Underwater Noise Pollution is Destroying Ecosystems. The Time to Act Was Yesterday.
By: Brenna E Van Skiver
Tags: Ocean Conservation, Shipping, Noise Pollution, Environment, Environmental Issues

Innovations exist for combatting the shipping industry’s contributions to noise pollution, but it’s up to international governments to take the next step toward concrete change.

Image by Kinsey via Unsplash

Ocean pollution is not a novel concept. However, underwater noise pollution is not what the average person would consider to be a environmental crisis. Unfortunately, it is.

The varied cacophony of an ocean soundscape demonstrates the encroachment of human activity into even the most remote ecosystems on the planet. Anthropogenic noise drowns out the natural sounds, harming marine life in its wake. From sonar that is loud enough to instantly kill marine animals to seismic surveys that lead to chronic stress, there’s no denying that underwater noise pollution is incredibly damaging. Existing in an environment where noise is amplified and often a more important sense than sight, underwater creatures are left defenseless against the noise pollution that causes them both immediate and chronic harm.

Currently, the shipping industry contributes the most to underwater noise pollution. As a result of globalization, shipping in international waters is increasing and is even expected to double by 2030 (Owens, 2019). This specific source of anthropogenic noise has a number of proposed solutions, but legislation must be put into place to ensure that solutions have the greatest effect.

2013 recording of a container ship in the Gulf of Mexico via Operation Toxic Gulf

Noise from ships is proven to heighten stress levels, which leads to harsh health consequences in marine life when prolonged (Robbins, 2019). As evident in a study of the effects of ship noise on marine mammals, certain mysticete species such as baleen whales use low frequency sounds that are extremely similar to those of large ships. While the study admits that the noise field of a ship depends on many factors such as the location of the noise on the ship, its frequency, and its direction, it also distinctly concludes that “watercraft noise radiates very well to great depth in the ocean” (Embling et al., 2019). In fewer words, even the creatures living at the remote depths of the ocean aren’t safe from the harmful effects of noise pollution.

Image by Ian Taylor via Unsplash

A ship’s main noise sources are cavitation, the engine, and hydrodynamic flow past the hull (Embling et al., 2019). Cavitation, the creation of vapor bubbles within the propellers, decreases a ship’s efficiency and increases its production of noise (Lubofsky, 2016). This can be minimized through the use of low-noise propulsion systems, as the larger and slower spinning propellers create fewer bubbles. Cavitation also increases proportionally to a ship’s increase in speed. Therefore, limiting vessel speeds will have a direct impact on diminishing noise production (Embling et al., 2019).

A Proposal to Place Speed Limits on Shipping Vessels

International governments must come together to enforce stricter shipping speed limits to address the problem of underwater noise pollution. This is because it causes extreme detriment to ocean ecosystems on which humans and the economy rely. Slowing down ships is a feasible and enforceable solution that has been proven to make a significant impact in the noise levels of the oceans. If taken into serious consideration by the United Nations, there is high potential for the imposition of shipping speed limits, despite there not being an official mandate yet (McGrath, 2019).

A 2012 paper by Seas at Risk, a conglomerate of environmental NGOs, outlines a plan to implement a global system for limiting ship speed. If supported by the IMO and MEPC, this plan could address the issue of ship speed on an international level. It’s proposed that each country would regulate the ships that carry their flag along with any ships entering their port. Most vessels are already required to carry (S-)AIS systems that monitor speed, so this solution would not require much additional technology (Faber et al., 2012).

Photo of UN Climate Emergency Meeting via un.org

Implementing an international shipping speed limit is a better option than other proposed solutions such as changing ship designs to isolate the engine from the hull (Lovro, 2019). Ship design is more difficult mandate and not nearly as cost effective as slowing down pre-existing ships. It would also take longer to have a noticeable effect on underwater noise levels. When comparing these two options, it’s clear that a shipping speed limit is the superior course of action.

While shipping speed limits are easy to implement, they unfortunately pose a question of economic feasibility for shipping companies. Seas at Risk also ran a cost benefit analysis for the proposed international shipping speed limit as it would apply to tankers, bulkers, general cargo vessels, and container vessels. While the speed limit would save costs on fuel, it would incur the extra costs of additional ships, engine modifications, higher inventory costs, monitoring costs, and safety considerations (Faber et al., 2012). Without a government mandate, shipping companies will not limit speed in favor of the environment if it means shrinking their margin of profit.

According to BBC News, a 20% speed decrease would lead to a 66% decrease in underwater noise (McGrath, 2019). With a direct link to curbing underwater noise, a shipping speed limit demonstrates the remarkable ability to save and improve the lives of marine animals. An accidental study in the Bay of Fundy after 9/11 showed that in just a single day of limited ship noise, whales had already displayed a decrease in stress hormones (Castellote et al., 2012). In the presence of a shipping speed limit, the effects would be just as miraculous. Now, it’s up to international leaders and the United Nations to enact this plan to ensure a quieter, peaceful ocean in future.

References

Embling, C., Erbe, C., Marley, S.A., Schoeman, R.P., Smith, J.N., & Trigg, L.E. (2019, October 11). The effects of ship noise on marine mammals- A review. Frontiers in Marine Science. https://doi.org/10.3389/fmars.2019.00606

Faber, J., Hon, G., Nelissen, D., Tsimplis, M., & Wang, H. (2012, February). Regulated slow steaming in maritime transport. CE Delft. https://seas-at-risk.org/images/pdf/RegulatedSlowSteamingSTUDY_1.pdf

Lovro, J. (2019, August 2). Confronting Underwater Noise Pollution. North American Marine Environmental Protection Association. https://namepa.net/2019/08/02/auto-draft/

Lubofsky, E. (2016, November 10). Commercial ships could be quieter, but they aren’t. Hakai Magazine. https://www.hakaimagazine.com/news/commercial-ships-could-be-quieter-they-arent/

McGrath, Matt. (2019, November 11). Climate change: Speed limits for ships can have ‘massive’ benefits. BBC News. https://www.bbc.com/news/science-environment-50348321

Owen, D. (2019, May) Is Noise Pollution the Next Big Public Health Crisis? The New Yorker. https://www.newyorker.com/magazine/2019/05/13/is-noise-pollution-the-next-big-publichealth-crisis

Robbins, J. (2019, January 22). Oceans are getting louder, posing potential threats to marine life. New York Times. https://www.nytimes.com/2019/01/22/science/oceans-whales-noise-offshore-drilling.html

Castellote, M., Corkeron, P. J., Hunt, K. E., Kraus, S. D., Rolland R. M., Nowacek, D. P., Parks S. E., & Wasser, S. K. (2012). Evidence that ship noise increases stress in right whales. Proc. R. Soc. B.2792363–2368 http://doi.org/10.1098/rspb.2011.24