EVANS SCHOOL OF PUBLIC POLICY AND GOVERNANCE University of Washington CLIMATE CHANGE, MIGRATION, AND THE PUGET SOUND REGION What We Know and How We Could Learn More By Alison Saperst
Introduction
Purpose and scope of this study
Public sector professionals in the Puget Sound region are increasingly examining whether climate change could drive a noticeable uptick in migration, sometimes described as climate refugees, and what that could mean for regional planning Planners and managers responsible for long‑term planning of transportation, public health, utilities, and other public services want to know whether population forecasts and demographic trends should be adjusted to account for possible climate‑driven changes in population flows.
To deepen understanding of how climate change could influence migration in the Pacific Northwest, the University of Washington’s Climate Impacts Group (CIG) commissioned a study CIG is an interdisciplinary research and stakeholder-engagement group that provides essential scientific understanding, projections, models, and adaptation guidance to help decision makers prepare for and manage the impacts of climate variability and change in the region The goal of this report is to answer two key questions about climate-driven migration in the Pacific Northwest.
1 To what extent does current knowledge about human migration support the claim that climate change will drive a significant increase in migration to the Puget Sound region?
2 What further research and analysis could tell us more about how climate change could affect future migration to Puget Sound?
This study outlines climate projections for the Pacific Northwest and the ensuing discussion of climate-related migration into the region, summarizing the research methods, data sources, and modeling approaches used to link climate risks with population movements (Section II–III) It then synthesizes the current state of knowledge on climate migration, highlights gaps and uncertainties, and introduces newly developed methods to incorporate climate-related forces into future population movement forecasts (Section IV–V) Applying this synthesis to the Puget Sound region yields answers to two central research questions and identifies promising questions and methods for future analysis to refine forecasts and inform policy (Section VI–VII).
Background
Warming is already driving change
Global climate change is an active, ongoing process driven by human activities, not a distant future phenomenon Since the pre-industrial era, warming of the Earth’s surface has led to losses of snow and ice, rising sea levels, shifts in precipitation patterns, and more frequent heat waves Climate models project a range of future impacts, yet the scientific consensus is that limiting global warming will require substantial and sustained reductions of greenhouse gas emissions This urgency underscores the need for ambitious climate action to protect ecosystems, food security, and communities.
Regardless of future climate scenarios, communities all over the world are coping with the effects of climate change upon their livelihoods, health, and economics (IPCC, 2014b)
Uncertainty in climate change projections largely stems from how societies will respond to the global phenomenon Physical science alone cannot answer this; explaining past decision-making and predicting future reactions requires an interdisciplinary approach that examines the interactions among social, economic, and cultural factors Communities are likely to pursue an evolving balance of mitigation and adaptation, reducing greenhouse gas emissions while adjusting infrastructure and daily life to a shifting climate In some contexts, people may relocate to avoid damaged infrastructure, disrupted economic activity, or other risks to community well-being The decision to migrate as an adaptation to climate stress is a dynamic area of social science research, focusing on when, how, and why individuals choose a migration strategy.
Climate change and the Pacific Northwest: Better off than the rest?
According to the latest U.S National Climate Assessment, the Northwest is projected to face several negative climate impacts, including a warming of about 3.3 to 9.7°F by 2070–2099 relative to 1950–1999, depending on greenhouse gas emission scenarios Summers, already dry, are expected to become even drier, increasing the vulnerability of regional forests to wildfires and insect outbreaks Snowfall is projected to decline and snowmelt to start earlier, shifting streamflows and potentially causing greater winter flooding along with summer water shortages for drinking, agriculture, and other uses.
Sea level rise jeopardizes low-lying coastal infrastructure in Puget Sound, and rising atmospheric CO2 levels drive ocean acidification that threatens coastal habitats, fisheries, and aquaculture (Mote et al., 2014) These changes will challenge human, natural, and economic systems across Pacific Northwest communities and will almost certainly require public service managers to rethink and redesign how systems are designed and managed to address these impacts.
Despite ongoing challenges, some experts note that the Pacific Northwest may be relatively shielded from the worst climate disasters A widely cited blog post by University of Washington atmospheric scientist Cliff Mass uses the National Climate Assessment to argue that the Pacific Northwest—especially the region west of the Cascades—could become a comparatively safe and even pleasant climate relative to other parts of the United States For example, Figure 1 highlights projected changes in average temperatures across the United States by the end of the century Because the Pacific Ocean provides cool, moist air to the area west of the Cascades, the Puget Sound region may experience a smaller rise in temperature than inland regions.
Across the Northwest, an equal-magnitude temperature rise would still yield relatively cooler conditions for the Puget Sound region because its present-day average temperature is lower than that of population centers to the south along the Pacific coast The Northwest is also not susceptible to the damaging hurricanes that threaten the South and East and which may worsen in intensity in the future (Walsh et al., 2014), nor to the severe winter snowstorms experienced in the Northeast and Midwest, which have increased in frequency and intensity since the 1950s (Ibid).
Figure 1 Projected average temperature changes (comparing the average from 1970-1999 with the average from
From 2071 to 2099, warming across the United States differs under an emissions-reduction scenario (left) versus a business-as-usual scenario (right) Notably, in both scenarios, warming in the Pacific Northwest is relatively lower than in many other regions, illustrating regional variations in climate change impacts Source: Walsh et al., 2014.
Although the Pacific Northwest as a climate refuge isn’t a new idea, it has reemerged in recent coverage with warnings that global warming could bring a wave of newcomers to the region The notion that climate change will push people away from harsh conditions elsewhere and toward the Pacific Northwest has drawn local and national attention Alongside bloggers and journalists, public service managers have warned about preparing for climate refugees and the potential impacts on Puget Sound’s population growth, economy, and culture.
Washington Health Department said, “We're going to have an influx of climate refugees This is going to have a tremendous impact on our public health (system).” (McClure, 2009)
There is growing uncertainty about the magnitude and timing of a potential influx of migrants, including where they would come from and where they would settle As this movement could influence how public services are delivered in Puget Sound communities, understanding its possible impacts has become a rising topic of public discourse.
The connection between climate change and migration is also the subject of a complex and evolving body of social science research This study identifies key experts, papers, and data
This article reviews seven key sources in migration and population studies that examine the relationships among climate, migration, and population dynamics By synthesizing the lessons from these authorities, it presents a more nuanced framework for understanding the climate change–migration nexus and applies this framework to assess the merits and limitations of the prevailing theories and models.
“climate refugee hypothesis” for Puget Sound
A note on the use of terms
Writers have used a wide variety of terms to describe the phenomenon of shifting migration patterns resulting from environmental or climatic changes Some Puget Sound area policy- makers and media outlets have adopted the term climate refugee, a phrase derived from environmental refugee, which was promoted in 1985 by El-Hinnawi (1985) However, use of the word refugee in this context is disfavored by today’s migration experts for many reasons, including its narrow definition as a legal term under the Geneva Refugee Convention and US and international immigration law (Kolmannskog and Myrstad, 2009) and the fact that many such migrations do not cross international borders or meet the other legal requirements for use of this term The term environmental refugees has declined in use, showing up in only thirteen of 350 recent publications on the topic (Laczko and Piguet, 2013) In its place, environmental migrant or climate migrant has been widely adopted Use of these term is generally accepted, but their frequent appearance within quotation marks suggests that their meanings remain ambiguous and possibly contentious (Faist and Schade, 2013) One source of controversy behind use of any blanket term is that it could be taken to represent a direct, mono-causal link between climate and migration, a characterization that has been largely rejected, as discussed in Section IV (Piguet et al, 2011) The remainder of this paper uses the terms climate migrant and climate migration, acknowledging that they are imperfect representations of the complex and nuanced relationship between climate change and human population flows.
Method
This paper presents a comprehensive literature review of both academic and grey literature and provides a conceptual synthesis of current knowledge to answer the research questions about climate migration and its impacts on the Puget Sound region Grounded in the research questions outlined in Section I, the study identifies three related sub-topics for the literature search: media coverage of climate migration to Puget Sound, climate migration research studies, and reports and forecasts about population change in the Puget Sound area A systematic search strategy was organized around these sub-topics, focusing on identifying relevant academic literature, policy analyses, and grey literature to illuminate the drivers, patterns, and projected impacts of climate-driven population change in Puget Sound Identifying relevant sources across these domains enabled a coherent synthesis of evidence and the assessment of knowledge gaps and policy implications.
8 databases, search terms, and inclusion/exclusion criteria established the primary approach to assembling the literature
A second strategy for gathering relevant documents involved citation-based searching—identifying and reading key sources cited in the studies found during the initial search For example, if a news article referenced a government report on climate change and migration, that report would be added to the bibliography for review This approach yields two main benefits: it uncovers additional sources on each sub-topic and reveals the interconnectedness among different works across academic and non-academic research, highlighting how climate change, migration, and related issues intersect across disciplines.
A final method for gathering key sources and information was interviews and correspondence with experts across each sub-topic These experts included Jacqueline Meijer-Irons, a doctoral student at the University of Washington studying climate migration, and Yi Zhao, a leading professional in the field Their insights provided nuanced, up-to-date perspectives that shaped the analysis of drivers, impacts, and potential responses to climate-related displacement, ensuring the work reflects current research and real-world considerations.
A demographer with the Washington Office of Financial Management (OFM) collaborates with researchers to understand and synthesize the theories, debates, and conceptual frameworks underpinning each sub-topic Through ongoing communication, this team clarifies how demographic methods inform policy analysis, integrates diverse perspectives, and applies rigorous theoretical constructs to complex issues By grounding OFM's demographic insights in robust theory and current debates, the work supports accurate, evidence-based policy recommendations.
Results are organized into tables that capture key attributes for each paper—authors, publication date, research method, geographic and climatic focus, data sources, key works and authorities cited, sample size, Web of Science citation counts, and main findings While the approach represents a systematic review, it does not provide a quantitative synthesis of study findings (Petticrew and Roberts, 2008) In total, the study reviews 47 news pieces, 72 climate-migration research studies, and 8 population-change reports focused on Washington or the Puget Sound region A complete list of research sub-topics, databases, search terms, filters, and the search results is available in the Appendix (p 39).
This exploratory study by CIG deepens the understanding of climate migration, identifies key research questions, and supports funding applications for this area It conducts a literature review using the described methods to reveal the state of knowledge, highlight gaps, and catalog data sources for potential future analysis of migration projections in the Puget Sound region By applying a systematic and comprehensive approach to gathering available research and information, the paper provides a balanced, unbiased perspective that synthesizes insights from media, government agencies, physical science research, and social science.
Transparency about the sources and databases assembled is essential to be accountable for any assumptions or unintended biases in the approach and to support future researchers who may continue work on this topic This synthesis of published research and grey literature offers a holistic picture of what is understood about the subject from a broader range of perspectives and research disciplines By integrating diverse evidence, the article highlights how different methods and viewpoints contribute to a more complete understanding and strengthens the credibility of the findings for readers and scholars alike.
Climate Migration Theory
An extensive review of climate migration literature identified books, studies, and reports—72 works in all—that together reveal a core set of concepts on which scholars largely agree, as well as several ongoing debates and emergent priorities and approaches This cross-cutting synthesis highlights themes in the recent literature that relate most directly to climate-driven migration to the Puget Sound region.
The link between climate change and migration is a focus of increasing scholarly interest A 2014 review by Piguet and Laczko of the climate-migration nexus for 1990–2011 shows a marked rise in publications, with 220 works from 1990–2007 and 350 works from 2008–2011 However, the apparent uptick in reports does not necessarily indicate more empirical research, as many recent studies rely on findings from earlier work Overall, there is a strong need for more empirical investigations in this field, particularly longitudinal studies that can reveal the long-term behavioral and migration responses to changing climate conditions (Obokata et al., 2014).
Migration scholars recognize a variety of factors that encourage people to move away from some areas and toward others A commonly-used three-category causal framework describes these forces:
(1) Push factors related to the place of origin, including downturns in economic opportunity, political persecution, and environmental risks and dangers;
(2) Pull factors related to the place of destination, such as demand for labor, attractive wages, or climate-related amenities; and
(3) Intervening factors that aid or hamper migration, including the existence of social networks, immigration policies, trade relationships, access to resources and capital (Black et al, 2013b)
Environmental and climate-related elements can function as push factors, pull factors, or intervening factors, depending on the context However, population studies overwhelmingly agree that attributing people’s movement to a single cause is unrealistically simplistic A flow chart illustrates how climate change interacts with multiple push, pull, and intervening factors to influence decisions about whether to migrate or to stay and adapt to changing conditions (Figure 2).
Figure 2 The multi-causal nature of migration decision-making Push factors encourage migration out of certain origins
Intervening factors can either facilitate or constrain mobility, and when a decision to migrate is made, the choice of destination is shaped by a variety of pull factors that make some destinations more attractive than others, including climate-change-sensitive drivers marked with a red asterisk Source: Adapted by the author based on Figure ES1 in Foresight, 2011.
Climate-related discomfort, difficulty, or danger prompts individuals and communities to pursue coping strategies that include both on-site adaptation and relocation On-site adaptation can involve measures like installing air conditioning to counter extreme heat or building flood defenses such as levees to reduce flood risk Relocation, whether temporary or permanent, is another option depending on circumstances The choice between staying and adapting versus moving is heavily influenced by economic, social, and cultural contexts, as noted by Piguet et al (2011).
Wealth and access to capital
Black et al (2013b) synthesize climate migration research to show that wealth—economic, social, and political capital—shapes decisions to relocate, stay, or adapt to climate extremes such as droughts, storms, floods, and heat waves Their model (Figure 3) links wealth to both vulnerability and the ability to relocate, illustrating an inverse relationship between vulnerability and wealth The analysis emphasizes that poor, disconnected, and disempowered individuals are highly vulnerable because they often live in hazard-prone locations and lack the financial capital or political power needed to plan and implement effective in‑place adaptation measures In contrast, higher wealth provides lower vulnerability by enabling safer living conditions and the resources to adapt through lifestyle changes, infrastructure, or greater political influence to participate in collective decisions that benefit them.
Figure 3 shows that greater access to social, economic, and political capital reduces vulnerability to climate extremes and increases mobility, while those most exposed to climate risks are also the most likely to remain trapped in place, hindering their ability to adapt Source: Black et al., 2013b.
Figure 3 illustrates a positive relationship between wealth and mobility: relocation can be an alternative to staying in place, but it is costly in terms of time, energy, financial resources, and social ties Those with low levels of wealth have less access to the capital needed to be mobile, while individuals with greater capital are more able to leave one location and resettle elsewhere.
Trapped populations refer to groups that lack the resources or capacity to relocate, leaving them especially vulnerable to harm Figure 3 highlights these communities in the lower-left corner, depicting people with low access to capital who are highly vulnerable to environmental extremes and without the means to relocate or adapt.
This model shows that extreme environmental events create stress that interacts with household wealth to shape mobility, resilience, and adaptation strategies In response, the wealthiest households tend to stay in place and invest in adaptation or protection, the middle-income group is more likely to relocate, and the lowest-income households face a relocation constraint, even as they would prefer to move As a result, the most vulnerable communities—those with the fewest resources—are most at risk of being trapped in hazardous locations due to limited mobility For example, low-income families may want to move away from flood-prone or drought-prone areas but cannot afford housing, transportation, or new livelihoods.
The U.S House of Representatives (2015, p 103) notes that lack of transportation access left about 70,000 New Orleans residents in place during Hurricane Katrina, despite evacuation orders Other studies suggest that climate-change–related economic damage could push more people into the category of those without the resources needed to relocate As a result, climate change could actually reduce mobility in some places rather than driving greater migration flows (Faist & Schade, 2013).
Several factors—race, gender, and education—combine to create unequal access to the resources, social networks, and institutions that make migration possible (Faist and Schade, 2013) At a larger scale, social factors such as land ownership and immigration policies largely predict population movements (Laczo and Piguet, 2013) Local studies of environmental disasters like Hurricanes Katrina and Rita reveal that race and socioeconomic status are significantly correlated with the duration of displacement and the timing and details of return (Adamo and de Sherbinin, 2013) For example, black residents of New Orleans were less likely to return home after Katrina than displaced white residents, primarily because they experienced worse housing destruction (Fussell et al 2010; Groen and Polivka, 2010).
In Ghana, socioeconomic factors are the main predictors of migration intentions, even though most residents cite irregular rainfall and drought-related bush fires as major household stressors The evidence shows that perceived unemployment risk and having previously migrated are significantly associated with intentions to migrate, implying that limited financial and social capital at home makes relocation more likely These findings highlight how economic insecurity and past migration experience influence decisions to move in response to climate-related shocks and livelihood pressures.
Relocation is costly, so people who can migrate tend to move to times and places where they expect the economic opportunities will offset those losses (Meijer-Irons, 2015, personal communication) Labor migration remains a common household coping strategy in the face of various stresses and threats to livelihood (Banerjee et al., 2013) Consequently, the gap in relative economic opportunity between sending and receiving locations is considered a major predictor of migration flows.
Evidence indicates migration is more sensitive to changes in economic opportunity than to climate fluctuations at present, though this does not rule out the possibility that future high‑magnitude climate shifts could tip the scales toward migration even when economic prospects are not as favorable In their review of climate migration in North America, Adamo and de Sherbinin (2013) summarize this nuanced picture and discuss how economic drivers currently dominate migration decisions, while climate factors may become more influential under extreme future conditions.
Forecasting future climate migration
Climate migration research clarifies the drivers of historical and current population movements, but it offers limited guidance for predicting future migration flows (Faist and Schade, 2013) Early demographic studies attempting to quantify climate-related migration were too spatially coarse to support regional or local planning (Curtis and Schneider, 2011) For example, Myers (2002) proposed that as many as 200 million people could be displaced globally by climate change These early estimates have been criticized for ignoring the nuanced mechanisms and factors that shape migration decisions, instead using a simple method that identifies climate-vulnerable regions and assumes a uniform share of the population will migrate (Findlay, 2011).
Integrating climate factors with economic and demographic data in population forecasting is a new and emerging field without established best practices and methods As noted, climate migration is rife with uncertainty about household decision-making under evolving economic, social, and climatic conditions However, the inherent lack of accuracy in projecting future movements should not stop researchers from making predictions to help decision-makers plan for the future (Abel, 2013) Recognizing this need, more recent research has focused on developing better methods for estimating the magnitude and character of likely future migration, accounting for climate change.
Recent multivariate regression analyses quantify how climate variables influence population movement, treating drought as an instrumental variable that directly reduces agricultural yields and indirectly spurs migration One study predicts that sustained water shortages could cause about 3.7% of the adult population to leave the rural U.S Corn Belt between 2020 and 2049 due to yield losses, rising to an 11% out-migration rate from 2070 to 2099 as heat and drought further suppress yields (Feng et al., 2012, p 17–18) A related evaluation of Mexico-to-U.S migration suggests drought-driven declines in crop yields could increase cross-border flows by roughly 8–10%, or about 5.5–6.7 million emigrants by 2080 (Feng et al., 2010, p 14260).
This method carries several caveats and limited predictive power for climate migration Claims are highly uncertain, particularly for the distant future, and regression approaches are better at smoothing relationships between climate conditions and migratory responses than at detecting threshold exposures where adaptation, mobility, or risk perception change abruptly—for example with sea-level rise, prolonged drought, recurring storms, or temperature increases Researchers often assume other factors will follow historical trajectories and may miss countervailing feedbacks among climate, social, and economic forces, such as reduced financial means to emigrate or lower agricultural labor demand in destination markets Additionally, studies using this approach typically focus on out-migration from areas with harsh climate conditions and overlook where migrants are likely to go.
20 here does not include any studies using regression analysis to predict in-migration to areas with preferable climatic conditions in the future
Cohort-component models are widely used for small-area population projections, drawing on a range of demographic data In recent work, climate data have been integrated into this framework: one study combines sea level rise projections with county-level population forecasts in four coastal states to generate local migration estimates over five to thirty years; another Brazilian study outlines a two-step approach where climate scenarios first inform economic forecasts and these in turn produce quantitative migration predictions A key advantage of this approach is that it treats climate change as an indirect driver of migration, acting through its impact on economic factors These models are already used in many places to reflect locally observed patterns of migration and natural population increase, including the Washington Office of Financial Management, which applies a cohort-component model to its population forecasts.
Application to Puget Sound
Section V shows that forecasting how climate change could influence migration toward Puget Sound requires examining economic, social, political, and other contextual factors that act as push, pull, or intervening forces in population movements This section assesses what is known and what remains unknown about these migration drivers in the Puget Sound region.
Insufficient regional evidence and analysis
A search of the literature found no peer‑reviewed research on the past, present, or future influence of climate on migration in Washington State or the Puget Sound region Washington’s official demographers do not currently have any measure or projection of climate-related migration (Yi Zhao, personal communication, 2015) Nevertheless, two non‑peer‑reviewed studies from neighboring regions demonstrate the kinds of approaches that stakeholders in nearby areas have used to assess the prospect of climate migration to the Pacific Northwest.
The first is a recent empirical study based on a survey and interviews with 40 providers of essential services for immigrants and refugees in British Columbia Researchers there found
Although clients do not explicitly report climate factors as the driver of relocation, researchers note that service providers do not routinely request or track such information (Dickson et al., 2015) The study provides anecdotal evidence that many service providers perceive indirect climate-related causes behind much of the current migration to the area For example, one respondent commented, “Right now the famine in South Sudan and Ethiopia…the crop failures and these huge variations in temperature…it’s really about climate but it gets played as a famine story” (Ibid, 17) Taken together, these findings suggest that climate change can influence migration dynamics even when not directly acknowledged, and the paper argues that British Columbia has an ethical obligation to prepare to accommodate and serve vulnerable international environmental migrants in the future.
Researchers from the Northwest conducted a second study, involving sixteen graduate students at Portland State University’s Toulan School of Urban Studies and Planning, to examine the potential for climate migration to the Willamette Valley and to assess the region’s readiness for growing populations (Environmental Migrants, 2011) The literature review reveals a lack of systematic research on climate-induced migration at a spatial scale usable for planning, and emphasizes that improving this knowledge is essential for guiding transportation, housing, land use, and other planning decisions in the region The study notes insufficient analysis to determine how many migrants might move, when they would arrive, or what demographic characteristics they would have It also outlines a data analysis workflow that planners can apply to detect shifts in migration patterns, characterize migrants from specific origins, and identify how environmental and other factors influence migration to the Willamette Valley (Ibid, p 22).
Climate migration tends to follow established migration patterns, so a logical first step is to describe and analyze current flows in the region Depending on stakeholders’ most pressing concerns, the analysis can focus on the most common migration origins, the origins of the most vulnerable migrants, or rapidly growing sources of migration The availability of extensive data on population movements enables in-depth analysis of current migration systems; however, recent literature reviews show that demographers have not yet analyzed the data in a way that supports future climate-migration research Below are the findings from and limitations of recent publicly available reports, primarily from the Puget Sound Regional Council (PSRC).
22 regional planning agency, and Office of Financial Management (OFM), the state agency responsible for population estimates and projections
Geographic origins of migrants to Puget Sound
Population growth in the Puget Sound region is driven primarily by net migration rather than natural increase, a pattern observed by PSRC and OFM who note that births and deaths have remained stable for decades Net migration—the difference between people moving into the area and those leaving—reflects the strength of the local job market and the overall appeal of Puget Sound Based on PSRC (2012) and OFM (2014a), the region’s migration dynamics are shaped by movements from across the country and beyond Using US Census data, PSRC reports that 40% of domestic migrants to Puget Sound originate from other parts of Washington State, 30% from the eastern United States, and 30% from the western United States (Figure 4, 2012).
Figure 4 shows that domestic migration to and from Puget Sound is dominated by intra-state moves, with a very high number of people relocating within the same state The remaining inter-state moves are roughly evenly split between eastern and western states, according to PSRC data from 2012.
Several studies use the same US Census data to publish state-level migration summaries, and a recent New York Times visualization (Aisch et al., 2014) maps state-by-state migration patterns from 1900 to 2012 The NYT charts identify the top locations where people living in Washington were born and the top destinations for people born in Washington who have moved, showing that California and Oregon dominate both inflows and outflows for Washington State Taken together, these analyses suggest that within U.S domestic migration networks, the Puget Sound region is most interconnected with locations in Washington, Oregon, and California.
Aisch et al report that 15% of Washingtonians were born outside of the United States, but the report does not provide a country-level breakdown of that migration PSRC cites federal
23 immigration policy as an important influence on migration into the region (PSRC, 2012)
According to Sahar Fathi, policy analyst for the Seattle Office of Immigrant and Refugee Affairs, Washington ranks eighth among US states in the number of legally recognized international refugees received, with the largest share currently coming from South and Southeast Asia, Sub-Saharan Africa, and the Middle East (Fathi, 2015), and the literature search for this paper did not yield a comprehensive description or analysis of trends in international migration to the Puget Sound region or Washington state.
The OFM has also published an analysis of state-level migration between 2005 and 2009 (OFM,
Figure 5 shows net migration to and from California, Oregon, Idaho, and other U.S states over the study period Net migration among Washington, Oregon, Idaho, and all other states combined declined during this period, while California alone maintained a positive net migration in 2009 International in-migration rose between 2005 and 2006, then fell to its lowest levels by the end of the study.
Figure 5 Net interstate moves between Washington and California, Oregon, Idaho, and other states combined International migration is omitted from this plot Source: OFM, 2011
Climate migration research consistently identifies economic factors as the primary driver of migration decisions, as noted in Section IV (p 13) The OFM likewise corroborates this finding, stating that most interstate population movements result from relative changes in the labor market.
24 and economic conditions among the states and that this has been historically true in
Figure 5 highlights a sharp decline in net migration from neighboring states into Washington as the economy entered a downturn The PSRC also notes that regional population growth slowed from 2000 to 2010, mirroring downturns in the Puget Sound economy along with the national recession and housing crisis, and argues that these economic pressures constrained mobility by limiting access to capital, especially the inability to sell homes with mortgages higher than their market value In more recent years, central Puget Sound has seen a rebound in population growth as a healthier economy has attracted more migrants.
Lack of spatial resolution and socioeconomic detail
Publications on net migration to Washington and the Puget Sound region typically report results using data aggregated to the level of whole states or multi-state regions, providing a broad-brush picture of population flows in and out of the region However, to fully understand the existing and potential future role of climate change on these flows, researchers need to examine the particular push, pull, and intervening factors operating on sending populations — including the distribution of access to financial, political, and social capital, the demographic and socioeconomic characteristics that determine vulnerability and mobility, the types and availability of economic and employment opportunities, and the types of climate change impacts and environmental stresses (see Section IV) Since these factors vary greatly within state boundaries, climate migration research would benefit from finer spatial resolution analyses that identify the locations sharing migration connections with the region and provide greater detail about the demographic attributes (race, age, gender, occupation, income, etc.) of migrants into the region.
US Census data are collected at the county level, enabling researchers to link migration data with localized socioeconomic and climate attributes across areas Another valuable county-level source for domestic migration is the IRS county-to-county migration data set, which has been used by Fussell et al to analyze migration patterns.
In 2014, researchers used tax records to study displacement stemming from Hurricane Katrina While these data are not as representative as the Census because they cover only the tax-paying population, they offer concrete counts and demographic details of people relocating across specific counties within states This level of geographic detail can align more closely with historical climate data and future climate projections, helping to analyze push and pull factors and other intervening motivations behind migration.
Climate change projections for Pacific coast states
Discussion
This section presents a discussion of the implications of the findings of this literature review for the research questions, which are:
1 To what extent does current knowledge about human migration support the claim that climate change will drive a significant increase in migration to the Puget Sound region?
Washington’s traded sectors—manufacturing, the federal government, information services, and professional and business services—anchor the state’s economy by generating revenue from outside the state These industries are regarded as traded because their output brings income into Washington For example, most software produced in Washington is sold to businesses and consumers outside the state, illustrating how traded sectors drive external demand (OFM, Long Term Forecast, 2014).
2 What further research and analysis could tell us more about how climate change could affect future migration to Puget Sound?
This section summarizes the study’s key findings and their implications for advancing knowledge on this topic It also supports CIG and its stakeholders in formulating a clear, evidence-based agenda for future research, guiding priority areas and actions to pursue in subsequent studies.
Overall validity of the “climate refugee hypothesis”
Better climate conditions in the Puget Sound region may be associated with shifts or increases in migration to Puget Sound, but there is no direct, unimpeded causal link between climate change and population flows The bulk of academic literature views climate as just one of many contextual factors that influence migration decisions, often not the most important Migration is multi-causal, driven by a complex mix of push, pull, and intervening factors, with economic considerations playing a particularly important role, and social, political, and cultural factors also shaping when and why people move in response to environmental change.
Migration entails substantial costs, including transaction expenses and the loss of social ties, employment opportunities, and other forms of capital Many people lack the resources to relocate even if they would like to move Those who are mobile tend to weigh the benefits and costs of relocation against the option of staying in place and adapting to changing environmental conditions, which itself can involve considerable costs.
There is evidence that climate change could influence migration patterns toward Puget Sound in the future, particularly if its economic impacts are less severe there than in other parts of Washington, Oregon, and California Raising the question of climate migration into Puget Sound is important, and further research could provide helpful insights to regional planners and policymakers The future influence of climate change on migration to Puget Sound is and will remain impossible to quantify precisely due to the multiple layers of uncertainty about climatic, economic, social, and political conditions Nevertheless, some questions about climate change, migration, and the Puget Sound region remain researchable, as described in the next section Rather than assuming that climate change will invariably result in a high-magnitude increase in net migration to the Puget Sound region, it will be important to continue examining this hypothesis through rigorous analytical methods and well-established principles of climate migration research.
Possible approaches to future research
This review identifies key research topics, methodologies, and data sources that can inform CIG and its stakeholders as they plan future research on this topic, helping to prioritize questions, choose appropriate study designs, and leverage data effectively It also highlights how these elements can shape strategic planning, stakeholder engagement, and actionable outcomes The following section offers several practical approaches for future research, outlining recommended study designs, data collection strategies, and analytic methods to advance understanding in this area.
What is the current influence of climate on migration to Puget Sound?
Climate-related factors influence migration patterns in many places today, but the specific impact of climate on moves to the Puget Sound region remains unknown because this area has not yet been studied in this context Studies from other locations often have limited external validity due to the unique social, economic, and environmental contexts of each community and migration system In climate-migration research, two common methods are qualitative approaches and regression analysis Future studies could employ either approach to determine whether climate acts as a pull factor drawing people to Puget Sound or as a push factor pushing residents away from other parts of its broader migration network.
Qualitative research methods, including focus groups, key informant interviews, and surveys, can reveal how environmental factors currently shape migration patterns and may continue to influence them in the future In North America, illustrative work includes Dickson et al.’s study in British Columbia (2015) and Veronis and McLeman’s Africa-to-Canada migration research (2014) Potential study populations encompass newcomers from other states, international immigrants, refugees, and Puget Sound-area professionals who routinely assist these migrants with services By conducting surveys, interviews, and focus groups with these groups, researchers can gain valuable qualitative insights into how climate-related constraints and opportunities affect migration choices.
Regression analysis provides a rigorous, math-based approach to quantify how climate factors influence population movement within Puget Sound’s migration system A comprehensive literature review highlights a range of regression modeling techniques that isolate the historical impact of storms, wildfires, rainfall, and natural capital on specific migration indicators (e.g., Nawrotski et al., 2013; Feng et al., 2012; Stringfield, 2010) By combining IRS county-to-county migration data or county-level US Census data with weather records, researchers can build models that explain migration outcomes These models can serve as a building block for forecasting the influence of climate factors on future population movement in Puget Sound’s migration system.
How sensitive to climate change is migration into Puget Sound?
An alternative approach is to assess how sensitive population flows into and out of Puget Sound are to projected climate changes over a policymaking-relevant timeline This integrated assessment approach is modeled in recent work by Black.
Kniveton and Schmidt-Verkerk (2013) examine flows of people into and out of Ghana by decomposing migration into identifiable components, such as seasonal labor migration and long-term rural-to-urban relocation For each component, they synthesize qualitative and quantitative information to identify the sending areas, destinations, and the main push, pull, and intervening drivers, as well as the climate variables that influence those drivers, the overall sensitivity of the flow to climate change, and the likely climate-related effects on the movement Although the approach does not produce precise numerical projections of changing flows, it helps policymakers understand where migrants are likely to go in the future relative to current patterns and to pinpoint key tipping points that could trigger significant rises or falls in migration to particular destinations (Black et al., 2013, p 49).
How will the economic impacts of climate change affect population flows?
Washington’s population forecasts rely on regional and national economic projections, but these models may not fully capture the economic impacts of climate change For example, OFM’s long-term economic and labor forecast projects that Washington will outperform the US in traded-sector employment and that mobility is expected to increase as housing markets recover (OFM, 2014a) However, these predictions apparently do not account for any economic effects of anticipated future climate changes Investigating the current or potential incorporation of climate-change projections into these economic forecasts or directly into population forecasting models could be a first step in establishing population forecasting that accounts for some of the indirect effects of climate change As described in Section V (p 20), some recent work has focused on incorporating climate scenarios into cohort-component population forecasting models like the one the OFM uses (Curtis and Schneider, 2011; Barbieri et al., 2010) The researchers who have developed these methods emphasize the importance of incorporating the indirect effects of changing climate to adjust migration predictions, with Barbieri et al noting that most migration is primarily driven by economic considerations and that climate change’s influence on migration will be at least partly indirect, by way of its impact on economic factors.
Climate migration encompasses many issues beyond this review, including the moral and legal question of whether some climate migrants should receive refugee status It also involves policy dimensions—public and private programs such as flood insurance and subsidized housing for migrant workers—that can influence the costs and benefits of relocation In addition, changing risk perceptions about future climate change, economic opportunities, and other drivers of migration may determine how future behavior diverges from historical patterns.