Why the numbers don’t add up: A review of estimates and predictions of people displaced by environmental changes

“Sub-Saharan Africa is expected to be particularly affected by migration associated with climate change-related drivers, including sea-level rise and declining or disrupted availability of resources due to shifts in climatic conditions or extreme weather events (Gemenne 2011).”

“As this view has spread to become a common element of discussions about climate change impacts (7, 8), it has increasingly diverged from scientific understandings of both migration and adaptive capacity.”

“See also Gemenne (2011).”

“However, confidence in these estimates is low (Biermann and Boas 2010; Stapleton et al. 2017; Gemenne 2011a; Hartmann 2010; IPCC 2014) although modeling efforts are becoming more sophisticated (e.g., Rigaud et al. 2018).”

“(Adger et al. 2014; Gemenne 2010); • Permanently uninhabitable land, e.g., as a result of sea level rise (Gemenne 2011a, b, c; Warner et al. 2009) calling for planned relocation.”

“It is expected that migration options will be limited in a warmer world (Gemenne 2011a).”

“…directly and indirectly influence the pattern and volume of human migration; ●● the consequences of migration, with a particular focus on three specific ecological regions particularly vulnerable to environmental change: low-elevation coastal areas, drylands and mountain regions; 6 Gemenne (2011).”

“…common in the popular press and in policy documents (e.g., Stern 2007; Warner et al. 2009), but the academic literature has become more skeptical, noting that the evidence is weak and that better methodological approaches are needed (François 2011; Kniveton et al. 2008; Laczko and Aghazarm 2009).”

“Currently, representative household surveys form the basis of the knowledge on climate-induced migration (Black et al., 2013; Bohra-Mishra et al., 2014; Gemenne, 2011; Gray and Mueller, 2012).”

“Such accounts, often expressed as aggregate estimates of so-called environmental refugees (Gemenne 2011), have stimulated demographers to question such numbers and engage with the environment as a major driver of migration.”

“Accordingly, some authors such as Werz and Hoffman (2016) take an “excessively alarmist” approach (Gemenne 2011) in the estimates and predictions of numbers of environmental migrants, arguing that a high level of vulnerability coupled with demographic pressure will lead to the influx of climate migrants from vulnerabl…”

“…Change 71 (2021) 102367 Our review complements previous methodological reviews (Auffhammer et al., 2013; Berlemann and Steinhardt, 2017; Dell et al., 2014; Fussell et al., 2014b; Gemenne, 2011; McLeman, 2013; Piguet, 2010; Warner, 2011) by adding a distinctive meta-analytical perspective.”

“…serious debate concerning how migration dynamics are affected by weather-related events has been swamped with discussions of climate refugees and estimation methods which generate, intentionally or not, large global estimates of populations at risk of being displaced (Gemenne 2011; Piguet 2013).”

“…such as droughts and rising sea levels (Foresight Migration & Global Environmental Change, 2011; Laczko & Aghazarm, 2009; Myers, 1997, 2002; for a critique, see Kniveton, Schmidt-Verkerk, Smith, & Black, 2008; see also Gemenne, 2011; Piguet, Pécoud, & de Guchteneire, 2011, and Piguet, 2010).”

“…a solid foundation for understanding the issues at stake, so that they are able to differentiate between the reality of future threats associated with environmental migration and the empirically questionable numbers and dramatic portrayals constantly circulating in the media (Gemenne, 2011).”

“Several authors have criticized the vagueness of what constitutes a “climate migrant” and the various attempts at numerical estimates of future climate migration [7–10].”

“Second, these studies do not account for different levels of vulnerability to environmental change and potential adaptation strategies (Adger et al. 2015; Hunter et al. 2015;McLeman 2014;Gemenne 2011; Black et al. 2011a, c; Kniveton et al. 2008).”

“The opposed faction, drawing on evidence from case studies (Carr 2005; Findley 1994; Henry, Schoumaker, and Beauchemin 2004), dismissed the large numbers as scientifically flawed rule of thumb estimates (Jakobeit and Methmann 2012; Brown 2008b; Gemenne 2011b).”

“) will be a critical component for the application of this study’s model to other situations [73].”

“Although scholars have criticised these studies as overly simplistic and inaccurate (Gemenne, 2011), evidence from the longer course of human history shows that climatic variability and weather extremes have influenced human migration behaviour across the globe (McLeman & Smit, 2006).”

“Within this conceptual terrain, the ensuing discussion has evolved from one focused on millions of ‘climate refugees’ (Gemenne 2011; Piguet, Pecoud, and de Guchteneire 2011) into one in which migration is promoted as a possible adaptive response to climate change (McLeman and Smit 2006; Black et…”

“Furthermore, the focus on potential displacement leads to exaggerated estimates of the number of “climate refugees,” which should be tempered by more theoretically informed and empirically based research (Gemenne 2011).”

“…Due to using a very fuzzy methodology, there have been doubts about Myers’s predictions regarding the worldwide environmental displacements (Gemenne, 2011). mainly in interaction with the society (Lei et al., 2013; McLeman & Smit, 2006; Neumann et al., 2015; Oliver-Smith, 2006; Warner et…”

“…migration is precipitated by complex situational and ecological stresses, the characteristics and effects of which are extensively debated among scholars and practitioners. at the same time, it is difficult to identify and enumerate either the populations or drivers involved (Gemenne, 2011).”

“However, this would not necessarily mean that all people affected would be permanently displaced (Gemenne 2011).”

“…a large body of scholarship and research on climate change and migration, which dates back three decades (Tickell 1990, Myers 1993, Myers 2002, Gemenne 2011, Marchiori and Schumacher 2011, Gray and Mueller 2012, Bohra-Mishra et al 2014, Mcleman 2014, Zickgraf et al 2016, Grace et al 2018,…”

“Furthermore, as the number of people who will potentially be forced to migrate remains unclear and controversial (Gemenne, 2011), we did not add such uncertainty into our analyses.”

“Over time, skepticism has increased, as evidence indicates that most environmentally induced moves are short-distance, temporary and possibly voluntary (Gemenne 2011; Piguet, Pécoud, and de Guchteneire 2011).”

“However, existing work harboring messages of mass exodus (Meyers, 2002; Gemmene, 2011) remains largely unsubstantiated over longer time periods and larger geographic areas.”

“…from tens of millions of people to a billion, which we find not only in the headlines of the mainstream press, but also in official communications and research reports (for a critical review see Gemenne, 2011), our results nevertheless provide an alternative estimate of environmental migration.”

“Furthermore, these estimates typically do not account for adaptation strategies and different levels of vulnerability to environmental change (Adger et al. 2015; McLeman 2014; Gemenne 2011; Black et al. 2011a, b; Foresight 2011; Kniveton et al. 2008).”

“This perceived vulnerability to displacement contributed to earlier predictions of a looming wave of “climate refugees” from low and middle-income countries, predictions that have not been realized (Gemenne, 2011).”

“Gemenne (2011) stresses that existing predictions and estimates of environmental migrants are highly controversial, as many lack sound documentation of underlying assumptions, uncertainties, and/or potential errors.”

“As these migrants are often missed by data collection [67], the challenges are enormous for them and their receiving communities, especially in coping with socio-political and contextual factors.”

“Predictions of large-scale climate-induced migration range from tens of millions to over 1 billion (Christian Aid, 2007; Gemenne 2011; Jacobson, 1988; Myers, 2002).”

“Projections of the number of climate refugees are grounded on a narrow environmental determinism, simply feeding the number of people living in places at risk into climate scenarios, without considering the degree of resilience and adaptive capacity of affected communities, as shaped by a multiplicity of social, econo…”

“The reported numbers of prospective environmental migrants assume that all populations facing environmental risks will move (17) and portray migration as principally an issue of border security (18).”

“Migration, including the seeking of political asylum, is also frequently characterised as having a purely social and “ economic ” causation [42].”

“As such, determining cause and effect is not straightforward, leading many authors to question climate change and migration links (Connell 2016; Gemenne 2011; Hartmann 2010; Nicholson 2014; Stal and Warner 2009).”

“With regards to rural mobility, displacement has been used to describe involuntary migration after natural disasters [15] and climate change [16]; eviction for state projects, such as conservation areas [17]; and land expropriation [18], among others.”

“…exception of inhabitants of small island nations likely to disappear or severely recede with rising sea levels, experts agree that climate change is unlikely to spawn a large number of international migrants (for overviews and forecasts, see Bardsley and Hugo 2010, Black et al. 2011, Gemenne 2011).”

“Extensive scientific and policy discussions persist regarding climate change migrants and variations of the term such as “climate refugees”, “climate change refugees”, and “environmental migrants” (Felli and Castree 2012 in their apt critique of Foresight 2011; Gemenne 2011; Hall 2013; Leckie 2014; Manrique et al. 201…”

“Instead, they have a degree of individual and collective agency to respond, and adapt to climate change (Gemenne 2011).”

“An analysis of numbers of environmental migrants (Gemenne, 2011, p. 48) found no reliable methods or numbers, concluding that many estimates “have been put forward to generate media attention rather than to provide empirically grounded estimates and predictions”.”

“…nloaded from http://direct.m it.edu/glep/article-pdf/18/4/107/1818280/glep_a_00482.pdf by guest on 14 O ctober 2021 The multicausality of migration, and uncertainties about time frames, has made it impossible to provide a rigorously tested estimate of how many people may be uprooted (Gemenne 2011).”

“As others have also concluded, climate science and earth systems models and projections have dominated existing analyses of the implications of long-term climatic and related changes for migration (Gemenne, 2011; Jakobeit & Methmann, 2012; McMichael et al., 2020).”

“Typically, recent migration research has attempted to capture human mobility through representative household surveys (Black et al., 2013; Bohra-Mishra et al., 2014; Gemenne, 2011), case studies (Kartiki, 2011), and fewer longitudinal studies (Gray & Muller, 2012).”

“As such, predictions and population estimates have become contentious issues in debates over environmental migration (Gemenne, 2011).”

“These figures (even though they are mere estimates) had an enormous impact on scientific literature and continue to be quoted in media campaigns (Gemenne, 2011).”

“Different forms of hazards have differential implications for local livelihoods and require different forms of adaptation (Gemenne 2011, Black et al 2011a).”

“In addition, strong criticism about forecasting migration exists: “Most of the predictions were affected by the same flaws and biases as were current estimates: a weak or inexistent methodology, and a tendency to use the numbers in order to raise awareness” (Gemenne, 2011).”

“Gemenne (2011) notes that estimates and projections of migration due to environmental drivers are not satisfactory, with many appearing to have been put forward in order to generate media attention rather than to provide empirically grounded estimates and predictions.”

“Actual figures will also depend on climate change scenarios and adaptation strategies, significantly reducing the expected number of climate migrants [47].”