Shanghai has vowed to make a huge effort to expand its per capita green coverage in the next five years. And to achieve that goal, the city is looking up.  

Workers planted various flowering trees on the roof of a five-story office building in Jing’an District. In one month, people working in the building and residents living nearby will be able to enjoy the cherry and peach blossoms, as well as various shrubs and even some vegetables. 

One engineer said other rooftop gardens will be planted on dozens of buildings across the city. Preparation work started almost one year ago and he said the most difficult part is coordinating with building property managers. 

“We have to deal with air conditioner tubes and all kinds of circuits. It took a long time to negotiate with the property managers. They worry about the pressure on the roof and whether it will cause water leaks,” said Li Xiangmao, Senior Engineer of Shanghai Planting Direction Station.

“So we invited third-party construction companies to calculate the weight limit of the roof and install water proofing materials.”

The city plans to build 400,000 square meters of rooftop gardens this year. The project also includes plants that flourish growing on exterior walls and on pillars under elevated highways. The goal is to add 2 million square meters of greenery, equal to 14 People’s Squares, by the end of 2020.

“We have three main goals with rooftop gardens. First is to increase the green space that we can see in the central city because there’s very little land to plant trees now. Second is to save energy in the summer,” said Li. 

“Buildings remain cooler when plants cover exterior walls or the roof, which means less air conditioning will be needed. Third is to absorb more rainfall, preventing it from clogging up older drainage networks. Rooftop gardens also reduce dust and increase humidity.”

Rooftop gardens first appeared in the city in the 1980s. Landscape and meteorological authorities released a report that said rooftop gardens can reduce power consumption by 6 million kilowatt hours, prevent 920,000 tons of rainfall from entering the sewer system and absorb 170 tons of air pollutants annually. 

One environmental protection and ecological planning expert said that although rooftop gardens aren't as good as green spaces on the ground, they definitely help.

“If they are designed well, the ecological effect is equal to 30 to 80 percent of the effect of ground planting of the same size. Rooftop gardens reduce 40 to 50 percent less oxysulfide and nitrogen oxide of green spaces on the ground of the same size,” said Prof. Wang Xiangrong, Chairman of Dept. of Environmental Sciences & Engineering, Fudan University.

Wang says there is an average of 2 square meters of green space per person in the city, far lower than the national average of 13 square meters. Because of limited space downtown, rooftop gardens will play a big role in boosting the city’s per capita green coverage. 

Wang suggests the city encourage more office buildings and companies to build rooftop gardens. He also suggests the government offer tax deductions or subsidies for those who build rooftop gardens.