The status of offshore wind energy generation as a relatively young industry has both positive and negative aspects for developing its potential in habitat creation. With few long-term studies of the changes in abundance and diversity of species within wind farms available, due to the relatively low number of developments currently operational, there are few datasets to fully analyse for the potential habitat gain which have been discussed in this chapter.
This problem of lack of long-term data also exists within the field of 'standard' artificial reefs, with few study programmes running longer than a couple of years in order to establish the initial stages of colonisation and succession (Perkol-Finkel and Benayahu, 2005).
In their research, Perkol-Finkel and Benayahu (2005) returned to previously-studied artificial reefs in the Red Sea, to determine what further developments occur ten years after deployment. It was noted that despite their close proximity, and equivalent depths, the community structure and species diversity differed between the artificial reefs and neighbouring natural reefs, which had acted as control sites for the early stages of the comparative study. Similar results are reported where shipwrecks and adjacent reef areas have been studied, with higher species diversity on the natural reefs. Naturally, the age of an artificial reef, whether intentional or not, will greatly affect its community structure, as certain species can only recruit after initial settling species have increased the complexity of the surface, making it suitable for secondary species. In one long-term study, it was estimated that the development of benthic communities in Pacific temperate waters might take up to fifteen years (Aseltine-Neilson et al., 1999).
These findings highlight the need to ensure surveys of already operational offshore wind turbines, and their associated scour protection and infrastructure, continue throughout the lifetime of the project, which can be up to fifty years (Centrica, 2009). The Perkol-Finkel and Benayahu (2005) study also highlights the fact that surveying the development of life on turbines alongside neighbouring natural communities will allow evaluation of the biological and environmental benefit of the turbines as artificial reef structures.
Despite the issue of the lack of long-term datasets, the 'youth' of the industry could also mean that any methods identified for increasing the benefits of offshore turbines in terms of habitat creation may still be incorporated into the design of future projects as they come into the detailed design phases, prior to construction, where appropriate. It is therefore even more important for the results of survey work which has been undertaken to be widely distributed and discussed, allowing any possible design adjustments to be made before the major Round 3 developments reach the turbine-selection stage.
Further study work should also be directed at the various types of material most commonly used for scour protection, where deployed. Calculations have already determined that the level of habitat created varies depending on the type of scour protection deployed around the base of offshore wind turbines (Wilson and Elliott, 2009), and this could be developed further to incorporate other variables. These calculations were based upon a single diameter for gravel and boulder scour protection; however with slight changes to the size of the material used, significant changes may be made to the area available for early colonizing species, which will in turn attract a wider range of species. Taking this further, combining the methods of scour protection used within a single development, could have an additional beneficial effect. By introducing gravelly substrate, rocky reef environment and sea grass environment into a predominantly sandy seabed area, habitat diversity will be significantly increased, with each habitat created bringing with it the various communities which inhabit them.
Detailed survey work of the colonisation and succession of species on a range of scour protection materials, in the field, will assist in demonstrating the potential that offshore wind farms have in creating viable habitat, as well as allowing countries to reach their renewable energy targets.
The usefulness of specially-designed reef materials, such as the Reef Ball, as scour protection, should be investigated. If these materials are able to perform the main role of scour protection, then their deployment around turbines may be particularly beneficial to the receiving marine environment.
Despite the many potential benefits which may occur as a result of habitat creation around offshore wind farms, there must also be some level of caution. The introduction of new habitats in environments where such habitats did not previously exist may also introduce new species into the area, outside of their usual ranges. In addition, there is the possibility for high concentrations of certain predatory species, such as starfish, to colonise the turbines in such high numbers that they may have a negative impact on existing communities. Therefore, future colonisation studies around offshore turbines and their associated infrastructure should take particular note of these new species, and any interactions which may be taking place with existing communities.
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