Office for Environmental Programs - Theses
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ItemThe Effect of Artificial Light at Night on the Ecological Soundscape: A Community Level Response( 2022)Artificial light at night (ALAN) is widespread, unprecedented and continues to expand rapidly due to increasing urbanisation. The biological effects of ALAN on natural systems and individuals have been uncovered over the last two decades, yet the impacts on ecological communities (interconnected groups of populations occupying the same area) have remained largely unexplored. In this study, I assessed the effect of ALAN on the ecological soundscape (the combination of sounds which define the environment) of different communities across an urban-rural gradient. I deployed bioacoustic recorders across six sites of differing levels of light pollution and urbanisation for two weeks, from sunrise to sunset, to analyse the variation of species diversity and acoustic complexity using established bioacoustic indices (Acoustic Complexity Index (a measure of species diversity), Root Mean Squared (as proxy for anthropogenic noise) and Acoustic Entropy (the complexity of sounds in an environment). Accounting for abiotic factors such as weather and anthropogenic noise, I found that natural variation in moonlight and light cues of key daily transitions were masked by artificial light, affecting species diversity and acoustic complexity in sites with greater urbanisation. Temperature was positively correlated, and windspeed and traffic noise were negatively correlated to species diversity. Both abiotic factors and masking can result in decreased fitness of individuals, altered trophic interactions and disrupted predator-prey mechanisms. Additionally, urban communities demonstrated stable levels of acoustic entropy despite species diversity decreasing, consistent with temporal niche partitioning (the coevolution of activities at differing times amongst species in a community to decrease competition). Understanding the mechanisms behind the impact of ALAN on ecological communities can assist in limiting the impact of anthropogenic pressures on the environment.
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ItemArtificial light at night: the influence of spectra on invertebrate community composition and structure( 2015-11-02)Ecological light pollution is one of the most rapidly increasing forms of environmental pollution on the planet, and is also one of the most poorly understood. The use of artificial light at night (ALAN) is increasing exponentially, and studies have shown that varying intensities of light it can negatively impact health. However, there is a significant gap in our understanding of how invertebrates are affected by ecological light pollution, and very little research has examined the broader community level impacts. Further, the link between the spectral characteristics of artificial light and the ecological impacts of light pollution have been largely neglected. This study provides an insight into the community level impacts of light pollution. A field experiment was conducted to determine if the presence of artificial light at night would alter the local ground dwelling invertebrate community. Additionally, it was examined whether changes in spectra (white, blue, yellow and red) altered the abundances and types of orders (community composition) attracted to artificial light. Results of this study suggest that regardless of spectra, there is a strong relationship between the presence of artificial light and an increase in the activity of ground dwelling invertebrates, which were collected in significantly higher numbers near artificial light than they were in the dark. This study did not find a significant link between spectra and community composition, with white, blue, yellow and red lights all collecting comparable samples of ground dwelling invertebrates, with one exception. Beetles were significantly more abundant in red-lit traps than any other order. This suggests that red lights may attract a community with a higher proportion of beetles than other lights. Overall, this study supports the findings of previous research, suggesting that the use of artificial light increases the activity of invertebrates at night, which may flow on to substantially alter the community. These findings represent those of a pilot study conducted on a small spatial and temporal scale. The expanding use and variations in the types of ALAN could have a significant impact on existing natural environments, and could result in long term changes. Further research should aim to infer if there are long-term ecological level consequences of light pollution, and attempt to ascertain if the effect varies depending on the spectra of light used. A more thorough understanding of these factors could be used to inform street and building lighting choices to minimise the negative ecological consequences of using light at night in both rural and urban environments.