A new study published in the Proceedings of the Royal Society B has found that human noise like traffic can have ripple effects on plants.
Lead author Clinton Francis of the National Evolutionary Synthesis Center (NESCent) in Durham, North Carolina, said the consequences of noise could last for decades, even after the source of the noise goes away.
Previous studies found that some animals increase in numbers near noisy sites, while others decline, but the results of the new study found that plants suffer from the ripple effect of it.
Many plants rely on birds and other animals to deliver pollen from one flower to the next, or disperse their seeds.
The team conducted a series of experiments from 2007 to 2010 in Bureau of Land Management’s Rattlesnake Canyon Wildlife Area in northwestern New Mexico to look into the ripple effect further.
They first did an experiment using patches of artificial plants designed to mimic a common red wildflower in an area called scarlet gilia. They dusted the flowers of one plant per patch with artificial pollen, using a different color for each patch.
The researchers found that the black-chinned hummingbird made five times more visits to noisy sites than quiet ones.
“Black-chinned hummingbirds may prefer noisy sites because another bird species that preys on their nestlings, the western scrub jay, tends to avoid those areas,” Francis said in a press release.
They determined that “hummingbird-pollinated plants such as scarlet gilia may indirectly benefit from noise,” Francis said.
In a second series of experiments, they set out to find out what noise might mean for tree seeds and seedlings, specifically the piñon pine.
To find out if noise affected the number of piñon pine seeds that animals ate, the researchers scattered seeds underneath 120 of the trees in noisy and quiet sites.
Two animals in particular differed between quiet and noisy sites: mice, which preferred noisy sites, and western scrub jays, which avoided noisy areas.
Francis said mice are not a good candidate to spread piñon pine seeds because the seeds do not survive the passage through an animal’s gut. So a boost in mice populations could be bad for pine seedlings.
However, western scrub jays may take hundreds to thousands of seeds, hiding them in soil to eat later in the year. The seeds they fail to relocate eventually germinate, leading to more piñon pines in quieter areas.
“Fewer seedlings in noisy areas might eventually mean fewer mature trees, but because piñon pines are so slow-growing the shift could have gone undetected for years,” Francis said in the press release.
“Fewer piñon pine trees would mean less critical habitat for the hundreds of species that depend on them for survival.”
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Image Caption: Human noise affects plants such as piñon pine, whose seed-dispersers avoid the clamor. Credit: Clinton Francis
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