• Early on in the coronavirus pandemic, around one-third of the world was under lockdown.

• Air traffic was down, fewer cars were on the road, and factories were closed; this meant that air pollution drastically decreased in many parts of the world.

• Milan, Italy, which has historically struggled with smog, is even thinking about ways to reduce air pollution post-pandemic by introducing a plan to reduce car use.           

• As humans hunkered down indoors early on in the pandemic, the natural world positively thrived. Wild animals roamed empty streets, and nature reclaimed urban areas.

In some places, air pollution noticeably reduced during lockdown: pollution levels in China were down an estimated 25% in February.

This makes sense given that a third of the world's population was under lockdown in March, and 96% of global destinations had introduced travel restrictions by April.

According to CNN, the TSA reported a 96% drop in air travel in April, while Allstate CEO Thomas Wilson told CNBC in April that driving was down between 35% to 50% in the US, depending on the state.

While the environment may have convalesced during these early lockdowns, experts didn't expect it to last. The short-term effects were pretty striking, however, as these before-and-after pictures show.

BEFORE: The BBC reported that Milan was named Europe's most polluted city in 2008, but that smog is still a problem today.

Source: BBC

AFTER: Once traffic dropped during lockdown, so did air pollution. In response, Milan is thinking about introducing a plan to reduce car use after the pandemic to avoid a rebound, according to The Guardian.

Source: The Guardian

BEFORE: Venice, Italy's, high-traffic waterways were generally murky.

AFTER: In March, photos emerged of the canals looking so clear that you could see to their bottom. However, the city's mayor told CNN that this was due to "less traffic on the canals, allowing the sediment to stay at the bottom."

Source: CNN

BEFORE: According to The New York Times, India was home to 14 of the 20 cities with the most hazardous air in 2019.

Source: The New York Times

AFTER: Delhi hasn't seen air this clear for decades. "I look at the sky quite often and enjoy its blueness from my balcony," a retired English professor told The New York Times in April.

Source: The New York Times

BEFORE: In 2019, CNN cited "dangerous levels of pollution" in New Delhi, describing India's capital as "shrouded" in "a toxic, throat-searing cloud of brown smog."

Source: CNN

AFTER: According to Reuters, New Delhi experienced "the longest spell of clean air on record" back in April.

Source: Reuters

BEFORE: When India imposed its first lockdown in late March, it encompassed 1.3 billion people, making it the world's largest lockdown, according to CNN.

Source: CNN

AFTER: According to the Washington Post, air pollution in New Delhi dropped by almost 60% within just a few days of the beginning of the lockdown.

Source: The Washington Post

BEFORE: New Delhi's air is so polluted it can be seen from space, according to USA Today.

Source: USA Today

AFTER: In April, CNN reported much lower levels of both noxious microscopic particulate (PM 2.5) and of nitrogen dioxide. In New Delhi, the PM 2.5 went down by 71% in a single week of lockdown.

Source: CNN

BEFORE: Air quality in New Delhi was so bad that a public health emergency was declared in November 2019, CNN reported.

Source: CNN

AFTER: Just one week into lockdown, NASA saw India's air pollution drop to a 20-year low.

Source: NASA

BEFORE: According to the World Economic Forum, air pollution alone kills 1.25 million people in India annually.

Source: World Economic Forum

AFTER: The Washington Post reported that India's "long-running battle with pollution may have rendered it particularly vulnerable to the novel coronavirus," citing Harvard research.

Source: The Washington Post

BEFORE: According to a previous Insider report, some parts of India saw the Himalayas for the first time in decades.

Source: Insider

AFTER: The Dhauladhar range is clearly visible during lockdown in Dharmsala.

Similarly, the snow-covered Pir Panjal mountain range was visible from a residential area in Jammu, India, in early May.

BEFORE: Jakarta's air pollution was so bad that The Guardian reported that a group of local activists decided to sue the Indonesian government to take action in 2019.

Source: The Guardian

AFTER: According to the Jakarta Post, the Jakarta Environment Agency reported improved air quality after social restrictions were put in place in late March.

Source: The Jakarta Post

BEFORE: Some days, Jakarta ranks as the world's smoggiest city, according to ABC.

Source: ABC

AFTER: Previously, blue skies in Jakarta were a sign of many of the city's residents leaving for the Eid al-Fitr holidays in June, ABC reports.

Source: ABC

BEFORE: A local publication reported that Islamabad's already poor air quality is worsening due to an increase in the number of cars, as well as steel mills.

Source: Dawn

AFTER: Thanks to a lockdown-induced decrease in traffic, visibility has improved.

BEFORE: Los Angeles is notorious for two things: smog and traffic.

AFTER: LA saw the most consecutive good air days in March than it has since at least 1995, according to CNN. However, whether this is lockdown related or due to factors such as recent storms is unclear, per Getty.

Sources: Business Insider, Getty