With so many cities in lockdown during the coronavirus pandemic, the world has become a quieter place. There are fewer people on the streets, fewer cars on the roads and less activity everywhere. In some places, animals are flourishing as they tentatively explore a calmer planet.
This silence extends to the oceans.
Normally, oceans are noisy. There's the din of cargo shipping and energy exploration in the oceans, while lakes endure the constant sounds of recreational boating. Loud above the surface, these noises also permeate underwater, disturbing the environment for the animals that live there. Many of these animals use sound to dodge predators, find mates and locate prey, so when their underwater world is noisy, they can't communicate or hear as well, and it becomes more difficult to navigate.
But with so much activity halted in and on the water, the oceans have experienced a drop in noise pollution.
Silence is golden
Researchers looked at real-time sound signals from underwater seabed observatories near the port of Vancouver. They found a notable drop in the low-frequency sounds associated with ships, reports The Guardian.
David Barclay, assistant professor of oceanography at Dalhousie University in Nova Scotia, noted a measurable drop in the 100 Hz range — both at an inland site and a site farther off shore. It averaged 1.5 decibels, or about a 25% drop in power.
"A lot of the larger whales use sound in this range," Barclay told The Narwhal. Baleen whales like humpbacks and grey whales are sensitive to low-frequency sounds because that's what they use to navigate and communicate.
Barclay and his team have submitted their findings in a paper that is currently under review. He calls this reduction in ocean traffic "a giant human experiment," as researchers are working to figure out the impact quiet has on marine life.
"We get this window, we get a snapshot into life without humans. And then when we come rushing back, that window will close," Cornell University marine acoustician Michelle Fournet tells The Narwhal. "It's really an important time to listen."
Learning from another quiet time
This isn't the first time researchers have studied the magnitude of a starkly quiet world and its impact on whales.
On the morning after Sept. 11, 2001, researchers from Woods Hole Oceanographic Institution in Falmouth, Massachusetts, set out to collect data on the behavior of North Atlantic right whales as they had done many times in the past. But this time, people and goods had stopped moving overnight and the world had become eerily still after the terrorist attacks.
The researchers were able to study the whales in a quiet ocean. They published their findings in a study that concluded ship noise was associated with stress in right whales.
"That paper is pretty beautiful evidence that industrial noise does have a stress impact on marine animals," Barclay says.
Now, nearly two decades later, scientists are listening again to a quiet underwater world. They're learning how silence helps marine life better communicate and navigate their habitat.
But they also question what will happen when things return to some semblance of normal.
"One of the critical questions we're facing, environmentally, is what kind of world we go back to once this catastrophe has passed," Michael Jasny, a marine mammal expert at the U.S. Natural Resources Defense Council, tells the Narwhal. "Do we rebuild the economy along the same, unsustainable and destructive lines as we have previously, or do we take the opportunity to build a greener economy and a more sustainable world?"