Designing nature-inclusive marine infrastructure

From 2020 to 2024, we partnered with Delft University of Technology to explore ways to scale up and optimise our solutions for nature development. Building on this collaboration, we adopted a step-by-step approach to designing nature inclusive marine infrastructure that delivers a widespread impact. This process can be applied to various types of marine and coastal infrastructure, including offshore wind farms, dykes, breakwaters and dredging and reclamation activities.

Step 1: Define objectives

Establishing clear operational objectives is the essential first step when designing nature-inclusive marine infrastructure. These objectives should consider policies, environmental conditions and foreseen infrastructural development. They should also be embraced by all stakeholders involved, including authorities, developers, contractors and environmental organisations.

Step 2: Identify potential

Identifying suitable environments requires focusing on features that can support ecosystem restoration and development. Past, present and projected environmental conditions, such as the (historic) presence of the targeted species or habitats and water dynamics and seabed conditions, should all be taken into account. When assessing these conditions, it is recommended to follow established standards, such as the EU’s Environmental Impact Assessment Directive or the International Association for Impact Assessment.

When assessing the suitability of the environment, it is important to keep the objective in mind. Depending on the objective – enhancing overall biodiversity, supporting threatened species or restoring specific habitats – specific design features may be required for success.

Step 3: Identify suitable design modifications

Marine infrastructure can serve dual purposes: meeting human needs while supporting marine life. Structures, such as dredged channels, breakwaters, seawalls and scour protection can be modified to enhance ecological values through small adaptations in materials, texture and shape.

The process begins by identifying suitable design modifications. Each proposed adaptation should then be evaluated through a quantitative assessment to determine whether nature-inclusive designs can have the intended effect on the ecosystem. This process also enables developers to make informed decisions by weighing the ecological benefits against associated costs.

Step 4: Apply interventions

Once viable and effective modifications are identified, they should be applied to marine infrastructure to enhance ecological value. Marine infrastructure offers long-term opportunities for habitat development due to its durability and persistence. By embedding nature-inclusive features in the marine infrastructure, these can support the settlement, growth and resilience of marine life over time.

Step 5: Achieve scale by combining scientific knowledge with industry practices

Achieving impact at scale remains one of the most challenging but also essential components of marine restoration. To scale restoration efforts effectively, it is essential to combine scientific knowledge with industry-based approaches. We defined the following five “golden principles” that demonstrate how collaboration between scientists and industry partners can enhance marine ecosystem restoration:

1. Pursue upscaling

To achieve positive impact at scale, use industry-based equipment and techniques instead of smaller-scale manual practices that are commonly used.

2. Landscaping

To replicate complex habitats cost-effectively and at scale, use nature-friendly designs of marine infrastructure instead of standalone artificial reef structures.

3. Induce life

To overcome the lack of connection between natural reefs and the newly built habitat, actively introduce the targeted species and habitats by installing broodstock instead of relying upon nature to slowly repopulate reef areas.

4. Support self-sustainment

To create suitable conditions for ecosystem restoration, use ongoing natural processes instead of one-time human interventions.

5. Ensure continuity

Shift from short-term restoration efforts during construction projects to long-term continuation of initiated efforts by local partners.

Following these principles for combining scientific knowledge with industry-based approaches increases the likelihood of achieving meaningful and long-lasting impact.

Applying the approach to oyster reef restoration in the North Sea

With this step-by-step approach, we investigated how offshore wind farms can contribute to European flat oyster reef restoration in the North Sea. By applying nature-inclusive design principles, we developed practical interventions that integrate ecological restoration with large-scale offshore wind farms.

Our review of policies and laws showed both the need for and support of oyster reef restoration in the North Sea, such as the Dutch government's commitment to recovering flat oyster beds as part of the European Marine Strategy Framework Directive.

In assessing the potential of offshore wind farms in the North Sea, we found that these sites typically have hard substrates in the form of scour protection around turbine foundations and at cable-crossings. The presence of these hard substrates provides settlement opportunities for oyster larvae, while the absence of bottom-disturbing fisheries allows oyster reefs to develop without habitat disruption.

We then considered various design modifications that leverage the features of offshore wind farms. In doing so, we evaluated their potential effects across multiple spatial scales. These scales help us understand the project’s impact at different sizes, from the entire North Sea region (mega-scale) to the areas between turbines in the wind farm (macro-scale), the protection around turbine bases (meso-scale) and the materials used in construction (micro-scale).

From this evaluation, we learned that oysters prefer hard, stony substrates, such as granite and concrete. Granite, already commonly utilised in offshore wind farms, proved the most favourable material for oyster settlement, making these sites particularly well-suited for oyster reef restoration efforts.

Offshore wind farms as promising sites for restoration

Offshore wind farms have rocky scour protection at the base of turbine foundations and cable crossing, providing hard surfaces that support reef formation. Additionally, offshore wind farms are closed to bottom-trawling, a fishing method that drags heavy nets across the seafloor, destructing seabed habitats such as oyster reefs. By incorporating nature inclusive designs, which integrate ecological needs into built infrastructure, these offshore wind farms can serve a dual purpose: generating renewable energy while also supporting marine biodiversity.

Our review of policies and laws showed both the need for and support of oyster reef restoration in the North Sea, such as the Dutch government's commitment to recovering flat oyster beds as part of the European Marine Strategy Framework Directive.

Our initial pilot projects involved the development and installation of oyster tables: large concrete structures onto which hundreds of adult oysters were attached. Oyster tables provide a solid foundation for this oyster broodstock to initiate reef development and are designed to remain intact for the lifetime of a wind farm. However, they are also heavy, and a vessel equipped with a crane is required for installation. This significantly increases cost and operational complexity. Though the oyster tables have proven to be a successful method for ongoing and future oyster reef initiation, cost considerations also resulted in the development of an alternative approach.

Droppable oyster structures as a scalable alternative

Our research resulted in an alternative to the oyster table: the droppable oyster structure (DOS). The DOS weighs up to 50 kilogrammes, making it nearly 100 times lighter than the oyster tables. Its manageable weight allows for manual deployment by two people using a small, standard vessel. In comparison, the oyster tables required advanced and costly equipment outfitted with a crane.

The DOS design was made possible through physical scale model studies conducted at Delft University of Technology, which identified two optimal shapes for the structure: the tetrapod and the cube. The design and shape of the structure were developed to meet the needs of the oysters while ensuring a controlled deployment. The structure should descend vertically, allowing for precise placement on targeted spots. Once landed, it should remain stable and avoid tumbling. This approach enables oysters to be introduced easily, affordably and on a large scale.

Oysters are attached to the structure before being lowered into the sea near rocky areas. Once placed, the oysters produce larvae that can settle on nearby hard surfaces, gradually contributing to the formation of a self-sustaining reef.

In the fall of 2024, these structures were deployed at the Borssele 1 and 2 offshore wind farm. To evaluate the methods’ effectiveness and monitor oyster settlement and reef formation, we collected video footage using a remotely operated vehicle (ROV). While it is too early to assess the full impact, the initial footage confirms that the structures landed as planned and remain undamaged after deployment. More importantly, the oysters are thriving. We will continue monitoring through the coming years, collecting valuable insights into the project's long-term impact.

Continuous innovation

In January of this year, we began working on a new initiative that could significantly impact future oyster restoration efforts. It involves designing mobile basins where oyster larvae can pre-settle on rocks. This so-called remote setting allows us to nurture oyster larvae in controlled environments, increasing their chances of survival and successful settlement in natural habitats, which could lead to more efficient and scalable restoration of oyster reefs.

Installation methods for these rocks are being developed and tested to identify the most effective solution. Later this year, we will install oyster larvae on rocks in a Dutch port, followed by another installation in 2026 at a cable crossing in the North Sea. We will monitor through 2027 to assess the effectiveness of the method.

Collaboration as the key to success

Over the years, governments and environmental organisations have increasingly encouraged the development of nature inclusive marine infrastructure. However, many well-intended initiatives aimed at promoting ecosystem restoration fall short of their desired impact because they lack alignment within a broader, cohesive strategy designed to achieve scale. As the need for sustainable solutions to protect marine biodiversity grows, the ability to integrate ecological principles into infrastructure development becomes ever more critical.

Collaboration is the key to successful outcomes. The knowledge of reef restoration is really developed within the scientific community, particularly at universities and research institutes. However, the feasibility of implementing these solutions at scale can only be confirmed by engineering companies and project developers. It is also vital that all relevant stakeholders in a given area commit to the same objectives and approach. This collaboration ensures that all necessary knowledge and expertise from various disciplines are included and limits the risk of conflicting efforts that could work against each other.

Nature-inclusive designs, such as those applied to offshore wind farms and other marine infrastructure, show that economic development and environmental preservation are not mutually exclusive. By rethinking traditional approaches and incorporating ecological restoration into the planning and development of marine projects, developers can make a significant positive impact on marine ecosystems.

The application of the methods presented has the potential to lead to the realisation of truly effective nature-inclusive marine infrastructure, driving lasting, impactful solutions for marine restoration. By leveraging the combined strengths of science and industry, we can lay the foundation for a future where marine infrastructure not only meets human needs but also contributes to the restoration and preservation of our oceans.