Abstract
The large-scale development of Offshore Wind Farms (OWFs) is on a trajectory to change the ecology of European waters, such as the North Sea. This will cause harm to its marine ecosystem, including collision, disturbance, displacement, entanglement and habitat loss for avian species, marine fauna and benthos. Simultaneously, OWFs offer major restoration potential for marine ecosystems. Naturally OWFs resemble sanctuaries for fish and benthos due to reduced fishing pressure and availability of hard substrate. This consequently instigates knock-on ecosystem functioning effects like increased food availability and fish stocks. This study offers a comprehensive framework of the mitigation and nature enhancement solutions that can be implemented in the design and planning of an OWF to mitigate its negative ecological impacts and enhance the positives. Touching on both infrastructural design options and planning considerations, a wide palette of nature inclusivity solutions is presented and evaluated in terms of deployability and mitigation effectiveness. The results reveal that many on-market solutions, such as noise reduction techniques during pile driving, bird collision avoidance measures and systems, and artificial reef structures, minimise but do not avoid all ecological impacts of OWFs. The most effective solutions are those that avoid an ecological impact in the first place, instead of minimising or restoring it. Currently this includes siting, routing and micrositing around valuable habitat and planning around sensitive periods, such as breeding, spawning and migration seasons. A promising technology is that of jetting monopile foundations to silently install them, which is more effective than emerging solutions that absorb and minimise sound pollution. Importantly, to effectively restore marine habitat, artificial reefs should be designed into the base case of an OWF instead of as standalone structures. Integrating heterogeneous calcareous rocks into scour protection represents the most cost-effective and scalable habitat restoration solution. Nevertheless, many existing and upcoming solutions that have gained popularity consist of heavily processed small-scale artificial reef structures. Additionally, this study considers adaptations required to nature inclusive solutions to suit future trends in offshore renewables. Floating turbine technology and the growing competition over ocean space, both pose new ecological risks as well as opportunities. Co-location with offshore hydrogen is a blind spot for nature protection and enhancement efforts within OWFs. As well, the long-term deployment and large-scale expansion of OWFs in the marine space form unresolved ecological uncertainties, which urgently require further research. Overall, this research underscores that there is a discrepancy between nature inclusive innovations being developed and ecological impacts that most urgently need addressing. Complementing the knowledge framework on nature inclusivity in OWFs, is a case study of a nature inclusive scour protection solution deployed in OWF Hollandse Kust Zuid (HKZ). This proof-of-principle study evaluates the suitability of marine ecological monitoring with an Remotely Operated Vehicle (ROV) on substrates prevailing in HKZ. It provides a valuable initial insight into the benthic and pelagic species present in this novel North Sea habitat. No statistically significant differences were found between the species composition of scour protection, reef, cable and sand substrate. However, the preliminary results appear to suggest that adding boulders of various sizes on top of conventional scour protection, could serve as suitable habitat for target species Gadus morhua.