The harmful effects of overfishing and deep-sea trawling have been extensively documented, but another huge, and less well-known, threat to marine life is noise pollution. Man-made sonar emanations disorientate cetaceans, sea turtles, and fish to such an extent that they end up being driven out of their natural habitats, or even suffering shoal collapse.
According to Ocean Care – whose new campaign, “Silent Oceans,” is hoping to draw attention to this insidious problem – levels of human-generated noise have increased at a staggering rate over the last sixty years, doubling every decade. They list the main causes of oceanic noise pollution as:
- Explosives: Explosives are detonated in the ocean on a regular basis by military forces, scientists, and the oil and gas industries. The sound of these explosions travel by large distances across the ocean bed.
- Airguns: Seismic airguns are used for oil and gas exploration purposes, and the sound reverberations they give off can penetrate thousands of meters into the ocean before heading deep into the earth’s crust. Because easily extractable oil and gas resources are quickly being depleted, this harmful practice is spreading to increasingly more sensitive marine habitats in a desperate bid to find more oil.
- Military Sonar: Military forces use low- and mid-frequency sonar in the ocean to detect objects such as hostile submarines. These sonar frequencies, which can reach up to 230 decibels, emit pulses of sound for over 100 seconds at a time, for hours on end.
- Shipping Traffic: Over 90 percent of the global transportation of goods involves commercial shipping vessels. Ocean Care says that these vessels “are generating an ever-present and constantly rising acoustic ‘fog’ that masks natural sounds and is the most common source of ocean noise along with seismic airguns.”
To date, Ocean Care has been undertaking a variety of political actions to reduce ocean noise, and are proposing for an internationally accepted ocean noise threshold to be implemented.