The ocean is celebrated worldwide as the home of some of the richest biodiverse ecosystems in the world. It also happens to be the single most vulnerable biome on Earth, plagued with environmental issues like overfishing, acidification, pollution, warming, habitat fragmentation—the list goes on. Perhaps one of the most urgent problems overlooked by both the public eye and scientists alike is noise pollution. Also known as sound pollution, the phenomenon is caused by manmade noise intruding in nature and can have devastating consequences.
That is not to say, however, that our understanding of the issue is entirely new. Though researchers in the field have known about the potential harm to marine life from anthropogenic noise for years, its severity was always overshadowed by its terrestrial counterpart. Contrary to oceanic sound pollution, which the average person may be unfamiliar with, terrestrial sound pollution in locations like urban cities boast significantly more public awareness as it is often taught in schools. Nevertheless, scientists’ studies and reports on the ocean’s noise pollution have been accumulating quietly but steadily over the past few decades.
On Feb. 5, a paper titled “The soundscape of the Anthropocene ocean” was published in the journal Science by marine ecologist Carlos M. Duarte and his team of over 20 other experts. They screened upwards of 10,000 papers written by other researchers and compiled their information to create the most extensive synthesis of evidence supporting the environmental repercussions of noise pollution in the ocean. All in all, its findings show that the situation is a lot more critical than what was previously thought.
Figure 1: Model depicting the temporal duration in direct comparison to the spatial magnitude of various biotic, geologic, and anthropogenic sources of sound.
Source Credit: science.sciencemag.org (LINK)
A soundscape is the sum of all the acoustic elements in a given setting, and the ocean soundscape is particularly vast. Sound plays a crucial role in the communication between aquatic organisms, such as in navigation and mate attraction. The Science article claims that prior to the industrial revolution, the ocean soundscape was in a relative state of balance. It was composed primarily of geophony (sounds from geological sources) and biophony (sounds from biotic sources) with little to zero interference from anthrophony (sounds from human sources). As technology advanced, so did the volume and ubiquity of manmade sounds in the ocean.
The two most prominent sources of anthrophony are ship traffic—which is doubling every decade—and oil and natural gas exploration. The latter is particularly concerning, as it involves massive explosions using seismic air guns to map out where fossil fuels lay in the Earth’s crust. These explosions are six to seven orders of magnitude louder than the noise produced by ships. Marine organisms are particularly sensitive to the increasing volume of anthropogenic sound in their natural habitat. The sound can hinder communication, cause permanent hearing damage, and even cause mortality. In 2002, for example, the orca whale population off the coast of the Broughton Archipelago in British Columbia faced a sharp decline when acoustic harassment devices were installed to prevent wild seals from feeding on salmon farms. The orca whales migrated out of the area to avoid the sound and were thereby forced to give up territory and compete for the same resources in a smaller area.
Figure 2: Diagram illustrating four separate situations of varying levels of noise pollution: the state of the ocean before the Industrial Revolution, the current conditions, and both a poorly-managed and optimal scenario as anthropogenic activity continues to increase into the future.
Source Credit: science.sciencemag.org (LINK)
Though the overall situation may initially seem bleak, there are multiple solutions that can theoretically be put into practice to reduce oceanic sound pollution. Some solutions are relatively straightforward: slow down ships to reduce the sound created, or shift maritime trade routes to avoid sensitive ecosystems. Other solutions require a more technical approach. The implementation of quieter propellers is a viable solution that not only significantly reduces cavitations, or loud screeches produced by the popping of vapor bubbles, but also increases fuel efficiency.
Scientists are also looking into alternative methods of oil and gas exploration that do not require seismic air guns. Marine vibrators, or vibroseis, do not produce the loud impulse noises that current practices do: at the same time, the limited sound that is produced is in a considerably narrower band of frequency. Currently, companies are already working on prototypes where the vibroseis devices are mounted on submarine vehicles that roam the seafloor, avoiding harmful impacts on marine life.
With all the tools set to mitigate noise pollution in the oceans, there are no tangible obstacles standing in the way of taking vital steps to resolve the issue. All that needs to happen at this stage is to inspire purposeful political action: the exact goal of Duarte’s article published last month. Historically, the law has never recognized noise as an impactful factor in the degradation of marine life. “There needs to be a policy that mandates acoustic mitigation in the marine environment,” said Duarte. “We have noise standards for cars and trucks, why should we not have them for ships?”
Q&A:
Jiwon: In your article, you mentioned how noise pollution in the ocean is not given the same treatment as terrestrial noise pollution in terms of global awareness and inclusion in school curriculums. How do you think awareness of this issue could be raised, and what would be the best course of action to mitigate oceanic sound pollution?
One possible step to work towards negating the harmful effects of noise pollution is more publicized research—the paper discussed in the article had this very purpose. The study was published in Science, but also garnered attention through articles through some of the most well-known newspapers and magazines, including the New York Times and Forbes. More awareness on this topic can lead to political action, which in turn could make some of the solutions a reality.
Sally: You mentioned briefly about how noise pollution can possibly cause mortality. Can you be more specific about how this can happen?
The case study of orca whales in the Broughton Archipelago, which is described in the article, is one example of this consequence. In this example, a population of organisms is forced to compete for limited resources—which would naturally cause a dip in numbers. There are, however, other ways that noise pollution can result in mortality. Studies show that anthropogenic noise can reduce the effectiveness of antipredator behaviours in young marine organisms, and even impede their ability to learn to avoid predators in the future. This, too, is solid evidence that noise pollution can cause an increased rate of mortality.
John: What are the most pressing economic considerations that we must make while devising solutions to this problem?
Like with any environmental issue, it is imperative that we bring the economic impacts of the solutions of oceanic noise pollution into consideration. With the issue already facing obstacles like not being recognized as an urgent threat, we cannot risk proposing solutions that greatly fall behind economically relative to the status quo; otherwise, policymakers may lack incentives to encourage positive environmental change.
Eric: How effective are the marine vibrators in comparison to the seismic air guns used in the status quo, and how long would it realistically take for this technology to become mainstream?
Marine vibrators face some obstacles with current limitations of modern technology. Compared to the standard seismic air guns, they are more complicated to operate while being less efficient. While the device’s narrower frequency bandwidth is certainly great for the environment, it becomes considerably weaker. As such, the technology is still in the prototype phase, and likely will not be available for commercial operation for some time.
Hannah: You mentioned that there were multiple solutions to this problem. Even so, why do you think so many of these solutions are not put into practice today?
As discussed above in my response to Eric’s question, some of these solutions still need more work before they are ready for mainstream use. But ultimately, the lack of these solutions’ presence in the real world is rooted in the absence of political recognition. Without policies that even acknowledge the existence of noise pollution, it is difficult to realize these solutions on a large scale.
Works Cited:
Baker, Aryn. “Humans Are Making Oceans Noisier, Harming Marine Life.” Time, Time, 5 Feb. 2021, time.com/5936110/underwater-noise-pollution-report/.
Duarte, Carlos M., et al. “The Soundscape of the Anthropocene Ocean.” Science, vol. 371, no. 6529, 2021, doi:10.1126/science.aba4658.
Imbler, Sabrina. “In the Oceans, the Volume Is Rising as Never Before.” The New York Times, The New York Times, 4 Feb. 2021, www.nytimes.com/2021/02/04/science/ocean-marine-noise-pollution.html.
Schiffman, Richard. “How Ocean Noise Pollution Wreaks Havoc on Marine Life.” Yale E360, 31 Mar. 2016, e360.yale.edu/features/how_ocean_noise_pollution_wreaks_havoc_on_marine_life.
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