Urbanization causes substantial alteration of ecosystem structure and function. Urban noise is considered one of the main pollutants that not only results in degradation of human health but has negative impact on animal communication. Although it has been documented that urban noise interferes with communication of vocal organisms and thus reduces their reproductive success, little work has been done to understand the acoustic characteristics and the interaction between biological communication and anthropogenic sounds across different urban-and-rural landscapes. The objectives of the study are to measure and quantify the acoustic patterns of various landscapes along an urban-rural gradient over different seasons and to investigate the impact that anthropogenic sounds have on biological acoustic properties. We established 19 recording locations across the city of Lansing, Michigan from February to December, 2006 to measure the acoustic signatures. Automated recorders at each site collected sound samples simultaneously, and the recordings were made six times a day for two consecutive days each month. We computed an acoustic habitat quality index (AHQI) to provide a method based on the amount of acoustic intensity in different frequency intervals to classify a place relative to its biological composition and human disturbance. Bird species were also identified from the acoustic recordings at each site, and bird diversity measures were estimated. Canonical Correspondence Analysis (CCA) was applied to investigate how species respond to environmental gradients by separating the distribution of species in an ordination plot.
Results/Conclusions
We found that the percent of anthropogenic acoustic intensity was highest in commercial sites, whereas the percent of biological acoustic intensity was highest in rural residential sites. The value of AHQI increased along the urban-rural gradient. Commercial sites and rural-residential sites had the lowest and highest values of AHQI respectively. Based on the identification of bird species from our recordings, 28 bird species were detected, and the highest number of species richness and bird density occurred in moderate urbanization land use. CCA revealed that the distribution of bird species was significantly related to the percent area of different land cover types. The study provided clear evidence that biological sounds were inversely correlated with anthropogenic sounds along the urban-rural gradient where recorders were placed. We suggest that urbanization affects not only the transformation of habitat structure for vocal organisms but also changes the characteristics of the soundscape, which can cause impairment of animal communication and breeding success.
