Rushing To The Coast – The Wrong Way To Adapt To Global Warming

You would think that climate-influenced human migration, especially in Southeast Asia, would be away from coastal areas that will be flooded by sea level rise, especially those already experiencing greater flooding.

But that’s not what researchers from across the United States and Europe are projecting. Led by Dr. Andrew Bell at New York University, the research indicates that low-lying coastal cities like Bangladesh, will gain more residents than they lose.

This will occur even as rising seas cause more frequent and severe coastal flooding, with its concomitant permanent loss of land, episodic submergence of land, salt water intrusion into drinking water sources, increased erosion and loss of agricultural productivity.

Global sea level began rising after the end of the last Ice Age, but has hastened a bit since the start of the 20th century, an epoch we lovingly call the Anthropocene. Between 1900 and 2016, the globally averaged sea level rose by 16–21 cm (6.3–8.3 in). More precise data gathered from satellite radar measurements (see figure below) reveal an accelerating rise of 7.5 cm (3.0 in) from 1993 to 2017, which is a trend of roughly 30 cm (12 in) per century.

In all scenarios that the research team modelled, large numbers of people moved toward danger, something that co-author Scott Kulp, Ph.D. (Climate Central) says could trap residents in higher-risk zones.

The study used agent-based models to simulate individual decision-making about whether and where to move. The modeling showed a number of economic factors driving migration from safer, rural areas into cities with higher flood risks, where populations grew in spite of the increasing potential for property damage and financial loss.

The findings contradict conventional assumptions that rising seas will encourage migration away from vulnerable coasts. Therefore, country’s planning for adaptation and resilience cannot assume that populations will move out of harm’s way.

The research team developed an empirically calibrated agent-based model of household migration decision-making that captured the multi-faceted push/pull and mooring influences on migration at the household scale. These constitute a complex set of social, economic, political and demographic conditions in both coastal and inland areas.

It’s more than just about finding jobs in the short-term, but the short-term economics are extremely important. And coastal cities have jobs that just pay better than rural areas, whether they’re manufacturing jobs or retail or high-tech.

Other groups of people are immobilized by not being able to find improved livelihoods. One finding found that access to credit was the greatest impediment for leaving coastal areas at risk.

The group then exposed about 4,800,000 simulated migrants to 871 scenarios of projected 21st-century coastal flooding under future emissions pathways. In none of their predictions does flooding occur in great enough magnitude to drive populations away from coastlines.

A major reason for this surprising result is that, while flooding does accelerate a transition from agricultural to non-agricultural income opportunities, livelihood alternatives are most abundant in coastal cities.

At the same time, some coastal populations are unable to migrate, as flood losses accumulate and reduce their set of livelihood alternatives, becoming what’s known as trapped populations.

However, even when the modelling increased access to credit, a commonly-proposed policy lever for incentivizing migration in the face of climate risk, they found that the number of immobile agents actually rose.

These findings imply that instead of a straightforward relationship between displacement and migration, projections need to consider the multiple constraints on, and preferences for, mobility. Their results demonstrate that decision-makers seeking to affect migration outcomes around sea-level change should consider individual-level adaptive behaviors and motivations that evolve through time, as well as the potential for unintended behavioral responses.

This research shows that the changes in society as a result of global warming are going to be a lot more complicated than we think.

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