The land became wilder and cleaner again, people stayed at home

As people around the world stay in their homes to stop the spread of the new coronavirus, the air has cleared, albeit temporarily.

Smog has stopped suffocating New Delhi, one of the most polluted cities in the world, and in India citizens can "see again" landmarks that have not been visible for decades.

Nitrogen dioxide pollution in the northeastern United States has been reduced by 30 percent. Rome's air pollution level from mid-March to mid-April was reduced by 49 percent compared to the previous year.

The stars appear more visible.

People also notice animals in places where they wouldn't normally be seen. Coyotes have started showing up along Michigan Avenue in Chicago and near the Golden Gate Bridge in San Francisco.

Even earlier, a cougar roamed the streets of Santiago, Chile.

Goats have "taken over" a town in Wales.

In India, the already daring wild animals have become bolder as hungry monkeys are now entering homes and opening refrigerators to look for food.

Simply put, when people stay home, the Earth becomes cleaner and wilder.

"It gives us a pretty clear picture of how much of a mess humans are making on our beautiful planet," Duke University scientist Stuart Pym told the AP.

"This gives us an opportunity to clearly see how much better it can be," said Chris Field, director of the Stanford Wood Institute for the Environment, which has assembled scientists to assess the ecological changes that occur while people are in isolation.

The scientists, most of whom are confined to their own homes, tell the AP they are eager to investigate unexpected changes in weeds, insects, noise and pollution.

The Italian government is working on an ocean expedition to investigate sea changes due to the lack of people.

"In many ways we've hammered the Earth system and now we're seeing what the Earth's response is," Field says.

Researchers are tracking dramatic declines in traditional air pollution, such as nitrogen dioxide, smog and fine particulate matter.

These types of pollution kill up to seven million people a year around the world, Dan Greenbaum, president of the Health Effects Institute, told AP.

The air from Boston to Washington is the cleanest since a NASA satellite began measuring nitrogen dioxide in 2005, says NASA atmospheric scientist Barry Leffer.

This pollution is mainly caused by the burning of fossil fuels for a short time, so the air is quickly cleaned.

Compared to the previous five years, air pollution in March is 46 percent lower in Paris, 35 percent in Bengaluru (India), 38 percent in Sydney, 29 percent in Los Angeles, 26 percent in Rio de Janeiro and 9 percent in Durban (South Africa), according to NASA data.

"We're getting a glimpse of what can happen if we start switching to clean cars," says Lefer.

Cleaner air is most prevalent in India and China.

Since April 2, residents of Jalandhar, a city in the Indian state of Punjab, have been enjoying a view not seen for decades: the snow-capped peaks of the Himalayas more than 160 miles away.

Cleaner air means stronger lungs for asthmatics, especially children, says Dr. Mari Prunicki, director of air pollution and health research at Stanford University School of Medicine.

Aerosols that trap heat and cause climate change remain in the atmosphere for 100 years or more, so the coronavirus pandemic is unlikely to affect global warming, says Zeke Hausfater of the Breakthrough Institute for Climate Studies.

Carbon dioxide levels are still rising, but not as fast as last year. Aerosol pollution, which does not stay long in the air, is also declining.

But aerosols are cooling the planet, so NASA climate scientist Gavin Schmidt is investigating whether their drop in levels might be warming local temperatures for now.

Field says he's most intrigued by the increased urban presence of coyotes, cougars and other wild animals that are becoming a fixture of social media and the media.

Herds like wild boars have been seen outside a mall in Arizona.

Even the New York birds seem "hungrier and bolder."

In Adelaide, Australia, police shared footage of a kangaroo hopping around a largely empty downtown, and a pack of jackals took over a city park in Tel Aviv, Israel.

We are not under attack. Wild animals have always been there, but many animals are shy, Pim says.

They come out when people stay in their houses. For sea turtles around the world, humans have made nesting on sandy beaches difficult.