1. Introduction
Due to the rapid expansion of cities and the rapid increase in population, the relationship between people and land in cities has changed, and the urban spatial structure has begun to transform. As a result, urban human settlements have been affected and disturbed by various events such as urbanization, industrialization, and natural disasters [
1]; the urban heat island effect [
2]; smog [
3]; wildfires [
4]; and urban waterlogging [
5]. The occurrence of a series of disasters has impacted the stability and adaptability of the urban human settlement environment system to a certain extent, seriously slowing down the sustainable development of cities [
6]. In this context, understanding the resilience of urban human settlements and planning to address their vulnerabilities are critical to high-quality sustainable urban development, especially in the wake of world health events such as COVID-19, and exploring its spatiotemporal pattern and influencing factors is also of great theoretical significance to enrich the theory of urban human settlement system.
As an important aspect of urban development, urban resilience provides a new perspective for cities to resist disasters and cope with risks. Urban resilience means that when facing the impact of natural or human-caused disasters, a city can not only resist pressure but also adapt to the changing environment on the premise of ensuring its basic functions [
7]. This process consists of five stages, namely, resistance, absorption, adaptation, transformation, and recovery [
8]. The scientific quantification of urban resilience is an important means for the high-quality construction of resilient cities. Therefore, scholars have engaged in extensive discussions on urban resilience. Considering the research field, the study of resilience has gradually extended from a single natural ecosystem [
9] to a complex natural–social system [
10,
11]. In terms of research content, studies have been mostly conducted from the perspectives of conceptual connotation [
12,
13,
14], comprehensive evaluation [
15,
16], influencing factors [
17], promotion strategies [
18,
19], etc. As for research methods, quantitative research initially focused on a single aspect has developed into a combination of qualitative and quantitative research [
20], such as comprehensive index methods and measurement methods. In terms of the research scale, it includes countries [
21,
22,
23], provinces [
24], city clusters [
25], prefecture-level cities [
26], communities [
27], and so on. In addition, some scholars have proposed that basic urban green infrastructure (UGI) can improve urban ecological resilience [
28] or can be used to study the association between urban form and urban resilience using special methods and exploring the relationship between the two [
29]. The abundant research results regarding urban resilience provide theoretical and methodological references for investigating the resilience of urban human settlement systems. On the one hand, a city with a high level of resilience can face sudden disasters without difficulty, while on the other hand, it can quickly adapt to the increasingly complex social and economic environment, thus ensuring the healthy development of the urban system [
30]. In recent years, resilient cities have gradually attracted the attention of the Chinese government. In 2020, China’s “14th Five-Year Plan” outlined the construction of resilient cities as a national strategy for sustainable development [
31]. At the same time, in order to enhance the resilience of Chinese cities, pilot projects such as adaptive cities and sponge cities have been introduced [
30]. However, due to the late start of the concept of resilient cities in China, both its theory and practice are not sufficient at present. Therefore, the strategic goal of building resilient cities will take time and effort to achieve.
The governance of urban human settlements is an important problem in the process of urbanization [
32]. Generally speaking, urban human settlements involve two types of environments: the hard environment and the soft environment. The hard environment emphasizes the unity of nature, humanity, and space, which mainly includes living conditions, environmental quality, and public facilities. The soft environment focuses on the sum of all non-material features, such as life comfort, social order, security, and a sense of belonging [
33]. Research on urban human settlements mainly originates from the theory of “human settlement” put forward by the Greek scholar Doxiadis [
34] and the theory of “human settlement science” put forward by the academician Wu Liangyong [
35]. Scholars mostly start with an evaluation of the human settlement environment [
36] and focus on evaluation indicators of the urban human settlement environment based on the five systems of the human settlement environment, nature, society, habitation, and support [
37]. The spatial and temporal evolution pattern [
38], influencing factors [
39], and driving mechanism [
40], as well as the interactions among human daily activities, the residential spatial structure, and the physical geographical environment [
41] are explored by investigating regional characteristic indicators. At the same time, some scholars have begun to pay attention to the vulnerability of urban human settlement systems, and the research results provide theoretical support for an understanding of the system’s response to risks and an improvement in its ability to reduce vulnerability [
42]. As an inherent attribute of the system, resilience aims to maintain the stability of system operation and improve the sustainable development capacity of the system [
1]. Recently, Li Xueming conducted a preliminary exploration of the resilience of human settlements in the Yangtze River Delta urban agglomeration based on the DPSIR model [
43]; Peng Kunjie discussed in more detail the spatial and temporal evolution characteristics of urban human settlement resilience in the Yangtze River Delta region [
44]; and Zhou Xiaoqi measured and evaluated the resilience of urban human settlements in China as a whole and built a driving mechanism based on geographic detectors [
45].
To summarize, although the current research results on resilience and urban human settlements are quite abundant, there are still several deficiencies. One is that “resilience” mainly depends on the attributes and characteristics required by the carrier, which remain independent when applied to different disciplines. As a complex and large system, urban human settlements have strong openness and inclusiveness, which are closely related to the research perspective of resilience. In view of the significant vulnerability of human life and the urban economy, it is necessary to introduce the theory of resilience into the human settlement system, aiming to enrich the theoretical framework of urban human settlements [
46]. Second, the current research on urban resilience mainly constructs an index system from the four dimensions of economy, society, ecology, and engineering, and the index focuses more on external environmental factors, ignoring the internal connection and mechanism interactions among human settlements, especially the subjective dynamic role of the “human system” [
47]. Third, the current research on urban human settlements mostly starts from a comprehensive evaluation and influencing factors, and there is a lack of research on how to deal with risks and resist shocks in the human settlement system. Moreover, there are still few studies that measure its space–time evolution from both time and space perspectives. Therefore, it is necessary and relevant to combine the theory of resilience with the urban human settlement system. In the context of climate change and rapid urbanization, improving the resilience of urban human settlements is conducive to strengthening urban emergency management capabilities and is an important way to achieve the high-quality sustainable development of cities.
As one of the four major economic sectors in China [
48], the three provinces in Northeast China represent not only the largest heavy industry base in China but also an important grain production base. However, over time, a series of problems such as environmental pollution, resource depletion, industrial structure imbalance, and market environment change have led to the phenomena of production lags, enterprise closures, economic regression, and brain drain in the three provinces in Northeast China. By studying the resilience level of urban human settlements in the three provinces in Northeast China, we can effectively improve the resistance, adaptability, and resilience of the three eastern provinces in the face of sudden disasters. In summary, 34 prefecture-level cities in the three provinces in Northeast China were selected as research areas, and methods such as the entropy weight method, the Dagum Gini coefficient, and the geographical detector were used to diagnose and perform empirical research on the resilience of urban human settlements in order to provide a new perspective for the study of urban human settlements and a reference for the revitalization of Northeast China, the new urbanization of Northeast China, and the implementation of territorial spatial planning.
5. Discussion
Because scholars have different understandings of the resilience of urban human settlements, and the establishment and selection of indicators are also different, there may be differences in the quantitative research on the resilience of urban human settlements. Li Xueming and other scholars conducted a preliminary exploration of the resilience of urban human settlements in the Yangtze River Delta region of China, and they found that the resilience of urban human settlements varies greatly in space, and the areas with high resilience are mostly large cities or central cities [
43]. In the same way, this study revealed that the distribution of urban human settlements in the three northeast provinces of China from 2005 to 2020 had significant spatial differentiation characteristics. Shenyang, Dalian, Harbin, and Daqing were the cities with high resilience, while the resilience of urban human settlements in the northern and eastern regions of the three Northeast provinces of China showed a “collapse” phenomenon. The main reason is that these regions have weak economies, imperfect infrastructure, and a single industrial structure; coupled with the “siphon effect” of large cities, this results in a continuous decline in the resilience of small- and medium-sized cities and the surrounding urban human settlements. Zhou Xiaoqi and other scholars found that the number of cities with a low resilience level among urban human settlements in China decreased year by year [
45]. However, this conclusion is not valid when studying the change in the urban human settlement resilience level in the three eastern provinces from 2005 to 2020. On the one hand, COVID-19 has severely affected large, densely populated cities dominated by the tertiary sector. On the other hand, surrounding cities such as Heihe, Qiqihar, and Hegang have been less affected by COVID-19 due to their small populations. However, due to geographical restrictions and the underdeveloped transportation facilities and economy, they have always been areas with low resilience levels among urban human settlements. In addition, the difference in the results may be caused by the different research areas.
The urban human settlements in the three northeastern provinces of China usually recover, adapt, and improve after the impact of a major event. However, the resilience, recovery level, and resistance ability of the urban human settlements in the three northeastern provinces of China are also very different with different subsystems. Therefore, strategies to improve the resilience of the urban human settlements in the three northeastern provinces of China should be targeted.
(1) Adjustment path of morphological resilience. Although the q value of the natural system increased from 0.217 to 0.412 during the 2005–2020 period, the effect strength of the natural system was still at a low level compared with the three subsystems including humans, habitation, and society. Therefore, it is necessary to improve the resilience of the natural system. Protecting the rich natural resources in the three eastern provinces is an important means to improve the resilience of the natural system in urban human settlements. It is necessary to return farmland to forest; increase the protection of forest land, grassland, water, and other resources; and maximize the ecological role of forest land resources. Furthermore, it is necessary to pay attention to the optimization of resources such as characteristic landscapes and green corridors, which not only facilitate the migration of organisms, but also maintain the integrity of green spaces, maintain the stability of the system, and provide rich natural resources and sufficient ecological space for urban development. At the same time, the combination of blue and green natural landscapes and urban construction land can create isolated green belts according to urban functions, which can effectively avoid the disorderly expansion of urban construction land and enhance morphological resilience.
(2) Density resilience adjustment path. Only by improving the resilience level of the human system, supporting system, and social system can the density resilience of the urban human settlement environment system be better enhanced. Specific measures are as follows.
The resilience level of the human system is in the middle level among the five subsystems of human settlements. The key to improving the resilience of the human systems is to adjust the population structure—for example, by increasing the investment in education funds to fundamentally improve the quality of the population. At the same time, the government should also implement relevant preferential policies focused on talent introduction, which will play a supporting role and help to achieve the goal of optimizing the population structure.
The role of the support system in improving the resilience of cities from 2015 to 2020 gradually diminished, mainly because of the logistics and transportation paralysis caused by COVID-19 and the absence of good policy support. Therefore, to improve the resilience of the support system, it is necessary to optimize the allocation of resources; gradually improve public resource facilities such as education, medical care, transportation, and networks, which are closely related to residents’ lives, in order to realize the fairness, rationality, and accessibility of resource allocation; and provide resources for urban development. At the same time, policy reform should be carried out in education, elderly care, employment, and other aspects, as active social policies are of great significance to improving the resilience of the urban living environment.
Social systems have always played a dominant role in making cities more resilient. On the one hand, the three eastern provinces should strengthen the rational distribution of industrial space, promote the transformation and upgrading of industries with the rapid growth of the equipment manufacturing sector, exploit the potential of economic innovation, and establish a modern industrial development pattern of social sharing and industrial advancement. On the other hand, it is necessary to strengthen scientific and technological innovation; integrate digitalization, information technology, intelligence, and other advanced technologies into the transformation and construction of industries; integrate traditional industries with the economy of the new era; and use the driving force of China’s large market consumption to facilitate industrial and economic progress together, so as to achieve high-quality development among urban human settlements.
(3) Regular resilience adjustment path. The central city strategy is an important tool to strengthen the resilience of urban human settlements in the three provinces in Northeast China. The Shenyang metropolitan area is not only the ninth metropolitan area in China but is also the first metropolitan area in Northeast China. In the long run, it is necessary to actively develop Anshan, Fushun, Benxi, Fuxin, Liaoyang, and other surrounding medium- and low-resilience cities; build “Shenyang” as the core; and realize the northeast region’s economic integration and the regional integration of Harbin, Changchun, Shenyang, and Dalian. Among them, Shenyang’s diversified industrial structure will enable in-depth cooperation with the industrial chain of the metropolitan area and even the three provinces in Northeast China, which will achieve complementary advantages. For Heihe, Chaoyang, Huludao, Shuangyashan, and other surrounding low-resilience areas, it is also necessary to make full use of the regional characteristics and continue to promote the revitalization strategy of Northeast China. Only by strengthening the radiation effect of the metropolitan areas and narrowing the differences in human settlement environment resilience caused by the large gap between central cities and marginal areas can the overall resilience level of the three provinces in Northeast China be significantly improved.
6. Conclusions
Based on the revitalization strategy of Northeast China, this paper discusses the spatial and temporal evolution of urban human settlement resilience and its main influencing factors in three eastern provinces from five dimensions: the natural system, human system, housing system, supporting system, and social system. Additionally, we found: (1) From the perspective of spatial and temporal pattern evolution, the average development level of urban human settlement resilience in the three provinces in Northeast China from 2005 to 2020 shows an N-shaped development trend, with significant differences among regions. The overall spatial pattern is “high in the south and low in the north”, with the characteristics of “stable growth in the southwest and a gradual decline in the north”. (2) Inter-regional differences are the main sources of the overall differences in the resilience of urban human settlements in the three provinces in Northeast China. The intra-regional differences in urban human settlement resilience in the three provinces in Northeast China are in the order of “Liaoning Province—Heilongjiang Province > Jilin Province—Liaoning Province > Jilin Province—Heilongjiang Province”. The intra-regional differences in Liaoning Province decreased, while the intra-regional differences in Heilongjiang Province and Jilin Province expanded. (3) At different time points, the effects of various influencing factors on the resilience level of urban human settlements in the three provinces in Northeast China are both correlated and different. From 2005 to 2020, the “social system” had the strongest influence on the resilience of urban human settlements. By combining the theory of resilience with the study of urban human settlements, this paper aimed to quantitatively analyze the resilience levels of urban human settlements in the three provinces of Northeast China and the influencing factors in order to provide a theoretical basis and practical significance for the revitalization strategy of Northeast China.
In the process of rapid urbanization, although the three provinces in Northeast China showed sustained population growth, rapid social and economic growth, increasingly adaptable service facilities, and the effective control of natural disasters, the uneven development of urban human settlement resilience remains significant. In order to improve the resilience levels of urban human settlements in the three provinces of Northeast China, corresponding measures must be taken according to the different regions and subsystems. This study not only fills the theoretical gap regarding the resilience of urban human settlements to a certain extent, but also proposes key methods and strategies to enhance the resilience of urban human settlements. Although the spatial scope of this study only included cities in the three provinces of Northeast China, it can also be used as a reference for other cities. For other regions in China, a combination of qualitative and quantitative methods can be used to quantify the resilience of urban human settlements, and, on the basis of analyzing spatial and temporal heterogeneity, the main factors affecting the resilience of urban human settlements can be explored so as to put forward reasonable suggestions.
Due to the lack of research results on the resilience of urban human settlements, there is still a great deal of work to be completed in this area. (1) Although the temporal heterogeneity in urban human settlements was analyzed in detail in this study, the time span was not long enough. In the future, dynamic research on the resilience of human settlements in long-term series should be carried out to improve its real-time performance. (2) In this study, the influencing factors of the spatial and temporal pattern evolution of the urban human settlement resilience level in the three provinces of Northeast China were only studied based on the geographical detector model, which is somewhat insufficient. The structural equation and spatial econometric model should be added in the future to further analyze the interactions among the influencing factors. (3) Although the influencing factors were identified and analyzed in this study, the number of influencing factors was limited. In the future, the indicators of the influencing factors could be enriched to improve the depth and objectivity of the resilience evaluation. In addition, the effectiveness of urban resilience can be verified in future studies by examining its performance in the face of social public health events or sudden natural disasters.