As social distancing has been practiced across the nation, many cities are showing decreased air pollution. The Environmental Protection Agency explains, “NO2 forms from emissions from cars, trucks and buses, power plants, and off-road equipment.”
In China, the world’s largest carbon emitter, experts estimate that emissions over the past month have been about 25% lower than normal. The New York Times reported "huge declines in pollution over major metropolitan areas, including Los Angeles, Seattle, New York, Chicago and Atlanta." Social media users have described dolphin and swan sightings as evidence of decreased human impact during the viral pandemic. One man’s viral tweet showed a video of a dolphin swimming along an embankment.