Draft National Wind Farm Development Guidelines - July 2010

D.5 Cumulative impacts
D.5.1 Definition
For the purposes of these Guidelines, cumulative impacts on birds and bats are defined as
the effects on key taxa of more than one wind energy facility. While effects on populations
of birds and bats may result from numerous anthropogenic changes to the environment, it
is not feasible to consider cumulative impacts other than those from wind farms in the
current context. In part this is because methods of impact assessment differ across different
industries and because some sources of impacts are not readily subject to any form of
assessment. For example, environmental assessments for no other industry sector in
Australia routinely require forecasts of the number of bird or bat fatalities that they might
cause. The statutory environment for assessments can most readily apply a consistent
approach to only a single industry.
D.5.2 Scope
In the Australian context, the appropriate scale for evaluation of cumulative effects of
wind farms on key species of birds and bats is the breeding gene pool for the taxon under
consideration. Unless the individuals at risk are part of a geographically or genetically
constrained gene pool (e.g. isolated to an island or other geographically discrete portion
of the species’ distributional range), consideration will be of effects on the entire
geographic population of the taxon.
D.5.3 Data standardisation
Standard metrics (i.e. a ‘common currency’) for evaluation of effects on birds and bats for
all wind farms is necessary in order to consider any cumulative impacts of multiple wind
farms. Standard bird or bat utilisation information should be obtained for each relevant
wind farm as outlined in assessment processes outlined for individual wind farms in these
Guidelines.
The real cumulative effects of wind farms can be determined only from investigations of
the effects of operational wind farms and pre-construction predictions of cumulative
impacts will have significant limitations. This is an important reason for soundly based
studies of the true impacts of functioning wind farms to be undertaken and for the
information they obtain to be made appropriately available.
Evaluation of cumulative impacts on key species will be feasible only after the
establishment of a central repository, or repositories, for results of bird and bat impacts at
individual wind farms. Evaluation of the cumulative effects on a particular species entails a
strategic overview that must be independent of any individual wind farm and, since
cumulative impact assessments are of primary interest to the relevant authorities for
conservation of bird and bat species, they will most naturally be the responsibility of
government, but could be taken by the wind energy industry as a body. A centralised
accumulation of data is a vital prerequisite and cumulative impact assessment cannot
proceed without it.
D.5.4 Method
Overview
The process of determining a cumulative impact on a key species is one of combining the
various impacts for all of the relevant individual wind farms and it is thus necessary to have
a comparable and quantified assessment of the effects on relevant species of each of the
wind farms involved. The processes outlined below require that demographic information
for the species in question is available for use in population modelling.
Some key differences between the ways in which different birds and bats use their
distributional ranges should be recognised and accounted for in the cumulative process.
Page 134 Draft National Wind Farm Development Guidelines – 2 July 2010