/ 9 May 2021

Noise pollution affects plants and their pollinators

(Jekesai Njikizana/AFP)

Researchers have found that long-term noise pollution may discourage normal plant growth, with the effects noticeable on habits years later. 

Studies on the consequences of excessive noise have been focused on humans, with loud sounds known to cause noise-induced hearing loss, sleep disorders, cardiovascular diseases and hypertension, among other health problems.

Although bearable noise level standards are still unknown for plants, a study by the California Polytechnic State University (Cal Poly) released in April found that regular exposure to elevated sound levels affect the long-term development of a plant even after the source of the noise has been removed.

According to the study, published in the Proceedings of the Royal Society B journal, noise pollution negatively affected tree seedling and the evenness of the wood. The research was first conducted 12 years ago at a piñon and juniper dominated woodland in New Mexico, United States, near natural gas wells. 

Researchers found the seedlings were 75% fewer where loud compressors were used as compared at sites with less noise.

When scientists returned to conclude the study, it was found that the noise had affected how the piñon developed and that seedlings had still not sprouted in previously noisy sites. 

According to Cal Poly: “Natural gas companies sometimes use loud compressors as a part of the extraction process. When companies move the compressors, previously noisy sites become quiet. 

“The research team found that in these areas, there were fewer seedlings and saplings compared with sites that didn’t have compressors added to the well pad to speed up gas extraction. 

“The decrease in saplings results from the time when the site was noisy, but the decrease in seedlings revealed that piñon pine seeds still weren’t sprouting despite stopping the noise.”

The study also found that the noise affected species that disperse and pollinate plants such as the Woodhouse scrub jaybird, which had learnt to avoid noisy areas. 

“While it’s possible that the piñon has decreased because of a lack of opportunities to produce, it’s more likely that the Woodhouse’s scrub-jay hasn’t returned to the formerly noisy area and so isn’t planting seeds. Piñons depend on scrub jays to carry their pine seeds away from the parent tree, and scrub jays are known to avoid noise.” 

The National Park Service reported that its parks were under excessive noise pressure, and found that loud sounds were having a negative effect on the wildlife and had forced some birds to adapt. 

The sound has affected natural animal activities such as hunting, establishing territories and protecting offspring, and had led to some birds singing at night to be heard.

The Cal Poly study emphasised that noise exposure affected more than just how a plant should grow and that researchers were looking at studying the effects of noise on plant-eating animals and on plant pollinators. 

“Continuing to look at long-term changes in floristic inventories over time will elucidate whether communities do eventually recover after long periods of noise pollution, even once it is removed from the landscape,” said Sarah Termondt, the co-author of the research and lead botanist.