1) Globally, there have been few comprehensive
studies of impacts of wind farms on birds, and even fewer have been published
in peer-reviewed scientific journals. Most studies suffer from a lack
of “before and after”, or “wind farm area and reference
area” comparisons, or completely lack any assessment of relevant
factors such as collisions or risk of collision, or differences in bird
behaviour between night and day, or are of inadequate duration to provide
conclusive results.
2) The available scientific literature identifies
the main potential hazards to birds from wind farms to be:
a. Disturbance leading to displacement or exclusion, including barriers to
movement;
b. Mortality caused by collision;
c. Habitat loss or damage resulting from wind turbines and the associated infrastructure.
3) There is a clear need for robust, objective baseline
studies on which to base informed decisions on sensitive siting to minimize
deleterious effects on birds, other wildlife and their habitats. There
is also a need for post-construction monitoring at installations for
which consents and approvals have been obtained, where there are environmental
sensitivities. The potential impacts must be put into context to determine
the spatial scales at which they may apply, for example at site, local,
regional, national and or international scales.
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Collision risk and mortality
1. We know very little about migration routes, prevalence of nocturnal movements
of birds, or even which species migrate, in New Zealand. We must therefore
rely on overseas information on which to base our assessment of wind farm
suitability.
2. The OSNZ recognizes the need for research into nocturnal movements and the
migrations of birds in general in New Zealand.
3. Most studies elsewhere quote low collision mortality rates per turbine,
but in many instances the data are based only on corpses that have been found,
which leads to under-recording of the actual number of collisions. Even where
collision rates per turbine are low, the collision mortality is not necessarily
insignificant, especially in wind farms consisting of perhaps several hundreds
or thousands of turbines. In addition, even relatively small increases in mortality
rates may be significant for populations of some birds, especially large, long-lived
species which generally have a low annual productivity and which mature slowly.
This effect is critical when such species are already rare.
4. Collision mortality at poorly-sited wind farms may have effects at the population
level. The cumulative mortality from multiple wind installations may also contribute
to population declines in susceptible species. Making projections of the potential
magnitude of wind turbine-related avian fatalities is problematic, because
of the over all lack of objective information.
5. The weight of evidence to date indicates that locations with high bird use,
especially by species of conservation concern, are likely to have significant
effects. Site selection is crucial to minimising mortality resulting from collision.
6. Wind speed and direction, air temperature and humidity, flight type, distance
and height, time of day, and topography all influence the risk of collision,
as do species, bird age and behaviour, and the stage of the bird’s annual
cycle. All these factors need to be incorporated in collision risk assessments.
Collision risk is greatest in poor flying conditions, such as strong winds
that affect the birds’ ability to control flight manoeuvres, in rain,
fog, and on dark nights when visibility is reduced. Lighting of turbines can
attract birds, especially seabirds in bad weather or fog, potentially increasing
the risk of collision.
7. Few studies report observations in poor weather; visual observations are
of course limited in such conditions anyway. However, remote techniques such
as radar, and thermal imagery can be used to extend observations beyond the
visible spectrum. Predictions of the likely frequency of weather conditions
that increase collision risk can be used in risk assessment.
8. Most studies have been of small turbines, often in small clusters. The effects
of newer, larger turbines and of larger wind farms are unknown but they may
well be both quantitatively and qualitatively different. The importance of
wind farm location and layout in determining the risk of collision by birds
with wind turbines is apparent from studies both onshore and offshore.
9. Mortality of birds from mechanical collision arises as a result of impacts
with with a range of man-made structures, including turbines, meteorological
masts, and power lines. Thus, assessment of bird collision risk and mortality,
arising from collision or electrocution, needs to include the wind turbines
and the associated structures, including overhead power lines transporting
energy from the wind farm. It is recognised that the actual rate of collision
is likely to be under-recorded, because of limitations of the study techniques,
particularly corpse searches. It is essential, therefore, that each site is
calibrated to enable correction factors to be applied to produce more realistic
estimates of collision mortality.
10. Collision risk models are potentially useful in predicting the scale of
the problem of collision attributable to wind turbines at a given location,
but only if the models incorporate actual avoidance rates in response to fixed
structures and post-construction assessment of collision risk at wind farms
that are built, to test the models. Population models provide a means of predicting
whether or not there are likely to be population level impacts from collision
mortality. These models also require post-construction verification at wind
farms that are constructed, to test the validity of the predictions and the
models.
Disturbance
1. The effects attributable to wind farms are variable and are species-, season-,
and site-specific. Disturbance can lead to displacement of some species and
their exclusion from areas of suitable habitat; this is effectively loss
of habitat.
2. Several studies indicate negative effects (i.e. a reduction in bird use
of, or absence) at up to 600 m from wind turbines. In a large wind farm, even
such a relatively small exclusion radius from individual turbines, can amount
to a cumulatively significant exclusion area, or area of reduced use for the
whole wind farm.
3. The scale of such habitat loss, together with the extent of availability
and quality of other suitable habitats that can accommodate displaced birds,
and the conservation status of those birds, will determine whether or not there
is an adverse impact. Habituation may occur, and differences in behaviour between
residents and migrants have been observed in some studies. Other studies over
several years show little evidence of habituation. Few studies have been long
enough to demonstrate whether or not habituation occurs. Disturbance potentially
may arise from increased human activity in the vicinity of the wind farms during
construction, maintenance visits, and improvement of road access, often in
areas where there was little human activity before the wind farm was built.
The presence and noise of turbines may also deter birds from using the area
close to turbines. Few conclusive studies are available, because most lack
well-designed studies both before and after construction of the wind farm.
Furthermore, very few studies have taken into account differences between diurnal
and nocturnal behaviour, basing assessments on daytime activity only. This
is inadequate for those species, including many in New Zealand, that are active
during darkness and which may behave differently at night.
4. Wind farm design, for example by including wide corridors between clusters
of turbines, may alleviate any barrier effect. Research and post-construction
monitoring at several pilot sites are necessary to determine whether and where
this is an acceptable solution.
5. There has been little research into the impacts of off-shore wind farms
on birds. Nonetheless, studies in progress suggest that responses vary in both
site- and species-specific ways, as for onshore sites. Most of New Zealand’s
extant endemic avifauna are pelagic tube-nosed seabirds. These species may
potentially be vulnerable to off-shore wind-farm development because of their
propensity to forage or move about at night. The siting of wind farms near
large or significant seabird colonies or sites of significant foraging or aggregation
should therefore be questioned and a caution be exercised until further data
are available.
Habitat loss or damage
1. Loss of, or damage to, habitat resulting from wind farm infrastructure are
not generally perceived to be of major concern for birds outside designated
or qualifying sites of national and international importance for biodiversity.
This does, however, depend on local circumstances and the size of the area
to be occupied by the wind farm and the associated infrastructure. The cumulative
loss of, or damage to, sensitive habitats may be significant, especially
if several large developments are located in places such as sandbanks in
shallow waters. Furthermore, direct habitat loss may have additive effects
to those of exclusion by disturbance.
2. Onshore infrastructure, including turbine bases, substations and access
roads involve direct habitat loss. The losses are generally relatively small
scale, but could affect local hydrology in sensitive habitats and, again, the
effects will depend on the size of the wind farm, and especially on the extent
of any road network required.
3. Offshore, direct habitat loss is generally limited, primarily to the turbine
bases and cables at sea. However, large wind farms, especially on feeding areas
such as sandbanks in shallow waters, may be of concern, and habitat change
or damage may be significant.
Other issues
1. Turbines may offer roosting or nesting sites for birds. However, research
is needed to assess the extent of bird use. In the offshore environment,
there may be adverse effects (e.g., collision risk for birds feeding among
turbines) on birds as a result of disruption to, or encouragement of, avian
food resources such as benthos and fish populations while turbine piles can
act as artificial reefs or fish aggregating devices. These aspects require
study to clarify whether or not they are significant issues. |
