Unexpected soundscape response to insecticide application in oak forests

Area of Science:

• Ecology
• Environmental Science
• Acoustic Ecology

Background:

• Pesticide use, including insecticides like tebufenozide, can harm non-target organisms and contribute to population declines.
• Rachel Carson's "Silent Spring" raised awareness of pesticide side effects, leading to policy changes.
• Tebufenozide is applied in oak forests to control Lepidoptera, which inhabit diverse insect faunas.

Purpose of the Study:

• To assess the impact of aerial tebufenozide application on bird populations using autonomous sound recorders.
• To analyze soundscape changes resulting from pesticide use during a spongy moth outbreak.
• To explore novel methods for quantifying anthropogenic stressor impacts via soundscape analysis.

Main Methods:

• A 3-year field experiment with replicated, full factorial design was conducted during a spongy moth outbreak.
• Autonomous sound recorders were used to capture forest soundscapes.
• Soundscape analysis involved automated aggregation into sound indices and expert species identification.

Main Results:

• Acoustic complexity significantly decreased in early summer after pesticide application, linked to reduced caterpillar activity and frass.
• Observed effects on bird vocal activity were less pronounced than anticipated from prior breeding success studies.
• No lasting legacy of pesticide treatment on soundscape variation was detected in the second year post-outbreak.

Conclusions:

• Insecticide application can induce acoustic variations not readily perceptible to the human ear.
• Multifaceted soundscape analysis offers a versatile approach for remote, continuous monitoring of anthropogenic impacts.
• This study demonstrates a novel way to quantify the ecological effects of pesticides using soundscape monitoring.