the fluctuation of the baselines on which their course depends. By way of reply to Dr. Árnadóttir’s suggestion, this article argues that fluctuating boundaries have no legal basis either in the United Nations Convention on the Law of the Sea or in judicial decisions. Moreover, the delimitation process in three stages, commonly applied by international courts and tribunals since the Black Sea judgment, appears to be ill-suited for establishing fluctuating boundaries. There seems to be other solutions to the problem of coastline change, which this article also briefly explores.

Aspects of species life histories may increase their susceptibility to climate change. Owing to their exclusive reliance on environmental sources of heat for incubation, megapodes may be especially vulnerable. We employed a trait-based vulnerability assessment to weigh their exposure to projected climate variables of increasing temperatures, fluctuating rainfall and sea level rise and their biological sensitivity and capacity to adapt. While all 21 species were predicted to experience at least a 2 °C increase in mean annual temperature, 12 to experience a moderate or greater fluctuation in rainfall and 16 to experience rising seas, the most vulnerable megapodes are intrinsically rare and range restricted. Species that employ microbial decomposition for incubation may have an adaptive advantage over those that do not and may be more resilient to climate change. The moderate microclimate necessary for mound incubation, however, may in some areas be threatened by anthropogenic habitat loss exacerbated by warmer and seasonally drier conditions. As with many avian species, little is known about the capacity of megapodes to adapt to a changing climate. We therefore recommend that future research efforts investigate megapode fecundity, gene flow and genetic connectivity at the population level to better determine their adaptive capacity.

Coastal plain stratigraphy is often over looked in paleo–sea-level reconstructions because carbonate sediments do not precisely constrain former sea level. Pacific Island sedimentology provides an invaluable record of geomorphic and environmental consequences of coastal evolution in response to changes in sea level and local tectonics. A series of coastal auger cores obtained from eastern ʻUpolu reveal a subsurface carbonate sand envelope predominately composed of coral and coralline algae derived from the reef framework. Coupling the sedimentological record with geophysical models of Holocene sea level, we identify a critical value (0.3–1.0 m) during the falling phase of the sea-level high stand (1899–2103 cal yr BP) that represents the transition from a transgressive to a regressive environment and initiates coastal progradation. Correlating the critical value with time, we observe nearly a millennium of coastal plain development is required before a small human population is established. Our findings support previous studies arguing that Sāmoa was colonized by small and isolated groups, as post–mid-Holocene drawdown in regional sea level produced coastal settings that were morphologically attractive for human settlement. As future sea level approaches mid-Holocene high stand values, lessons learned from Pacific Island sedimentological records may be useful in guiding future decisions related to coastal processes and habitat suitability.

Sea-level rise during the late Pleistocene and early Holocene inundated nearshore areas in many parts of the world, producing drastic changes in local ecosystems and obscuring significant portions of the archeological record. Although global forces are at play, the effects of sea-level rise are highly localized due to variability in glacial isostatic adjustment (GIA) effects. Interpretations of coastal paleoecology and archeology require reliable estimates of ancient shorelines that account for GIA effects. Here we build on previous models for California's Northern Channel Islands, producing more accurate late Pleistocene and Holocene paleogeographic reconstructions adjusted for regional GIA variability. This region has contributed significantly to our understanding of early New World coastal foragers. Sea level that was about 80-85 m lower than present at the time of the first known human occupation brought about a landscape and ecology substantially different than today. During the late Pleistocene, large tracts of coastal lowlands were exposed, while a colder, wetter climate and fluctuating marine conditions interacted with rapidly evolving littoral environments. At the close of the Pleistocene and start of the Holocene, people in coastal California faced shrinking land, intertidal, and subtidal zones, with important implications for resource availability and distribution.

Benefit-cost analysis (BCA) aims to help people make better decisions. But BCA does not always serve this role as well as intended. In particular, BCA’s aim of aggregating all attributes of concern to decision makers into a single, best-estimate metric can conflict with the differing world views and values that may be an inherent characteristic of many climate-related decisions. This paper argues that new approaches exist that can help reduce the tension between the benefits of providing useful, scientifically based information to decision makers and the costs of aggregating uncertainty and differing values into single best estimates. Enabled by new information technology, these approaches can summarize decision-relevant information in new ways. Viewed in this light, many limitations of BCA lie not in the approach itself, but with the way it is used. In particular, this paper will argue that the problem lies in a process that begins by first assigning agreed-upon values to all the relevant inputs and then using BCA to rank the desirability of alternative decision options. In contrast, BCA can be used as part of a process that begins by acknowledging a wide range of ethical and epistemological views, examines which combinations of views are most important in affecting the ranking among proposed decision options, and uses this information to identify and seek consensus on actions that are robust over a wide range of such views.

Global sea level is rising at an increased rate since the late 19th century as a result of rising global mean temperatures. This rise is geographically non-uniform, with substantial spatial differences, and in the latest decade faster than expected. New evidence suggests that more rapid changes than indicated in the Fourth IPCC report take place in the two large continental ice sheets, Greenland and Antarctica. Consequently, the projected sea level rise threatens low-lying countries like the Netherlands. The process of ‘climate-proofing’ the flood protection system of the country offers, however, new opportunities for innovative solutions, providing not only higher flood protection, but also possibilities for multifunctional land-use.

In light of the urgent need for coastal adaptation policies and the impediments to their implementation, this article examines the early experience with coastal adaptation policies in the EU (in particular the Netherlands and the UK) and Australia, with a view to identifying the important features of an effective regulatory framework for coastal adaptation. We conclude that an integrated approach to coastal adaptation law is currently needed to lay the foundations for the required long-term strategy. Such an approach would establish processes by which adaptation objectives are agreed for each part of the coast, ensure land use planning that can accommodate future change and does not expose new communities to risk, integrate coastal adaptation with biodiversity and coastal zone policy, allocate regulatory responsibility in a way that promotes subsidiarity and consistency, and ensure that funds are available for future measures.