There are numerous threats to marine biodiversity that many of us are aware of - climate change, overfishing and habitat degradation are just some of them. But very few of us know that something as seemingly harmless as noise can also have devastating effects on sea life.
Although sound is not the first thing that comes to our minds when we think of the marine environment, it is in fact crucial for the survival of most marine animals, such as whales, fish and invertebrates. Sound helps them to navigate, find food and avoid predators. It is also essential for communication in order to attract mates, announce location and territory, to establish dominance and maintain social interaction. Flooding these creatures’ world with intense noise interferes with these activities and results in serious consequences.
Noise that people produce as a result of various activities at sea is responsible for a growing number of deaths and serious damage to underwater biodiversity. Unfortunately, this threat has been increasing at an alarming rate: in some areas, noise levels have doubled every decade for the past 60 years.
“Over 90 % of world trade is transported by ship, which creates an ever-present and rising aural ‘fog’”, says Kristina Gjerde, IUCN's High Seas Policy Advisor . “This ‘fog’ masks crucial natural sounds and it is the most pervasive source of underwater noise today”.
Other sources of underwater noise include explosives, oceanographic experiments, underwater construction, military exercises, air guns used for oil, and gas exploration, as well as oil drilling and shipping activities.
For creatures that depend on their sense of sound to survive this is a severe threat and its consequences are alarming. The noise deafens animals and interferes with their communication. For instance, the blue whale once communicated with others of its species across entire oceans. Today, the distance over which these whales can hear each other has been reduced by around nine-tenths, because of increased noise levels. Underwater noise causes whales to move away from their feeding and breeding grounds and it masks the sounds necessary for animals to avoid ships and fishing gear.
As a result, a growing number of whales and dolphins has been found stranded on the shore, which is believed to be directly connected with underwater noise. In 2000, two minke whales, 15 beaked whales and one spotted dolphin were stranded in the Bahamas due to noise pollution caused by a US navy exercise, and in 2005, 34 pilot whales, one minke whale and two dwarf sperm whales died in a similar incident in North Carolina. These examples are only indicators of a much larger problem, as many whales and dolphins which become stranded go undiscovered.
IUCN has been stressing the gravity of the problem for many years now, recognizing underwater noise as a form of pollution and calling on governments to properly assess its impacts on marine biodiversity and to avoid further powerful noise production underwater. Other organizations, such as the European Union and the United Nations, have also called for underwater noise to be regulated at an international level.
“Underwater noise is a form of pollution that knows no boundaries,“ says Kristina Gjerde. “Nations must therefore act together to protect marine living resources and ecosystems from its damaging effects. They should gather scientific information on underwater noise and its impacts on marine biodiversity and agree on appropriate management proposals”.
For more information, please contact Kristina Gjerde, IUCN's High Seas Policy Advisor.