Little is known about noise pollution in oceans because it is impalpable and invisible. And yet, its effects are felt by marine animals. Noise is far louder underwater than in air; it is a threat to marine fauna and alters the balance of natural ecosystems
In the 1950s, Jacques Cousteau described the marine environment as the “world of silence”. Nowadays, scientists use the term “aquatic underwater jungle” meaning that marine environments are now extremely noisy places. Since the beginning of the 20th century, noise generated by human activity in oceans has been continually increasing. It now poses a particularly harmful threat to marine fauna.
Oceans bombarded with anthropogenic noise
Noise is generated by ships, military sonar equipment, various construction works, oil exploration, wind and water turbines, and so on: sound travels five times faster underwater than in air and noise pollution travels very long distances.
According to researcher Nicola Jones from the Overseas Development Institute, shipping adds three decibels of noise to oceans every 10 years. She says that this equates to “a doubling of noise intensity in oceans.” And it’s not just large vessels that are the problem. The Noise and Biodiversity report by the BruitParif observatory highlighted that the oil and gas industry, whose geophysical engineering projects and off-shore extraction sites produce deafening levels of noise, must also be taken into account. Powerful sonar equipment is also used in the military sector and industrial fishing. Lastly, the installation and operation of tidal turbines adds to this cacophony of noise, with devastating effects on biodiversity.
Noise in the sea affects animals and ecosystems’ ability to survive
Many species of fish and marine mammals are highly sensitive to sound and depend on it for orientation, food, detecting predators and communication. Consequently, a number of scientific studies have reported behavioral changes linked to anthropogenic underwater noise; the masking effect of humanmade noise, changes in reproduction, birthing, feeding or resting behaviors, and disruption to diving habits, can all result in the stranding and death of certain marine mammals.
Noise pollution also has an impact on animal health, preventing their metabolism from functioning properly. For example, underwater noise pollution can cause chronic stress. A study conducted for the first time in the aftermath of the attacks on September 11, 2001, demonstrated that there is a direct correlation between a decrease in large commercial ship traffic and a dramatic reduction in stress hormone levels in Atlantic right whales.
Noise can also cause hearing loss, as the International Fund for Animal Welfare (IFAW), OceanCare and the Natural Resources Defense Council (NRDC) have warned: “If animals are in proximity to the seismic source, it can even cause hearing loss and irreversible hearing damage.” In some invertebrates, it can also lead to malnutrition and stunted growth.
Furthermore, scientists have reported that seismic air guns, used in the oil industry, can destroy entire swathes of zooplankton. Anthropogenic noise thus alters the fundamental building blocks of life in aquatic ecosystems. As a result, it also has a negative impact on the balance of human life, particularly as fishing in these noisy areas is largely futile.
The essential need for silence: a concept still in its infancy
Since 2005, the United Nations has recognized underwater noise from human activities as a source of marine pollution and a threat to marine ecosystems. However, there have been few studies on underwater noise pollution by biologists and ecologists because it is so difficult to assess.
This lack of scientific data is compounded by governance issues related to the special status of international waters. In fact, there are no clear regulations, conventions or legislation to regulate noise pollution in oceans. There is a legislative silence in this area that governments and civil society are attempting to overcome through effective initiatives, which are unfortunately still few and far between.
For example, in the Pelagos sanctuary, a maritime area covered by an agreement between Italy, Monaco and France, a consultative process has been set up to monitor construction projects at sea. As for associations, a team of scientists from the Oceans Initiative is currently searching oceans for acoustic sanctuaries. In France, the Quiet-Oceans company has launched its mission to “develop ocean use in harmony with nature.” For its part, the International Maritime Organization has established the International Convention for the Prevention of Pollution from Ships (MARPOL). In turn, such initiatives help encourage governments and private companies to break the code of silence on the dangers associated with noise pollution.