WTS: the avian dilemma

Feature article

42 Renewable Energy Focus July/August 2007

WTS: the avian dilemmaWHEN IT COMES TO WIND TURBINES AND THEIR EFFECT ON BIRD AND

BAT POPULATIONS, LOBBYISTS ON BOTH SIDES OF THE DEBATE TEND TO

CHERRY PICK FACTS AND FIGURES TO SUIT THEM. RENEWABLE ENERGY

FOCUS LOOKS FOR THE MIDDLE GROUND.

In the US, a new bill could throw a hefty spanner

into the works of large-scale clean, emission-

free wind energy.

According to the American Wind Energy

Association (AWEA), the bill (introduced by

Chairman Nick Rahall in the House Natural

Resources Committee) aims to bar any new

wind power project, until rules are issued by the

Fish and Wildlife Service; a process that could

take “years”, says the AWEA.

The rules would require all existing turbines

– even small residential units – to stop operating

6 months after issuance of the new FWS rules,

until such time as they become certifi ed. And

it would become a crime to even construct an

unapproved turbine.

While this is one of the more extreme

manifestations of opposition to wind power,

it does epitomise a strand of public sentiment

that carries weight. Woe betide any wind farm

developer who pays insuffi cient attention to the

wildlife issue in the initial planning and consent

process. And once in operation, propagandists

have found they can enlist public sympathy

with pictures of dead animals, purported to be

victims of wind turbines.

But to what extent are wind farms really a threat

to wild life, over and above the many other ways

that animals have lost out as man infringes on

their territories?

Victims of WTs

Unfortunately, there is no doubt that turbines

can and do kill, and certain installations – such

as the Altamont Pass in California – have

become notorious symbols among wildlife

supporters.

Animals flying into the plane of a turbine’s

swept disc may get through without harm, but

some encounter a moving blade and are killed

or injured. Raptors (birds of prey), migrating

birds and bats appear to be most at risk.

George Marsh

Copyright: WWF

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Sub_Environment/Cat_Wind

Renewable Energy Focus July/August 2007 43

BioResource Consultants of California have

suggested, on the basis of a study funded by the

US National Renewable Energy Laboratory and

the California Energy Commission and carried

out there with the cooperation of the wind farm

operators, that bird fatalities per Mw per year range

from 0.8 to 2.2, depending on various location-

associated factors. Disproportionate mortality is

suff ered by raptors and owls, which are lured by

the presence of prey.

Bats at risk

The potential for adverse impact on bat populations

of wind farms in the eastern US has previously

been described as signifi cant by the National

Research Council of the National Academies.

The AWEA joined forces four years ago with Bat

Conservation International, the US Fish and Wildlife

Service, and the National Renewable Energy

Laboratory to study the situation. The resulting Bats

and Wind Energy Cooperative (BWEC), has worked

with state and Federal agencies, private industry,

academic institutions and non-governmental

organisations, to expand the knowledge base.

And a BWEC-led study carried out in the

Appalachian Mountains during 2004 was

supported by Clipper Windpower, FPL Energy, GE

Wind Energy, NedPower, PPM Atlantic Renewable,

US Wind Force, Vestas North America and Zilkha

Renewable Energy. One of the fi ndings suggested

that wind farms located on forested ridges are

specifi cally of higher risk for bats. Investigators

also noted that most deaths involve bats that are

migrating in the autumn and during a limited part

of the day, chiefl y the two hours after sunset.

According to BWEC, research is on-going into

aspects such as seasonal and weather infl uences;

whether feathering the blades during periods

of low wind can reduce mortality; the eff ects of

surrounding landscape; and the simultaneous use

of video, radar, acoustics and thermal imaging to

improve knowledge of bat behaviour. Technology

can certainly help. In one instance, Babcock

and Brown is using a Merlin avian radar from US

company DeTect Inc to collect pre-construction

environmental data for the planned Gulf Wind

1 wind farm in South Texas. This mobile unit is

shedding light on local movements of fl ying

animals (see image above, right).

Although the US’ experience of wildlife impacts,

augmented by scientifi c study, is arguably

unsurpassed, similar issues exist wherever

wind farms are in operation, or proposed. In

Spain for example, a country with a large wind

infrastructure, instances of Griff on Vultures (see

image above, left) and Eagles being killed by

turbines in Navarre and Tarifa have been widely

publicised. Turbines in countries as diverse as

Germany, Denmark, Norway, Australia and the

UK are similarly implicated.

Sense of proportion

Given the polarisation of positions that accompany

emotionally charged issues, a sense of proportion

is often missing from the propaganda on both

sides, and on occasion, there is artful presentation

of the facts.

For instance, when wildlife campaigners cited the

“obliteration of an entire breeding population of

an endangered species,” one needed to know that

campaigners were referring to nine birds that died

at a 68-turbine site in ten months; unfortunately,

these were white-tailed sea eagles, Europe’s largest

bird of prey, and were a family with all the previous

year’s chicks, so the matter was understandably

not trivial.

But any attempt to form a balanced judgement

requires all the essential facts and some context,

rather than an emotionally-charged statement.

In order to consider the wildlife issue overall, it

needs to be pointed out to members of the public

that millions of birds are killed each year by road

vehicles, aircraft, trains, power lines, buildings,

cellphone towers, barbed and razor wire, guns,

traps, farm machinery, pesticides and other man-

made hazards. Additionally, many are killed by

other animals, especially domestic cats. According

to the Canadian Wind Energy Association, it is

estimated that more than 10,000 migratory birds

die each year in Toronto alone, between the hours

of 11pm and 5am, in collisions with brightly lit

offi ce towers. In comparison with all these hazards,

wind farms seem insignifi cant as killers.

Campaigners say that this argument is simplistic

because there are as yet relatively few wind farms

and as turbines multiply, they will take a more

comparable toll. US studies actually suggest an

average mortality for all turbines of about two birds

per turbine per year, but this may not necessarily

follow since birds are able to learn about new

types of hazard and avoid them, just as they learn

that roads are dangerous. Wildlife lobbyists are

apt, wilfully or otherwise, to understate this ability.

Naturalists point out that buildings and windows

do not generally kill golden eagles, swans and

geese while turbines tend to victimise the more

treasured species. But these birds, too, may

develop avoidance strategies over time.

Wind energy proponents of course for their part

seek to trump all the arguments with their case that

the most dangerous hazard of all is climate change.

They can quote numerous studies to support this.

Singling out just one, a 2004 study reported in the

respected journal Nature estimated that up to a

quarter of all bird species could become extinct by

2054 due to global climate change. Wind energy is

put forward as a means for avoiding this.

New fi gures

Actually, turbines might not be as dangerous to

winged animals as the wildlife lobby suggests.

Monitoring carried out in Spain over a ten-

Babcock and Brown is using a Merlin avian radar from DeTect Inc to collect environmental data for the planned Gulf Wind 1 wind farm in South Texas. mobile unit is shedding light on local movements of fl ying animals.



44 Renewable Energy Focus July/August 2007

The AWEA joined forces four years ago with Bat Conservation International, the US Fish and Wildlife Service, and the National Renewable Energy Laboratory to study the situation. The resulting Bats and Wind Energy Cooperative (BWEC), has worked with state and federal agencies, private industry, academic institutions and non-governmental organisations, to expand the knowledge base.

year period, principally by developer Acciona

Energy (formerly EHN) and the Navarre regional

Government’s Environment Department,

indicated a casualty rate of just 0.22 birds per

turbine per year. In monitoring 964 turbines

across 26 wind farms in northern Spain, great care

was taken to ensure a high casualty detection

rate – for instance by ensuring that casualties

were found before they could be removed by

predators. Acciona says that this mortality rate

does not put at undue risk any particular species,

even the Griff on Vulture which is the most

frequent casualty. Golden Eagles bred successfully

at a number of wind farms, sometimes quite

close to the turbines. The Navarre Environment

Department recorded a 0.1%-0.2% mortality rate

among birds which passed through turbines, and

its investigators concluded that the impact of

wind farms is low relative to other hazards such

as electricity power lines.

And Acciona argues that the mortality, whilst

regrettable, should be set against avoidance of 4

million tonnes of CO2 emissions, and the burning

of 3.1m tonnes of coal.

The off shore question – potential risk

Limited experience to date suggests that

the exploiting of off shore wind might have a

signifi cantly lower cost to bird life than onshore.

According to the European Wind Energy

Association (EWEA), extensive monitoring at the

Danish wind farms built in 2002 at Horns Rev and

2003 at Nysted has shown that birds learn to avoid

the turbines and that casualties are minimal. When

the 108Mw off shore Egmond aan Zee plant with

its 3Mw machines was planned, developers Shell

and Nuon at fi rst feared that thousands of birds,

mainly ducks, would be killed by fl ying into the

blades. The Danish results helped assuage their

worst fears.

Instead, an issue arose with sea mammals,

particularly porpoises. A number were found

dead during operations to drive piles into the sea

bed. Subsequently, the developers took to using

underwater sonic signals to keep curious animals

away from the piling site, while postmortems

carried out on dead mammals sought to establish

whether their ear drums had been damaged.

Sonic disturbance to porpoises, dolphins and

other marine animals is a topic that requires

further investigation, but this is not any more

applicable to off shore wind farm construction

than to other underwater activities such as oil

and gas exploitation and shipping. And it is

believed that off shore farm development might

even benefi t marine life, because exclusion zones

implemented around new installations will deny

access to fi shing vessels, including destructive

bottom-scouring trawlers.

Objecting to wind projects

Several respected wildlife and environmental

bodies support wind energy in principle, and one

of these is the UK’s Royal Society for the Protection

of Birds. According to John Lanchbery, principal

climate change advisor, the Society regards

climate change as the greatest long-term threat

to biodiversity and bird life. It sees renewable

energy as an important part of the solution and

wind energy as a crucial contributor. Enlarging on

this point John Clare, a spokesman for the Society,

says,

“We back the UK targets of 10% of energy being

developed from renewable resources by 2010

and 15% by 2015, and we see wind energy – the

most mature of the technologies available – as an

essential part of the renewable energy mix that

will help meet those targets. But, as far as we

are concerned, habitats and wildlife must be

protected, so wind farms have to be planned and

sited in such a way as to minimise impacts. We

believe it’s perfectly possible to meet the stated

UK energy objectives in a way that also respects

the needs of wildlife.”

This view is also shared by the WWF, who sent us

this statement:

“Climate change is the biggest threat facing the

world – and all of its plants and animals – at the

moment. WWF has identifi ed that with enough

investment in clean and environmentally sound

technology the world can meet its growing

need for energy without exceeding the 2 degree

centigrade rise in global temperatures that

would start to bring about some of the worst

impacts of climate change. However, WWF also

believes that it is vital that any planned clean

energy production sites are subject to careful

environmental impact assessments before they

are given the go ahead.”

This issue of assessment is seen as crucial.

The RSPB’s own special interest means that it

cannot support planning applications that pose

a threat to bird populations, and that means

taking into account not just possible blade

collision, but cases where bird populations can be

scared away by land clearance and construction

operations: “We scrutinise proposed schemes

with all three impacts in mind before deciding

whether we should object.”

Rather than formally objecting to certain

projects, the society says it prefers to engage

with developers, hoping to persuade them to

act on its concerns. In this way, it believes it can

have a stronger infl uence on fi nal confi gurations



Renewable Energy Focus July/August 2007 45

than if it adopted a more confrontational

approach, says the RSPB’s Clare.

“In the fi rst instance, our local conservation

offi cers talk to the developers, who tend to be

receptive to our arguments. After all, most want

respect for their green credentials and, at the

end of the day, are loath to engage in expensive

public enquiries.”

The RSPB’s pragmatic stance and specialist

knowledge are widely respected, and the

organisation is frequently consulted in the

early planning stages of new schemes in the

UK. When it does take issue with an application,

which happens in a minority of cases, its case is

listened to. An example of a proposal to which

the RSPB has marked objections is that currently

under consideration for Lewis in the Scottish

western isles, but the RSPB has not objected to

the equally extensive London Array scheme

proposed for the Thames Estuary.

Mitigation

Much can be done to mitigate the eff ects of

wind turbines and wind farms. At Altamont Pass,

for instance, consultants proposed encouraging

small mammals to populate areas away from

the turbines rather than close to them, allowing

vegetation to grow near the turbines so that small

mammals are less visible to raptors, moving rock

piles away from turbines and preventing cattle

from congregating near the turbines. Blade paint

schemes and placing diversionary structures at

the ends of turbine rows were other proposed

measures.

Ornithologists had suggested that the lattice

towers used to support the original turbines at the

Pass, dating back to the 1970s, might be tempting

raptors with easy vantage points from which to

spot prey. Their theory was that the birds would

then follow their instinct and dart out on sighting

a quarry, sometimes colliding with a blade. This

notion gained credence as some improvement

seemed to follow the replacement of the original

turbines by larger, more powerful successors

supported on monopole towers. However, it is

now thought that mortality reduction may have

owed more to the wider spacing of these more

powerful replacements, allowing greater passage

room between them, than to tower structural

infl uences. BioResource Consultants concluded

that perch availability might be less important

than once believed, and that the type of tower

therefore makes little diff erence.

In Spain, Acciona Energy has adopted various

measures to reduce bird casualties. In particular,

it has painted turbine blades in bright colours

and changed the turbines’ software program

so that there is a slightly higher band of wind

speed before blades start turning.

Careful siting of wind farms can go a long

way to minimising avian risk. Guidelines from

environmental organisations like Greenpeace

and the Sierra Club recommend avoiding areas

where endangered species are present. EWEC

points out that the interaction between wind

farms and birds is highly site-specifi c and that

the high mortalities recorded at places like

Altamont Pass and Tarifa are not indicative of

the day-to-day experience at the thousands

of wind energy developments now operating

around the world.

Use of more powerful turbines can allow

spacings between turbines to be increased,

giving a greater chance for birds to pass

through a facility unscathed. Existing farms can

be monitored to enhance knowledge of bird

and fl ight paths, timings and other behaviour.

Turbines can be stopped during peak migratory

periods. Blades can be made more visible with

paint schemes, and night illumination can be

designed for minimal interference with animal

sensory perception.

Environmental best practice dictates that

developers, as far as is possible, return habitats

to original condition or better once wind farms

have been constructed. Restitution has become a

big theme in environmental impact planning and

approval. Sometimes compensation is negotiated

to cover the costs of this; at other times, developers

carry out habitat renewal themselves. At the Black

Law farm in Scotland, for example, ScottishPower

restored some 1400 hectares of land between

and around the turbines to a mixture of blanket

bog, peat and wetland. This is said to provide a

more attractive habitat to a range of wildlife, than

the managed fi r tree plantations and spoil from

mining that were there originally. Improvement

of the previously scarred site at Black Law was a

major factor in earning from trade association

Scottish Renewables its award for Best Renewable

Project in 2005. Simon Zisman, central Scotland

conservation offi cer for the RSPB said that the

change would benefi t breeding waders, farmland

birds and other wildlife, and professed himself

impressed by the commitment and resources that

the developer had invested in this project.

Survivors

History records that there were some 10,000

windmills across Europe alone, before the

industrial revolution. Clearly, these were a

diff erent type of threat to the modern machines

but, nevertheless, all the avian species we have

today survived this human encroachment into

their windy domain. Chances are that, given

due care in wind farm design and location,

consistent with proper respect for wildlife, their

survival will not be threatened by the windmills

of the 21st Century.

Facts and fi gures – what do the proponents on both sides say?

A study funded by the US National Renewable

Energy Laboratory and the California Energy

Commission and carried out there with the

cooperation of the wind farm operators, found

that bird fatalities per MW per year range from

0.8 to 2.2, depending on various location-

associated factors;

Disproportionate mortality is suff ered by

raptors and owls, which are lured by the

presence of prey;

Mortality among birds and bats at the 44-

turbine Mountaineer wind plant in West

Virginia is estimated as 4000 per year, consulting

conservation biologist Dan Boone asserted in a

presentation made last year (available on the

web site of Industrial Wind Action Group, USA).

The US Fish and Wildlife Service described

these estimates as “among the highest ever

reported in the world”;

Reports suggest that wind farms located on

forested ridges are locations of higher risk for

bats;

But monitoring carried out in Spain over a ten-

year period, principally by developer Acciona

Energy (formerly EHN) and the Navarre regional

government’s Environment Department,

indicated a casualty rate of just 0.22 birds per

turbine per year;

The Navarre Environment Department

recorded a 0.1%-0.2% mortality rate among

birds which passed through turbines, and its

investigators concluded that the impact of

wind farms is low relative to other hazards such

as electricity power lines;

Millions of birds are killed each year by road

vehicles, aircraft, trains, power lines, buildings,

cellphone towers, barbed and razor wire, guns,

traps, farm machinery, pesticides and other

man-made hazards;

According to the Canadian Wind Energy

Association, it is estimated that more than

10,000 migratory birds die each year in Toronto

alone, between the hours of 11pm and 5am, in

collisions with brightly lit offi ce towers;

Questions for the future

The UK’s respected RSPB regards climate

change as the greatest long-term threat to

biodiversity and bird life. It sees renewable

energy as an important part of the solution and

wind energy as a crucial contributor;

To what extent can birds learn about new

types of hazard and avoid them? Opponents

to wind farm development can underplay this

innate abiltity.


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WTS: the avian dilemma