Letters

Greening Beijing's rooftops

Some experts have opposed Beijing's green roof project, for which the government has allocated millions of yuan a year. They argue that the cost of greening rooftops in Beijing outweighs the benefits, but there are enough reasons to believe that it's worth the effort.

Air pollution is Beijing's worst environmental problem, with smog posing a threat to people's health. According to Tan Tianying, president of Beijing Roof Garden Association, if all the rooftops in Beijing were covered with vegetation, they would absorb carbon dioxide at the rate of 4,835 tons a day, minimizing the concentration of PM2.5 in the air. PM2.5 refers to particulate matter with a diameter of 2.5 micrometer or less, which can enter the human respiratory system and cause health problems.