Coastal areas that are characterized by coastal squeeze are highly vulnerable to the contemporary threats of climate change, sea level rise and biodiversity loss. Innovative coastal adaptation policies are necessary to accommodate these threats and have become salient issues on the agendas of mandated decision-makers on a global scale. This article provides a perspective on how historical–geomorphological knowledge can be integrated as an evidence base for coastal adaptation in such vulnerable zones when re-thinking and re-designing coastal adaptation policies. Our historical–geomorphological perspective proposes that we explicitly need to account for the geological, natural extent of human-modified and squeezed areas to fully understand their present-day developments. The geo-historical extent provides information on the long-term development of sedimentary structures and the functioning of coastal systems, and evaluates their effects on coastal protection, conservation and necessary adaptation. We use the Wadden Sea coastal zone as a case study to illustrate the necessity of the development of a geo-historical perspective and operationalize its integration into contemporary decision-making. The North European Wadden Sea is the largest continuous region of intertidal sand and mud flats in the world, and was recognized for its outstanding universal value by UNESCO in 2009. Nonetheless, it is an area that suffers intensely from coastal squeeze and has lost 70–80% of its coastal zone due to land reclamation and dike building. In short, our geo-historical perspective demands: (i) geo-historical risk assessment of coastal areas, (ii) geomorphological modelling that links the historical-induced risk to contemporary dynamics, (iii) assessment of ecological and societal values that are capable of estimating trade-offs between different coastal adaptation options in the contemporary system, (iv) evaluation of feasibility and legitimacy of potential coastal adaptation on the local scale of coastal inhabitants and (v) applying a transdisciplinary process that enables effective knowledge co-production between science and societal stakeholders.

Blue spaces are recognised as vital public resources that support human health and wellbeing through pathways such as physical activity, psychological restoration and social connection. Coastal environments are especially distinctive for their multisensory stimuli, expansive vistas and cultural significance, with benefits shaped by environmental quality, accessibility and usability. Climate change threatens these benefits via extreme events, such as storm surges and flooding, and gradual processes, including rising sea levels, erosion and warming temperatures, which can also alter people’s perceptions, engagement patterns and cultural connections. A conceptual framework is proposed to explore the mechanisms through which climate change affects coastal amenities. This framework offers a structured approach to understanding how environmental processes, interventions and social factors interact to shape health and wellbeing outcomes, and identifies where, why and at what scales adaptation interventions can be most effectively applied. Adaptation measures can help sustain wellbeing benefits under climate hazards by reinforcing positive feedbacks, such as stewardship and investment in amenities, while mitigating negative feedbacks from environmental degradation or overuse. Climate-informed adaptation of coastal amenities, integrating ecological, social and governance considerations, is essential to preserve quality, access, usability and the equitable delivery of health benefits. The framework therefore offers both a theoretical basis for understanding climate–wellbeing interactions and a practical tool to support internationally relevant interventions, policy development and co-designed justice-sensitive adaptation strategies that sustain the health, cultural and social value of blue spaces under climate change.

Coastal fisheries are central to Pacific Island nutrition, livelihoods and cultural identity, yet growing microplastic contamination threatens food security and public health. This study integrates fishers’ knowledge of locally important coastal fish species with empirical measurements of microplastic loads to identify priority taxa for monitoring across Fiji, Tonga, Tuvalu and Vanuatu. Interviews with 110 fishers documented commonly caught species, and the number of times each taxon was reported was calculated. Family-level catch data and mean microplastic loads were each standardised between 0 and 1 to generate Catch and Microplastic Scores, which were multiplied to create an Exposure Index reflecting both social relevance and contamination levels. Regionally, Lethrinidae and Scombridae had the highest Exposure Index values, while Acanthuridae, Lutjanidae, Scaridae and Serranidae emerged as country-specific priorities. Gendered fishing patterns revealed differences in catch, influencing potential exposure pathways and highlighting the need for gender-disaggregated data in future assessments. This approach of combining local knowledge with contamination studies offers a replicable, regionally-grounded method for identifying key indicator species for future microplastic monitoring. Species within the Lethrinidae family, particularly Lethrinus harak, stand out as regional priorities because of their importance to subsistence and artisanal fisheries, exposure to microplastics and consistent occurrence across the region.

J.N. “Ding” Darling National Wildlife Refuge (DDNWR) is located on Sanibel Island along the southwestern coast of Florida, USA. There, eutrophication attributed to agricultural discharge along the Caloosahatchee River has affected the area’s aquatic habitat. In anticipation of additional nutrient loading, we experimentally fertilized mangrove forests with nitrogen (+N; NH4) and phosphorus (+P; P2O5) for 3 years, and monitored soil and pneumatophore CO2 fluxes and tree sap flow from two mangrove species. Furthermore, we modeled individual tree and stand water use, from which we developed carbon (C) budgets for +N and + P vs. control simulations based on a novel application of water use efficiency conversion. Many of the measured response variables provided hints of subtle changes in response to +P rather than +N, which were enhanced when scaled. From this, we found that additional P loading is expected to reduce both gross and net primary productivity as well as CO2 uptake via net ecosystem exchange of C, likely pressing the system beyond metabolic capacity and leading to a 48–62% decrease in projected lateral C export. Greater eutrophication will likely compound vulnerabilities to sea-level rise submergence, especially where P concentrations are high and already reducing soil surface elevations.

Early warning systems for coastal erosion and flooding are currently primarily designed for local applications, offering high-resolution, site-specific predictions. Only a few early warning systems (EWS) are used at large regional or national scales. There is also a lack of standardised indicators and thresholds, which vary widely across systems and hinder cross-regional applicability. While current EWS perform well in binary hazard detection (Yes/No hazard; 80–95% accuracy), they struggle to accurately classify intermediate hazard levels. A lack of comprehensive field datasets has impeded rigorous validation for most systems, with many assessments relying on qualitative observations. Improving the reliability of the EWS requires improving their validation against field data obtained during storms and regular updating of the topobathymetric data to include the actual pre-storm morphology. Currently, most EWS rely on outdated or synthetic morphological inputs, which increases prediction uncertainty. The computational constraints of physics-based models may prevent warnings from being issued in time and have led to the adoption of surrogate approaches that depend on robust training datasets. Furthermore, most systems focus solely on hazard detection, paying limited attention to the risk to assets or populations. Future development must prioritise stakeholder engagement and the co-design of systems that incorporate both hazard and risk assessments, in order to improve their usefulness and facilitate decision-making by end users.

The Chignecto Isthmus is the sole land connection between Nova Scotia and mainland Canada, supporting national trade, agriculture and transportation. Much of this low-lying corridor is protected by aging dikes that are increasingly vulnerable to compound flooding from tides, storm surges and sea-level rise. This study combines static flood modeling and GIS-based land use classification to evaluate the elevation-based flood exposure of infrastructure and agricultural land. A planar water surface modeling approach validated with differential GPS measurements was applied to a 1-m-resolution digital elevation model. Results indicate that water levels in the adjacent basin can reach within 1 m of the mean dike crest elevation during spring tides. Planar surface modeling scenarios demonstrate that relatively modest increases in water level beyond this threshold could result in inundation, affecting thousands of hectares of cropland and hundreds of hectares of developed land, along with critical transportation infrastructure. This exposure has the potential to disrupt agricultural productivity, rural livelihoods, groundwater quality and interprovincial supply chains across the isthmus. While simplified, this analysis highlights the diminishing safety margin afforded by existing dikes, underscores the need for more detailed scenario-based modeling and reinforces the importance of proactive adaptation planning to safeguard this nationally significant corridor.

Sea-level projections are highly anticipated outcomes of climate model simulations, relevant for coastal management worldwide. Ideally, any model simulation needs to be validated against observations, but this is impossible for the most recent sets of future climate model simulations, which start near to the present day (2020). Here, we compare satellite observations of regional sea-level change against projections from the Intergovernmental Panel on Climate Change Fifth Assessment Report for total sea-level change and its individual components over their overlapping period, from 2007–2022. We first test and compare three different methods to reduce the internal variability in the observations, which hampers the comparison with models, in particular for shorter time periods. While all three methods reduce the internal variability, we find the low-frequency component analysis (LFCA) removes most of the internal variability. We find that the regional projections are in good agreement with the LFCA-filtered observations, for 96% of ocean area within the 90% confidence interval. For the total sea level and sterodynamic component, the projections both under- and overestimate the observations, depending on the region. For mass-driven sea-level change, the regional projections tend to overestimate the observations. Our analysis gives confidence in sea-level projections for the instrumental era.

Saltmarsh habitat provides important ecosystem services, such as water quality regulation, carbon sequestration and flood defence, but is experiencing losses globally. Historically, this has been caused by land claim, and more recently by rising sea levels. Several methods have been implemented to compensate for saltmarsh habitat loss, including realigning defences, transplanting vegetation, and building structures such as sedimentation fields to enclose areas of mudflat and encourage sediment deposition. It has been suggested that sedimentation fields may offer saltmarsh restoration without the limitations identified in other restoration approaches, such as poor drainage and anoxia caused by changes to the sediment structure due to prior human activity. In this article, we argue that restoration through sedimentation fields should be viewed as a continuation of human activity influencing natural processes, rather than a method that overcomes the influence of prior human activity on saltmarsh ecosystem functioning. This opinion is evidenced by a critical review of the (pre-)historic human activity and saltmarsh restoration attempts at Rumney Great Wharf, Severn Estuary, Wales, where sedimentation fields were constructed between 1989 and 2005 and extended in 2024. We then evaluate the research requirements that need to be addressed to ensure the successful implementation of future schemes, including further understanding of the interactions between physical and biological processes, to enhance ecosystem functioning in sites restored using sedimentation fields.