Balancing urbanization and ocean sustainability: the evolution of eco-shorelines through cross-disciplinary collaboration in Hong Kong

1 Introduction

1.1 Consequences of urbanization and shoreline hardening

Urbanization, defined as the growth of urban populations and the expansion of infrastructure, is a dominant driver of global environmental change (Seto et al., 2012). By 2050, it is projected that nearly 70% of the world's population will live in urban areas (United Nations Department of Economic and Social Affairs Population Division, 2018). Coastal cities are especially affected, with over 60% of the world's largest cities situated in coastal zones (Neumann et al., 2015). Urbanized coastlines across the globe are increasingly dominated by gray infrastructure, including seawalls, breakwaters, and revetments, that protect property but often come at the expense of ecological integrity. Firth et al. (2014, 2016a) characterized this trend as being “between a rock and a hard place,” highlighting the widespread reliance on hard engineering solutions despite their environmental trade-offs. Seawalls and other forms of hard armouring are often preferred for their perceived effectiveness as sea defenses, providing immediate protection, particularly in densely populated coastal cities facing accelerating sea-level rise and intensified storms (Scyphers et al., 2011).

Despite these benefits, hard engineering solutions carry ecological costs that are often overlooked in urban planning. Traditional designs, such as vertical seawalls, drastically simplify natural habitats by lacking microhabitat features like crevices, pools, and varied substrates (Chapman and Underwood, 2011; Lawrence et al., 2021). As a result, hardened seawalls generally support lower species richness and abundance than natural rocky shores, with intertidal invertebrates and algae particularly affected by harsher abiotic conditions (Chapman and Underwood, 2011). The construction of seawalls and bulkheads has also been shown to degrade intertidal habitats, undermining biodiversity and ecosystem functionality (Airoldi and Beck, 2007). For instance, research in Sydney Harbor has documented marked declines in intertidal invertebrate diversity and abundance along armored shorelines compared to natural rocky shores (Chapman and Underwood, 2011). Similarly, coastal armouring in the Gulf of Mexico has reduced nursery habitat for juvenile fish, affecting fishery productivity (Meyer et al., 2008). Urban shorelines also favor the dominance of resilient, opportunistic species, resulting in homogenized communities with reduced ecological resilience (Mayer-Pinto et al., 2018).

The conversion of natural land cover to impervious surfaces and hardened infrastructure also causes habitat loss, fragmentation, and degradation of ecosystem services, including flood regulation, water purification, and carbon sequestration, particularly through the loss of vegetated coastal ecosystems that play a significant role in long-term “blue carbon” storage (Gedan et al., 2009; Barbier et al., 2011; McLeod et al., 2011). Coastal armouring with seawalls and bulkheads disrupts sediment transport and ecological connectivity, increasing vulnerability to erosion and storms (Bishop et al., 2017; Pilkey and Wright, 1988; Dugan et al., 2008; Nordstrom, 2014). In Tokyo Bay, seawall development has been linked to increased shoreline erosion and loss of natural wave buffering capacity, increasing exposure to storm damage (Ferrario et al., 2014). The simplified designs of hardened shorelines may also alter local temperature regimes and water retention patterns, further deterring colonization by sensitive species (Lawrence et al., 2021). In heavily urbanized settings, this loss of habitat complexity disrupts ecological connectivity and reduces ecosystem resilience, weakening key functions such as productivity and food-web support (Mayer-Pinto et al., 2018; Bishop et al., 2017).

The ecological drawbacks of traditional coastal defense highlight the urgent need to integrate ecological principles into engineering designs by incorporating habitat complexity into shoreline structures, ensuring that the protection of coastal assets does not come at the expense of biodiversity and ecosystem function. In light of global climate change, sustainable urban coastal management that integrates development with ecosystem preservation has become a primary focus of urban coastal development (IPCC, 2019).

1.2 Ecological engineering in coastal management

Ecological engineering integrates ecological knowledge with engineering design to restore or create “novel” ecosystems that deliver invaluable services such as flood control, water quality improvement, and habitat provision (Hobbs et al., 2009; Mitsch and Jørgensen, 2003). Nature-based infrastructures, like constructed wetlands and mangrove forests, offer a sustainable alternative to hardened coastal defenses by reducing wave energy and stabilizing shorelines (Morris et al., 2022; Temmerman et al., 2013; Barbier et al., 2011). Oyster reefs have also been shown to attenuate wave energy while supporting biodiversity (Morris et al., 2021; Scyphers et al., 2011). Living shorelines, which combine natural elements with structural reinforcement, are gaining traction for their ability to maintain ecological function and shield coasts against erosion and sea-level rise with minimal human intervention (Gittman et al., 2016; Bilkovic et al., 2016). Integrating restoration with hybrid green-gray infrastructure (e.g., eco-engineered concrete structures with microhabitats, salt marshes and oyster shells) can amplify habitat complexity while providing coastal protection and enhancing water quality (Sutton-Grier et al., 2015). Overall, these approaches demonstrate the potential of integrating ecological and engineering principles and represent an important direction for future coastal management and urban development strategies.

1.3 The emerging concept of eco-shorelines

Although there is no globally standardized definition, “eco-shoreline” is commonly used interchangeably with terms such as eco-engineered or living shorelines, referring to coastal infrastructures designed to emulate natural habitats by integrating ecological and structural elements that support biodiversity while providing shoreline protection (Bilkovic et al., 2016; Firth et al., 2016b). The core principle of eco-engineering is to enhance ecological function on traditionally “hard” built structures by increasing habitat complexity. This can be achieved through textured surfaces to provide shade and refuge, artificial rock pools and water retention features, modular interlocking blocks, or biogenic materials such as oyster shells, all of which promote colonization by diverse marine organisms and strengthen ecosystem services related to coastal protection and resilience (Chapman and Underwood, 2011; Firth et al., 2016a). In recent years, interest in and implementation of eco-shorelines have expanded rapidly in urban coastal centers worldwide. Examples include Vancouver's Habitat Skirt initiative, which encourages marine life on seawalls (Leonard and Kullmann, 2012), Sydney's Living Seawalls program, which uses textured panels and oyster reefs to increase biodiversity (Bishop et al., 2017), the Delaware Estuary Living Shorelines project, combining natural vegetation with engineered features for erosion control and habitat restoration (Bilkovic et al., 2016) and the Seattle Seawall Project for creating an eco-engineered corridor for migrating endangered salmons (Sawyer et al., 2020). These initiatives illustrate efforts to reconcile ecological, engineering, and social objectives in urban coastal management.

The success of eco-shoreline interventions is increasingly recognized as multidimensional. Rather than focusing solely on biodiversity outcomes, effective eco-engineering projects must balance several interconnected objectives, including engineering performance, ecological enhancement, and social value. Morris et al. (2019) emphasize that eco-shorelines should simultaneously provide shoreline protection, support biodiversity and ecosystem functioning, and contribute to human use and appreciation of coastal spaces. In Hong Kong, this framework has recently been codified through the publication of the Hong Kong Nature-based Solutions Design Guidelines (Civil Engineering and Development Department and Agriculture Fisheries and Conservation, Department, 2026), demonstrating the translation of academic principles into official government practice. Evaluating eco-shoreline initiatives against such multidimensional criteria is therefore essential, and the Hong Kong experience offers a valuable case study of how these concepts can be operationalized.

Hong Kong provides a particularly relevant context for exploring eco-shorelines. Over the past century, extensive land reclamation and urban expansion have transformed around 16% of the city's natural shoreline, often at the expense of ecologically valuable habitats such as mangroves, mudflats, and rocky intertidal zones (Leung, 2013; Lai et al., 2015). These modifications have led to habitat fragmentation, biodiversity loss, and reduced ecosystem resilience (Gotama et al., 2024). Growing awareness of these impacts has prompted interest in ecological enhancement and eco-engineering approaches. Pilot projects, revised environmental guidelines, and collaborations between scientists, engineers, and policymakers signal an emerging shift toward more sustainable coastal development and management at the city scale. By examining Hong Kong's evolving shoreline practices, this paper highlights the potential of eco-shorelines to restore coastal biodiversity in highly urbanized and heterogeneous coastal environments, where hardened shorelines have been historically established. Focusing on Hong Kong as a city-scale case study, this paper illustrates how eco-shorelines can be integrated both into complex, densely developed coastlines through adaptive designs, ultimately supporting the translation into policy and urban planning frameworks. Importantly, it demonstrates how strong collaboration between academic institutions and government agencies has enabled the testing, scaling, and institutionalization of eco-shoreline approaches across the territory. In doing so, this study provides insights relevant to other highly urbanized coastal cities seeking to integrate ecological enhancement into shoreline infrastructure.

2 Historical and policy context of shoreline development in Hong Kong

2.1 Historical shoreline development

Hong Kong's mountainous terrain and limited developable land have historically placed strong pressure on the government to expand urban space through coastal reclamation (Ng and Cook, 1997; Lai et al., 2015). Shoreline development in Hong Kong began during the British colonial period in the mid-19th century, initially driven by military and trading imperatives. Early infrastructure, including piers and port facilities, established Hong Kong as a strategic maritime hub (Endacott, 1964; Bard, 1991). As the population and economic activity increased rapidly during the twentieth century, reclamation became one of the primary strategies for creating land to support housing, transport infrastructure, and commercial development. Consequently, large portions of the territory's natural coastline were progressively replaced by engineered shorelines designed primarily for coastal protection and land creation (Ng and Cook, 1997). These developments initiated extensive modifications to the natural coastline, laying the foundation for the large-scale land reclamation projects that followed (Carroll, 2007). As the city's economy and population expanded, land reclamation became a central urban strategy. Major projects transformed Victoria Harbor and the Kowloon Peninsula into reclaimed land, accommodating dense urban growth and critical infrastructure (Wong, 1998). Through large-scale reshaping of the coastline, these projects resulted in one of the world's most extensively modified urban coastal environments at the time.

2.2 Policy recognition of eco-engineering in coastal development

By 2012, the Hong Kong SAR Government marked a policy shift by explicitly recognizing biodiversity loss as a key concern in coastal reclamation and identifying eco-shorelines as a proposed mitigation approach in land creation through reclamation (Civil Engineering and Development Department (CEDD), 2014). Further articulated by Mr Paul Mo-po Chan, former Secretary for Development of the Hong Kong SAR Government, said, “We will explore the opportunities of adopting eco-shorelines in lieu of conventional seawalls to improve the environment. The concept of an eco-shoreline is to make use of inter-tidal water channels or to plant mangroves, construct mudflats and create wetlands along artificial shorelines to increase the biodiversity of the nearby water bodies.” (Chan, 2014). This official endorsement of eco-engineering principles reflected an institutional shift away from conventional reclamation practices that historically prioritized engineering efficiency, toward an integral approach with ecological considerations for coastal development.

3 The development of eco-shorelines in Hong Kong through government–academia partnerships and knowledge co-production

3.1 Knowledge curation for implementation

In response to the policy call for the implementation of eco-shorelines in Hong Kong, the Civil Engineering and Development Department (CEDD) of the Hong Kong SAR Government initiated feasibility studies in 2014 to evaluate the applicability of eco-shoreline designs to local coastal conditions. As part of this effort, as a government institution, CEDD engaged in a co-production of knowledge with academic researchers through a series of feasibility studies led by a university research team, which informed evidence-based policymaking and eventually contributed to the design of Hong Kong's first integrated eco-shoreline at the Tung Chung East New Town Extension. The feasibility assessment was conducted through a structured, multi-stage approach, commencing with desktop-based knowledge synthesis and expert consultation, and subsequently progressing to empirical field testing based on the knowledge gained.

A comprehensive review of international theories and best practices in eco-engineered shorelines was first undertaken to inform the development of locally appropriate design principles (Perkins et al., 2015). This was complemented in 2016 by an international workshop, co-organized at the University of Hong Kong, on eco-shoreline design for sustainable coastal development which brought together overseas experts to share experience in enhancing marine biodiversity along man-made shorelines. Subsequently, the first field trial of eco-engineered shoreline interventions in Hong Kong was conducted through a 12-month small-scale study between 2016 and 2017, as part of the World Harbor Project (Bradford et al., 2020). The performance of custom-designed eco-tiles by Reef Design Lab, with and without seeding by local rock oysters, was tested at vertical seawalls in Lantau Island and Tuen Mun. The results demonstrated that increased habitat complexity, particularly when combined with oyster seeding, significantly enhanced marine biodiversity on seawalls (Bradford et al., 2020), providing empirical evidence that supported the application of eco-engineering approaches for biodiversity enhancement on hardened urban shorelines.

3.2 Expanded trails for concept validation

Building on the empirical outcomes of the initial eco-tile trial, a second comprehensive eco-shoreline trial was undertaken through continued government–academic partnership and implemented at an expanded scale to establish a scientific foundation to guide and support future eco-shoreline applications throughout the territory. The project also aimed to assess the feasibility and ecological effectiveness of eco-engineered seawall features, combining both hard and soft engineering approaches with a retrofitting method, in enhancing marine biodiversity and ecosystem services across the city's coastal waters.

Three coastal sites in Hong Kong representing distinct hydrological conditions with established seawalls, including Sai Kung (oceanic), Lung Kwu Tan (estuarine), and Ma Liu Shui (semi-enclosed), were selected for the study (Figure 1A). At each site, two designs of concrete eco-panels (imported from ECOncrete^®, Israel) were installed onto the existing vertical seawalls, while eco-engineered tidal pools and armouring units (from ECOncrete^®) and oyster baskets were retrofitted onto existing sloping riprap seawalls within the intertidal zone. Eco-engineered panels and armouring units incorporated ecological design elements such as ridges and grooves, creating microhabitats to support colonization by marine organisms (e.g., Firth et al., 2014; Loke and Todd, 2016 and Sella and Perkol-Finkel, 2015). Oyster baskets contained a mixture of live Magallana hongkongensis (Hong Kong oyster) and cured, recycled oyster shells, testing the viability of using nature-based solutions to enhance biodiversity and deliver ecosystem services along artificial shorelines with a variety of environmental conditions.

After 2 years of deployment, both eco-engineered panel designs significantly increased alpha diversity and taxon richness relative to control plots, with each design supporting unique species (Lo et al., 2025). At the sloping seawalls, both eco-engineered tidal pools and armouring units could significantly enhance marine biodiversity, while the latter performed better (Lo, 2023). In general, community composition shifted from autotroph-dominated assemblages toward ecosystem engineers, including bivalves. Notably, oyster baskets yielded an average 3.8-fold increase in marine biodiversity across sites when compared with the sloping seawall control (Bradford et al., 2025b). The epibiotic communities on these oyster baskets were estimated to filter between 19,000 and 38,000 liters of water over 24 h (Bradford et al., 2025b). Therefore, by supporting robust filter-feeding communities, ecologically enhanced artificial seawalls added ecological value to conventional coastal infrastructure (Bradford et al., 2025b; Lo et al., 2025). These results demonstrated the potential for enhancement with both hard and soft eco-engineering interventions in all three different water bodies in Hong Kong and emphasized the importance of diverse design features to maximize α and β diversity gains.

3.3 Designing eco-engineered features for localized adaptation

Building on the prior success of retrofitting imported eco-shoreline features, the subsequent phase of Hong Kong's eco-shoreline development prioritized the design and testing of locally adapted features with an ultimate aim to enhance the scalability of eco-shoreline implementation. In collaboration with the Development Bureau of the Hong Kong SAR Government, locally fabricated features were retrofitted alongside imported ECOncrete^® alternatives on existing seawalls to allow comparative evaluations (Bradford et al., 2025a) at Tsuen Wan Promenade (Figure 1A). As a typhoon shelter with high marine traffic within the nutrient-rich Victoria Harbor, the site represented a typical environmental setting along Hong Kong's urbanized coastline. Four concrete feature types were integrated into the riprap shoreline: two ECOncrete^® imports (the previously tested Tidal Pools and Armouring Units) and two locally designed features (Multi-Positional Pool and Multi-Positional Unit, Figures 1B, C, respectively). The installation of the imported Tidal Pools and Armouring Units required the provision of a flat surface to ensure feature stability, and the cube shape was not suited to the existing configuration of local sloping seawalls. The Hong Kong designs were, therefore, intentionally shaped to resemble the quarried granite armor boulders commonly used in local riprap seawalls, ensuring visual integration with existing coastal defenses. Their multifaceted structures were also highly compatible with the sloping seawall profile, avoiding the need for the provision of a flat surface for installation, making them highly adapted to local settings.

The 18-month trial results indicated that locally designed Multi-Positional Units and Pools performed comparably, if not better than imported features in enhancing riprap α biodiversity (Bradford et al., 2025a). The Multi-Positional Pool, with integrated shading and deeper water retention, was also particularly effective at supporting filter-feeding taxa such as bivalves, sponges, and tunicates. Structurally tailored for riprap shorelines, these local designs proved both ecologically effective and installation-friendly (Bradford et al., 2025a), while the successful implementation at a highly urbanized site further highlights the potential for broader adoption of eco-engineering to restore biodiversity and ecosystem function along other degraded coastal environments across the territory. By aligning structural design with local environmental conditions and construction practices, these eco-features demonstrated a low-impact intervention to enhance biodiversity along urbanized shorelines. Furthermore, the results underscore the importance of site-specific design considerations in achieving both ecological and engineering objectives when mainstreaming eco-shorelines in coastal development, providing a transferable framework for future eco-shoreline projects in highly developed coastal settings.

3.4 Mainstreaming eco-shorelines across urban coastal environments

Building on the success of earlier pilot trials, a series of eco-shoreline projects have been launched alongside Hong Kong's ongoing coastal development initiatives since 2022. These efforts, driven by close collaborations between government agencies and research institutions, aim to integrate ecological enhancements into the city's highly urbanized shorelines. Collectively, they represent one of the most concentrated regional initiatives in eco-engineering within dense urban environments, demonstrating the practical application of sustainable approaches to coastal development.

Typhoon shelters (i.e., marinas/ports/quays) are common coastal facilities in Hong Kong that are subjected to high anthropogenic pressures, including constant vessel traffic, associated pollution, and public access, making them challenging environments for eco-shoreline interventions. The feasibility of eco-engineering in such high-stress environments was tested at the revitalized Causeway Bay Typhoon Shelter within Victoria Harbor (Figure 1A), where locally designed concrete eco-tiles (Figure 1D) and oyster shell features (Figure 1E) were retrofitted onto existing seawalls in collaboration with the Development Bureau and academic institutions (Harbourfront Commission, 2025). After 2 years, preliminary analyses showed that both features significantly enhanced biodiversity relative to control plots of scraped seawall sections with oyster shell-based features supporting a greater number of species than concrete eco-tiles (Figure 2), demonstrating that combining hard and soft engineering strategies can provide ecological benefits even in heavily modified, high-use urban areas. Further evaluation of oyster-based eco-features was conducted in collaboration with CEDD at the Water Sports and Recreation Precinct in Wan Chai Basin (Figure 1A), a semi-enclosed basin frequently used for leisure and recreational activities. Various oyster-based habitats were deployed to assess their effectiveness in recruiting filter-feeding species, including hanging ropes of recycled shells (Figure 1F), hanging lanterns containing live oysters (Figure 1G), and combinations of live oysters with recycled shells. Preliminary findings suggested that all oyster-based features supported high abundances of ecologically important taxa, such as bivalves, tunicates, sponges, and sea anemones, and showed comparable patterns of biodiversity recruitment (Figures 3A, B). These two trials suggested that recycled oyster shells alone may offer a practical and cost-effective solution for enhancing biodiversity and ecosystem services on sheltered urban shorelines, particularly in resource-limited settings such as typhoon shelters, corroborating previous findings in (Bradford et al. 2025b). To further scale up eco-shoreline implementation across Hong Kong, the New Yau Ma Tei Typhoon Shelter (NYMTTS) and West Kowloon Cultural District (WKCD) projects were also launched through government-academia collaboration (Figure 1A; Civil Engineering and Development Department (CEDD), 2025). These initiatives expand beyond localized experimental installations, deploying a diverse array of locally adapted, multifunctional eco-engineered features across multiple coastal environments, including both high-use urban areas and ecologically diverse waterfronts. Features have been installed along sloping (Figure 1H) and vertical seawalls (Figure 1I), covering a total area of approximately 400 m.

The retrofitting of eco-shorelines into urban shorelines represents a broader shift toward balancing coastal defense with ecological enhancement and public value (Ng et al., 2017; Lai et al., 2015). This transition is further reinforced by policy frameworks such as the Biodiversity Strategy and Action Plan, which emphasizes the mainstreaming of biodiversity across sectors (Environment and Ecology Bureau (EEB), 2025). By actively integrating ecological enhancement into coastal infrastructure, eco-shorelines act as a practical means of translating biodiversity concepts into urban development practice in dense urban contexts like Hong Kong.

While eco-shorelines provide clear ecological benefits, they also deliver social value by enhancing the biodiversity and ecological function of existing seawalls and transforming hardened coastlines into multifunctional public assets. Their visibility and accessibility offer opportunities for education and community engagement, fostering greater awareness of sustainable coastal development and highlighting the potential for wider adoption in urban coastal environments. In doing so, eco-shorelines may also help counteract “shifting baseline syndrome”, a phenomenon whereby each generation gradually accepts increasingly degraded environmental conditions as the normal state (Pauly, 1995; Papworth et al., 2009). By providing visible, accessible examples of functioning coastal ecosystems, these installations may help to recalibrate public and institutional perceptions of what constitutes a healthy shoreline, fostering higher expectations for restoration outcomes and encouraging more ambitious coastal management goals (McClenachan et al., 2015; Roman et al., 2015).

3.5 From co-produced knowledge to pioneering eco-shoreline construction

Supported by the completion of these pilot trials and the subsequent cross-departmental collaborative experience, the Tung Chung East (New Town) Extension (TCE) Eco-Shoreline represented a pioneering approach of integrating ecological enhancement into large-scale coastal urban development as part of the land reclamation. Spanning approximately 3.8 km of reclaimed waterfront, the project incorporates diverse shoreline typologies, including vertical seawalls (Figure 4A; 1.8 km), rocky shorelines (Figure 4B; 1.2 km), and mangrove and mudflat habitats (Figure 4C; 0.8 km). Its objectives extend beyond shoreline protection to include enhancing coastal biodiversity, improving ecosystem resilience, and providing a suite of ecosystem services such as shoreline stabilization, flood mitigation, and recreational opportunities for local communities (Civil Engineering and Development Department (CEDD), 2022).

The project employs a variety of eco-engineered elements, including precast tidal pool modules, textured concrete panels, and mangrove planting zones, all designed to increase habitat complexity and facilitate colonization by marine species. Embedded monitoring programs assess biodiversity outcomes and ecological functions over time, enabling adaptive management based on empirical data (Civil Engineering and Development Department (CEDD), 2022; Environmental Protection Department (EPD), 2023). This integrated strategy reflects a shift toward nature-based solutions and sustainable coastal management while allowing coastal development, aligning with global trends in climate adaptation and urban resilience.

The infrastructure leverages multidisciplinary expertise through collaborations between government agencies, academic institutions, and private sector partners, ensuring robust design, implementation, and long-term sustainability. Large-scale, built-in eco-shoreline concepts require strict adherence to engineering codes, including those for climate change adaptation, making this cross-departmental collaboration essential. Lessons learned from TCE are expected to guide future eco-shoreline developments in Hong Kong, contributing to improved coastal resilience in the context of rapid urbanization and climate change (Civil Engineering and Development Department (CEDD), 2022; AECOM, 2024).

The progression from initial literature review through to large-scale construction at Tung Chung East was not a linear process driven by academia alone, but rather a sustained cycle of knowledge co-production between researchers and government agencies. This multi-stage collaborative process, which involved iterative testing, international expert engagement, and cross-departmental problem-solving, is summarized in Table 1. The table synthesizes the key academic inputs at each stage and the collaborative outcomes they generated, illustrating how scientific evidence was systematically translated into practice.

Table 1. Knowledge of co-production and collaborative outcomes in Hong Kong's eco-shoreline development.

4 Collaborative pathways through governance and policy

Collaborative pathways through governance and policy are a key determinant of success in eco-shoreline development. The case of Hong Kong demonstrates that effective governance structures, supportive policy priorities, and strong collaborative networks are critical for advancing nature-based coastal infrastructure. These factors influence both the feasibility of eco-shoreline projects and the emphasis placed on ecological objectives within urban coastal planning. Government-led initiatives are particularly pivotal in mainstreaming eco-engineering practices. In Hong Kong, eco-shoreline concepts have been progressively integrated into major reclamation projects, reflecting an evolving policy landscape that increasingly values ecological resilience alongside traditional flood protection (Civil Engineering and Development Department (CEDD), 2022). This policy commitment has been consolidated in a formal policy instrument through the territory's first Nature-based Solutions Design Guidelines (Civil Engineering and Development Department and Agriculture Fisheries and Conservation, Department, 2026). Additionally, eco-shoreline implementation in the Guangdong-Hong Kong-Macao Greater Bay Area of China was also standardized via publication of the “Technical Guide for Ecological Design of Sea Dike” (Chinese Hydraulic Engineering Society, 2024). Critically, these guidelines are not merely standalone documents, but products of the iterative, collaborative process described throughout this paper, synthesizing insights from long-standing government–academia partnerships, alongside more than a decade of pilot studies and international workshops (Table 1). By providing standardized design principles and evaluation criteria, these guidelines offer a replicable policy instrument for other cities seeking to transition from ad-hoc experiments to systematic, institutionalized implementation of nature-based coastal infrastructures. Such policy-driven integration of nature-based solutions is also increasingly reflected in international coastal management frameworks, where green infrastructure policies support nature-based solutions for sustainable coastal management (Narayan et al., 2017; Temmerman et al., 2013).

Effective implementation of eco-shorelines also benefits from adaptive regulatory frameworks that support innovation and long-term habitat sustainability. Hemraj et al. (2024) highlight that legal safeguards are essential to ensure restored habitats maintain ecological function over time. Their findings underscore the importance of coupling restoration or reclamation initiatives with robust governance mechanisms, such as strategic environmental assessments, biodiversity offset programs, and adaptive permitting systems, to embed ecological objectives into coastal infrastructure decision-making (Cheong et al., 2013; Narayan et al., 2017; Temmerman et al., 2013).

Beyond institutional and regulatory frameworks, public support further strengthens the feasibility of eco-shoreline implementation. A questionnaire survey study with 308 respondents indicates that Hong Kong's general public is willing to play a role in the implementation of eco-shorelines, with a particular preference for constructing mangrove eco-shorelines (Hau et al., 2025). Similar support has been found in Sydney, Australia (Dodds et al., 2025). Based on a between-subject experiment and the data from 5,258 participants, another recent study revealed that positive framing and education can effectively increase public willingness to support eco-engineering of manmade seawalls (Huang et al., 2025). As highlighted by Hau et al. (2025), public engagement is therefore crucial for building the social license to operate in Hong Kong, offering an important lesson for other cities where waterfront developments may encounter resistance from local communities. Harnessing this public willingness and translating it into effective policy, however, requires skilled intermediaries who can bridge the gap between community values, scientific evidence, and government decision-making. Researchers play a particularly important role in this process by linking scientific knowledge with policy development. Pielke (2012) describes scientists as “honest brokers,” providing policymakers with credible, evidence-based options rather than advocating for a single course of action.

Successful eco-shoreline initiatives have depended on multi-sector partnerships that bring together academic, governmental, NGO, Indigenous landowners, industry, and community stakeholders to leverage shared expertise and navigate both technical and policy challenges (Emerson and Nabatchi, 2012). Moving forward, strengthening adaptive co-management, participatory monitoring, and stakeholder co-design will be critical for sustaining the long-term impact of sustainable coastal development initiatives (Ansell and Gash, 2008). These inclusive governance strategies not only enhance ecological outcomes but also foster shared stewardship among government agencies, scientists, and local communities, supporting the continued integration of ecological objectives within urban coastal planning.

5 Challenges in Eco-shoreline development with interdisciplinary solutions

Despite growing recognition of eco-shorelines as nature-based solutions for sustainable coastal development, their implementation involves a complex set of technical, ecological, and socio-economic challenges. Effective design, execution, and long-term management require an interdisciplinary approach. While many restoration initiatives achieve rapid early gains in biodiversity, long-term benefits often remain uncertain and may not fully recover historical ecosystem baselines (Hemraj et al., 2022). From a technical perspective, eco-shoreline projects frequently confront constraints related to design and construction (O'Shaughnessy et al., 2019). For instance, integrating ecological features into vertical seawalls demands precise engineering to ensure both hydrodynamic resilience and viable habitats for marine species (Moschella et al., 2005). Additionally, long-term maintenance of these features in dynamic coastal environments remains poorly understood yet is critical for sustaining ecological and structural function. For instance, eco-engineered concrete structures are designed for long-term durability (Oyebisi and Alomayri, 2025), whereas soft components like oyster shells have a shorter lifespan, with half-lives of only 2–10 years documented in estuarine environments (Powell et al., 2006; Waldbusser et al., 2011) and therefore may require more frequent maintenance. Eco-shoreline outcomes also vary with construction materials, tidal positioning, and habitat complexity (Airoldi and Beck, 2007; Strain et al., 2017). Concrete substrates, for example, may support communities distinct from those on natural rock, raising discussions about the functional equivalence of artificial habitats and highlighting the need for biologically-informed designs (Firth et al., 2020). Socio-economic and policy constraints further complicate implementation. Limited funding, insufficient regulatory incentives, and low public awareness can impede the adoption of eco-engineering solutions (Temmerman et al., 2013). As a result, in rapidly developing urban zones, infrastructure expansion often takes precedence over ecological considerations unless strongly guided by policy or community engagement. Particularly in densely urbanized coastal cities with reclaimed land, the development of eco-shorelines requires careful consideration of space constraints, wave exposure, sediment movement, and the stability of underlying structures. Hong Kong's experience demonstrates that such constraints can be mitigated through innovative designs, such as Multi-Positional Units integrated with existing infrastructure, offering a key lesson for other constrained cities.

Addressing these multifaceted challenges highlights the need for interdisciplinary approaches that integrate ecological principles with engineering design to achieve both structural and ecological objectives. Crucially, collaborative frameworks are needed to secure stakeholder buy-in and co-produce knowledge (Ng et al., 2022). Reed (2008) demonstrates that sustained engagement of government agencies, academia, industry, and local communities enhances decision legitimacy, supports adaptive learning, and improves outcomes. Case studies from Europe and Asia further highlight that early and continuous involvement of ecologists, engineers, policymakers, and citizens strengthens the success and resilience of eco-shoreline interventions.

6 Conclusion

This review has examined the design, implementation, and governance of eco-shorelines, drawing on both international evidence and the evolving practice in Hong Kong. While eco-shorelines are increasingly recognized as essential nature-based solutions, their deployment faces technical, ecological, and socio-political challenges. Effective implementation requires the integration of ecological and engineering principles, supported by long-term monitoring, adaptive management, and inclusive, collaborative approaches. Case studies and recent literature highlight the importance of biologically informed materials, stakeholder co-design, and early engagement across sectors to optimize ecological and structural outcomes (Firth et al., 2020; Ng et al., 2022; Cooper and Pilkey, 2012; Reed, 2008). When reinforced by robust policy frameworks and sustained interdisciplinary collaboration, eco-shorelines have the potential to enhance biodiversity, mitigate climate impacts, and shape the trajectory of urban coastal development. Hong Kong's recent codification of these principles in its Nature-based Solutions Design Guidelines (Civil Engineering and Development Department and Agriculture Fisheries and Conservation, Department, 2026) demonstrates that multidimensional success, balancing ecological enhancement, engineering performance, and social value, can be systematically embedded into coastal infrastructure planning.

Looking forward, continued investment in longitudinal ecological assessments, experimental approaches to habitat and material design, and enabling policy mechanisms will be critical. Knowledge co-production and governance models that emphasize flexibility, legitimacy, and shared stewardship should be prioritized (Ansell and Gash, 2008). Early-career researchers, as bridges between science and policy, offer particular promise in advancing interdisciplinary innovation (Pielke, 2012). Crucially, the Hong Kong experience offers a transferable roadmap for other coastal cities: one that moves from pilot trials to policy codification through sustained government–academia partnership, demonstrating that nature-based solutions can be mainstreamed even in densely urbanized settings. Ultimately, the evolution of eco-shoreline strategies in Hong Kong and globally will require not only technical ingenuity but also a broader cultural shift toward designing with nature. By embedding eco-shorelines as integral components of coastal infrastructure rather than peripheral enhancements, urban societies can move toward more resilient, ecologically rich, and socially inclusive coastal futures.

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Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/focsu.2026.1704716/full#supplementary-material

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Footnotes

Edited by: Ashley Deevesh Hemraj, Aarhus University, Denmark

Reviewed by: Tingting Pan, Ningbo University, China

Peng Qin, Zhejiang Water Conservancy and Hydropower College, China