EFFECTS ON MARINE LIFE: Marine life has no borders
Since research into the impact of offshore wind farms on the marine life started more than 15 years ago at Denmark’s Horns Rev 1, there have been several multi-year research and monitoring programmes in Denmark, Germany, Belgium and the Netherlands. A large part of it funded by the wind farm developers themselves, and governments also investing in gaining knowledge.
Offshore WIND spoke to Sytske van den Akker, the Environmental Specialist at Dutch utility Eneco Wind and in charge of coordinating ecological research. Before starting at Eneco she has worked as an environmental specialist for the non profit organisation The North Sea Foundation (Stichting De Noordzee).
She explains that there are significant differences between countries and their regulations concerning offshore wind and marine life, leading to a different focus on the research and monitoring programmes. Much knowledge about the impact of offshore wind farms on marine life has been gathered and certainly the general conclusion today is that it does not seem to be anywhere near as bad as was originally feared.
She gives the example of the Netherlands where there was the assumption a few years ago that fish eggs and larvae would be killed within a 1 kilometre distance of the piling activities. Several research (laboratory) projects, funded by the Dutch government and Eneco, showed that the impact of piling on fish larvae and juvenile fish was far less than assumed. Field studies on fish larvae in Belgium during construction confirmed this.
When it comes to the subsea community there are positive changes in the enlargement of the biodiversity present. The wind turbine foundations effectively become artificial reefs where for instance mussels and anemones find a place to live. This attracts other species, which can find food or shelter. And clearly these creatures would not be there at all without structures to live on.
Fish might also benefit from offshore wind farms. For instance, researchers found that young cod seem to be quite comfortable hanging around the turbines. There are also indications that more sandeels live and flatfish are larger inside wind farms compared to outside wind farms. Marine mammals like seals and harbour porpoises are found within wind farm areas. Birds show different reactions to offshore wind farms. Some species avoid wind farms, some species don’t seem to care and other species, like cormorants are even attracted by wind farms (see insert).
Gaps to fill
However, there are still gaps in knowledge. The most important research questions at the moment are what the cumulative impact is of many offshore wind farms together and the long term impact on populations. Another important question is what the long term impact will be of construction noise on the marine life.
Eneco Wind is also involved in environmental monitoring of offshore wind farms. Their first programme started at Eneco’s offshore wind farm Prinses Amaliawindpark in 2009 and closed in 2014. Currently they have an environmental monitoring programme related to the wind farm Eneco Luchterduinen, that started in 2013 (a year before construction). This programme covers 11 subjects, which range from measuring under water noise during construction, bird collision/avoidance with the turbines to research into seal behaviour and impact of construction on fish. Mrs van den Akker is coordinating this monitoring programme. She explains ‘Eneco is taking the environmental impact very seriously. In our monitoring approach we want to fill in gaps in knowledge, relevant for a sustainable development of offshore wind. We want to build on the knowledge from previous research and share our results. In close cooperation with the Competent Authority we propose research programmes for each subject, which sometimes can deviate from the original permit requirements’.
A good example is the research on harbour porpoises. The permit requirement was to measure to what distance harbour porpoises should be deterred during piling. This can be measured by using C-PODs at different distances from the construction field, which detect the bio-sonar ‘clicks’ from porpoises and aerial surveys.
By measuring before, during and after construction the impact of piling can be determined. This has been investigated already at different offshore wind farms e.g. in Germany and Belgium, having comparable findings. During construction, harbour porpoises stay or swim away and this can be up to a 20-25km distance. And after piling finished, it can take a few hours to a few days before they return.
Mrs van den Akker says: “We could measure the deterrence distance during construction of Eneco Luchterduinen again. But more important is to understand the impact beyond these few days on the porpoise population. Is it really just irritating them or having a more serious impact?”
Instead of measuring location specific deterrence distance, Eneco Wind was allowed to join an international research project, DEPONS (Disturbance Effects on the Harbour Porpoise Population in the North Sea) carried out by Aarhus University, Denmark. Eneco Wind is now one of five offshore wind developers who joined forces to look into the impact of piling noise on North Sea harbour porpoise population. The other four developers are Vattenfall Wind Power Ltd, SMart Wind Ltd, Forewind, and East Anglia Offshore Wind Limited. DEPONS is an important initiative
to consider the longer term impact of piling on the population. The project will also enable the assessment of the cumulative impact of offshore wind farms on the porpoise population. “It may be that one wind farm has little impact but what if 10 wind farms are constructed together in a designated region or very quickly after one another within a few years?”, she explains. The study got underway in 2013 and is a great example of collaboration within the industry.
The first runs of the DEPONS model looking at even very extensive offshore wind development scenarios in the North Sea suggest that piling noise disturbance is unlikely to trigger long-term effects on the harbour porpoise population. However, it should be stressed that these are preliminary results, and further work and data collection is needed before firm conclusions can be drawn.
Offshore wind is an international business and the marine life is not stopping at borders. Currently, there remain vast differences between the regulations for offshore wind in each country, making offshore wind development complicated.
She explains that, for example, in Germany companies are only allowed to pile at noise levels less than 160dB at a distance over 750 metres to reduce the underwater sound exposure levels to marine life. However, in the Netherlands it is forbidden to pile between January 1 and July 1 whatever the noise levels. The Dutch government is considering new regulations but at the moment the industry does not know the outcome yet.
Although firm and final conclusions are difficult to draw at this stage, the good news going forward is that up until this point studies have shown that very large negative impact on marine life does not seem to occur. Since the first research, a lot of information has been gained, both by governments and the sector itself. There are still gaps in knowledge (like population impact and cumulative impact). The challenge is to fill in these gaps in knowledge. This can be done by further research and monitoring, focusing on the most urgent questions and more importantly, by international collaboration.
“The questions to be answered exceed individual projects and even borders. I think we have made great progress during the last decade, both in collecting information and in cooperation. I hope we will continue this way and that we will use the information to show that offshore wind and marine life can be combined in a real sustainable matter.”