Noise Disturbance Along Highways: Kuranda Range road upgrade project

[Extract]\ud Research Objectives\ud \ud This review of scientific literature was undertaken in order to identify known effects to wildlife caused by exposure to traffic noise.\ud \ud Such effects include:\ud \ud • Physiological impacts such as ear trauma and raised hormone levels; and\ud \ud • Behavioural responses such as elevated stress levels, acoustic adjustment and road avoidance.\ud \ud Due to paucity of data on animal species, the review also includes known noise effects on\ud human subjects.\ud \ud Significant Findings\ud \ud • Most literature discussed animal avoidance responses to roads, and mostly in the temperate climes of the northern hemisphere.\ud \ud • Information lost from calls and noise attenuation is determined by the loudness of sound, frequency range, the receiver’s ability to detect the sound and the attenuation characteristics of the habitat – losses in forests are raised by five to ten decibels over areas with no obstruction. Animals adapt their calls to compensate for the type of habitat so that individuals can be recognised and distances estimated.\ud \ud • Researchers link traffic noise with reduced bird diversity and species abundance adjacent to roads to distances of up to 1,750 metres from highways through forests and further through other habitats. Edge effects in the absence of noise may contribute to the reduced bird density. Frogs also exhibit reduced populations although it is unclear whether this is due to noise, pollution or mortality from traffic. Avoidance in coniferous forests has been measured and varies between forty and 1,750 metres depending on species and traffic levels, with even greater distances observed in less dense habitats such as grasslands.\ud \ud • Traffic noise impedes movement by mammals through culverts under highways constructed in Canada for habitat connectivity and causes deer to flee in other areas. Noise also increases stress hormone levels in mammals. Some mammals also suffer raised stress hormone levels.\ud \ud • Studies on acoustic responses to noise by fauna (mostly birds) have been predominantly laboratory-based, finding traffic noise to impede the recognition of mating calls in five North American frog and toad species, and to induce raised amplitude levels in songs or calls of tree swallow nestlings, zebra finches, lovebirds, African bush shrikes, nightingales, canaries and budgerigars.\ud \ud • Field experiments have found some temperate birds overcome traffic noise blanketing by singing louder or by making adjustment to the pitch of their songs. This may impact their general fitness by requiring expenditure of greater amounts of energy. Birds singing songs with higher dominant frequencies appear, in some cases, to be less affected.\ud \ud • Anthropogenic noise in the range of 65-85 dB(A) has caused flight and alert responses in birds and behavioural changes.\ud \ud • Mating behaviour of North American frog species is altered by playback of traffic noise in the field. Similar responses might be expected in rainforest frogs.\ud \ud • High traffic noise levels induce a range of severe, often chronic clinical responses in humans, with limited tests on selected fauna indicating similar adverse reactions.\ud \ud • No studies have examined the effect of traffic noise on tropical rainforest fauna including those communicating by sound such as birds and frogs.\ud \ud Management Implications\ud \ud • Some species previously considered to comprise viable populations may now be at risk due to increasing traffic noise levels.\ud \ud • Noise levels previously considered to be safe may negatively affect some fauna.\ud \ud • Low-frequency sound and vibration from traffic sources may be impacting on some fauna.\ud \ud Recommendations\ud \ud • Studies should be undertaken on the effect of traffic noise on bird species living in tropical rainforests.\ud \ud • Existing and future roads (including upgrades) should be designed to minimise the extent of traffic noise propagation into surrounding landscapes.\ud \ud • Sections of highways generating high noise levels should avoid habitats occupied by rare or threatened fauna.\ud \ud Further Research\ud \ud • Wildlife populations in areas close to heavy traffic need to be assessed using indicators of highway avoidance, such as species richness and population density surveys combined with noise measurements within the habitat.\ud \ud • Species which appear to alter vocalisations in order to exist in high traffic noise environments need to be assessed for stress to energy budgets, and ability for individuals to recognise calls from other individuals.\ud \ud • The sphere of research into traffic noise effects should include more faunal groups including invertebrates and frogs.\ud \ud • This research should include noise effects from the frequency spectrum edges including infrasound