Are wind turbines good for Koalas?
Roger Martin, a wildlife ecologist specializing in Koalas, raises concerns about the impact wind turbine noise could have on the mating patterns of Koalas living nearby. His research indicates we should be alarmed at the prospect of the Upper Burdekin wind development in North Qld, recently approved, to be located on the habitat of a thriving Koala population.
Above: A recent photograph of Athey, the male koala we rescued from a power pole in Atherton 3 years ago. Credit: Amy Shima
Image above: Roger Martin with a Koala that has just been released after having been examined and having his tracking collar checked. Credit: Amy Shima
Koalas are primarily solitary animals that communicate with each other by means of low frequency (LF) contact calls. These calls are particularly important during the summer breeding season when males bellow repeatedly to attract receptive females.
Both sexes show major adaptations to the larynx (‘velar folds’) and to the middle ear (‘enlarged auditory bullae’) that enable them to both make and hear these low frequency calls. LF sound is not attenuated by the canopy of the forest, and we believe that koalas use it to communicate over surprising large distances.
In our research, we also rely on this LF sound and use bioacoustic recorders to detect and locate male Koalas with it. One of our study populations is in the vicinity of the Kaban Wind Farm and, as well as Koala bellows, we inadvertently record the low frequency noise made by wind turbines. Our equipment is not as sensitive as the instrumentation used by acoustics professionals but on the spectrograms derived from our recordings, it is obvious that the amplitude of wind turbine noise is sufficiently large to mask the lower amplitude bellows of male Koalas. We suspect that this could have a significant impact on the range of their call and on its efficacy in attracting distant females and therefore have a negative impact on their breeding success and fertility rate.
But this ‘masking effect’ aside, the persistent 24/7 noise of wind turbines could also cause koalas to avoid forested areas close to turbines. When talking of the loudness of a sound as it is experienced by wildlife, it is important to address how this loudness is measured. Most acoustic reports on wind turbine noise use ‘A-weighted’ decibels (dBA). The decibel is a relative measure of sound pressure level. The base against which ‘A-weighted’ decibels are measured is the sound pressure level at the threshold of human hearing which occurs at a frequency of 20 Hz. It is meaningful for stipulating what constitutes uncomfortable sound levels for humans - but not necessarily for koalas.
The hearing threshold of many mammals is well below 20 Hz. For example, African elephants can hear sound at frequencies as low as 8 Hz. The hearing threshold for Koalas hasn’t been measured but we do know that the fundamental frequency of the male bellow is 11- 15 Hz. It is reasonable to suggest that the lower threshold of their hearing also occurs around this frequency. The anatomy of the koala’s hearing apparatus, particularly the greatly enlarged auditory bullae, further suggests that the koala’s ability to hear low frequency sound is acute. It follows that a decibel measure of what constitutes uncomfortably loud noise to a koala would need to be based on the sound pressure level measured at their hearing threshold. This figure would undoubtedly be much larger than the figure calculated on the A-weighted scale: to a Koala a 45 dBA noise may sound more like 100 dBA sounds to a human. A more appropriate measure of loudness for koalas would perhaps be in ‘G-weighted’ decibels which take infrasound (sound < 20 Hz) into account.
On limited evidence we suspect that the Bluff Forest koalas avoid going closer than 4 km to the Kaban wind turbines. If this is the case, and wind turbines do have a noise footprint that extends over an area of 50 square kilometres, this has very serious implications. For example, a major loss of habitat for koalas who would also not use any of the so-called forest ‘offsets’ located within 4 km from a wind turbine.
- Roger Martin
The EPBC Act was proclaimed in 1999 when there were no commercial wind turbines operating on mainland Australia. It is understandable that the Act does not address any potential impacts of the low frequency noise emanating from wind turbine on wildlife.
Legislation to update the EPBC Act has been recognized by numerous authorities as long overdue but even in its present form it does recognize the need a ‘precautionary principle’. Embracing such a principle implies that further investigations of the acoustics of wind turbine noise and the impact of low frequency sound emanating from wind turbines on wildlife are urgently needed. They should certainly be undertaken before any more wind turbines are put into areas of native forest in North Queensland.
Roger Martin, November 2024
We now need to ask what impact the operation of these wind turbines is likely to have on this resident Koala population.
Clearing the forest that they rely on for food and shelter will obviously have a huge negative impact on them. But the constant low frequency noise made by these enormous turbines may be just as significant as this noise may cause the population to abandon large areas of forest surrounding the wind turbines.
Roger’s main concern is the location of the wind development in high elevation eucalyptus woodlands close to the Wet Tropics World Heritage Area. In work published in 2016, wildlife scientists identified these areas as potential climate change refugia for koalas. In 2018, environmental consultants working for the proponents of the Burdekin wind development discovered an abundant Koala population living there. In 2022, the Koala was listed as an Endangered species throughout Queensland.
On these three grounds alone, this Upper Burdekin wind development should not have proceeded.
Support our legal challenged to stop the Upper Burdekin wind farm from proceeding.
