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Industrial roar changes nearby plant reproduction

Plants don’t need ears to show signs of noise pollution

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7:29am, March 21, 2012
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Noise pollution can stomp its soundprint on plants, a study of motors chugging in a Western forest finds.

Of course, plants don’t have ears, but birds and other animals hear the throb of humankind’s motors. The uproar drives away some species and sometimes encourages others, swapping their various influences on plants, says Clinton Francis of the National Evolutionary Synthesis Center in Durham, N.C.

Around noisy gas wells in a northwestern New Mexico woodland, Francis and his colleagues found that the reshuffling of birds and small mammals changed the odds of success for crucial steps in plant reproduction. Hummingbird pollination, important for certain wildflowers, increased. Yet birds likely to spread around pine seeds without eating all of them largely gave way to seed-eating mice, he and his colleagues report online March 21 in the Proceedings of the Royal Society B.

The new experiments are the first to show that sounds affect the structure of a whole biological community, says behavioral ecologist John Swaddle at the College of William and Mary in Williamsburg, Va. With such cascading consequences, “whole ecosystems can be restructured by noise pollution,” he says.

The automated gas wells in a squat forest of pinyon pine and juniper create a natural experimental setup for separating the effects of noise from other quirks of landscapes, Francis says. About half the wells need compressors that run day and night, which blast such a din that anyone working up close needs ear protection to prevent permanent hearing damage. The rest of the wells don’t use compressors but have the same basic set-up.

Earlier work concluded that for bird nesting, noise matters (SN: 8/27/11, p. 26). About the same number of individual birds nested around both the roaring and quieter wells, but the quieter neighborhood had a greater variety of species. Western scrub jays hardly showed up around the noisy sites, possibly because the noise masked the jays’ hunting cues. But house finches and black-chinned hummingbirds were actually more common there, perhaps avoiding some noise-averse predators.

Curious about the effect of noise on plants, Francis and his colleagues created a red artificial flower inspired by the real scarlet gilias that hummingbirds pollinate. Tracking the appearance of a fluorescent dye, a stand-in for pollen, the researchers found more hummingbird pollination at the noisy sites.

Previous studies had revealed that the loud places have fewer pine seedlings. This began to make sense when researchers set out little windfalls of seeds, and found more mice and fewer jays at the compressor sites compared with the quieter wells. Their idea that engine noise could cut back on the next generation of trees “would represent not just an effect of noise on birds, plants or communities, but eventually on the entire habitat, since you could argue that trees provide the framework on which the whole woodland is built,” says Caitlin Kight of the University of Exeter’s Cornwall Campus in Tremough, England.

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