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Exploring of the Changing Roles of Landscape Design in Nature-based Solutions: A Reflection on Professional Practice over the Last Two Decades

(UK) Lee Parks, LIAO Jingjing

1 Introduction

1.1 Nature-based Solutions

Cities are facing an increasing frequency of disruptive events and many sustainable development challenges, such as climate change,biodiversity loss, drought, extreme heat, wildfires,and water ecological security. Our cities need more pioneering approaches to greening to meet sustainability and carbon neutral goals, address biodiversity loss whilst also benefiting people’s health and well-being.

Following the 2008 World Bank report, the concept of Nature-based Solutions (NbS) has attracted much attention in dealing with the interrelated crises of climate change and biodiversity loss[1]. NbS reconsiders the relationship between humans and nature. It is a change in attitude towards nature from resource utilization to functional thinking. It is a revolution in the field of nature protection and city resilience[2]. NbS compliments China’s Ecological Civilization Construction①. In terms of core concepts and governance methods, it emphasizes the use of ecosystem services provided by nature and effectively responds to complex challenges by protecting, repairing, managing, or the building new ecosystems. This also helps comply with increasing expectations of governments and the private sector to meet environmental, social and governance(ESG)②outcomes for the public, for investors and shareholders.

Landscape Architects are uniquely positioned to bring about positive systemic change, and support advocacy for the reversal of biodiversity loss and protection and the restoration of habitats,ecological corridors and ecosystems. This article is a reflection of professional practice over the last two decades and illustrated NbS at different scales with three clear stages transitioning from single-purpose solutions to systematic thinking and holistic design,together with a change from experiential decision making to quantified solutions. The authors then question if NbS alone will be enough to tackle the inter-related crisis of climate change and biodiversity loss without significant contribution from individual life style changes together with political changes.

1.2 Learning from Nature

Lee Parks journey in NbS practices began in the Highlands of Scotland. Mountains, lochs (lakes),forests, streams, rivers, and rugged coastlines were scenes of everyday working life for local government. Additionally, public sector work included social and civil infrastructure such as roads and bridge projects, public realm improvements for pedestrian oriented streets, design of schools and senior living healthcare facilities (Fig. 1).

In the late 1990s The Scottish Office③published Landscape Design and Management Policy to encourage sustainable development for roads, bridges, and traffic in the countryside. The publicationCost Effective Landscape: Learning from Natureencouraged environmentally progressive attitudes and aimed to harness the efficiency, power, and beauty of nature with considerations for value for money, aesthetics, and biodiversity[3]. It inspired professional humility, to understand ecological processes and to appreciate that landscapes which are relatively self-sustaining,requiring minimal long-term intervention, can only be developed if the design works with nature rather than fights against it. The publication was mainly aimed at landscape designers working on infrastructure projects but also applied to any landscape task; large or small scale; urban or rural and whether planning, design or management.

In 2001 Lee Parks moved to China. Passionate to explore the relationship between humans and nature, his two decades of work have been driven by the goal of learning from nature, bolstered, and inspired by some notable international precedents which opened the door to convincing clients that nature-based solutions could be delivered with significantly positive impacts. These inspiring projects included:

1) Shanghai Houtan Park created for the 2010 Expo by Turenscape[4]. The project successfully demonstrated a regenerative living system to treat polluted river water, mitigate urban flooding,and increase habitat and biodiversity, while celebrating the regional culture and beautifying the riverfront for public use. The project was an important precedent to support the advocacy of Nature-based Solutions in cities and gained incredible exposure during the 2010 Expo. It was an innovative demonstration of ecological water treatment, reclamation and re-use of materials and native planting[5].

2) The 2012 London Olympic Park (Queen Elizabeth Olympic Park) Meadow designed by Professors James Hitchmough and Nigel Dunnett from the University of Sheffield and garden designer Sarah Price. The plantings created high impact balanced perennial communities, with extensive meadows to demonstrate a whole new approach to the design and management of public landscapes.Placing ecology with sustainability at the forefront,the plantings combined strong aesthetic to create drama and excitement during the Olympic Games.Research on the planting style confirmed colour as having the greatest impact on the visitor’s emotional response to a garden. Public perceptions of naturalistic planting concluded that, in the context of the UK, increasing public exposure to naturalistic meadow-style planting and its pollinator benefits may be the factor to increase acceptability of naturalistic urban planting schemes[6].

3) The planting design for the High Line in New York by Piet Oudolf inspired by the selfseeded landscape that grew wild for 25 years after the trains stopped running. The design aesthetic reflects natural cycles of life and death and evokes feelings of being in a wild space. The project outcome has strongly advocated sustainable practices to operations and maintenance, including integrated pest management, composting on-site,and pollinator-friendly practices by leaving displays of dried leaves, stalks, and seedheads standing through the winter, providing both beauty for visitors and habitat for birds and other animals.

The article explains a learning process from nature and how inspired knowledge and experiences have supported application of landscape design at different scales and in three main subject phases:1) greening grey infrastructure, 2) incorporating naturalistic landscape into the public realm, 3) a nature positive future.

2 Phase 1: Greening Grey Infrastructure

2.1 Ning-Hang Expressway Landscape Design

As a young landscape architect moving to China in 2001 in the middle of an era of a massive boom in transport infrastructure and urbanization,the scale and magnitude of change was awe inspiring. However, the environmental, landscape and visual impacts of roads traversing the agricultural and natural landscape were a significant concern. Significant background understanding in the publicationCost Effective Landscape:Learning from Naturebecame a valuable source of inspiration to advance ecological landscape along the Ning-Hang Expressway.

The project extended some 115 km through Jiangsu Province countryside including twelve intersections, toll plazas, tunnels, and three service areas. Inspired by natural vegetation patterns and landscape character, recommendations included:1) reclaiming natural stone from mountain cuts as materials for local walling or culvert details, utilizing boulders as landscape features; 2) advocating ecological green slopes using hydroseeding with seeds of local provenance, wide scale application of bioswales to treat road run-off and stormwater retention ponds to hold stormwater and provide habitat (Fig. 2); 3) the protection of forest groves and planting of native fruit trees at community connections where village roads passed under the new expressway intended to create social benefits to villages from free windfalls from persimmon and plum trees; 4) wildflower grasslands and wetlands were created at intersections to enhance the scenic,rural character and for self-sustaining planting to reduce maintenance and provide a wider range of habitat.

The expressway opened in 2004 and was hailed as a new era for the Jiangsu Provincial Expressway network to include ecological,environmental, tourism and landscape design strategies to enhance the sustainability of their road networks[7].

Despite strong advocacy and relative success of environmental strategies for transport related infrastructure, the focus of local leaders was largely on single-purpose solutions of mitigating highway engineering structures and drainage. Reduced costs and greener solutions to slope treatments, highway drainage and stormwater management were key highlights from a political standpoint but were not yet enabling the landscape architect to apply holistic solutions.

Native forest regeneration was promoted through designed matrices and guidelines④for creating new native woodlands using young trees. However the immediate impact of “ready landscapes” were of greater concern to local leaders. Additionally, methods of working drawings and the skills of workers employed to undertake landscape construction were not prepared to implement more complex ecological planting techniques in the use of young trees or the management/maintenance required. The result was a higher cost and less long-term ecological result.

3 Phase 2: Incorporating Naturalistic Landscape into the Public Realm

3.1 NbS for City Green Infrastructure

Qufu, a county-level city in Jining, Shandong Province, is the birthplace of Confucius and Mencius,the great Chinese sages of the Spring and Autumn period. Around 2010, impressions of Jining were of a coal-based economy needing a transformation of city image. When considering a transformation towards an ecological future, an article published in 2001 by renowned Confucian scholar, Tu Weiming,a professor at Harvard University and Peking University called Ecological Turn inThe New Confucian Humanism: Implications for China and the World[8], inspired a landscape concept called the ‘Ecological Turn’. This concept by Lee Parks promoted an ecological image for a new streetscape,canal and lake for the southward expansion of Taibai Lake District. It also provided an opportunity to put Nature-based Solutions into practice in Jining.

Taibai Lake District landscape design development covers some 350 hectares where AECOM led the planning and design of a new lake and park, new canal parkland, streetscape and administration center. The project challenged formal urban streetscape planting in favor of naturalistic swathes of ornamental grasses and perennial communities. A proposed land use plan placed a large new commercial complex over a planned canal and was challenged by the landscape architect, who subsequently shifted the development parcel 200 m northwards, realigned roads, adjusted the land use plan and restored the integrity of the planned green and blue infrastructure. Nature-based Solutions were employed to create vegetated canal embankments provide purification of water and ensure habitat creation through to the new lake (Fig. 3).

To the south of a new government building a major road was sunken to protect the integrity of new civic parkland, putting people, place and nature first. A planned bridge that would have cut the lake in half was recommended to be canceled to safeguard the integrity of the lake and park.Extensive new forest, wetlands, lotus ponds and meadows were planted to enhance wildlife habitat.

3.2 NbS for Flood Resilience

Following the successful implementation of a wide range of natural habitats in Jining, a tidal riverside regeneration to the Yong River Park, Ningbo, offered a chance to retain riparian wetlands, restore floodplains to wet meadows and implement storm water management strategies within a new community park. As the park levels were predominantly below a flood protection levee,the site was graded to balance cut and fill and consequently retain, harvest and filter storm water run-off regimes. Reevaluating rainwater as a visible design element in the park could contribute to public education about the water cycle. The project repurposed existing docks and created barrier-free connections over wetlands to enjoy river and sunset views, an experience called the Platform Walkway.

NbS were advocated to restore the floodplain functions and to encourage reed wetland as a protective buffer with richly planted wet meadows including spring bulbs, perennials, and grasses to inland areas with less frequent flooding. The preservation of reed wetland to the frontline of tidal mudflats safeguards habitat for mud skippers(Periophthalmus cantonensis) and crabs as well as providing a buffer to tidal storm surges in the typhoon-prone eastern coastal city. Wildflower meadows achieved higher diversity of plant species and create an attractive transition between urban park and riverside (Fig. 4). The project won merit awards for urban design in the 2015 AIA Hong Kong Awards and an Outstanding Award in the public open space category at the 2017 IFLA Asia Pacific Awards[9].

3.3 NbS for Forest Restoration and Wildlife Corridors

As air quality in China came under increasing scrutiny for unacceptable levels of pollutants, an Air Pollution Prevention and Control Action Plan released in 2013 increased efforts in governance,haze control, carbon reduction and energy restructuring[10]. For landscape architects, the worsening air quality gave weight to advocacy for urban afforestation to improve the quality of the ecological environment in conjunction with other measures to improve atmospheric pollution.Binjiang Forest Park Phase II in Pudong New Area,Shanghai, aimed to increase urban forest in the city whilst expanding forest networks, ecological corridors and access to open space.

Inspired by trees that become entwined and eventually grow together as one such as the 400-Year-Old Lianli Tree Beijing Forbidden City[11], the park was designed to bind ecological connections between phase I and phase II using wildlife passages, wetlands, forest, and grassland.Extensive areas of wet forest were planted and trees that shape culture, food and climate mitigation were planted to create regenerative forest belts and groves, with over 54,000 new trees.

During site investigations, a 100-year-old tree was observed in the path of a newly planned road. The road was rerouted by the landscape architect and elevated to enable an eco-passage for wildlife, most notably the Chinese Water Deer[12].The expansion of urban forest will support the fight against air pollution, sequestering carbon and increasing habitat coverage and migratory corridors for wildlife. Additionally, a new lake was created by diverting, cleansing, and improving water quality through constructed wetlands using nature as a living system to purify the water. This was inspired by the achievements of Houtan Park and the increasing advocacy for Sponge Cities by Kongjian Yu (Fig. 5, 6).

4 Phase 3: Towards a Nature Positive Future

4.1 COP26 Advocacy

Prior to the 15th meeting of the Conference of the Parties to theConvention on Biological Diversity(CBD COP15) held in 2021, leading scientists put forward a conceptual shift which puts forward Nature (the environment) as the context for all life, human society, and all human activities (including all economic activity)[13].Equally at COP26, the 2021 United Nations Climate Change Conference, British monarch his royal highness, the Prince of Wales who has for over fifty years championed action for a sustainable future said:“After billions of years of evolution, nature is our best teacher, in this regard, restoring natural capital,accelerating Nature-based Solutions and leveraging the circular bio-economy will be vital to our efforts.”[14]

Putting nature at the core is the key to a nature positive world, or one in which the dominant importance of nature to humanity is recognized and human actions are governed accordingly[13](Fig. 7). China’s embrace of eco-civilization as a national development objective is aligned with this conceptual shift, recognizing that humans are completely dependent on a healthy planet for our survival, which in turn depends on a functioning living biosphere. As Urban development is still predominantly driven by urban planners aiming to balance the competing interests of economic,social and environmental development goals,landscape architects need to rise to the forefront of the process, to prioritize nature (the environment)as the context for forms of physical, social and economic development.

4.2 Will NbS Be Enough?

Will NbS alone be enough to tackle the interrelated crisis of climate change and biodiversity loss? It is important to recognize that individual behavioral choices can collectively have a significant effect on our planet’s future health. In addition to reducing consumption, reducing waste and bending the curve on fossil fuel dependence and excessive growth, one of the biggest potential shifts we can make is through our diets. Brent Loken, Global Lead Food Scientist at the World Wildlife Fund(WWF) proposes a global shift to diets that contain a larger proportion of plant-based foods relative to animal-source foods to release enough agricultural land to sequester 5 Gt to 10 Gt of CO2-equivalent per year if this land was restored to native vegetation[15].

We cannot feed the world without agriculture yet where and how we produce food is one of the biggest human-caused threats to biodiversity and our ecosystems. This makes the transformation of our global food system more important than ever, particularly considering urbanization and land development pressures to the countryside. We all need to make the connection between what we eat or consume and the impact the global food system has on our planet[16]. This should also include the positive application of urban food production as part of urban landscape plans.

4.3 Nature Positive World

In a proposal by leading world scientists entitledA Nature-Positive World:The Global Goal for Nature, three measurable temporal objectives are put forward: zero net loss of nature from 2020,net positive by 2030, and full recovery by 2050[17].When combined with development and climate goals the emphasis on nature is to create an integrated overarching direction for global agreements of an equitable, nature positive, carbon-neutral world.

4.4 A Systematic Nature Positive Practice

Jiangxin Island in Nanjing, now referred to as Singapore Nanjing Eco Hi-tech Island (SNEI) is a township development project jointly supported by Jiangsu ＆ Nanjing Government as well as Singapore Ministry of Trade and Industry[18]. To transition from experiential/qualitative decision making to quantified solutions, the creation of a new scenic waterfront belt on the island’s Yangtze River embankment offered a chance to apply NbS using systematic thinking and holistic design. The brief was to create a 12 km long (210 hectare)ecologically restorative park providing scenic attraction for the increasingly urban island community. Using the concept of ‘Sustainable Footprints’, ecological goals and data driven targets were established to minimize water footprint(water used for landscape irrigation), carbon footprint (embodied carbon in landscape structures and materials) and ecological footprint (impact on the environment) whilst creating a base for healthy lifestyles, jogging tracks and even possible marathons races, cycling events and retaining traces of the island’s “cultural footprint” (such as agricultural and industrial heritage)[19](Fig. 8).

Inspired and spurred by the success of the 2012 London Olympic Park Meadow and iconic projects like the Highline in New York with planting design by Piet Oudolf. The project found ways to introduce dynamic and colourful planting and a water conservation sponge solution[20].

The project subsequently brought together Nature-based Solutions for resilience to flooding and naturalistic plantings to enhance a wilder aesthetic rather than succumb to an urban landscape approach. Complex forest restoration techniques for succession planning, riverbank wildflower grassland mixes and native forest understory planting were implemented. Dead wood, stone boulders, fruit and nut producing plants all add richness to the planting, establishing habitats diverse with insects, amphibians, reptiles,birds and small mammals.

Sponge city demonstration bioswales and flood attenuation ponds all come together to create a diverse opportunity for wildlife, biodiversity,habitat enhancement and creation. Traces of industrial memory were retained through the reuse of concrete, gravel, and weathering steel for park features, whilst reducing carbon footprint had these materials been disposed to off-site landfill (Tab. 1).

After the construction, according to a survey conducted by the China Bird Watching Record Center, Jiangxin Island (Singapore Nanjing Eco Hitech Island) has attracted 19 species of wild birds from 16 families. In addition to common forest birds and waterbirds such as magpies and egrets, it also includes migratory forest birds such as spotted thrush and black capuchin, as well as migratory waterbirds such as common cormorants and green shanks, which have become important indicators of this ecological stepping-stone in the East Asian-Australian bird migration route.

The popularity of Singapore Nanjing Eco Hi-tech Island was boosted by the introduction of Pink Muhly Grass (Muhlenbergia capillaris),which is known for its pink to purple clumpforming inflorescences. However tourists flocked to the island in droves during the peak National holiday week in 2017, trampling the grasses and requiring security guards to protect the area. This led to adjustments to the planting layout for future years. Opening-up paths between inflorescences to make the fields more accessible to large numbers was essential to limit further damage. Across China, similar projects have experienced damage by hordes of tourists posing for selfies, triggering outrage on social media. This raised awareness of the need for greater efforts in educating the public on protection of plants and nature and to strive for greater use of native species in the hope to increase acceptance of less exotic and more indigenous naturalistic landscapes.

The project not only aims to leave “sustainable footprints” but also aims to restore ecological systems, food chains and biodiversity. It has won multiple international awards for Wildlife,Biodiversity, Habitat Enhancement or Creation at 2018 IFLA and was a finalist at the Landscape Institute Awards 2021[21].

The efforts to quantify solutions and demonstrate performance against ecological goals and data driven targets enabled the project to secure a Sustainable Future Award for Urban Design from the American Institute of Architects(AIA) International Region in 2020. Demonstrating performance outcomes against the AIA Committee on the Environment (COTE) rigorous criteria for social, economic, and ecological value[22].

4.5 Embracing Nature in Our homes, Our Workplace, and Communities

Making behavioral changes as individuals can start in our homes, workplace or communities.Balcony gardens, green roofs, community gardens,greening in kindergarten and schools, or creating natural areas in pocket parks all add value to embrace nature in our cities. Community driven grassroots initiatives help close the gap between top-down policies like Sponge City implementation with public acceptance when implemented at a community level. At the Knowledge Innovation Community (KIC) in Yangpu District, Shanghai,international companies like AECOM have led roof garden initiatives to engage employees,increase biodiversity and mitigate increasingly intense rainfall events by slowing run-off from the roof[23]. Green roofs also insulate buildings,reducing heat in summer and loss of heat in winter.The use of a diverse range of plants increases passing visits from insects and birds. The roof supports employee health and well-being through access to nature in the workplace. The roof garden is used as a research base for plant trials which assess performance in full sun exposure, full shade,wind exposure and exposure to drought (largely due to limited maintenance). Reviewing resilience to the harsh conditions of roof top environment enables our horticulturalists to monitor species that would be able to perform in similar microclimatic conditions and with similar maintenance regimes in Shanghai and nearby cities (Fig. 9).

4.6 City Resilience and Popular Science in the City

A large-scale exploration of city resilience is taking place to one of Shanghai’s largest wedge greens at Zhangjiabang. Following a multi-international award-winning analysis and planning stage in 2015, clear quantifiable goals were established to guide the downstream implementation of the master plan[24].

Implementing the design across multiple phases, the leading landscape architectural team applied systematic thinking and holistic design solutions working in close collaboration with ecologists, water specialists, local engineers and consulting specialist advisors such as The Nature Conservancy[25]. Decision-making was driven to establish ecological habitat to provide a base for monitoring performance and enable future surveys to quantify outcomes. As part of an extensive area of constructed wetlands, flood alleviation lakes will support city resilience to increasingly intense storm events whilst found also to have established habitat to support over 22 species of birds identified by the IUCN Red List of Threatened Species[26]. A nature education center for popular science and bird hides for bird watching enthusiasts will provide a base for educating school groups and official visitors.This all helps to advance the planning objective and improve the understanding of local people and public officials to embrace a new large-scale ecological park in the urban core area of Shanghai.

Public education in caring and respecting the landscape of parks and open spaces is important,there needs to be greater opportunities for local people, schools, and tourists to engage in environmental learning to connect people with the natural environment.

With wetlands, meadows, an agricultural themed island and forest, the project aims to create an ecological park that provides open space and protected areas with diverse and inclusive opportunities for public access and experiencing nature to improve health and well-being (Fig. 10).

When complete the Green Wedge will cover a total area of more than 600 hectares. This is twice the size of Central Park in New York. NbS is applied to increase flood alleviation for Pudong New Area, forest buffers for air quality and thermal comfort and provide extensive areas of emergent wetland habitat and open water across the site.Phase I and phase II are approaching completion and have established nature protection wetlands with protected islands for bird habitat. Bird hides located in wetlands for nature enthusiasts will provide opportunities to watch and learn from nature in the city. The park frames view corridors to Lujiazui, the financial heart of Shanghai dynamically reminding of being in the city, despite being in a very naturalistic park (Fig. 11). It will also include a popular science ‘Discovery Center’ for school education tours.

As the park evolves, an ideal goal would be to establish a framework to measure performance together with the client to demonstrate outcomes scientifically to enhance quantification of the project’s environmental, economic and social benefits. This can be seen from the excellent example, that brings us back to the Highlands of Scotland, where learning from nature has become a Natural Capital Laboratory (NCL)[27].

4.7 NbS for a Natural Capitals Accounting Framework

With many Nature-based Solutions,quantifying the impacts is an increasing priority as scientists and economists try to put a monetary value on natural capital or how much nature is worth. Being able to put a price on ecosystem services is how we can make sure nature – or rather, natural capital – is given due weight at the decision-making table in the same way the global carbon market is being discussed.

Accounting for environmental, social, and economic impacts is an increasing priority for many organisations and is a key future measurement factor. The Natural Capital Laboratory, set up in 2019 by AECOM and the Lifescape Project, is a unique project to do just this: a live environment for identifying, quantifying, and valuing the impacts of rewilding[28](Fig. 12).

Alongside restoration of the site, the living laboratory aims to: 1) Test innovative new approaches for capturing data on social and environmental change such as drones, AI and remote sensing technologies. 2) Develop a ‘capitals accounting framework’ that records, quantities and values the environmental and social changes on the site. 3) Create engaging ways of communicating the findings and the benefits of rewilding such as virtual reality and digital platforms which provide an important public educational transmission.

It is an interesting project to learn from,and annual reports of progress will be available online for everyone to learn from this timely and innovative investigation[29].

5 Conclusion

Through a career dedicated to the pursuit of working with nature, the article explores the evolution of a landscape planning and design approach from single-purpose solutions to systematic thinking and holistic design, together with a change from experiential/qualitative decision making to quantified solutions.

Nature-based Solutions need to be embedded in every aspect of our lives. A nature positive future is a necessary complement to our carbon neutrality goals and is the prerequisite for equitable sustainable development, a robust economic recovery, and the health of the planet, people and all other species.

The three explored phases of NbS: 1) greening grey infrastructure, 2) incorporating naturalistic landscape into the public realm, 3) advocacy for a nature positive future.

For greening grey infrastructure, Naturebased Solutions can protect against erosion,manage stormwater, reduce impacts of noise and pollution[30]. By restoring forestry, wetlands, coastal and riparian habitats, we can address air and water quality, increase carbon sinks and provide habitat for wildlife.

By increasing nature inside urban public open space, we can reduce urban heat islands, enhance human well-being and health, manage stormwater and increase biodiversity. Additionally, accounting for environmental, social, and economic impacts is an increasing priority for many organisations to quantify and demonstrate the benefits of NbS.

Finally, NbS alone will need additional understanding of the inter-related crisis of climate change and biodiversity loss impacted by human pressure on the biosphere. COP26 outcomes left many frustrated that the world may quickly return to business as usual: The time to act at a grassroots and individual level is now. This is a pivotal moment for landscape architects to rise to the challenge, to make our voices powerful and to make an ever bigger impact on the environmental,social and governance of landscapes in our cities and to deliver a thriving future for people, nature and the planet. We must go beyond Nature-based Solutions by advocating a nature positive future through our work as landscape professionals and as individuals.

Notes:

① Ecological Civilization Construction is an critical part of the socialist cause with Chinese characteristics. It emphasizes the concept of ecological civilization that respects nature, conforms to nature and protects nature to achieve sustainable development.

② ESG (environmental, social and governance) is an investment philosophy and evaluation standard that focuses on corporate environmental, social and governance performance rather than financial performance.

③ The Scottish Office was a department of the United Kingdom Government from 1885 until 1999, exercising a wide range of government functions in relation to Scotland under the control of the Secretary of State for Scotland.

④ Matrix planting is a form of self-sustaining gardening with mixed plants, and a modular planting unit that can be replicated.

Sources of Figures and Table:

Fig.1-6, 11?Lee Parks; Fig. 7?E. Asselin, source from Reference[13], redraw by the authors; Fig. 8?Zoom Arch; Fig. 9?Chen Liang, Lee Parks; Fig. 10?AECOM;Fig. 12?Chris Coupland; Tab. 1?Lee Parks, Liao Jingjing and Jiang Xin.

(Editor / LIU Yufei)