Draft National Wind Farm Development Guidelines - July 2010

In order to determine whether predicted effects on populations are ecologically important
or not, the following should be taken into account:
• Unless otherwise advised by the relevant authorities, the definition of the ‘population
of a species’ should follow that provided in Matters of National Environmental
Significance: Significant Impact Guidelines 1.1 Environment Protection and
Biodiversity Conservation Act 1999 (DEWHA 2009), i.e. “A ‘population of a species’
is defined under the EPBC Act as an occurrence of the species in a particular
area. In relation to critically endangered, endangered or vulnerable threatened
species, occurrences include but are not limited to:
• a geographically distinct regional population, or collection of local populations,
or
• a population, or collection of local populations, that occurs within a particular
bioregion.”
• Migratory and nomadic birds or bats at a wind farm site may comprise or include
animals from populations that breed in distant locations.
• Whether mortalities are expected to affect particular demographic components of
the population (e.g. sex or age classes, breeders/non-breeders).
• Whether mortalities are expected to have an effect on demographic functioning of
the population.
• Due to the small numbers of individuals usually considered in these predictions, actual
number of mortalities that might occur at a wind farm will almost certainly fluctuate
from year to year around an average over the life of the facility and this should be
expected and taken into account in evaluation of effects on populations.
Population Viability Analysis (PVA) is an appropriate mechanism to model and predict the
effects in terms of altered extinction probability for the population. However, demographic
parameters — which are pre-requisites of PVA — are not well known for many taxa and
some informed assumptions will usually be integral to this component.
In the instance where a PVA model is not deemed appropriate or achievable, an
alternate is Potential Biological Removal (PBR) value. This can be assessed with estimates of
just the mean annual mortality resulting from the wind farm, the estimated total population
size and basic demographics (adult survival and age at first reproduction) of the relevant
key species.
On the basis of such an analysis a determination can be made about the likelihood that
projected levels of mean annual mortality due to the wind farm will negatively affect
maintenance of the population of the key species under consideration. This is measured in
PVA as a material increase in extinction probability and in PBR by the estimated number of
mortalities caused by the wind farm relative to the calculated PBR value. The mortality rate
in any animal population varies around a mean value from year to year and according to
natural environmental variables. A minimum objective for any development should be that
any impact it causes is well within the range of such natural variation.
While such quantitative analyses have a sound ecological basis, demographic information
about the taxon in question may not be sufficient to permit analysis by methods such as
PVA or PBR. In such cases a qualitative evaluation of potential impacts on the population
can be undertaken. This can use criteria such as those provided in guidelines such as
Matters of National Environmental Significance: Significant Impact Guidelines 1.1
Environment Protection and Biodiversity Conservation Act 1999 (DEWHA 2009).
Once the results of effects on the population are available a judgement can be made
about the acceptability, or otherwise of any potential impact of the proposed wind farm.
In general, an acceptable outcome will be a zero net impact on the population in
question. Judgements of the levels of impacts that are considered undesirable or
unacceptable will at the discretion of relevant authorities. The project impact will be
Draft National Wind Farm Development Guidelines – 2 July 2010 Page 127