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.