Migration—the movement of a person or group of persons—is a complex and multi-causal phenomenon. Many factors influence migration decisions. These factors are so intertwined, we cannot consider them in isolation from one another. Instead, migration decisions result from the complex interplay of demographic, economic, environmental, political, and social factors that vary across scale. Climate and environmental changes intersect and interact with these existing drivers, changing the relationship between them and their relationship to the decision to stay or move. Climate change impacts human mobility either directly or indirectly. Changing precipitation patterns create longer-term drying trends and impact water resources and affect the sustainability of livelihoods including agriculture, forestry, and fishing. Rising sea levels make low-lying coastal areas uninhabitable in the longer-term, and combined with storm surges and high-tides, cause damage in the short-term.[1] Increased frequency and severity of natural disasters such as floods, hurricanes/typhoons/cyclones, destroy infrastructure and communities.[2] Experts categorize climate hazards into two types: sudden onset and slow onset events. Sudden onset events (extreme weather) tend to displace people immediately; whereas slower onset events provide a less obvious link to displacement and we can perceive such movement as voluntary migration (see following section for discussion of migration vs displacement). [1] Robert McLeman, “Migration and Displacement Risks due to Mean Sea-Level Rise,” Bulletin of the Atomic Scientists 74, no. 3 (April 2018), 149, https://doi.org/10.1080/00963402.2018.1461951. [2] Susan Martin, International Migration: Evolving Trends from the Early Twentieth Century to the Present, (Cambridge: Cambridge University Press, 2014), 216.

Many of the terms used related to forcible movement and environmental change (or crisis) are used interchangably, though there is a lineage that is important: the earliest terminology used to talk about environmental change that influenced human movement rested on a broad understanding of the degredation of natural systems - water sources, food systems, forest cover - and the forms of mobility it might generate. United Nations Environment Program (UNEP) expert Essam el-Hinnawi was the first to popularize the termenvironmental refugee"in 1985, when he wrote of them as "people who have been forced to leave their traditional habitat, temporarily or permanently, because of marked environmental disruption (natural and/or triggered by people) that jeopardied their existence and/or seriously affected the quality of their life'. The term environmental refugee, like climate refugee after it, were entirely rhetorical in nature, with no legal standing or direct poliy implications; they were used to raise the issue of those who were losing their homes directly and indirectly due to the collapse or change of natural systems. Because of the confusion that the refugee terminology created, many academics and the UN system started to use (and often still do) "environmental migrant," as framing that had more agency for those moving, and did not raise messy legal questions. However, as prominence around these terms continues to grow, many activists and academics started to normalize terminology around displacement, as a way to distinguishing these types of movement from something more voluntary in nature, as migration often does. Today, climate change displacement, and climate displaced persons are more and more commonly used terms. As of 2015, they were also formalized in the United Nations Framework Convention on Climate Change (UNFCC), where a decision was made to strike a Task Force to explore ways to avert, minimize, and address climate change displacement. CDPI generally uses the term climate change displacement, but environmental migration and environmental displacement are generally suitable, too. Because of both its speciticity, and the rhetorical power of linking displacement to climate change, CDPI uses this terminology most commonly. While environemntal or climate migration can be useful terms, as well, CDPI generally does not use the term "climate refugee" because of its complex legal implications and conceptual imprecision.

Environmental displacement has existed throughout human history, with notable recent events like the North American Dust Bowl during the Great Depression and the Syrian Civil War as two devastating examples. But there is something distinctive about the moment of climate crisis we now find ourselves in. The International Displacement Monitoring Centre (IDMC) has found that, since 2008, there have been an average of 24.5 million new instances of forcible displacement per year. It is impossible point to a single moment in time when trends of internal and international displacement became worse specifically because of climate change, but as the numbers of displacement have continued to grow, and projections get worse, it is clear that we live in a moment of intense displacement.

Climate displacement thinking often distinguishes the triggers of displacement into ‘sudden onset’ or ‘slow onset’ events. Sudden onset events include severe storms, floods, extreme winter conditions, and wildfires. People may need to evacuate, find temporary housing, and then return once the disaster abates and their home is safe or rebuilt. Sometimes the displaced people cannot return and are in limbo for months or years before they integrate into their temporary relocation site or resettle in a third community. Slow onset events, meanwhile, can evolve gradually from incremental changes occurring over many years or from an increased frequency or intensity of recurring events. Examples include gradually warming temperatures or sea level rise. It may take decades for their full impact to be seen.

According to the Internal Displacement Monitoring Centre (IDMC), in 2020 there were 30 million new internal displacements globally due to weather-related disasters. This was troublingly high: prior to 2020, new internal displacements due to weather-related and geophysical disasters and conflict added together was 24.5 million per year on average.

Within the broad types of sudden and slow-onset drivers of displacement, there are many different types and experiences of vulnerability that may drive some to move. Every individual or household weighs a large, diverse number of environmental, political, social, demographic, and economic considerations as to whether or not they need to move. As with most questions in climate change adaptation and impacts, it is the most marginalized members of society - the poor, people of colour, women and children, the disabled, and many others - are the most exposed to dangers. This is often due to marginalized communities being forced to live in difficult or dangerous areas, such as those exposed to floods, forest fires, or sea level rise. When an entire community is affected, those who are already vulnerable tend to be most impacted and have their situations worsen the most. Importantly, however, not every household in a community facing displacement factors will move. For instance, in Bangladesh, high-income families are more resilient and can adapt to and remain in adverse circumstances while low-income families can become ‘trapped,’ unable to afford the costs of moving. Thus, it is middle-income families who move in greatest proportions. Likewise, sometimes not everybody within a household moves. In some Bangladeshi households, younger healthy people move and send remittances to older or less mobile family members who remain. These patterns are not universal but reflect coping mechanisms for people in different circumstances facing environmental stress, showing that migration is context-specific and often a collective rather than individual decision. Furthermore, while Indigenous communities comprise 5% of the population in Canada, they currently make up 30% of those displaced every year. Indigenous communities have already endured forced relocation for non-climate-related reasons including making way for aluminum smelters, parks, cattle farms, hydro dams, urban housing, or for the government’s purposes of administering social programs more cheaply or asserting Canadian sovereignty over the Arctic. Climate change, and, sadly, sometimes action to address climate change, has continiued to cement and enhance these patterns of both displacement and control for Indigenous peoples.

CDPI takes the view that pojections of climate-related population displacements are inherently challenging and fraught exercises. The climate is dynamic all on its own, with feedback loops and “tipping points” that make predictions deeply challenging. Human systems make these infinitely more complex still. That said, inputs from natural and social science research, have been used repeatedly to make models and projections. Arguably the most credible analyses have come from the World Bank and their Groundswell reports from 2018 and 2021. These massive research and modeling exercises have produced some of the more credible – and cautious – projections of displacement due to climate change impacts. The 2021 update of the World Bank’s Groundswell report is sadly striking that, four years later, with significantly more data and other research inputs, the picture remains as dire as it does uncertain. As they say in the preface: “The new Groundswell report builds on the work of the first, modeling three additional regions, namely East Asia and the Pacific, North Africa, and Eastern Europe and Central Asia—to provide a global estimate of up to 216 million climate migrants by 2050 across all six regions. It’s important to note that this projection is not cast in stone. If countries start now to reduce greenhouse gases, close development gaps, restore vital ecosystems, and help people adapt, internal climate migration could be reduced by up to 80 percent—to 44 million people by 2050.”

There is not a single clear answer for what must be done to, as the Paris Agreement in 2016 said, to “develop recommendations for integrated approaches to avert, minimize and address displacement related to the adverse impacts of climate change.” Broadly speaking, across CDPI’s research and the many actors, including the global Task Force on Displacement (part of the UNFCCC), a broad series of actions are crucial, both individually and collectively, to addressing the displacement challenge: Cut greenhouse gas emissions in line with the IPCC’s outlined emissions pathways to prevent warming greater than 1.5C Eliminate or otherwise constrain human practices that increase risk (e.g., building on floodplains, deforestation, etc.) Address poverty and the vulnerability of less mobile and less privileged populations Invest in prevention, adaptation, and mitigation infrastructure where appropriate Enact local, bottom-up approaches that support safe, voluntary migration and relocation Account for those who choose not to move Gather disaggregated data, including qualitative data, on internal human migration patterns to better inform decisions Develop funding mechanisms and policies to support human mobility. CDPI is actively working on more actionable recommendations; but these eight actions should be seen as the high-level structures that guide displacement planning within the larger universe of climate and resilience planning. At the most granular level, we believe that preparations for climate displacement fundamentally rest on planning for and investing in community-scale resilience.