Ocean Noise

Most marine animals, especially mammals and fish, depend on sound to communicate with each other. Many have poor eyesight and use sound as their primary method of navigation, hunting prey or avoiding predators, and finding a mate. Sound travels much further under water than through the air, and some marine creatures can communicate over hundreds or even thousands of kilometres. Over the past hundred years, human activity on and beneath the sea has increased dramatically and this is generating ever greater amounts of noise that interfere with marine communications. This is resulting in the death of many animals and putting significant pressure on many ecosystems.

Man made noise in the ocean comes from several sources. First there are the ships, often powered by loud engines. These engines and other shipboard activity can cause the hull to vibrate, sending strong sound waves out in all directions. Military activity, especially sonar, can also have a large impact. Our insatiable need for oil has led us to actively search for new sources under the sea. This oil exploration often involves the use of seismic surveys, which can be very disruptive to marine communication. Undersea construction, of oil rigs for example, also has an effect.

The problem is not any individual source of noise but the cumulative effect of all man made noise sources. Scientific studies have confirmed that some creatures respond to this with longer and louder songs, while others may simply not be able to compensate and their communications are essentially cut off. Unfortunately as some species communicate louder, this may drown out or mask the communication of other species, making the problem worse. It's like being in a packed room, with music blasting, where everyone keeps talking louder and louder to be heard.

One of the impacts of this noise is a reduced ability to navigate. Many scientists have identified noise pollution, and sonar specifically, as one of the causes for increasing incidence of marine mammals becoming stranded or beached. In some cases, physical damage to the ears of beached whales has been documented. Of course, difficulty in navigation doesn't lead only to beaching. Animals can become separated from a group and are sometimes no longer able to successfully reach seasonal feeding or mating grounds. Obviously this problem means that more members of a species could die, and less are able to reproduce.

Many species also depend on sound to hunt for food, or to avoid being eaten themselves. Some predator species have poor eyesight, but can detect the slightest vibrations in the water to home in on their prey. Loud external sources of noise can disrupt the effectiveness of this hunting method. Deeper in the ocean there is complete darkness, so eyesight is completely useless here, and sound becomes even more important. However, water conducts sound very well, so even at great depths, species are still impacted by human noise.

From 1950 to 1975 alone, ambient noise in the ocean increased by a factor of ten. The growth of human population and the expansion of economic and industrial activity since 1975 suggest that this has likely continued to increase at a significant rate. Ocean noise pollution is a serious problem by itself, but unfortunately our oceans are suffering from many other environmental problems. This includes growing dead zones, pollution, overfishing, and ocean acidification. The combined effect is devastating. While species might survive one stressor, a whole host of threats will often overwhelm them.

With the threat of global warming, we already know that we need to reduce our use of fossil fuels. We cannot afford to burn all the oil we have already discovered, yet we continue to search for more. This means we should restrict any future oil exploration beneath the sea. That would help to reduce the noise pollution. We can also put pressure on the world's militaries to reduce the use of low-frequency sonar, which is especially harmful. Many activists are already working towards this end, and there are also pending lawsuits.

As we reduce our use of fossil fuels, either voluntarily in order to reduce carbon emissions, or because of the impact of peak oil, this should also lead to a reduction in powered shipping. Attempts to reduce overfishing, and especially trawling, will also help with this reduction. These changes can help to reduce ocean noise as well as helping the environment in other ways. It is possible that ship travel could become more common in a sustainable future, but this might involve a greater use of sail rather than loud engines, and this would also be beneficial.

There seems to be almost no end to the way in which humans are often blindly destroying the environment. Ocean noise pollution is just another example. There's no easy fix here, but as with many other environmental problems, we know what needs to be done. We must dramatically reduce our consumption and our exploitation of the natural world. We must leave fossil fuels in the ground, and use much less energy than we do today. We must live simpler, less material and more sustainable lives. That's not the end of the world, but the alternative is.