Large offshore wind farms do not necessarily cause "significant damage to nature", provided projects are subject to proper spatial planning, a major Danish study has concluded.
The peer-reviewed research looked at long-term impacts on fish species, sea birds, seals and harbour porpoises from Denmark’s first two offshore wind farms with capacities exceeding 100MW. These were: 180MW Horns Rev 1, commissioned in 2003, and 165.5MW Nysted, completed in 2003. Cumulative impacts were also addressed.
The results suggest that negative impacts on birds and porpoises are minor and that fish species may benefit from offshore wind development. Seals are not viewed as being negatively impacted.
The research showed a higher number of fish species now present inside the area occupied by 80-turbine Horns Rev 1 wind farm. As has been indicated by other studies, some fish species make use of turbine foundations and scour protection as "refuge areas for hide and forage". Fish populations may also benefit from the ban on commercial fishing within wind farms areas.
The cumulative effect of multiple offshore wind projects being built "close together" could be beneficial to fish numbers and species diversity, suggests the Danish Offshore Wind: Key Environmental Issues – a Follow-up. The report presents the findings of a research programme that began in 2007 following on from an earlier 2000-06 series of biodiversity investigations. It is a joint effort of the Danish Energy Agency, Danish Nature Agency and wind farm operators, Vattenfall and Dong Energy.
The study concludes that a device used to deter porpoises from an offshore wind construction zone is highly effective. Noise from installation vessels and wind farms has "a minor effect" on harbour porpoise populations. In contrast, initial findings of computer modelling suggest that by-catches by commercial fisheries may reduce porpoise numbers "substantially".
Sea bird collisions with offshore turbines are "rare events", states the report, although it acknowledges that more research is needed to understand the cumulative effects of multiple wind farms on protected bird species.
In line with findings by research at Egmond aan Zee wind farm, the Danish study has found that different bird species behave differently toward offshore turbines. A study of one migratory species’ response to the UK’s Lynn & Inner Dowsing offshore wind farms also found that collisions are rare.