Earth has gone quieter in lockdown. And that's a good thing, say scientists

Researchers have been delving into the positive effects social distancing measures are having on pollution levels and wildlife worldwide

03 May 2020 - 00:02 By Sanet Oberholzer
A lonely gull in the Cape Town CBD.
A lonely gull in the Cape Town CBD.
Image: Ruvan Boshoff

It wasn't long after much of the world entered lockdown to deal with the spread of the coronavirus that news articles reported that dolphins and swans were returning to the canals of Venice. We read, too, about elephants that wandered into a village in China, got drunk on corn wine and passed out happily.

At least there was some good coming from the pandemic strengthening its grip on the world, we told ourselves. Then National Geographic burst our bubbles: the dolphins, the drunk elephants - none of it was real.

But despite the fake animal stories that have circulated around Covid-19, Earth has, in fact, responded to the pandemic in a positive way. As people have retreated into their homes, the planet has grown quieter.

Thomas Lecocq, a seismologist at the Royal Observatory of Belgium, compared seismic data from the day before Belgium began a nationwide lockdown on March 18 with data on the morning after the lockdown commenced. 

Posting to its Twitter account on March 20, the observatory reported a drop in ground movements due to human activity, chalking this up to the containment measures implemented by the government. Lockdown has made it easier to listen to the Earth.

"We're used to seeing changes in seismic noise when human activity changes (for example when it snows, when there are major strikes or during school holidays) so I was expecting it," Lecocq wrote in an e-mail.

"The idea of sharing it was meant to serve as motivation for the people to understand it's a common, shared thing - we're all in this together."

In sharing his findings, he sparked interest amongst seismologists across the world. Researchers in the US, France and New Zealand similarly reported on the effects that nationwide lockdowns and social distancing measures were having on seismic activity.

Dr Paula Koelemeijer, a global seismologist at Royal Holloway, University of London, has
been keeping track of seismic readings in London. According to Koelemeijer, the instruments she's been looking at continue to show lower levels of activity when compared to the last few weeks before London entered into lockdown on March 23.

The quiet provided by the lessening of anthropogenic noise - noise from human activity - provides seismologists with a unique opportunity
Dr Paula Koelemeijer, seismologist

In residential areas in London, she's picked up 20% less activity due to a reduction in the usual hum of public life - trains, buses, people pounding the pavement: a slowing down of our lives.

Koelemeijer says the quiet provided by the lessening of anthropogenic noise - noise from human activity - provides seismologists with a unique opportunity.

 "Recording smaller events potentially allows us to better characterise local natural seismicity in normally noisy environments, while picking up clearer signals for events further away may be used in imaging studies of subsurface structures," she says.

Professor Raymond Durrheim, who holds the South African research chair in exploration, earthquake and mining seismology at Wits University, says he is aware of the phenomenon that's been observed in other countries and while no urgent special analysis related to the Covid-19 lockdown has been performed locally, it has been suggested.

He says he would be surprised if the same decrease in seismic activity was not picked up locally. "Our broadband seismometers are incredibly sensitive. For example, the level of seismic noise in Joburg is affected by the ocean waves crashing against the coastline."

Seismologists usually obtain most of their information following disasters, and in that respect the Covid-19 pandemic is no different. Says Koelemeijer: "Earthquakes are our major source of information, but are often destructive and come at considerable human cost. We never wish for the events, but feel it is nevertheless the right thing to do to make the most of the data created by these events. This situation is essentially the same."

Lecocq says he believes that the latest readings are positive for humans. "This also shows the effect of the reduction of pollution in general," he says.

The reduced traffic volumes in cities, a significant decrease in air travel globally and lower combustion by industry means a reduction of the greenhouse gas emissions that cause global warming.

Coinciding with lockdown and social distancing measures put in place in countries across the world, satellites detected a decrease in the amount of nitrogen dioxide, a harmful gas emitted by power plants, industrial activity and cars.

Nasa in the US and the European Space Agency (Esa) detected significant decreases in nitrogen dioxide in China between January 1 and February 25, first appearing in Wuhan, the original epicentre of the coronavirus pandemic, and later spreading across the entire country.

A deserted Muizenberg Beach in Cape Town.
A deserted Muizenberg Beach in Cape Town.
Image: Ruvan Boshoff.

According to data on the Esa website, scientists from the Royal Netherlands Meteorological Institute also noted a drop in nitrogen dioxide concentrations in several big European cities, including Rome, Madrid and Paris during March.

Professor Paida Mhangara, head of the Geography, Archaeology and Environmental Studies School at Wits, says it's also expected that the temperatures in urban areas will reduce with lockdowns in place.

"The combination of anthropogenic heat and air pollution impacts on the urban microclimate through a phenomenon known as the urban heat island effect, where temperatures in cities tend to be more elevated relative to the neighbouring non-urban areas," he explains.

The urban heat island effect can have detrimental health effects, such as contributing to respiratory disease.

"The lockdowns imposed due to Covid-19 have a positive effect on human health due to cleaner air and lowered urban temperatures. The control measures also impacted positively on [climate] change because there's a reduction in greenhouse gas emissions."

An unintended, but welcome, consequence of Covid-19 has been a smaller collective carbon footprint. This is a tiny win for Mother Nature - for now. The hope that humans have been clinging to of returning to normality will also mean these small gains won't mean much in the larger scheme of fighting global warming.

But innovative use of internet technologies like Zoom and virtual private networks have enabled many people to work and attend meetings from home. As Mhangara says, "It's also proved that humanity can still reverse the upward trends of global warming and work remotely from home."

Despite the centuries of damage that humans have been inflicting on it, Earth has responded positively to the lack of industrious human activity in a matter of days. The coronavirus pandemic has shown us that we can be kinder to the planet - we only need the motivation.

LESS NOISE IS GOOD NEWS FOR WILDLIFE

City dwellers might now be hearing sounds that can get muffled by the usual drone of traffic, construction and industry. According to the World Health Organisation, noise pollution affects more than 100-million people across Europe.

In Western Europe alone, road traffic accounts for premature deaths equivalent to the loss of roughly "1.6-million healthy years of life". Take the disturbance to human health out of the equation, and noise remains a big source of pollution for the other inhabitants of the planet as well. But how much have animals and insects in countries on lockdown really benefited from the drop in noise levels?

BIRDS

The most visible animals found in cities and the most vocal are the biggest beneficiaries of quieter streets and parks. The signals birds send each other through song are a means of survival. Without the ability to sing, hear and be heard, birds have a difficult time finding a mate or defending their territory from predators.

Birds sing louder when they have to compete with noise pollution, which puts a strain on their bodies. The current period of quiet could mean birds might be singing more softly than usual, which would already be of huge benefit to them.

AQUATIC LIFE

According to a study published in the journal Biology Letters, noise pollution affects creatures from frogs, shrimps and fish to mammals, mussels and snakes.

It's known that a reduction in shipping traffic seems to make whales calmer

Bioacoustics expert Christopher Clark says the noise from oil and gas activity, for example, is filling entire ocean basins with "one big storm of noise". It's known that a reduction in shipping traffic seems to make whales calmer.

With cruises suspended, oil freighter traffic impacted by an oil price crash and rig activity run by skeleton crews to curb the spread of Covid-19, marine biologists believe they'll find a wealth of recorded sound data once they're allowed to go back into the field. - dw.com

WE'LL HEAR EARTHQUAKES COMING TOO

The heightened stillness during self-quarantine could allow seismologists to detect faint or distant earthquakes they previously might have missed.

Natural Resources Canada and University of Victoria earthquake seismologist John Cassidy says in some cases the seismographs are now able to record tiny tremors with a negative magnitude.

"Very tiny earthquakes can tell you something about future volcanic eruptions, as the magma is moving deep in the Earth, as we saw at Mount St Helens about 40 years ago," says Cassidy.

He says the increased sensitivity could also open the door to new research projects, as scientists observe phenomena they've missed in the past because of background noise. - globalnews.ca