Environmental Engineering Reference
In-Depth Information
threatenedandmigratorytaxa.Thereforea'population'approachshouldbeapplied
where a population estimate is available. Estimates of population size for many
threatenedspeciesaredetailedinRecoveryPlansandareavailableforallAustralian
threatened birds in the
Action Plan for Australian Birds 2010
(Garnett et al.
2011
).
Population estimates for migratory shorebirds within the East Asian-Australian
FlywayareprovidedinBamfordetal.(
2008
) and estimates for the Australian por-
tions of those populations are provided in Geering et al. (
2007
).
Ideally, modelling using methods such as population viability analysis should be
usedtoevaluatetheinluenceofimpactsonextinctionrisk.Butthatlevelofanalysis
requires more detailed demographic information than just a population census.
Populationviabilityanalysishasbeenusedtoevaluateimpactsofwindfarmmor-
talities for a few threatened Australian species for which the required level of demo-
graphic data was available (Smales
2005
; Smales and Muir
2005
; Smales et al.
2005
). The results suggest that wind farm mortalities as modelled and subsequently
reflected in documented collisions, have been far too few to noticeably alter popula-
tion extinction risk for those species.
However, the level of demographic information for most species is not sufficient
tosupportpopulationviabilityanalysis.Nonethelessapopulationapproachisstill
the most appropriate and it seems reasonable to consider that if the number of indi-
viduals of a particular species affected by collisions with turbines at a wind farm is
well within estimated natural population fluctuations, then that effect would not
constitute a significant ecological impact.
To-date, detected numbers of mortalities and modelled collision predictions for
such species at wind farms have all been well below the thresholds for a significant
impactsasdeinedbythosecriteria.Nonetheless,inmanycasestheproposalfora
wind farm appear to have been determined to be a Controlled Action under the
EPBCActduetothe
possibility
of a significant impact.
Cumulative Risk of Multiple Wind Farms
Regulatoryauthoritiesareincreasinglycallingforevaluationofcumulativeimpacts
of multiple wind farms on threatened birds and bats, although they have not pro-
vided policy guidance about how this might be accomplished. A set of underlying
principles,standardsandmethodshavebeendescribedinsomeworkBiosisunder-
took for the then Commonwealth Department of Environment and Heritage (Smales
2005
).
Cumulative impacts can be validly considered only for an entire and discrete
population.Forinstance,in2010wewereaskedtoconsiderthecumulativeimpacts
oftwoproposedwindfarmsinwesternVictoriaonthe'local'populationofwedge-
tailed eagles. The problem with this concept is that the species' population is con-
tinuous across the entire Australian mainland and any attempt to subdivide it would
require placing boundaries around an arbitrarily defined 'local'population. This
makes no ecological sense. For a species such as this, it is meaningful to consider
the potential impacts on its entire population, or not at all.
