Global commercial shipping is a crucial part the world’s transportation infrastructure – ships carry everything from high-tech electronic machinery to basic foodstuffs. Unfortunately, commercial shipping also accounts for more than 3 percent of all annual global emissions. According to a new report released today, global shipping also has another unseen effect – it alters the behaviour of the world’s whale population and affects them physically. A team from the New England Aquarium found that during the reduction in shipping traffic after 9/11, sound pollution also dropped – and for the first time they were able to study the effect of shipping noise on cetaceans.
For four years from July 2001, the team used trained dogs to find whale faecal matter floating on the surface of the water. Not many of you will know this, but whale poop contains hormone-related chemicals, called glucocorticoids, while mirror stress levels that could change from day to day, or even hour to hour. When the researchers noticed the drop in underwater noise levels after 9/11, they realized it would be an opportunity to investigate whether sound pollution was a cause of stress for right whales. The team discovered that changes in the concentration of the hormone matched perfectly the sudden drop and gradual renewal of maritime traffic in the area.
Dr Rosalind Rolland, who led the study, said of the findings: “To our knowledge, there were no other factors affecting the population that could explain this difference besides the decrease in ship traffic.” “We showed whales occupying oceans with high levels of ship noise have a chronic stress response. We knew whales changed the frequency of their calls to adapt to the ship noise, but this work shows it is not merely an annoyance – it is having a physical effect.”
The team discovered that ships’ propellers emit sound in the same frequency range that whales use for communicating. While previous studies have shown the whales change their calling patterns in noisy places, such as where the military conduct exercises and around oil and gas exploration sites, the results have been controversial. Some environmental groups have said the noise has the potential to kill the animals, but this has yet to be proven.
What is clear is that over the past 50 years, noise in the world’s oceans has increased in intensity and new vessels are being equipped with high-decibel sonar. The International Maritime Organization and the European Union are both investigating how to reduce marine noise, and the researchers hope that their report will aid this endeavors.
Via BBC News