Climate change shapes individuals’ migration considerations (e.g., Adger et al.,
2018; Cattaneo et al.,
2019; Hoffmann et al.,
2020). In the following, we build on this existing literature, which notes that a better understanding of environmental influences for migration dynamics necessitates the examination of how and why people are vulnerable to climate change, as well as the different strategies individuals develop to adapt to environmental stress (Piguet et al.,
2011: 2). We, consequently, argue that a useful way to gain additional insights into the relationship between climate change and migration is to focus on the interaction between (1) the characteristics of a climate event that make adaption more or less likely and (2) an individual’s abilities to adapt to the impact of the particular climate event (Field et al.,
2012; Piguet et al.,
2011; McLeman & Smit,
2006). More precisely, we focus on sudden/short-term and gradual/long-term climate events (Field et al.,
2012: 117), which differ in the extent to which in situ adaptation is possible. To assess an individual’s adaptive capacity, we concentrate on her human and financial capital. From this interplay of climate events and individual adaptive capacity, we expect to find out more about the drivers of environmental (im-)mobility.
Types of climate events
We base our theory on the argument that different types of climate events affect the decision to migrate in diverse ways (Cattaneo et al.,
2019; Koubi et al.,
2016a,
b,
c; McLeman,
2014). We distinguish between sudden/short-term and gradual/long-term climate events to this end (see also Field et al.,
2012). Sudden/short-term climate events, e.g., floods and storms, tend to have severe, immediate impacts on the well-being of individuals by inflicting injuries and casualties as well as causing economic disruption and food insecurity (Wallemacq et al.,
2018). In such cases, “people must flee from a rapid-onset environmental event to save their lives” (Warner,
2010: 405). Here, individuals can hardly adapt in situ and, hence, the costs of migration as an adaptation strategy should be lower than the ones associated with staying where they are. As a result, the “aspiration to migrate”
1 is high and, indeed, existing literature shows that sudden/short-term climate events are linked to a higher probability of migration (Cattaneo et al.,
2019; Koubi et al.,
2016a,
2016b).
Gradual/long-term climate events, e.g., droughts or water/soil salinity, are usually not regarded as sufficiently extreme to trigger migration, since they have less of an immediate impact on individuals (Adams,
2016; Farbotko et al.,
2018). People are more willing (and able) to adjust their productive strategies in the presence of gradual climate events (e.g., Al-Amin et al.,
2019; Jamero et al.,
2017; Soglo & Nonvide,
2019) and, therefore, adaptation in situ is more likely (Field et al.,
2012: 44). When subscribing to the (anticipated) effectiveness of adaptation strategies, in general, gradual/long-term climate events are likely to have a weaker effect on migration compared to sudden/short-term events. In turn, slow-onset events are often associated with immobility (Cattaneo et al.,
2019; Koubi et al.,
2016a,
2016b).
However, not everyone suffers equally from a particular climate event, and individuals’ differentiated vulnerability to climate events thus has diverse effects on their (im-)mobility. The level of vulnerability and, hence, whether it triggers mobility is linked to how severely people
perceive events to affect their lives (Carling & Schewel,
2018; Zickgraf,
2018).
2 In line with other studies (e.g., Hunter et al.,
2015; Koubi et al.,
2016a,
2016b), we assume that individuals rarely react to climate events as measured objectively, but rather act based on their
perceptions of and vulnerability to them (Field et al.,
2012; Dessai et al.,
2004; Zander & Garrett,
2020; De Longueville et al.,
2020; Koubi et al.,
2016a,
2016b,
2016c).
Taken together, this first part of our argument (first column in Fig.
1) assumes that the type of climate event affects the ability of individuals to adapt in situ. Perceived sudden/short-term events should leave little to no room for in situ adaptation (path B in Fig.
1) whereas perceived gradual/long-term events likely leave much more leeway to do so (path A in Fig.
1). Having said that, we expect these patterns to be mediated by individual and household characteristics potentially allowing an identification of involuntary immobility.
Individual and household factors as moderators of climate effects
Beyond the room for adaptation bestowed by a particular climate event, an individual’s capacity to adapt in situ is also important for actual mobility dynamics (Carling,
2002). We argue that personal and household-level characteristics moderate the impact climate perceptions have on migration (see also Carling,
2002) and that, by modeling these interactive effects, we can better explain climate-induced migration (Baez et al.,
2017; Hunter,
2018; Piguet et al.,
2011; Thiede & Gray,
2017; Zickgraf,
2018). Panels 2 and 3 in Fig.
1 summarize this part of our theory.
The range of adaptive options varies among individuals, depending on attributes such as human and financial capital (Field et al.,
2012: 67). Individuals with adequate access to resources (e.g., Black et al.,
2011; Piguet et al.,
2011) or education (e.g., van der Land & Hummel,
2013) are less vulnerable to climatic changes and, hence, more likely to adapt. Recent studies indeed find that the impact of climatic changes on migration varies considerably among sub-populations with respect to socio-economic indicators (Afifi et al.,
2016; Baez et al.,
2017; Bohra-Mishra et al.,
2017; Gray & Mueller,
2012; Gray & Wise,
2016; Thiede & Gray,
2017; Thiede et al.,
2016). For instance, Bohra-Mishra et al. (
2017) and Gray and Mueller (
2012) suggest that low levels of education may be an important factor impeding climate-related migration. We submit that different climate events are likely to induce diverse effects on the likelihood of an individual migrating given her human (education) and financial (profession and wealth) capital. By jointly considering the chances for adaptation in situ allowed by a certain climate event and an individual’s adaptive capacity—as driven by her financial and human capital—we can improve our theoretical leverage in explaining why people migrate or not
3 in the presence of climatic changes.
On one hand, we argue that
sudden/short-term events inflict significant costs on all affected people, thereby leaving, on average, little room for variation in individual adaptive capacity (Warner,
2010). As a result, we expect individual and household characteristics to play a
weak role in mediating the effects of climate events on migration in this context (path B in Fig.
1). It is precisely in the case of these sudden climate events where we would expect to see general mobility (Cattaneo et al.,
2019; Goldbach,
2017; Warner,
2010)—
irrespective of the type or degree of individual capital. That is, following path B in Fig.
1, we expect that migration is more likely in general, i.e., independent of individual level capacity to adapt in situ, in such a scenario. However, if an individual’s human or financial capital is significantly associated with a lower likelihood of mobility in the presence of such sudden/short-term events, we argue that this can be interpreted as involuntary immobility (right-hand side panel in Fig.
1). Consequently, if the
ability to move is weakly pronounced, migration becomes less likely regardless of the
readiness (i.e., motivation) and
willingness to do so in the presence of a sudden climate event (Williams & Gray,
2020).
Gradual/long-term climate events, on the other hand, are initially likely to have a smaller immediate impact, allowing people to adapt (path A in Fig.
1). Accordingly, these events have a different impact on individuals depending on their adaptive capacity. For example, the influence of gradual/long-term climate events is expected to be greater on people who primarily depend on natural and agricultural resources for their livelihood (Thiede & Gray,
2017; Field et al.,
2012). Moreover, those individuals with high adaptive capacities can make use of these capacities to adapt to gradual/long-term climate events (Black et al.,
2011; Piguet et al.,
2011). That is, although a specific climate event might bring about a certain need to leave, individual adaptive capacity allows for adaptation in situ. In the framework of Schewel (
2020), this is considered as voluntary immobility.
Consequently, if specific types of individuals possess a higher adaptive capacity, we expect these to be more likely to choose in situ adaptation over migration. Those who lack adaptive capacity in the presence of gradual/long-term climate events, however, should be more likely to leave. As a result, migration depends to a great extent on individual factors in the case of gradual/long-term climate events (following path A). This leads to the following theoretical expectations. First, people with low capacity to adapt are more likely to migrate (path A.1 in Fig.
1). Second, those able to adapt due to their higher capacity will stay and not migrate (path A.2 in Fig.
1). And third, if those who possess lower adaptive capacities, i.e., the less educated and poorer individuals, are
less likely to migrate in the presence of gradual/long-term climate events, we view this as involuntary immobility. This mechanism is illustrated in Afifi et al. (
2016: 257f) who examine rainfall variability and report that “while the most affluent residents had no need to migrate, trapped populations were forced to cope locally with rainfall variability as they did not have resources to facilitate migration.”
More precisely, with respect to
human capital, individuals with high levels of education should find it easier to adapt to changing climatic conditions and, thus, gradual/long-term climate events do not significantly influence their decision to leave. Staying, in this scenario, then indicates voluntary immobility. Note that this is independent of the general propensity to migrate. While more educated individuals are generally more likely to migrate, this is independent of the type of climate event (Bohra-Mishra et al.,
2017; Gray & Mueller,
2012). Hence, better educated individuals might be more likely to migrate per se; yet, in the presence of gradual/long-term climate events, we should not observe any difference. In contrast, those with low levels of education are likely to find it harder to adapt to gradual climate events.
With respect to
financial capital, it is both the type of profession and wealth that determine whether people stay or migrate. Gradual/long-term climate events are more likely to have a greater impact on people who depend on natural and agricultural resources for their livelihood (Thiede & Gray,
2017; Field et al.,
2012). Consequently, farmers and salesmen of farm/forest products may be the most likely to leave. This implies that the opportunity cost for moving decreases and, eventually, is relatively lower in comparison to other professions. Recent studies provide evidence that climatic changes increase the likelihood of migration via a reduction in agricultural yields in the Philippines (Bohra-Misha et al.,
2017), India (Dallmann & Millock,
2017; Viswanathan & Kumar,
2015), Pakistan (Mueller et al.,
2014), and Tanzania (Kubik & Maurel,
2016). Finally, while wealthy individuals are able to relocate, wealth can still help them to withstand economic hardship and adapt in the presence of long-term climate events (McLeman & Smit,
2006).
To recap, we identify
involuntary immobility in the context of
sudden/short-term climate events if certain sub-populations with low individual capacities stay, since we generally expect a uniform reaction by all types of individuals to move in the presence of these events (path B in Fig.
1). Similarly, in the case of
gradual/long-term events, those who are adversely affected and do possess lower adaptive capacities are less likely to migrate. This also constitutes evidence for
involuntary immobility (path A1 in Fig.
5). However, people with stronger adaptive capacities are better able to deal with gradual climatic changes and, hence, we observe
voluntarily immobile in this case (path A2 in Fig.
1).