Advancing Urban Sustainability in China and the United States: Proceedings of a Workshop (2020)

Copyright National Academy of Sciences. All rights reserved.

Both the United States and China are experiencing major urban challenges due to rapid population growth and other factors. For instance, in the United States, the urban proportion of the population has grown to over 80 percent in the last decade. Demographers forecast that it is expected to reach about 89 percent by 2050. During this same period, China will experience even more dramatic urbanization: Its urban population will increase from about 50 percent to about 78 percent. This growth is taking place as cities face growing challenges in multiple fronts, including, among other things, climate change, water and energy shortages, pollution, and aging infrastructure. As the growth of Chinese and U.S. cities continue to accelerate, it is important for the scientific community to support research that will further collective understanding of the interconnections between the natural and built environments and how they interact with society.

On December 16, 2019, the National Academies of Sciences, Engineering, and Medicine’s Science and Technology for Sustainability program, in collaboration with the Chinese Academy of Sciences, convened a one-day public workshop on urban sustainability in China and the United States. The workshop focused on the intersection of urban climate change mitigation and adaptation, urban health, and sustainable transportation, including green infrastructure and urban flooding in both countries.

The second panel of the workshop focused on urban design and landscape architecture as critical components for urban sustainability. The use of nature-based solutions; microclimate regulation for connecting science, policy, and design; and efforts to maximize human well-being through urban design in both countries were discussed.

NATURE-BASED SOLUTIONS AND PERFORMANCE

According to Kongjian Yu, professor of urban and regional planning and landscape architecture at Peking University, nature-based solutions will be critical to addressing urban sustainability challenges (see Box 4-1). Most cities in China are facing multiple environmental and ecological challenges including floods and urban inundation, drought, groundwater reductions, water pollution, habitat loss, and air pollution, and single-goal minded, industrial technology-based gray infrastructure is not sufficient to solve these interconnected problems. Dr. Yu noted that looking to ancient wisdom

as a source of nature-based and holistic solutions can inform decisions about how to address urban challenges and secure ecosystems services.

BOX 4-1

Three Key Challenges in Practicing Nature-Based Solutions for Urban Systems Dr. Kongjian Yu described three key challenges in practicing naturebased solutions for urban systems, including:

(1) Planning challenges—Space and land are limited and it is critical to consider how to identify and plan the most efficient ecological infrastructure to produce ecosystems services. Identifying ecological security patterns across scales based on analysis of ecological processes can help to address this.

(2) Design and engineering challenges—Nature-based solutions and ancient wisdom might not be efficient nor standardized for modern engineering. We need to conduct research on design and engineering to strengthen performance and standardize them for modern practices.

(3) Policy challenges—Policy changes, including changes to values and education around urban issues, are needed. Such changes require rethinking of the way to build cities based on industrial technologies and calls for nature-based solutions.

Over a period of 20 years, Dr. Yu reported having tested and built over 500 projects in 200 cities in China that have integrated nature-based solutions to address key urban challenges at various scales. For example, Dr. Yu described work at Yongning River Park in Zhejiang in 2003, which demonstrated an ecological approach to flood control and stormwater management while offering space for public enjoyment (Figure 4-1).

Dr. Yu described another example in Yanweizhou Park in Jinhua City, Zhejiang Province, using natural mechanisms to clean contaminated water that introduced an ecological embankment to reduce peak flow. This initiative, if implemented comprehensively throughout the drainage, can result in reducing the flow by more than half at the basin's outlet, making the city more water resilient.

FIGURE 4-1 Use of a resilient ecological embankment to replace the former concrete flood control infrastructure, Yongning River, Taizhou, Zhejiang.

SOURCE: Kongjian Yu, Presentation, National Academies of Sciences, Engineering, and Medicine, December 16, 2019, Washington, DC.

As a solution for water management challenges, Dr. Yu described a demonstration project of a “sponge city”[1] in Sanya, Hainan Province, that addresses urban inundations and floods through a constructed wetland inspired by the ancient wisdom of pond-dyke practice in the middle of the city. The project was designed to retain and filtrate stormwater, which solved multiple urban water issues in a symbiotic way.

In another project for Houtan Park in Shanghai, Dr. Yu demonstrated a strengthened nature-based water cleansing process that can clean contaminated river water to nonpotable clean water through a constructed wetland park, suggesting one hectare of this kind of wetland can produce 800 tons of nonpotable water. This nature-based water cleansing design has been replicated in many cities in China, such as Haikou’s Meishe River (Figure 4-2). Dr. Yu added that today more than ever, a paradigm shift in the planning and design of cities is needed to adapt to the changing climate and to address a multitude of urban ecological issues. Such a shift calls for rethinking the way cities are built, moving toward nature-based solutions. Moving forward, Dr. Yu posed the following questions for informing future research on nature-based solutions to urban sustainability challenges:

• How can we change our mindset (and policy) to move toward nature-based systems?

• How can we fully assess the performance of nature-based solutions?

• How can we standardize nature-based solutions for climate change adaptation and ecological restoration and scale them to meet larger economic and policy needs?

FIGURE 4-2 Constructed wetlands to cleanse contaminated water, Haikou Meishe River, Hainan, China.

SOURCE: Kongjian Yu, Presentation, National Academies of Sciences, Engineering, and Medicine, December 16, 2019, Washington, DC.

[1] For additional information related to the sponge city concept, see Yu, K. 2017. Green infrastructure through the revival of ancient wisdom. Bulletin of the American Academy of Arts & Sciences:35–39.

Yanweizhou Park in Jinhua City, Zhejiang Province