Washington, May 7: Noise pollution caused by humans is 'pervasive' in the US protected areas, posing a threat to land masses that harbour wildlife and provide places for respite, recreation, and natural resource conservation. Protected areas in the US represent about 14 per cent of the land mass.
Researchers, including those from Colorado State University in the US, analysed millions of hours of sound measurements from 492 sites around continental US. The results summarised predictions of existing sound levels, estimates of natural sound levels, and the amount that human-made noise raises levels above natural levels, which is considered noise pollution.
Researchers found that human-made noise doubled background sound levels in 63 per cent of US protected areas, and caused a ten-fold or greater increase in background levels in 21 per cent of protected areas.
In other words, noise reduced the area that natural sounds can be heard by 50 to 90 per cent. This also means that what could be heard at 100 feet away could only be heard from 10 to 50 feet, researchers said.
This reduced capacity to hear natural sound reduces the restorative properties of spending time in nature, such as mood enhancement and stress reduction, interfering with the enjoyment typically experienced by park visitors.
"The noise levels we found can be harmful to visitor experiences in these areas, and can be harmful to human health, and to wildlife. We were encouraged to see that many large wilderness areas have sound levels that are close to natural levels," said Rachel Buxton, from Warner College of Natural Resources in the US.
“Protecting these important natural acoustic resources as development and land conversion progresses is critical if we want to preserve the character of protected areas. Although plants cannot hear, many animals that disperse seeds or pollinate flowers can hear and are known to be affected by noise, resulting in indirect impacts on plants." she said.
High levels of noise pollution were also found in critical habitat for endangered species, namely in endangered plant and insect habitats.
The study also found that high noise pollution levels within protected areas were in specific locations, where noise reduction techniques may best be targeted.
The biggest noise-causing culprits were roads, aircraft, human development, and resource extraction.