Nocturnal Light and Sound Pollution and Combined Effects on Urban Wildlife Communication

Abstract

The process of urbanization has altered the natural sensory landscapes with anthropogenic persistent
noise and artificial night light (ALAN), which has increasing consequences for wildlife
communication. Although the independent action of these stressors is well characterized, the joint
action on the animal communication of different taxa is not adequately measured. The research paper
is a synthesis of the available evidence based on a standardized cross-taxon analytical tool to assess
the combined effects of nocturnal noise and ALAN on wildlife communication. Normalized
effectiveness indices (01) of birds, bats, amphibians, and insects were used to measure communication
performance that included various communication elements such as call rate, timing stability, signal
clarity, and synchronization. Effectiveness in communication was maximum when there was a
reference (0.88) and minimum when there were isolated noise (0.63) and isolated ALAN (0.59). The
greatest decrease was when it was in noise and ALAN exposure, when the effectiveness was reduced
to 0.31, which is more than 60 % of that in the reference conditions. Combined exposure showed that
amphibians (0.33) and insects (0.29) had low communication indices compared to birds (0.40) and
bats (0.51). Temporal communication elements were also the most impacted across the taxa, with
timing stability and synchronization exhibiting lower indices than call rate or signal clarity. The
findings suggest that nocturnal noise and ALAN have a synergistic effect on the communication of
wildlife, and that the issue of multisensory conservation and planning of biodiversity in cities must be
considered simultaneously.