Is Pollution Clearing While We're Staying Home?

Although quarantine challenges us all, the reduction in human activity has meant good things for nature and our environment. Can we sustain that progress?

Sabrina Stierwalt, PhD
4-minute read
Episode #369
empty city street
The Quick And Dirty
  • Air pollution and coal use are down across China and Italy due to quarantine restrictions related to COVID-19.
  • Water pollution will take much longer to clear up. 

In this time of self-quarantine, exponential viral spread, and so much uncertainty, we could all use some positive news. With a large fraction of the population staying in their homes and only venturing out for essential items, many businesses shuttered, and only the most essential of us still commuting and traveling, how has nature responded?

Just in my little corner of the world, my car sits almost entirely quiet, unheard of for a resident of Los Angeles, and with the absence of all the hustle and bustle, my coyote neighbors have gotten more brazen with their visits. Let’s look at what this slow-down has meant around the world.

Air pollution is clearing up drastically 

NASA posted 2 maps of the mean tropospheric density of nitrous oxide (or NO2) over China and Hong Kong from their Earth Observatory program. Nitrous oxide is a particularly nasty greenhouse gas. It’s produced via the combustion of fossil fuels and emitted during agricultural and industrial activities. It’s not as abundant as CO2 in the atmosphere, but it lasts a lot longer and so its contribution is on the rise. NO2 also works to deplete the ozone layer, even more reason we don’t want it in the atmosphere.

The first map, dated January 1-20, 2020, shows the amount of NO2 gas observed in the troposphere (a layer of the Earth’s atmosphere) before widespread quarantine orders were enacted in Wuhan and other large cities in China. The second map, dated February 10-25, 2020 shows the same region after quarantine orders were in place. The polluting gas has been reduced by as much as 30 percent. 

Such a clear and persistent reduction [in nitrous oxide emissions] is likely due to the decreased traffic and industrial activity.

The gap in time between the two maps marks the days around the Chinese Lunar New Year celebrations when pollution levels normally decrease as factories and businesses close for the holiday. But pollution levels usually rebound by mid February as seen in maps from last year. That rebound didn’t happen this year, very likely due to the quarantine. 

Coal use is also down in China, dropping by as much as 36 percent in the month since the Lunar New Year celebrations. With demand reduced and many mining operations in the US shut down in efforts to slow the spread of the virus, the US Coal mining industry has asked the federal government for a bailout. 

The European Space Agency also noted a drastic decrease in nitrous oxide emissions over Italy in the January, February, and March through their climate monitoring program. They note that while variations in cloud cover can influence the results, such a clear and persistent reduction is likely due to the decreased traffic and industrial activity. 

Polluted waters will take longer to rebound

Not all the viral stories about nature reclaiming the planet have been true. Some photos claimed dolphins and swans had returned to the Venetian canals, normally completely overrun by human traffic. But the dolphins were actually in Sardinia, hundreds of miles away, and the photos of the swans were really taken in the less crowded nearby Burano where they are not that unusual of a sight.  

The water in the canals is likely clearer now than residents have ever seen it, but that’s not because the waters are less polluted.

The water in the canals is likely clearer now than residents have ever seen it, but that’s not because the waters are less polluted. With nonessential businesses closed and tourism cut off, there is no longer a constant stream of boat traffic stirring up sediment from the bottom and clouding the waters. Sadly, it would take a lot longer than a few weeks to de-pollute the waters where humans have left their mark. For example, take a look at Lake Fulda in southern Minnesota. It took an expensive, consistent effort over 22 years to return the lake to its pre-polluted state. 

When we start to have a better handle on the spread of coronavirus and the pandemic subsides—and it will subside—no doubt there will be a rush and an eagerness to restart the economy. Without a move toward cleaner energy overall, these air pollution gains will be short-lived. We may even see a bounce back to even worse polluting behavior. After the global financial crisis in 2008, carbon emissions increased by 5 percent when stimulus spending went heavily into fossil fuel driven industries. The Environmental Protection Agency in the US, meant to be a watchdog for the environment, has already suspended all enforcement of environmental laws during the coronavirus outbreak, giving polluters free license to pollute. 

Take a moment to step outside, breathe the fresher air, and enjoy the clearer than usual view. And when we return to a less quarantined society, let’s try to remember these gains and continue moving forward.

So for now, take a moment when you can to step outside, breathe the fresher air, and enjoy the clearer than usual view. And when we return to a less quarantined society, let’s try to remember these gains and continue moving forward. I hope everyone is safe, healthy, and staying home whenever possible. 

About the Author

Sabrina Stierwalt, PhD

Dr Sabrina Stierwalt earned a Ph.D. in Astronomy & Astrophysics from Cornell University and is now a Professor of Physics at Occidental College.

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