*1.3. The Case Study: Suzhou's Shift in City Planning and Manufacturing*

Suzhou is a prefecture-level city in the Yangtze River Delta region and has greatly developed since the reform and the establishment of the Suzhou Wuzhong Economic Development Zone in 1993 [53]. In fact, in 1990, its gross domestic product (GDP) was RMB 20.214 billion (USD 4.23 billion), and in 2019 it skyrocketed to RMB 1.92 trillion (USD 290 billion) with a registered foreign capital of RMB 646 billion (USD 99.9 billion) and per capita GDP of USD 25,900, ranking third in China. In 1990, the population of permanent residents in the metro area was 1,067,000; in 2019, it was 7,070,000 [54].

Suzhou is a production hub in the Yangtze River Delta area and China's third-largest manufacturing city [53]. In the future, it will keep attracting new inhabitants if it remains competitive. With this goal, the local government is promoting the re-branding of its manufacturing, a shift to creative and innovative productions according to the policy of the central government [8]. To realize this shift, Suzhou needs to attract the ones who can support this digital empowerment: talents and high-level professionals with their families [55]. In fact, according to the report *Chinese Cities of Opportunity 2021*, by the China Development Research Foundation, Suzhou is in a good position for technical maturity but not for intellectual capital and innovation. The city established some policies to attract talent and train graduates in 2020 [56]. Together with these high-skill jobs, the city will attract lower-income workers such as babysitters, cooks, cleaners, carpenters, and health and well-being workers: every high-skill job produces at least five jobs in other sectors [57,58]. These newcomers must find a long-term accommodation that fits their expectations in the city.

In compliance with the national guidelines for supporting sustainability, the recent Master Plan for Suzhou 2020–2035 promotes the preservation of natural resources and stops massive urbanization. This master plan does not establish the future threshold of population growth; this is because in the past development proved that each planned threshold of the total number of inhabitants was underestimated [59].

#### *1.4. Sustainability Versus Growth: A Potential Contradiction in the Development Goals*

In a city becoming wealthier such as Suzhou, if the limits to new urbanization are implemented, a problem in quantities of the housing stock can be foreseen, as well as in the quality of the built environment. Very probably, the middle class in Suzhou will keep increasing in number and spending capacity, and very likely, the low-income people will increase their income and their requirements in choosing the family house [60–62].

Suzhou has a significant housing vacancy rate; the data are unavailable, but likely it is around 20%, as in similar cities in China [63,64]. This could be considered for future demand, but in general, the empty stock cannot be considered for renting, mainly because the real estate investment target is quick and consistent value increase, not rental returns, which decreased to less than 3% in 2018 [65,66].

Given these premises, the implication of the policies is that a larger population must occupy a limited urban land, but at the same time, a wealthier society requires higher living standards. Starting from the hypothesis that in Suzhou land must be used efficiently and that housing quality should improve, this research discusses the issue of density. If the GDP per capita of Suzhou and its population keep growing while the city wants to avoid sprawl, Suzhou could consider renewing some already developed areas, increasing density, housing offers, and overall livability.

#### *1.5. The Structure of the Paper*

This research explores the possibilities of densification in Suzhou to accommodate a larger quantity of population of different incomes and consume less agricultural land for urbanization. This paper discusses a strategy for sustainable urban renewal with densification; the strategy defines three options of intervention, which answer the main research question: where, how, and why requalification with densification can be applied.

This paper has the following structure. The first part presents the background of the research: the new-type urbanization policy in China, the idea of high density as a solution for sustainability, the growing population in Suzhou and its increasingly middle-class status, and the possible contradiction caused by the limits of land consumption in the Chinese context. The second part of the paper explains the reasons for urban densification in high-density urban areas and introduces some examples. The third part presents the resettlement communities in Suzhou as a relevant case for the densification strategy. The fourth and fifth parts investigate the case study with GIS-based analysis and propose some options for densification, combined with improving the built environment's quality. The last part proposes some conclusions about the potentialities of densification in a specific context, and the research limits.

#### **2. Growing Population, Land Consumption, and Densification**

#### *2.1. Density Parameter*

As introduced in paragraph 1.2, the parameter of density is a quantity and results from the combination of housing types and compactness. Usually, the quantities of population density and floor area ratio (FAR) are used to indicate density level. FAR is the parameter adopted in the regulatory plans in China to calculate built-up area density: it expresses the ratio between the total built surface and the dimension of the site where the buildings are [67]. FAR varies among the various urban areas in Suzhou, and the city as a whole cannot be classified as a high-density city if the rankings of some authoritative institutions are considered such as the World Atlas [68], UN-Habitat, Demographia World Urban Areas, the Atlas of Urban Expansion, and the Global City Power Index [29].

Population density expresses the ratio between the quantity of the population and the location [69–71]. The population density in the central district of Suzhou and the five adjacent districts (Gusu, Xiangcheng, Suzhou Industrial Park, Wuzhong, Suzhou New District, and Wujiang) was 2315 people/sq km according to the local government in 2021. The ratio between urban population/urban area in the metropolitan area is roughly less than 1/3 of the ratio in Singapore (generally ranked around 10,000 people/sq km), half the density of Shanghai, which is not ranked as one of the densest in the world (Table 1). These quantities allow us to claim that Suzhou is not a high-density city and to call the recent expansions of Suzhou "high-density sprawl" [30–33].


**Table 1.** Area and population indicators of each district in Suzhou.

### *2.2. Densification in High-Density Cities in China: The Direction already Taken*

Actions for densification have already been taken in China: in 2003, the "prohibition of land supply for villas" was issued to stop low-dense developments by the Ministry of Land and Natural Resources. The rule had to be repeated five times because it was not fully implemented. In 2019, the Ministry of Housing and Construction issued an urgent notice requesting the suspension of the approval of projects proposing villas. Subsequently, the limit to the minimum FAR was extended to all low-density typologies such as villas, double-family row houses less than four stories, and townhouses.

The "prohibition of villas" is justified by China's arable land sharply decreasing [72]. The National Land Planning Outline required in 2006 that by 2020 the amount of cultivated land would be maintained at 1.865 billion mu, a goal implemented by the "red line of cultivated land" and the construction land quotas mentioned in paragraph 1.2. The goal was achieved, and the same amount of 1.8 billion mu is set for the future [73].

Beyond the prohibition of low-density developments and the red line, densification processes are happening: two very relevant cases are Shenzhen and Shanghai.

Shenzhen is running out of land supply for development: only 2.23% of the 195,284 hectares of the city is still available for growth, and real estate prices have skyrocketed. Therefore, Shenzhen is demolishing and densifying some already high-density residential areas. This phenomenon interests mostly the "villages in the city", where in the 1980s, after opening up, the original 1-story buildings were extruded to several stories and almost to the whole lot, forming in several stages a hyper-compact urban fabric [74,75]. An example of this process is Dachong village (Table 2). The area used to house 931 families in 1400 buildings on 69 ha (13.5 families per ha), but in 2011 the whole village was demolished, the building type changed, and the density increased from 1.1 million sqm to 2.8 million sqm and 7382 residential units (107 units per ha). The transformation also increased the land uses, shifting from residential to mixed-use conditions. These actions of densification can be controversial because they often start gentrification [76,77].

**Table 2.** Comparison of Three Typical Update Project Indicators.


In Shanghai, the FAR of low-rise and high-density houses has generally increased. In recent years densification has happened mostly along the metro lines and central streets, for example, in Hengshan Street, where towers have substituted the original low-rise urban tissue [78].

Moreover, resettlement communities are impacted by densification. High rises fill empty lots, such as the "Vertical courtyards apartments" in Hangzhou by Wang Shu [79] and "The third space" in Tangshan by Li Xing Gang or entire parts are demolished and rebuilt, such as the Tuanjie Village in Kunshan, Jiangsu province. A trend of increasing the FAR of the resettlement communities can also be noted in Suzhou over the years after 1999: the new communities are designed to be slightly denser than the previous ones.
