1. Introduction
It seems that people in extremely impoverished regions face a dark future when confronting the environmental change resulting from greenhouse gas emissions. Myers claims that there could eventually be hundreds of thousands of “environmental refugees” at risk of displacement owing to direct or indirect environmental problems [
1]. Hence, there has recently been an increasing interest in the relationship between human migration and environmental variation (including the environmental risk, stress, and uncertainty caused by climate change). Regardless of the debates on controversial terminology, such as “environmental refugees” and the diverse predictions concerning the amount of future migration flow, the role of the environment and environmental change in driving human migration activities still requires robust research.
A decision to migrate usually means that a family or an individual cannot obtain sufficient utility or support from the original location and seeks to move to a substitute location to better satisfy their needs and desires [
2,
3]. However, the decision to migrate is determined by many different drivers [
4]. Richard Black developed a framework that identified five clusters of drivers (including economic, political, social, demographic, and environmental drivers) in the context of climate variability and environmental deterioration [
5]. Therefore, the environment is regarded as a new primary factor driving the displacement of people. The mechanism is that climate change causes a series of environmental disruptions, including storms, floods, droughts, land degradation, sea level rise, and so on, resulting in the inability of people with high vulnerability to survive. These people have no choice but to leave their homes [
6]. However, precisely distinguishing environmental factors from all driving forces is likely to be difficult because the motivations of migrants coupled with family characteristics, which are influenced by vulnerability and adaptation strategies, are generally diverse and complex [
7]. It is generally believed that migration is a conventional choice used by households to cope with slow or sudden environmental variation to temporarily or permanently establish new livelihoods [
8]. There is a perception that environment-induced relocation is an invalid mitigation of family in origin and a passive livelihood reconstruction in destination [
9,
10]. However, some researchers argue that this assumption was derived from merely common sense and that the relations postulated between environmental change and human mobility have not been explicitly demonstrated [
11]. In reality, migration is treated as a result of far more complex behavioural decisions. A persistent perspective is that focusing on environmental factors in the process of making migration decisions may overlook the influence and underestimate the adaptive capacities of local residents [
12]. Black notes that although one may be forced to migrate in response to climate change, the migration may not necessarily take place. A variety of living strategies are affected by personal and family characteristics, and barriers or obstacles may influence outcomes [
5]. Rather, the effect of environmental drivers associated with other drivers can hardly be demonstrated in detail [
13]. This inadequacy is partly because of the high levels of uncertainty about the nexus between climate change and human society, and partly because it is not clear whether migration means a failure to adapt or if it is an initiative diversification strategy [
14]. Tacoli holds the idea that changing the radical understanding of the role of mobility is urgent, especially after drawing on some specific examinations and classifications of displaced persons. Migration is a useful strategy for reducing vulnerability and increasing economic and social flexibility rather than simply an escape from environmental marginalization in one’s home [
15]. Thus, Brown argues that the scarcity of reliable evidence regarding the relationship between environmental change and migration has rightly suggested this heated topic to be ‘complex and unpredictable’ [
16]. Additionally, there is still a lack of rigorous research and empirical evidence regarding the details of the main drivers that promote migration. There is a growing consensus that multiple and interdependent causes (i.e., economic, social, political, demographic, and environmental factors), work together to impact migration flows in the context of environmental degradation [
17,
18,
19].
The Intergovernmental Panel on Climate Change (IPCC) report predicted that decreases in rainfall could pose a grave threat to human society over time, and as many as a billion people in Asia could face freshwater shortages by 2050 [
20]. A reduction in rainfall is one of the culprits of drought and desertification in arid and semi-arid areas across Africa, Asia, Central America, and Southern Europe [
21]. Thus, a desertification trend could be a direct and predominant contributing factor to migration owing to variations in rainfall. Consequently, declines in crop productivity could induce families to migrate if their livelihoods cannot be sustained. Laczko deemed it a common response of people who live in areas at the risk of desertification to seek new opportunities elsewhere when agricultural and animal production fail to sustain local life [
22]. Jacobson stated that land degradation has spoiled millions of hectares of cultivated soil and resulted in hundreds of thousands of poverty-stricken farmers sending themselves into exile in sub-Saharan regions [
23]. Nonetheless, the existing evidence indicating that drought and land desertification cause migration and human mobility in any straightforward way remains insufficient. Many researchers have agreed with the opinion that the linkage between drought and emigration is complex, and the latter is generally believed to be the last resort when in situ coping strategies have been exhausted. A case study investigated 45 sub-Saharan African (SSA) countries that were identified as having severe desertification and soil erosion conditions. The study demonstrated that the nexus was not simple and immediate because the motivations of contemporary emigrants were dominated by political and economic drivers, and the contributions of demographic and environmental pressures were less important and had an indirect impact on the migration decision [
24]. For thousands of years, a tradition of the Sahel people has been to depart for a short period of time in the dry season, which is called ‘circulation’. Nomadic pastoralism is usually called ‘eating the dry season’, which involves a range of adaptive strategies to relieve water stress and to diversify family livelihoods [
25]. The remittances from these temporary labour migrants had been an important income resource for families, and sustained the lives of the family members remaining in the original locations. However, temporary human mobility is not equal to permanent relocation. Temporary migrations are an important way for families to reduce agricultural pressures and diversify their livelihood opportunities during dry periods [
26]. Hence, desertification-induced migration is somewhat limited because environmental decline does not represent the main reason for people’s flight, and desertification may be an overemphasized environmental factor that makes a small contribution to this myth [
27]. There have been some quantitative analyses on the role of desertification on large migrations that evaluates the importance of environmental factors out of all the driving forces. To date, no consensus exists, and the conclusions of some reviews differ greatly and sometimes even contradict each other. For example, Gray found that outmigration doubled under severe drought in the rural highlands of Ethiopia, demonstrating that drought truly influenced population mobility [
28]. In contrast, Naudé argued that political and economic factors were the predominant drivers in sub-Saharan Africa rather than environmental factors [
24]. In summary, the conclusions of past studies, both qualitative and quantitative, concerning desertification-induced migration are still fragmented, and robust evidence on this issue is lacking.
By 2015, more than 55.75 million rural residents in China were living in complete poverty according to official government standards, and their annual income was less than 2300 yuan (at a constant price in 2010). The vast majority of these people lived in alpine regions, limestone mountain areas, the Loess Plateau, and other territories that could hardly sustain the livelihoods of local dwellers. These regions are characterized by harsh ecological conditions, fragile infrastructure, a low availability of public services and severe environmental degradation. Hence, the Chinese Central Government implemented a round of poverty alleviation and development programmes called “Targeted Poverty Alleviation Programmes” in the contiguous poor areas to “take targeted measures to help people lift themselves out of poverty” [
29]. One of the measures in these poverty alleviation programmes was to relocate people living in ecologically fragile and climate-sensitive areas with insufficient natural resources. Guizhou Province, which is famous for its karst landforms, suffers from rocky desertification and is a typical representative of this type of area in China. The programme was intended to take five years and help a total of 1.34 million people in the poverty-stricken mountainous areas of Guizhou resettle to other regions with relatively good living conditions to re-establish sustainable livelihoods. The decision to move or stay in the original location was completely voluntary. Therefore, developing an understanding of the procedure of decision-making to migrate could help us to explore the drivers of individuals when facing climate change. Research on China’s environmentally induced migration is a typical case study for the nexus between rocky desertification and population migration.
The aim of this study was to increase our general understanding of what factors drive migration in typical desertification regions of China under the background of frequent natural disasters, variations in rainfall, land degradation, and vegetation deterioration. More specifically, (1) in-depth analysis of the individuals’ perception and evaluation of the importance of all factors during the procedure of making a decision to relocate was performed, and (2) the relations between each driving force and the internal mechanism of migration decisions were examined.
4. Discussion
First, we investigated the drivers of migration and found that all types of factors had an influence on the migration decision to some extent. The decision to migrate is the result of the contribution of multi-criteria pull and push factors. It is impossible to isolate a single typeof factor, especially environmental factors from others [
51]. The role of environmental variation is not a predominant factor among all drivers because it coincides with other structural changes [
52]. The socioeconomic drivers are strong driving forces that facilitate migration decisions because the regions characterized as fragile ecosystems could not provide enough services for local residents, resulting in high degrees of poverty. This situation directly threatened people’s local sustainable livelihoods. Environmental factors were weak driving forces in facilitating migration decisions because the actual influence of environmental change is highly dependent on economic, social, and political factors. In this context, the role of environmental drivers should not be overemphasized. Relocating to another location was considered a rational decision to avoid risks and maximize families’ net benefits to sustain themselves. Understanding the complex causes underlying migration can help populations address climate change in high vulnerability areas. The socio-economic drivers are more dependent on the different choices of families at the personal level, and the environmental factors are chronic and rooted in other drivers at the regional level. Therefore, to alter the negative effects of environmental degradation, long-term adaptation and mitigation strategies need to focus on underlying and indirect factors, which requires international and regional cooperation within a broader framework, such as balancing the development level of different regions, formulating blueprints to reduce global greenhouse gas emissions, and establishing a harmonious relationship between humans and ecology. Simultaneously, to take better care of environmental migrants, contemporary assistance needs to focus on the strong and direct factors. These factors enable the realization of the core development goal, which is to strengthen the ability of resilience and reduce the vulnerability of a family when facing the risks caused by environmental variation [
53,
54]. Both environmental and non-environmental drivers constitute a systematic force in shaping migration. Isolating and overemphasizing environmental factors from other factors neither strengthens our in-depth understanding of this scientific issue, nor brings more help to migrants on the practical level [
13,
52].
Second, we synthesised the main factors that drove migration in typical land degradation areas. To express the internal mechanism of making a migration decision, a picture was designed for visualization. As shown in
Figure 3, meteorological disasters and land degradation were at the top level of the decision process, which means that the environmental factors had indirect effects on migration decisions and had a great influence on the other factors. Moreover, meteorological disasters and land degradation facilitated each other in the worst situations. To better care for the populations suffering from environmental degradation, long-term measures to adapt to climate change are crucial in reducing local negative environmental impacts. Environmental factors directly caused population pressures and a lack of sufficient substances to sustain family living. Together with family characteristics, these three factors constituted great livelihood risks, especially for highly vulnerable families. Hence, family risks were at the core position of the decision-making process. To effectively reduce family risks, a cluster of measures, including economic, social, and political factors, was taken into consideration. Long-term development support was an economic safeguard that could help families gradually escape poverty. Social networks could be a strong internal motivator to facilitate migration by providing social capital. Relatives and friends could provide some key support, including job information, material assistance, spiritual encouragement, and the provision of new social ties, when a family resides in a new location [
55]. A housing allowance policy made considering migration possible. These needy families cannot afford the cost of migrating without some external financial support. Finding shelter constitutes the largest proportion of the cost of migrating. The core consideration of long-term development support was to effectively improve household income by diversifying income sources. The improvement of household income directly affected two drivers. Over short periods, more stable job opportunities were a conventional way for a family to obtain income; over long periods, migrants needed to improve their professional skills to obtain better paid jobs. Bettering children’s education effectively contained a family’s poverty because the children could provide support for their family when they are grown up [
56].
5. Conclusions
This paper seeks to combine classical theories of human migration with the practices in Zhijin County to develop a deeper understanding of the internal mechanism of migration decisions in the context of global climate change in typical rocky desertification regions of Southwest China. We attempt to explain the complicated relations among the environment, migration and poverty alleviation in a ‘micro’ sense by investigating 213 respondents from 12 villages regarding their personal perceptions of their instinctual motivations and possible scruples when facing the choice of staying or leaving. Different drivers were weighed and classified as strong, moderate, and weak forces in promoting the relocation process, and we elevated the relations between different factors to explain the internal mechanism. The key research findings and their implications for policy and measure recommendations are discussed below.
First, after detailed performing a assessment of the migration decision process, we found that the economic, social, political, demographic, and environmental drivers all impacted on the choice to stay or leave. Moreover, different had a different effect on the process. Among all the driving forces, economic factors were the strongest driving forces and hada direct relationship with the sustainable livelihoods of migrants. Political drivers also had a great influence on the migration decision and ranked after economic drivers. This finding was related to the inability of poor families toafford the cost of moving and reconstructing their livelihoods without external assistance. Social and demographic factors wereweaker driving forces than economic or political factors. However, they werevital for the flow, direction, and type of migrations. The choice of migration was positively correlated with family characteristics and social networks. Environmental factors were the weakest driving forces. Although environmental factors themselves were less influential, they had a direct or indirect impact on other factors in migration decisions, especially through economic and demographic drivers. In sum, the decision to migrate was the result of the contribution of multi-criteria pull and push factors.
The second important contribution of the analysis was the identification of the underlying internal mechanism of migration decisions by clarifying the relations of different factors and positioning them in a hierarchical structure. The results indicated that environmental drivers are underlying factors that are deeply embedded in a family’s socioeconomic status. A lack of substances and population pressure were caused by environmental degradation. Together with family characteristics, they constituted a great threat to sustainable livelihoods and increase the hardship of sustaininglocal populations. Hence, family risks are at the core of a family’s decision-making process. Resettlement was treated as a conventional family strategy in order to both increase household income and reduce the risk of household expenditure failure by diversifying the source of revenue in a more developed economic region [
57]. As a result, direct and strong drivers were deeply related to the migrants’ livelihoods. The environmental factors wereweak and indirect drivers, and had their influence through socioeconomic drivers on peoples’ choice.
Finally, future policies related to migration should be aimed at improving the lives of disadvantaged groups to facilitate the free movement of domestic populations instead of imposing restrictions on voluntary migration or exerting influence on the volume, direction, and types of human mobility. To achieve broader development goals, it is essential to radically change the obsolete perception of migration. Migration or human mobility could be an effective method of diversifying family income sources and to narrowing the widely unequal development levels of the economies between rural and urban areas [
15]. Policymakers need to consider climate change-related rights for migrants, help migrants establish migration pathways, and treat both host and receiving areas together when facing global warming [
58]. Reducing barriers to migration could not only greatly benefit the residents in highly vulnerable environmental areas and help them cope with climate change, but also balance the unequal development levels between the original and destination locations [
59]. Based on the Zhijin County case, voluntary and managed resettlement could be an effective method ofreconstructing the living situations of climate-sensitive populations in their target destinations and restoring the ecosystems in the original locations. This planned resettlement could not be organized and implemented without some external assistance.