The classification and assessment of vulnerability of man-land system of oasis city in arid area

Abstract

Oasis city system is the center of the man-land relationship in arid area and it is the most influential spatial and temporal multiple dynamic system. Oasis city system is not only the largest area where artificial disturbances occur at a regional scale but also the most concentrated area of human activity in arid area. In this study, we developed an applicable and convenient method to assess vulnerability of man-land system of oasis cities with vulnerability indicator system, respectively evaluating the sensitivity, adaptability and vulnerability of the eco-environment system, the economic system and the social system. The results showed that the sensitivity and vulnerability of oasis cities in Xinjiang, China have significant differences while their adaptability does little. In order to find the inherent differences in the vulnerability of oasis cities, triangle methodology has been adopted to divide Xinjiang oasis cities into five types. Some adaptive developing policies specific for individual cities are also proposed based on their vulnerability type and constraining factors.

Keywords

vulnerability / sensitivity / man-land system / oasis cities / arid area

Introduction

Vulnerability is the state of susceptibility to harm from exposure to stresses associated with environmental and social change and from the absence of capacity to adapt (Adger, 2006). Vulnerability is currently a high frequency word of concern and an important analytical tool in the research field of global change and sustainability science (Smit and Wandel, 2006). Vulnerability research, gradually developing into a basic science knowledge system (IHDP, 2001), has been paid close attention to by many international scientific research programs and institutions (IHDP, IGBP, IPCC, etc.), and has become a focal point for research in the field of global change and sustainable development. In the line of research on geographical science strategy, the research on the vulnerability of the coupling system between people and the environment has been put forward as one of eleven major research topics for future study (National Research Council, 2010). Vulnerability research has gradually become a very basic science knowledge system for analyzing the degree, mechanism, and process of man-land interaction and the regional sustainable development (McCarthy et al., 2001). Based on this idea, the following questions are raised: the city as the most important man-land system, will the ecological environment system and social economic system face serious risk under the condition of being exposed to external disturbances? In such a case, what kind of negative effect will the vulnerability of man-land system exert? Is it possible for some regions to better cope with the negative impact brought about by the external disturbance? What kind of adaption shall we make in the future to reduce the damage?

Over the past few decades, vulnerability research has made considerable progress and produced various approaches to assessing the vulnerability of different conceptualizations and representations (Yan and Xu, 2010). Eakin and Luers (2006) summarize the difference between vulnerability conception and assessment practice, and argue that the vulnerability of social-environmental systems might be characterized as disparate fields of research. Several quantitative and semi-quantitative metrics of vulnerability have been proposed and applied, such as composite indicators, BP neural networks, fuzzy analytic hierarchy processes, and spatial analyses based on RS and GIS (Wang et al., 2008a; Li et al., 2009a; Li et al., 2009b), etc. The recent vulnerability research has moved from analyses focusing on either ecological systems or social systems toward social and economic dimensions (Alessa et al., 2008; Li and Tong, 2008; Wang et al., 2008b; Taylor, 2011), and more attention was paid to coupled man-land systems (Huang et al., 2010; Xiu et al., 2011; Liu et al., 2013). From above, it can be seen that most related research done in the past focused on climate change factors, while man-land system research has only been done on some mining cities. However, the vulnerability of man-land composite system as well as its adaptability or sustainable capacity can be affected by geographical differences (Kates et al., 2001; Berkes et al., 2002), with different areas varying in their cases of being exposed as well in their sensitivity, vulnerability and adaptability (Smit et al., 1999; Turner et al., 2003; Gallopín, 2006). Furthermore, we cannot focus only on natural events. Attention should also be paid to how the vulnerability of man-land composite system will change under the action of unnatural pressure and disturbance (Young et al., 2006). So it is imperative to carry out vulnerability research on the man-land composite system of typical arid regions. Currently, most research concerning oasis cities in arid areas have focused on water and soil resources, sustainable development (Lei et al., 2012), and spatial structure optimization of oasis cities (Sun et al., 2010; Yang et al., 2010). Some research has been done on the vulnerability of the ecological environment system and economic system of Xinjiang oasis cities (Gao et al., 2012a, b).Yet, until currently, no research has ever comprehensively analyzed the vulnerability of the man-land system of oasis cities.

The problems concerning population, resources, economy, and environment in Xinjiang are becoming more and more serious, and the contradiction between human and land is becoming increasingly prominent, especially in recent years. In such a background, it appears more and more significant and imperative to carry out research on the man-land relationship. Especially, since western development began, the continuous high-speed development of the social economy has caused great changes to the man-land relationship in oasis regions in Xinjiang. A right evaluation of characteristics of man-land relationship development and the vulnerability of Xinjiang oasis cities does not only matter for oasis cities’ own developing prospects, but also for the sustainable development of Xinjiang province and the whole western region. In this paper, an integrated, but applicable, method for vulnerability assessment is set up, and the computed result is classified using the triangle methodology. Vulnerability indices seek to provide relative vulnerability scores for regions. The main purpose of vulnerability assessments is to identify adaptation strategies that are feasible and practical in communities. This integrated and rapid assessment method will add to the paucity of literature on vulnerability assessment of the man-land composite system.

Study area and methodology

Study area

In this study, 21 cities in Xinjiang were selected as case study object, including the city of Urumqi, Shihezi, Karamay,Turpan, Hami, Changji, Yining, Tacheng, Altay, Bole, Korla, Aksu, Artosh, Kashgar, Hotan, Fukang,Wusu, Kuytun, Wujiaqu, Alar, and Tomushuk. There were 21 samples in total (Fig. 1). Human activities in arid regions were mostly distributed in oasis areas. As the concentrated center of population and economy in Xinjiang, oasis cities here played a very important role in the process of regional economic development. In total, population in oasis cities in Xinjiang amounted to 8.1079 million, accounting for 38.05% of the total population of 21.3081 million in Xinjiang province. So, as far as economy was considered, the gross domestic product (GDP) in Xinjiang oasis cities was 306.885 billion CNY, accounting for 73% of the total GDP in Xinjiang province. Setting oasis cities as its study object, making vulnerability assessment on their man-land system, trying to classify the vulnerability types and reveal the intrinsic differences among Xinjiang oasis cities so as to find out the vulnerability factors, this study was intended to have an important practical significance for realizing the sustainable development of oasis cities.

Methodology

The vulnerability model

The vulnerability (V) of the man-land system of oasis cities is the quality of the oasis city system (subsystem, system components) that is sensitive to internal and external disturbance but lacks of adaptation capacity, and in consequence causes the city to evolve to a way that is adverse to sustainable development. Sensitivity (S) and adaptability (A) are the basic attributes of vulnerability. The system vulnerability is formed by the combined action and interaction of sensitivity and adaptability that influence each other. Vulnerability is a function of the interaction between sensitivity and adaptability, namely, V = ƒ (S, A), in which the vulnerability evolves in direct proportion to sensitivity and in inverse proportion to adaptability. The higher the sensitivity is the higher the vulnerability, and the lower the adaptability. At the same time, when being disturbed, the system will suffer some loss in the process of interaction of the sensitivity and adaptability. The system loss is in direct proportion to its vulnerability. The greater the loss is, the higher the system vulnerability is. Therefore, through the above analysis, a model for assessing vulnerability can be set up as follows:

(1)V_i={\displaystyle \sum _{j=1}^n{w}_{ij}{V}_{ij}},

(2)V_i=f(S_{ij},A_{ij})=k{S}_{ij}/A_{ij}.

In the formula, V_ij represents the vulnerability index of city i and system j; S_ij represents the sensitivity index of city i and system j; A_ij represents the adaptability index of the city i and the system j.

The assessment indicator system and data sources

An oasis is not only the most concentrated area of human activity in arid areas but also the largest area where artificial disturbances occur at a regional scale (Liu et al., 2010).Compared to cities in other regions, oasis cities have their special characteristics in such fields as ecological environment, economic development, and social development. This is mainly reflected in the following aspects: their space for human activities is limited; they are short of water resources; their atmospheric pollution is serious but the related controlling capacity is weak; their industrial structure is of prominent rigidity; their substituting industry is underdeveloped; their urban economic space is in poor connection and the job-providing capacity is relatively weak; there are defects of city function and underdevelopment of urban rail traffic, etc. In this paper, the vulnerability assessment indicator is established right on the base of the developing characteristics of man-land system of oasis cities in arid areas, which is intended to be able to fully reflect the characteristics of the vulnerability of the oasis city. The indicator system is divided into two aspects: sensitivity and adaptability, and in it, 13 aspects relevant to urban vulnerability are determined. For each key aspect, 53 concerning indicators are selected and established, among which, 14 indicators are used for describing the eco-environment vulnerability, 20 for economic system vulnerability, 19 for social system vulnerability. The indicators are shown in Table 1.

The data used for vulnerability assessment are obtained from official statistical data and monitoring data publicized on the internet. Among them, social economic development data comes from the Xinjiang Statistical Yearbook and Xinjiang Survey Statistics Yearbook for years 2001-2010; while the eco-environment data are collected from the Xinjiang Environmental Statistical Yearly Report for years 2001-2010 and monitoring data publicized on the related website (www.xjepb.gov.cn).

Analysis method

(1) Evaluation method

The evaluation process is carried out at three levels, among which the evaluation on subsystem sensitivity and adaptability is a basic one. Because too many factors can influence the development of the man-land system in oasis cities and many of them are of uncertainty, a comprehensive evaluation method has been used to assess and analyze city vulnerability. Considering the complexes and huge scope of index system, main component analyzing method has been adopted to reduce index dimensions. In the measuring process in the comprehensive indicator system, subjective and objective weighting methods are respectively adopted to determine index weight. In order to avoid the influence of subjective factors in the weighting process, the entropy method is applied in determining weight. At the basic evaluation level, the principal component analysis method and entropy method are used. By the means of reducing dimensions through principal component analysis method, multiple variants are turned into only a few principal components, then, the weight of each principal component is determined by entropy calculating and the result finally is obtained by weighting and summation. At the second evaluation level, each subsystem’s vulnerability is obtained by calculating the value from the basic evaluation level and according to the established vulnerability model. At last, the highest level evaluation result is determined, namely, the evaluation result of the vulnerability of the man-land system in oasis cities.

(2) Triangle methodology

Triangle NSE is an equilateral triangle (Fig. 2). Point N represents that V_N of oasis cities is 1, while at point E and S, the V_N value is 0. From point E(S) to point N, the V_N value changes from 0 to 1. In a similar way, at point E, the V_E value is 1, while at point N and S, it is 0. Still, V_S value at point S is 1, while it is 0 at point E and N. The vulnerability of man-land areal system of oasis cities is formulized as V_T= V_N + V_E +V_S=1, which complies with the application condition of triangle methodology. Therefore, any annual V_E / V_N / V_S value can be put into the triangle for analyzing the variation of its vulnerability.

In this paper, based on the proportion made up in V_T (vulnerability index of man-land system of oasis cities) by V_N (vulnerability index of eco-environmental system), V_E (vulnerability of economic system index), and V_S (vulnerability of social system index) , and holding the proportion of 80% as a criterion (a determining proportion either made up by the vulnerability index of a single subsystem or by the summation of the vulnerability of 2 subsystem ), we have classified the man-land system of oasis cities in 7 categories: N type (with vulnerable system of eco-environmental), E type (with vulnerable economic system), S type (with vulnerable social system), NE type (with vulnerable eco-environmental and economic system), ES type (with vulnerable economic and social system), NS type (with vulnerable eco-environmental and social system) and ENS type (with vulnerable economic, eco-environmental and social system). As for the E’, N’, and S’ area in the chart, the vulnerability index of neither a single subsystem nor the summation of the vulnerability index of any 2 subsystems can reach the proportion of 80%, but the vulnerability index of some single subsystems in this area reach a proportion of 60%. In such a case, E’, N’, and S’ are respectively listed into E, N, and S categories instead of being listed into 3 additional separate categories to avoid yielding too many and complex categories, which, otherwise, would not be conducive for making the sustainable developing strategy for oasis cities.

Results and discussion

Evaluation of vulnerability

Sensitivity index

According to the evaluation method and model designed in the evaluation index system mentioned above, the oasis city man-land system sensitivity index is figured out from the point of view of eco-environment system, economic system, and social system. The result is shown in the Table 2.

As indicated in the table, the man-land system sensitivity assessment result shows that the highest sensitivity index value comes out for the city of Urumqi, followed by Shihezi and Hami, respectively, being 0.4793, 0.2326, and 0.2169. According to their score in the sensitivity assessment, oasis cities are divided into three classes: high sensitivity cities, middle sensitivity cities, and low sensitivity cities. High sensitivity cities refer to those ones of which the sensitivity value is above 0.2, including the cities of Urumqi, Shihezi, and Hami. Middle sensitivity cities refer to those ones of which the sensitivity value is between 0.1-0.2. Altogether 11 cities fall into this class, including Korla, Karamay, etc. Low sensitivity cities refer to those of which the sensitivity value is below 0.1. Altogether 7 cities fall into this class, including Artosh, Wujiaqu, etc. Seen from the point of view of spatial distribution, the mean sensitivity index values of cities in North Xinjiang, East Xinjiang, and South Xinjiang are 0.16, 0.18, 0.12, respectively, showing a trend of East Xinjiang>North Xinjiang>South Xinjiang in their sensitivity values.

According to the proportions made up in the total scores by their scores in eco-environment system, economic system, and social system, oasis cities could be classified into three categories: city with sensitive eco-environment system, city with sensitive economic system, and city sensitive with social system. Specifically, Korla, Urumqi, and Hami belong to cities with sensitive eco-environment systems. Kunton, Bole, Tomushuk, and Alar belong to cities with sensitive economic systems; Hotan, Yining, and Kashgar belong to cities with sensitive social systems.

Adaptability index

The adaptability index reflects the potential and capability of an oasis city to resist external disturbance, regulate internal imbalance, and promote the whole urban man-land system to develop in a sustainable way. The assessment results of adaptability indicators of the man-land system of oasis cities are shown in Table 3.

The adaptability indicator assessments result reveals that the man-land systems in Xinjiang oasis cities have relatively small differences in their adaptability. Among them, the city of Urumqi has the highest adaptability while Hotan and Artosh have the lowest adaptability. There is no significant difference in adaptability for all other cities. Most of them get an assessment value between 0.1-0.2. Seen from spatial distribution, the mean value of adaptability assessment of cities in East Xinjiang, North Xinjiang and South Xinjiang respectively is 0.116, 0.156 and 0.122, showing a trend of North Xinjiang>East Xinjiang>South Xinjiang in their adaptability values. As indicated by Table 3, Alar and Tomushukare leading in eco-environment adaptability, with a proportion of more than 60% in total. The city of Shihezi is leading in economic system adaptability, with a proportion of up to 50%. As for most of all other cities, there is no significant difference in the proportion made up by the adaptability score of their eco-environment system, economic system and social system in total score.

The assessments results of the vulnerability

The vulnerability of man-land systems in oasis cities is the result of the combined action of economic system, social system, and eco-environment system. It is also the function of the interaction of the above three factors that influence and refrain each other. Vulnerability is a function of the interaction between sensitivity and adaptability. The man-land system vulnerability could be obtained by the method of weighting and summation. The vulnerability model of eco-environment system, economic system, and social system is V_N =S_N/A_N, V_E =S_E/A_E, V_S =S_S/A_S, respectively, among which S_N, S_E, and S_S represent the sensitivity index of the eco-environment system, economic system and social system, respectively, while A_N, A_E and A_S represent their adaptability index. The above analytical result (Tables 2 and 3) is calculated by the formula: V_T = V_N + V_E + V_S, and the vulnerability index of each city is obtained as the following:

As seen in Table 4, the vulnerability of man-land systems in different oasis cities has clear differences. According to their scores in vulnerability indicators assessments, the research objects are divided into three categories: ones of high vulnerability (V_T>4), ones of middle vulnerability (3< V_T<4), and ones of low vulnerability (V_T<3). Specifically, Hami, Urumqi, and Karamay are cities of high vulnerability. Eleven other cities are of medium vulnerability, including Korla, Turpan, Shihezi, etc. Still 7 other cities are of low vulnerability, including Altay, Alar, Wusushi, etc. Seen from the point of view of spatial distribution, a general trend is shown as East Xinjiang (4.87)>South Xinjiang (3.39)>North Xinjiang (2.86) in their vulnerability. It is also found that most cities in South Xinjiang are of medium vulnerability, with less difference among themselves in vulnerability, while cities in North Xinjiang vary greatly in vulnerability. For instance, the vulnerability value of Urumqi (city with highest vulnerability) is 3 times as high as that of Changji (city with lowest vulnerability).

Vulnerability classification

The values of V_N, V_E, and V_S are applied in the formula V_T = V_N + V_E + V_S to figure out V_N’, V_E’, and V_S’ (the proportion made up in V_T by V_N, V_E, and V_S, respectively) (Table 5). Then, the latter are used as the final value in the triangle chart for man-land system vulnerability classification.

Put the figure in the above table into the triangle and the final classification chart for vulnerability of man-land system of oasis cities is obtained. In the triangle chart, the size of the circle indicates the degree of vulnerability of the city it represented, as shown by Fig. 4.

From the triangle chart, it can be seen that the 21 cities in Xinjiang can be classified into five types of vulnerability. They can be further classified according to their size and which region they are in (Table 6). Seen from a regional point of view, among all 21 related cities in Xinjiang, only 2 (Karamay and Korla) belong to the type of vulnerability of a single subsystem (N type). Most of oasis cities belong to the type of vulnerability of multiple subsystems. Among them, 9 belong to the ES type, showing a highest number, and 6 of the 9 are in North Xinjiang. Cities of NES type come on the second place with a number of 6. Further, there are 6 cities of ES type in North Xinjiang. In East Xinjiang, the city of Turpan as well as Hami belongs to NES type. In South Xinjiang, Artosh, Alar, and Tomushuk belong to ES type, while Aksu, Kashgar and Hotan to the NES type. Seen from the point of view of their city size, the metropolis of Urumqi is of NS type, while most medium-sized cities are mainly of NES type and most small cities are mainly of ES type. In this paper, the information about the type of vulnerability of each related city is clearly presented. According to this information, those factors that restrain the development of the city can be accurately identified. This would help to make sustainable development strategy research specifically for a city of certain type of vulnerability.

Preliminary discussion on sustainable developing strategy

(1) Karamay and Korla are cities of N type, of which the internal problems in their environment system are the main contradiction that restrain the development of them though they are rich in resources. Therefore, for the sustainable development of these two cities, the related adjusting strategy should focus on improving their environmental situation, controlling the exploit of oil sources, increasing investment in environment protection, strengthening pollution treatment, improving environmental facilities, and in the meantime, saving water resources and enhancing its utility efficiency as well as improving the utilization rate of the three wastes.

(2) Hami, Turpan, and Kunton are cities of NE type. The internal problems in their economic system and environment system are the main contradiction that restrains the sustainable development of such cities of NE type. In consequence, for sustainable development, the main strategy should be to: readjust industrial structure and intensify the effort to attract foreign investment; control the over exploitation of water resource and improve the utility efficiency of them; increase the utilization level and rate of the three wastes and improve the environmental situation.

(3) Yining, Tacheng, Altay, Bole, Wusu, Wujiaqu, Atosh, Alar, and Tomushuk are cities of ES type. The internal problems in their economic system and social system are the main contradictions that restrain the sustainable development of such cities of ES type. In consequence, for sustainable development, the main strategy should be to readjust industrial structure and increase the investment in fixed assets and the expenditure in science and education.

(4) Urumqi is a city of NE type. The internal problems in their environment system and social system are the main contradictions that restrain the sustainable development of such cities of NS type. In consequence, for the sustainable development, the main strategy should be increasing investment in environment protection, strengthening pollution treatment, improving environmental facilities, increasing the utilization rate of the three wastes, improving urban infrastructure, and enhancing social security level.

(5) Hami, Changji, Fukang, Aksu, Karshgar, and Hotan are cities of NES type, which have certain problems in all three subsystems. These problems play a restraining role in way of relative equilibrium in the sustainable development of the man-land system in oasis cities. Therefore, what should be done is to coordinate the relation of the three subsystems and adjust the restraining factors in the subsystem that has a relatively higher vulnerability, and address problems specifically.

Conclusions

In this paper, we develop an applicable and convenient method to assess vulnerability of man-land system of oasis cities, respectively evaluating the sensitivity, adaptability and vulnerability of the eco-environment system, the economic system and the social system of 21 oasis cities in Xinjiang. Through analyzing the result of evaluation, it is found that from the point of view of spatial variation, the sensitivity and vulnerability of the man-land system of oasis cities in Xinjiang have significant differences while their adaptability does little. In order to find the inherent differences in the vulnerability of man-land system of oasis cities, triangle methodology has been adopted to divide Xinjiang oasis cities into five types, and the result indicates that cities in North Xinjiang are mainly of ES type. In East Xinjiang, Turpan is of NE type while Hami is of NES type. Cities in South Xinjiang are mainly of ES or NES type. Seen from the point of view of city size, the metropolis of Urumqi is of NS type; medium-sized cities are mainly of NES type while small cities mainly of ES one. Some adaptive developing policies specific for individual cities are also proposed based on their vulnerability type and constraining factors.

Generally speaking, the methods developed in this study are useful, as the assessment results seem to closely reflect the real situation of the oasis cities. Of course, these methods are not perfect and need further improvement in some aspects. In contrast to normative approaches, the outcomes are likely to be accepted by the local governments who would implement the recommended policies. Nevertheless, the vulnerability of a city will change dynamically along with the change of time and space, therefore, the research on temporal and spatial patterns of vulnerability is strongly suggested for further study. The analysis on adaptability, sensitivity, and adapting questions at a level of local dimension as well as the research on their correlation with larger dimensions will further enrich vulnerability research.

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