Sea-Level Rise and Migration

“Salt from rising seas harms fertile land and fresh water supplies. Coastlines erode. Land is submerged. Populations fail to make a living. People move.” (Climate Vulnerability Monitor)

As other slow-onset events, such as increasing temperatures, ocean acidification, glacial retreat or land and forest degradation, sea-level rise is a slow, gradual process, in this case of inundation, which also contributes to the severity of other rapid-onset events, such as storm surges and flooding. Environmental changes of this kind will influence economic, social and political drivers which themselves affect migration.

It is very difficult to distinguish individuals for whom environmental reasons are the sole driver of migration.  Nevertheless, sea-level rise may displace coastal communities permanently, which is why population movements related to sea-level rise are considered by many to be the clearest cases of  ‘climate migration’.

Since the beginning of the 20th Century, sea level has already rose by 20 centimeters which, at first, may sound to most of us like not much.  However, 20 are also the maximum of centimeters calculated to have risen during the previous 6.000- year period, which perhaps put these figures into perspective. Rising temperatures causing polar ices to melt and thermal expansion of the sea are the primary cause of the sea level increase. According to the Central American Integration System in its Climate Change Regional Strategy for Central America:

“It is indispensable to evaluate vulnerability to climate change in coastal zones, considering sea-level rise as the main threat.” (ERCC, SICA 2010)

Recent studies performed by glaciologists have warned that the melting of some of the unstable ice sheets in West Antarctica is probably now irreversible, while others have recorded alarming ice loss in the more stable and vast East Antarctic ice sheets. The retreat of ice in the Amundsen sea sector of West Antartica, an area as big as France with 6 glaciers, is now unstoppable, with major consequences – it will mean that sea levels will rise one metre worldwide. What’s more, its disappearance will likely trigger the collapse of the rest of the West Antarctic ice sheet, which comes with a sea level rise of between three and five metres. Such an event will displace millions of people worldwide.  According to the Australian Antarctic Division’s Tas van Ommen,  what’s concerning is that with a heavily populated planet it’s going to reshape our coastlines in ways that matter in this century. 

The following is a very interesting video with the largest glacier calving event ever recorded:

Approximately 10% of the world’s population resides in coastal communities that are 10 m or less above current sea level. Thirteen of the world’s fifteen largest cities are on coastal plains.

20 cities

Most often than not, the poorest inhabitants of cities in developing countries are forced to settle in flood plains or other risk-prone areas due to lack of alternatives. Approximately 40 cms of sea level rise would already increase five-fold the number of people flooded by storm surges. Small islands, specially those with low elevation above sea-level and coastal lowlands, currently densely populated and fastly growing, are particularly at risk at this stage. Taking into account that all studies show rising sea levels for the next centuries, reducing risk of disasters in coastal settlements will require, as McGranahan et al point out, a combination of mitigation, migration and settlement modification (2007).

mapa nasa coastal threat


The rising tide: assessing the risks of climate change and human settlements in low elevation coastal zones (McGranahan et al, 2007)

Sea level and global ice volumes from the Last Glacial Maximum to the Holocene (Lambeck et al, 2014)


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