Towering over Suzhou Creek in Shanghai’s Putuo District, hundreds of pedestals double as giant planters holding trees and shrubs that shoot up from artificial mountains. Visitors will soon be able to look up at this aerial forest, with trees embedded in the building’s supports, as they walk, shop, eat, and work below in the new development.
The 1000 Trees project from Heatherwick Studio combines greenery with integral pieces of the structure. Expanding natural spaces has become a priority in Shanghai, which ranks among the most densely populated cities in the world. This density has come at the cost of green space: In Shanghai’s city center, green spaces shrank from 30.9 square kilometers to just 2.6 between 1980 and 2005. Efforts have slowly reversed that trend, and greenery has increased downtown as part of a push to make Shanghai an “ecological city” replete with forests and greenways. This undertaking is due in part to the ecosystem services that urban forests, especially trees, provide.
“They produce a huge cover that can alter the environment in terms of temperatures, in terms of pollution, and in terms of water flows because they intercept water and evaporate water. They store carbon as they grow, which affects climate change,” said David Nowak, a senior scientist with the U.S. Department of Agriculture Forest Service. Urban forests also provide habitats for wildlife and promote well-being, providing mental health benefits for city residents.
However, if not selected and planted carefully, trees planted in a city can have drawbacks, like adding more pollen or sometimes trapping air pollutants beneath their canopy rather than removing them. But, Nowak said, “generally the benefits outweigh the negatives.”
Designing for Nature
In 2012, Heatherwick Studio, headquartered in London, was invited to design a development between Shanghai’s M50 art district and a park bordering Suzhou Creek for Tian An China Investments Company Limited. Studio founder Thomas Heatherwick’s designs are famous for weaving trees and plants into structures—like bridges and buildings—that have historically replaced nature rather than integrated it.
Trying to incorporate the artistic flair of the M50 and the riverine environment, the Heatherwick team designed a massive commercial development covered in deciduous and evergreen trees. Some of the trees were grown in advance for the project in Chongming, a Shanghai island district in the Yangtze River.
Likened to the Hanging Gardens of Babylon, the large building looks like it was carved from two mountains, covered in an organized display of trees. At the site’s western end, phase 1 of the project, a 60-meter-tall mountain, houses a shopping mall and connects to phase 2, a separate mountain that will likely include office space and restaurants, among other amenities. Phase 1 will tentatively be ready for the public toward the beginning of 2022, but phase 2 is still under construction.
The 1000 Trees project shows that development doesn’t have to exist in place of nature. Usually, “when you put buildings everywhere, it’s either vegetation or buildings. They’re exclusive,” said Nowak. “In this case, they’re designing the vegetation space not as an afterthought; they put it right into the design.”
Seeing the Forest Through the Trees
Qicheng Zhong, a senior engineer at Shanghai Academy of Landscape Architecture Science and Planning, monitors ecosystem services provided by Shanghai’s green areas. From his perspective, green buildings are helpful to promote nature. But 1000 Trees provides limited benefits to the urban environment. “They’re just little trees and shrubs, single trees, not an ecosystem,” said Zhong.
Green buildings have value, but experts like Zhong argue that sustainable cities need more than environmentally conscious construction. “We have to build or conserve more green areas, but we have to do that with wisdom,” he said. Supporting interconnected park, forest, and wetland systems throughout the city, for example, could advance Shanghai toward becoming a more sustainable, resilient city in a cost-effective way. Unlike structures that are built over natural landscapes, a network of natural areas in the city can provide vital ecosystem services such as absorbing excess rainwater through soil and supplying migration corridors for wildlife.
As a development, 1000 Trees has a lot of impervious surfaces and won’t provide a flood buffer that wetlands or even parks could provide. But according to a Tian An representative who asked not to be identified, they’re conscious of these concerns, and their development preserves 90% of riverside trees and continuity with a greenway near Suzhou Creek.
The 1000 Trees development also introduces unique challenges to engineers and architects. For example, trees need to be securely anchored to planters dozens of meters above the ground. Those planters restrict tree roots, limiting their growth, though the Tian An representative specified that this limitation keeps the trees at a safe, manageable height. Urban forestry experts suggested that tree replacement could present problems, as securing new trees high above the ground could be costly. According to the representative from Tian An, however, the trees have been planted for 3 years with minimal maintenance required, and they don’t anticipate replacing any for at least 5 years.
But urban forestry encompasses more than the natural environment, and Zhong said that 1000 Trees could provide a convenient place for people to socialize in nature within city limits. The representative from Tian An said 1000 Trees could be a better alternative to a conventional development project. “We created a new green area in that space. That area has more possibility to be a green community, a creative community.”
—Jackie Rocheleau (@JackieRocheleau), Science Writer