Nature-inclusive design (NID) of marine infrastructure comes in different forms, but always refers to the creation of optimized artificial habitat to locally enhance biodiversity. In essence, NID comprises the local addition of something non-natural to infrastructure with the aim of providing habitat for biodiversity assets in its widest sense. In its purest sense, NID is inspired by how the local environment would be without the infrastructure being present. NIDs of marine infrastructure, however, often comprise actions that promote biodiversity which does or did not naturally occur at that location. To ensure consistent use of terminology, we recommend adopting an NID trichotomy when reflecting on the appropriateness of NID applications in the marine realm, distinguishing between (i) restorative NID, linked to the restoration of lost local ecosystem values, and (ii) creative NID, referring to artificially created ecosystem assets and containing either (a) optimized infrastructure or (b) add-on structures. Restorative NID refers to measures which facilitate and speed-up nature restoration, while creative NID refers to measures to boost biodiversity ‘beyond the natural’. Beyond the importance of distinguishing different types of NID, it is important to also reflect on which biodiversity assets we elect to boost. Nowadays, much focus is placed on species richness or select species of commercial or conservational interest, while a focus on functional ecosystem assets may be more effective. A focus on functional ecosystem assets also provides better options for climate-proof NID designs. To adopt NID in an offshore renewables context, it is imperative to hold our horses and carefully consider what is the target to be achieved and how to get there. This requires a careful selection of the ecological assets that we aim to promote, while preserving the functional purpose of the marine infrastructure and incorporating the differing societal viewpoints on any potentially negative ecological consequences that may be incurred by NID solutions. In summary, restorative NID can be actively promoted, whereas creative NID requires more careful reflection; NID preferably prioritizes functional ecosystem assets and explicitly considers which ecological values to promote and why.

For the European Commission, the EDITO consortium is creating the European Digital Twin Ocean, a platform that integrates coastal and oceanic modelling tools with ocean observation databases and computing infrastructure. Building on EMODnet and CMEMS, EDITO Model Lab will contribute by making the next generation of ocean models more accessible. This work demonstrates one of the capabilities of the Digital Twin Ocean, focussing on human exploitation impacts on carbon fluxes. More specifically this what-if scenario is about the impact of upscaling the cultivation of shellfish in the North Sea on the carbon cycle. Upscaling the cultivation of shellfish is part of the envisioned “blue economy” and a promising option for multi-use of offshore wind parks. As shellfish are respiring organisms, they are a carbon source. At the same time shells are a carbon storage as they are built through biocalcification, a process that turns dissolved carbon and calcium into calcium carbonate. The research aims to quantify the effects of upscaling shellfish cultivation in the North Sea on the carbon cycle. This is done by implementing a biocalcification module (Stechele & Lavaud, manuscript submitted for publication in 2024), in the Dynamic Energy Budget (DEB) module integrated in Delft3D-FM’s water quality process library (Troost et al., 2010; Deltares, 2023). Our work includes assumptions about how harvesting accounts for calcium carbonate leaving the sea and is therefore sequestrated.