As humans multiply, we have penetrated deeper into habitats in the wild, creating a pervasive increase in environmental sound with our equipment, traffic, and industry. An increasing amount of research has shown how noise pollution adversely affects the behavior of animals – but a study suggests that the harmful effects also failed on plants.
To investigate the long-term ecological effects of persistent noise, researchers selected the Rattlesnake Canyon Habitat Management Area in New Mexico. The area in the southwestern United States is dominated by forest plants and contains high-density natural gas wells, some of which are combined with compressors that run continuously and generate chronic noise up to 100 decibels. It’s just as hard “as being next to the speakers at a Black Sabbath concert or standing right next to the train track as the train passes,” says Dr. Jenny Phillips, who was lead author of the study while attending the California Polytechnic State University in San Luis Obispo. Other boreholes are without compressors.
The vegetation and human activity in both types of wells are similar – so in 2007 one set of researchers compared the vegetation in both contexts and found that noise pollution disrupts the natural community in two ways: dispersal of seedlings and germination (known as recruitment) of the bushveld species – pinyon pines – have been reduced because the community of animals that feed and disperse the plant’s seeds is adversely affected. Hummingbirds meanwhile thrived amidst the noise, which led to increased flower pollination.
Twelve years later, researchers have been trying to assess the long-term ecological impact of this noisy ecosystem. They checked the plots after initial data collection to determine if the previously reported patterns for pinion seedlings continue, but also included analyzes of another tree species, the Utah gin, as well as other flora. Of the 115 plots initially investigated, however, some changed from noisy to quiet because compressors were removed, and vice versa.
As for the pinyon – the researchers found that seedlings were found less in noisy areas (according to the findings in 2007) and the trees (plants between two and 12 years old) also grew more slowly in the persistently harsh environment. The same pattern was observed in the gin plants.
However, when looking at plots that were previously noisy but quiet, they saw more recruiting for gin than for pinyon, according to the study published in the journal Proceedings of the Royal Society B.
This diverse recovery problem can be attributed to the different seed distributors per plant, Phillips said.
The California scrub meat eats the seeds of the pinyon, but they also bury it to save later. Then they forget about the seeds, and this is what makes the forest regenerate again.
‘What we think could potentially happen … is that jays are smart birds, that they have episodic memory and that they can remember negative experiences. So if they explored an area a few years ago and if it is noisy, they will remember it and not go back to the area again, ‘she said.
Juniper seedlings were more frequently distributed by mammals and other birds for which the noise was not quite as disruptive, she added.
‘We do not really have the ability to say how serious the impact is [of noise pollution] is, especially when we look at the ecosystem level, ”says Sarah Termondt, who co-authored the study when she was at Texas A&M University.
“If you change the ability for a seed to grow somewhere because a bird no longer drops the seed there, it can change the habitat for a multitude of species.”