Not so conclusive final results

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Researchers have plenty of good news to report on the minimal impact of offshore wind farms on marine life after an expensive six year study paid for by Danish electricity consumers, but when told that more studies are needed, the wind industry had a hard time keeping its exasperation under control at a recent conference

A good many offshore project developers were lured to an environmental conference in Denmark by the promise inherent in the event's title, "Final Results: The Danish Monitoring Program." But for some the trip to Denmark to hear definitive answers on the ecological impact of offshore wind power was a disappointment. What they learned is that research into the behaviour of marine plants, mammals, fish and birds in the vicinity of a wind power station is a never ending exercise likely to keep biologists in business on wind industry pay well into the future.

Nearly every researcher who spoke to the 200 delegates in Helsingør in late November added one of two caveats to their otherwise overwhelmingly positive conclusions: first, results of studies at Denmark's two major wind farms cannot be applied to other sites; second, more research is needed to understand long term impact, as well as the cumulative effects on the ecology of several offshore wind farms.

The topics created plenty of discussion in the packed conference room and corridors, as ferries and container ships sailed by just outside the big conference windows looking onto the strait between Denmark and Sweden. Yet despite the uncertainty attached to the Final Results, the overall message from the Danish program was good. "It's very clear that the concerns many people have had about environmental impacts have been largely dispelled by the monitoring program," said Robert Furness, a seabird ecology professor from the University of Glasgow, Scotland, and chairman of the Danish government's international advisory panel for offshore wind development. "The program has generally shown that the impacts on the environment are extremely small."

The government-led study monitored the environment between 1999 and 2006 at Denmark's pair of offshore demonstration projects: the 160 MW Horns Rev plant in the North Sea and the 165 MW facility on the Rødsand bank off Nysted, in inland waters in the southern Baltic Sea, south of the island of Lolland-Falster. The research focused on benthic (seabed) fauna and vegetation, fish, marine mammals, birds and also people's attitudes towards the wind farms, which is largely positive.

Baseline studies for the program were done at the two sites prior to construction between 1999 and 2001 as part of each project's environmental impact assessments. After that the monitoring program had a budget of DKK 84 million (EUR 11 million) between 2001-2006, financed out of the public service obligation levy on Danish electricity consumers.

Several delegates praised the Danes for taking on such a huge and useful project and making the results publicly available, both online and in a glossy 140-page book suitable for coffee table display. "The Danish monitoring program at Nysted and Horns Rev provides by far the best information on environmental effects of marine wind farms available at present," said Furness.

Before and After

Researchers adopted a "before-after-control-impact comparison" structure for data collection, more colloquially referred to as BACI. The method required expensive, long term data assessment to establish the impact of an offshore wind farm separately from each location's normal change over time. BACI brought in data from pre-construction, construction and operational periods, giving a statistical basis for making firm conclusions.

"It may seem obvious that this type of study should be done using BACI design, but it's not normal," Furness said. In a recent German review of 127 published studies examining the impact of wind farms on birds and bats, for example, only eight used BACI. And more than half the studies were based on data collection spanning just one or two years, compared to Denmark's six.

Also, BACI required the development of new data collection tools by the Danish researchers. Two such systems -- T-POD, which monitored porpoises with hydro acoustic recordings underwater, and a thermal animal detection radar called TADS, to measure bird collisions, were technological breakthroughs.

Birds in the clear

Discussion of bird collisions was the most eagerly anticipated topic in Helsingør -- with several mentions made of the recent white-tailed eagle kills from wind turbine blades at the large Smøla wind farm in Norway (Windpower Monthly, March 2006). Adult seabirds live for 20-30 years and an increase in mortality has a much greater impact than on most terrestrial birds, which are short lived and reproduce quickly. While many bird species were registered at both offshore sites, discussion focused mainly on common eiders (Nysted lies on a main migration route for these ducks) and common scoters at Horns Rev.

The study found that the effects of the developments on overall bird populations is negligible. A combination of radar and aerial surveys show that birds generally fly around both wind farms; 71%-86% of all bird flocks heading for both sites at 1.5-2 kilometres distance avoided going through them. "And they were actually showing signs of avoiding them at a quite substantial distance -- up to five kilometres," said Tony Fox of Denmark's National Environmental Research Institute (NERI). "Of the birds that were actually entering the wind farms, they then reoriented themselves to fly down between the rows of turbines, frequently at equidistance between them."

Of the 235,000 eiders passing the Nysted plant each autumn, the collision risk was predicted to be 0.02%, or 44 birds. The TADS radar reported zero collisions, Fox noted, "In Denmark no fewer than 70,000 eiders are shot by hunters every year. Therefore 44 potential deaths by a single autumn passage through the wind farm is worth thinking about," he added.

Habitat displacement

The fact that birds were not colliding with wind turbines was good news to many, but researchers presented a conundrum: if the birds are avoiding the turbines it means they are wasting energy to travel further to get to their feeding grounds or habitat area, a concern on a thousand mile migration passage. More research is needed to find out how big a problem this may be, but neither Horns Rev nor Nysted are close enough to nesting areas to affect reproduction, the report said. Researchers admit that the slight extension to flight distances is unlikely to have any major consequences for bird populations.

Birds avoid nesting or foraging between the turbines, implying that future wind farms in favoured feeding areas for some birds could cause some habitat loss, even if the habitat and feeding resources remained intact.

Some delegates were concerned about the plans for an extension to Horns Rev, to be built adjacent to existing turbines. As NERI's Ib Krag Petersen, one of the scientists in the field at Horns Rev, expressed it: "We don't know what would happen with two Horns Rev installations." The Danish Energy Agency's Steffen Nielsen noted that the developer of Horns Rev II will be obliged to undertake monitoring, building upon the existing data from Horns Rev I. "It is part of the contract, among other conditions, to undertake continued monitoring and place data in the public domain so further knowledge can be generated," Nielsen said.

Other results

Most of the monitoring results for other marine life, both plant and mammal, confirmed those revealed two years ago at the midterm report of the Danish monitoring program (Windpower Monthly, November 2004). With two or three more years of data, research conclusions were more statistically sound.

Of the more notable presentations, the effects of electromagnetic fields on fish are still cloudy -- partly due to the difficulties in measuring them at Nysted. "We would have wished to have our [monitoring] set-up very close to the cable, but for some security reason, we couldn't get closer than 300 metres," said Danish consultant Christian Hvidt. A report on monitoring of seals, complete with photos of seals with satellite transmitter antennae glued to their heads, raised a deal of laughter, as did Svend Tougaard's campfire stories of working with the appealing mammals. The conclusion is that seal colonies are unaffected by wind farms. Porpoises, however, are making a slow recovery to their former population level at Nysted. Nobody at the conference knew why.


A clear divide among scientists and non-scientists at the conference reflected the frustrations of both groups. From the science side, Furness was not the only one stressing the need for further studies on the cumulative effect of groups of several offshore wind farms. "Although the results from the two sites are very clear, there are a lot of buts as well. It is not certain the results can be generalised for all wind farms -- we've only had three years of post-construction monitoring. We can't say whether there will be future changes in things like benthos, fish, birds and marine mammals. It would be wonderful to continue monitoring and see how things change over another, say, ten or more years. We would predict that they would change," he said.

From the floor, a delegate from Swedish utility Vattenfall expressed disappointment at the caveats expressed by Furness, particularly with regard to not being able to draw generalised conclusions from the results and apply these to other projects "That is why most of us are here," he said.

"Everybody moans, you never get a straight answer out of an ecologist," said Ian Simms from the Bird Management Unit of the UK's Central Science Laboratory, though with a smile. Simms works with bird detection radar monitoring. With reference to his bird collision results, Sims said: "Can you extrapolate this to other species of ducks? The answer is no." The same sentiment was expressed by Jeremy Firestone, a marine policy and law teacher at the University of Delaware in the United States. "Some people think they can come here with all the answers given to them. They're very na•ve," he said. "It's just two studies. From a statistical standpoint, a sample of two is very small. Maybe the sites are very anomalous. Maybe they're very representative. We don't know yet."

When is enough enough?

One delegate asked when project developers could stop paying for such intensive studies for each and every new wind farm. Good planning is one way of avoiding environmental issues, responded NERI's Fox. "There's no need to go into the depth we have with this particular study. But just as we don't just plop down motorways or cities anywhere on land, there should be a certain planning framework offshore so that you avoid environmental issues," Fox said. "On the strength of what we've done, there's a lot of specific data to help give you inference about your specific site, which means you don't have to do everything all the time. The general body of information is growing." Firestone added: "You're going to have to do site-specific work. Not forever. But the conclusions are very encouraging, and certainly the methods are all very useful."

The Danish Energy Authority's Nielsen said there is now a clear call for international cooperation in a European context. "When you look at the bird discussion, you're speaking of possible effects of population levels and for it to make any sense, you must look at the possibilities in an international context." He called for a follow-up on the Copenhagen Strategy on European Offshore Wind Power Deployment (Windpower Monthly, December 2005), which recommends multilateral cooperation on various offshore environmental issues. A bilateral Danish-German agreement to study offshore environmental issues is hoped to continue in the near future, he said.

US consultant to the Department of Energy, Bonnie Ram, pointed to an issue not dealt with in the research so far. "We all know from biologists that there is never enough information. But more information doesn't give you answers. It's the risk framework that helps you understand what the information means in the bigger picture," she said. Relative risk has not been assessed in Denmark, in Europe or anywhere, she claimed.

"There are some huge developments in the pipeline in Europe. Something is bound to happen. We need to prepare for the future, to understand the relative risks compared to other activity offshore -- oil and gas, but others too -- that cause a change in flora and fauna," continued Ram. "Right now from what we learned, we know that the risks to birds are relatively insignificant," she added. "But what does that mean?" Without knowing the vulnerability of a species to adding wind turbines to the offshore environment there is no framework to find out what these numbers of bird deaths mean. "What is unacceptable? We don't understand yet. We've seemed to think that [44 eiders per year] is acceptable, but what is unacceptable?"

Organisers and delegates

The around 200 participants at the conference included representatives from wind project development companies, power companies and suppliers to the wind industry, with the research community well represented along with environmentalists -- and even a few anti-wind group representatives from the United States. Delegates came primarily from Denmark, Sweden, Germany, the Netherlands and the United Kingdom, with a good showing from the US, France and Spain.

The Danish environmental monitoring program was coordinated by a steering group made up of the Danish Forest and Nature Agency, the Danish Energy Authority, the co-owner of Horns Rev, utility Vattenfall and Denmark's DONG Energy, the co-owner of Nysted.

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