Drought-stressed trees broadcast ultrasound that may attract insect pests.

Evidence

The active role of the acoustic performance of some organisms is responsible for the magnification of the effects of climate change, an interesting thesis on which very few data are available. Drought produces stress on trees and hence an increased vulnerability to insect attack. Insects are drawn to stressed trees using chemical signals but also (probably) are attracted by the sounds emitted by cells. These sounds, which are produced by forest trees when under drought stress, are known as cavitation, which is the result of cells collapsing by gradual dehydration and water stress. The majority of sounds emitted are within a frequency range of 20 kHz to 200 kHz and may represent an important signal for insects. For instance, bark beetles are the perfect candidates to hear such sounds because there is increasing evidence that they emit signals in the ultrasound range (Dumm and Crutchfield, 2013). Considering that the increase of temperature favors the activity of defoliating insects that exacerbates the amount of CO2 in the atmosphere through their high metabolism, it seems probable that a positive feedback between insects can spread, signaling favor by cavitation, defoliation, forest decline, and CO2 increase. — Bernie Krause and Almo Farina, Using Ecoacoustic Methods to Survey the…, 83

Categorization

• DEFINE: Introduces ‘cavitation’ as the acoustic byproduct of drought-stressed plant cells collapsing.
• QUESTION: Audio bandwidth beyond human hearing as part of a soundscape is worth pursuing — ‘deep listening’ usually concerns the audible; the ultrasonic plant-insect channel stretches the soundscape concept.
• ADDENDUM: Reinforces the trees-as-infrastructure worldbuilding piece as a real, uncanny plant signaling pathway.
• XREF: Expands the biophony/anthropophony binary: plants emitting ultrasonic stress signals complicate who counts as an acoustic agent. — connects to: Trees may signal drought through cavitation sound audible to pest insects — Almo Farina, Soundscape Ecology: Principles,…, 792; Drought-stressed plants emit cell-collapse sounds bark beetles use to locate trees. — Almo Farina, Soundscape Ecology: Principles,…, 360; Bark beetles combine long-range chemical with short-range acoustic signaling — Almo Farina, Soundscape Ecology: Principles,…, 788

Related

• Trees may signal drought through cavitation sound audible to pest insects (similarity 0.93)
• Drought-stressed plants emit cell-collapse sounds bark beetles use to locate trees. (similarity 0.92)
• Bark beetles combine long-range chemical with short-range acoustic signaling (similarity 0.85)

Broader Connections

• Drought-stressed plants emit cell-collapse sounds bark beetles use to locate trees. #expands (0.95) — Almo Farina, Soundscape Ecology, 360
• Trees may signal drought through cavitation sound audible to pest insects #corroborates (0.90) — Almo Farina, Soundscape Ecology, 792
• Bark beetles combine long-range chemical with short-range acoustic signaling #expands (0.80) — Almo Farina, Soundscape Ecology, 788