The Influence of Sea-level Rise on Migration 

di Roberta Croce - 1 Marzo 2020

Dublin, Ireland

The Influence of Sea-level Rise on Migration 

Climate change has and will have a relentless impact on human life. Among the many environmental issues, here we will focus on a specific one – sea-level rise – in the context of an increasingly debated area, such as migration. There is much evidence regarding the fact that the sea level is rising, leading to greater concern towards floodings that are becoming more frequent and reaching farther inland. Low-lying coastal zones will be the most affected, especially those in developing countries. Consequently, it is thought that this phenomenon will contribute to higher rates of migration. This is a much-contested discussion area, as many factors may induce people to migrate and, there are different patterns of adaptation to this phenomenon depending on the region of origin. However, it is crucial to bear in mind that migration is a possible outcome, but not necessarily the only one.


Sea-level rise: anthropogenic causes

It is believed that sea-level rise will represent a crucial challenge to fragile coastal ecosystems and to the growing concentration of population in maritime cities (Hallegatte et al. 2013). Indeed, the increasing concentration of greenhouse gases (GHGs) into the atmosphere contributes to global warming (Twardy, 2007). This, in turn, causes the melting of land-based glaciers and major ice sheets of Antarctica and Greenland, leading to the global sea level to rise (Jevrejeva et al. 2016). The increase of global temperatures is directly correlated to the growing speed at which ice sheets are racing into the ocean.

Another contribution to sea-level rise is thermal water expansion: when water molecules are heated, they absorb energy which speeds their movement and, in this way, they take more space (Smithsonian Ocean, 2018). Considering the vastness of oceans, this phenomenon can be visible. From 1880 to 2009, the global average sea-level rise is about 210 mm and the trend of this phenomenon is accelerating (Church and White, 2011). According to the 2019 International Panel on Climate Change (IPCC) report, the phenomenon of sea-level rise due to melting ice sheets is irreversible (Oppenheimer et al. 2019).


Consequences of sea-level rise

The increased level of the oceans will have serious contingent environmental hazards. Sea-level rise is considered a slow-onset change, however, it will contribute to increasing manifestations of rapid-onset phenomena, such as storms and flooding. Negative impacts of flooding are increased salinization of wetlands, pollution of aquifers and soil erosion. In turn, the invasion of coastal areas threatens farmland and housing and affects flora and fauna, through the loss of habitat for fish, birds and plants (Oppenheimer et al 2019; Nunez, 2019). Moreover, a higher seal level would disrupt the fragile balance of tropical and coastal areas with more dangerous hurricanes and typhoons which move slower, consequently they release more rain and they become more powerful (Welch, 2018).

A higher sea-level will likely contribute to soil erosion. Higher and stronger sea waves will tear-out the marsh grass which keeps soil together, causing a deterioration of the soil and a physical loss of land. Likewise, higher sea level will lead to “water intrusion” (IOM, 2019). Not only the excess presence of water would disrupt soil, but also the quantity of salt which comes with it. In fact, salinization of soil will represent another critical impact on land as it will kill plants and change the chemistry of land, making it infertile. Frequent inundations reduce source of income, deteriorate infrastructure, disrupts daily activities and adversely impacts health and nutrition (IOM, 2019).


Potentially affected populations

At present, about 40 percent of the world population lives within 100 km from the coast (Crowell et al. 2007) – the so-called Low Elevation Coastal Zones (LECZs). Thus, almost half of the population is exposed to coastal environmental hazards, including flooding. Moreover, according to the UN, around 10 percent of the world’s population lives in coastal areas that are less than 10 meters above the sea level, making them even more vulnerable to sea-level rise (UN Ocean Conference, 2017).

This is crucial as most economic activities in the world are carried on in coastal areas, hence, it is fundamental to assess the socio-economic scenario of those regions in the future. Indeed, natural resource-based economies and livelihoods are disproportionately vulnerable to climate impacts (IOM, 2019). It is clear the impact of human-caused sea-level rise onto populations in the next years is of an urgent significance. In this light, it is important to pinpoint that, globally, populations in coastal zones will rise by 2050, especially in Africa and Asia (Merkens et al. 2016).

The most affected populations will be Small Island Developing States (SIDS) such as the Maldives, Kiribati and Tuvalu which are located about 1 meter above the sea level. The populations of such islands (52 in total) emit less than 1 per cent of the global GHGs, yet they suffer disproportionately from the climate impacts GHGs cause. Also, low-lying countries, such as Bangladesh, Indonesia and the Netherlands, are in a disadvantageous condition as they are likely to assists to an increased rate of extreme weather events causing floodings.


Sea-level rise and migration

As the sea level rises, populations living in coastal areas face difficulties and increased uncertainty. According to Reuveny (2007), people can adapt to environmental problems created by climate change in three ways: (i) remain in the area at risk, do nothing and pay the cost; (ii) remain in the area at risk and try to mitigate the problem; (iii) leave the affected area (migration).

Reuveny (2007) believes that, although every country located in a LECZ will face growing hazardous environmental phenomena, population responses will vary between developed countries (DCs) and less developed countries (LDCs). Populations in DCs will likely stay in place using technology and expertise to alleviate and prevent such dangerous phenomena, while LDCs are most likely to leave their area of origin.

Individuals decide to migrate if the net benefit (total benefit minus total cost) from migrating is larger than that from not migrating. Consequently, it is assumed that people decide to migrate, but if they face threats to their life – including environmental ones – they are forced to.

It is believed that, as sea level rises more people will see migration as the sole way to escape potential life threats, especially in developing countries, where life, economy and culture are linked to the land close to the sea. Permanent migration is more likely in the context of slow-onsets of environmental degradation, such as sea-level rise (IOM, 2015), but also in increased occurrences of rapid-onset phenomena related to it, storms and hurricanes would influence people’s decision to migrate. Furthermore, it is important to underline that, contrary to the widespread opinion, most environmental migration flows will likely be internal (intrastate) rather than cross-border (interstate) – mostly landward in the case of sea-level rise. This phenomenon is likely to create cultural clashes which may threaten domestic and international security.


Populations already affected

According to Oxfam, in Cuba, Domenica and Tuvalu, almost 5 percent of the population has been internally displaced annually due to extreme environmental disasters linked to sea-level rise (Oxfam, 2019). The rapid-onset disasters caused by sea-level rise, such as storms and tropical cyclones, forced approximately 95% of people in SIDCs to be moved from their home between 2008 and 2018 (Oxfam, 2019).

Also, regions located in major river deltas will face an extreme and more frequent rate of flooding. For example, Bangladeshis living in the Ganges Delta are already affected by increased inundations which pollute their drinking water and ruin vital farmland with salty ocean water (Dickinson, 2016). In such areas, housing is mostly constructed with bamboo canes and other rudimental materials that are hardly resistant to stronger storms and hurricanes, thus, throughout time, more people are likely to leave their homes.

However, even in developing countries, those who will be able to migrate are those who have the financial means to move away from their community and their source of income. On the contrary, the poorest individuals in the communities affected by sea-level rise might not be able to move because they do not have adequate resources for long-distance migrations, leading to immobility (Cattaneo et. Al. 2019). This is known as the notion of trapped populations who may wish to move but have to stay face the risks of increased flooding (Cattaneo et al. 2019).


Debate on “climate refugees”

The debate on climate change-induced migration is a contested topic. The first issue regards the definition of “climate refugee” as there is no international recognition for such a status. Some scholars are in favor of the creation of the “climate refugees” status, arguing that it would be a matter of global justice as most of the environmental migrants would be in developing and poorer countries which have contributed the less to GHGs emissions in the last century. Consequently, the industrialized countries should help pay for the environmental damage they have caused (Dickinson, 2016). Moreover, climate-induced migrants do not have any set of rights to protect them because the Refugee Convention requires political prosecution for offering protection (Methmann and Oels, 2015), thus, only recognizing the “climate refugee” status for migrants escaping environmental hazards would offer protection.  However, it is difficult to make individual decisions regarding eligibility for climate refugee status.

Other scholars are against the creation of “climate refugees” suggesting that environmental change will directly cause migration because this would reduce the complexity of real situations (Upadhyay et al. 2015) and it would not take into consideration other existing vulnerabilities. Dina Ionesco, the Head of the Migration, Environment and Climate Change Division at the International Organization for Migration (IOM) states that reducing the issue of migration in the context of climate change to the status of “climate refugees” fails to recognize other key aspect that define human mobility in relation to environmental degradation (Ionesco, 2019).


Policies at local level to countermeasure sea-level rise: developed countries

Developed countries which face the increasing risk of flooding due to sea-level rise are usually more prone to adapt and their population is much less likely to migrate. Indeed, they are beginning to design projects to avoid inundation. For instance, New York City is building an ambitious $335 million flood wall in Manhattan to guard against future flooding, called the BIG U (Garfield, 2018). However, these projects will take a long time to be finished and we do not have the certainty that they will be enough. At the same time, not all the cities risking inundation are mobilizing to avoid them: Venice, Italy, is constructed on a lagoon and the sea level could reach 20 centimeters above the current level by 2030. However, the Italian Government is only now considering “necessary and urgent measures” (Adnkronos, 2019), as it is not considered as a priority to address.

Policies at local level to countermeasure sea-level rise: developing countries

In developing countries located in low-lying areas the issue of internal displacement due to sea-level rise has been growing but very little measures have been taken for preventing migration. Preventing migration means implementing countermeasures to adapt to future increase flooding. In Indonesia, the Government has launched the National Action Plan on Climate Change Adaptation to shape policies aimed at the adaptation to increased flooding due to sea-level rise (IOM, 2019).

The strategies are very ambitious, among others, there are plans to raise ground floors, elevate roads, develop drainage pumps. However, elevating infrastructures and constructing water pumps is extremely costly and require massive resources for maintenance that the country cannot afford (IOM, 2019). Moreover, most strategies that could prevent flooding is the construction of mud walls, placement of sandbags at the entrance of houses and wave breakers with stones. The challenge is that those are temporary measures only to prevent house flooding but will not be able to cope with increasing sea-level rise in the future (IOM, 2019).



In conclusion, even though there is clear evidence of the harm that could be done by increased flooding caused by sea-level rise, there is not yet enough mobilization at the global level to tackle the causes of sea-level rise and floodings. At the local level, developed countries are planning great infrastructure to physically keep coastal areas protected with high walls. On the contrary, developing countries which would suffer the most internal migration, should be focused on policies avoiding migration through adaptive measures, however financial resources and lack of technological expertise are a continuous challenge to their implementation. Consequently, the creation of inland migration corridors would avoid unsafe and irregular migration flows in low-lying developing countries due to increased flooding.



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Autore dell’articolo *Roberta Croceaddetta alla comunicazione del think tank Trinità dei Monti. Studentessa di Master of Public  Administration in Development Practice e Dottoressa in Politics, Philosophy and Economics all’Università LUISS Guido Carli di Roma. Come sempre pubblichiamo i nostri lavori per stimolare altre riflessioni, che possano portare ad integrazioni e approfondimenti.

* i contenuti e le valutazioni dell’intervento sono di esclusiva responsabilità dell’autore.