The review by Dr Andrew Gill of Cranfield University found that despite an explosion of academic interest in the subject - almost 400 papers on renewable energy were published in peer-reviewed journals in 2003, compared with fewer than 35 in any year before 1991 - only a fraction of the papers looked at environmental impact, either positive or negative. "Less than 1% of the articles considered the potential environmental risks of renewable energy exploitation and none was specifically related to coastal ecology. Ecological factors are not being considered properly and are under-represented in any discussion of the costs and benefits of adopting offshore renewable energy sources," Dr Gill says.
Climate change and rising fossil fuel prices are driving interest in developing renewable energy sources including offshore renewable energy. Northern Europe leads the world in offshore renewable energy developments (ORED) in coastal waters where many human pressures already exist. While offshore developments may attract less opposition from communities concerned about their aesthetic impact, they are likely to have a range of direct and indirect environmental effects.
According to Dr Gill: "Construction and decommissioning are likely to cause significant physical disturbance to the local environment. During day-to-day operation, underwater noise, emission of electromagnetic fields and collision or avoidance with the energy structures represent further potential impacts on coastal species, particularly large predators." Any such environmental effects need to be considered in addition to the existing pressure exerted on our coasts.
In the absence of published studies on the ecological impacts of building ORED, Dr Gill looked at studies on the impact of fishing and marine dredging on benthic habitats. "Assuming fishing- and dredging-related disturbance to be analogous to construction and decommissioning of an ORED, local loss of sedentary infauna and reef builders would be expected, while non-sedentary marine benthos would be displaced," Dr Gill says.
Also as yet uninvestigated is the potential impact of noise and electromagnetic fields from ORED on coastal animals. According to Dr Gill: "Underwater, where a large number of species interact acoustically, the potential for disturbance from long-term ORED operation is high. Sound is used for communication, finding prey and potential mates, and avoiding predators. The high voltage alternating and direct current cables that transmit power between devices and the mainland also have the potential to interact with aquatic animals that are sensitive to electromagnetic fields. This affects mainly fish, particularly sharks and rays, and marine mammals that use the Earth's magnetic field to navigate."
However, ORED could also represent an environmental enhancement by increasing the opportunity for benthic species, enhancing survival and growth, creating new food opportunities and refuge for juveniles, and recycling of local energy.
The important message of this review is that our current lack of knowledge means we do not know which effects, if any, could benefit or harm our coastal ecosystem. But it is imperative that this ecological knowledge gap be plugged, Dr Gill says: "The stability of coastal ecosystems worldwide is under threat, hence ORED must be planned appropriately to protect the ecosystem from further degradation, and to enhance it wherever possible, and ecologists must play a fundamental role in this process."