This is Scientific American 60-Second Earth. I'm David Biello. Your minute begins now.
It's Lunar New Year, the "year of the horse."
Of course, horse is not how millions of Chinese are currently traveling, as they return home from the growing cities where they are trying to better their lives.
Within the last five years, China has built a network of high-speed rail that covers most of the main routes between cities.
But that's not how most Chinese people are getting home, it's too expensive.
Cheaper, slower, dirtier trains are more popular, but don't go everywhere people want to be.
No, buses carry the bulk of the travelers back home and will return them to the cities when the holiday season ends.
But buses are not the only vehicle plying the ever more crowded roads.
With increased wealth has come a growing love affair with the car.
China is now home to 120 million private cars, up from just 15 million at the turn of the century.
That's bad news for air quality.
As one city environmental official told me when I recently visited, no matter how much he curbs pollution from industry, smog continues to suffocate because of more and more cars.
Should China eventually approach the number of cars per capita in the U.S., they'd see more than a billion vehicles on their roads.
The smog may stop them from seeing much else.
Your minute is up, for Scientific American 60-Second Earth. I'm David Biello.