Should they stay or should they go? Coastal residents have much to consider when navigating sea level change (SLC)

May. 19, 2021

While climate scientists are not exactly sure how fast or high sea levels will rise, they agree on these principle impacts: submergence and flooding of coastal land, saltwater intrusion into surface waters and groundwater, increased erosion and overwhelmingly negative social and economic repercussions. They also agree the effects will be widespread, accelerate with time, and continue to reshape our world and influence where we live and work. It is estimated that about four out of every five people living in east or south Asia will be impacted by sea-level rise by 2050. For those living in areas with increased flooding, and loss of agricultural land and clean drinking sources infiltrated by sea water, you would think the most logical thing would be to would move away from coastal areas.

A team of researchers, led by Dr. Andrew Bell at New York University, that includes AEDE’s professor Joyce Chen, project just the opposite effect, especially in southeast Asia.

“Our projections show that low-lying areas in Bangladesh will likely gain more residents,” says Chen.

So, why are residents moving into high-risk areas instead of away from them? Their recently published research tells the story of how economic reality is as influential as climate adaptation and resilience in deciding where people live and work.

To examine this phenomenon, the team developed an agent-based model (ABM) that simulates dynamic, multifaceted migration decisions in Bangladesh and overcomes the methodological issues related to oversimplified SLC migration and erroneous assumptions surrounding 
'trapped' populations. The ABM allowed the researchers to integrate these competing migration pressures to evaluate the extent to which SLC should be assumed to redirect migration to inland areas. Further, the ABM distinguished the contributions of economic constraints from social constraints on immobility by including a policy of credit provision to all agents during peak changes in exposure to SLC. This allowed them to evaluate some of the drivers of immobility. The research team modeled multiple scenarios that ultimately showed residents move into areas impacted by sea-level change due to economic and personal factors. While the decision to move to coastal areas is influenced by the increased availability of jobs that pay better than jobs in rural areas, some move because urban areas offer more access to credit that can be used to start and maintain businesses.

In reality, as more people flock to coastal cities, many will become trapped there due to continued economic and personal loss after each flood or deluge of water into their homes and businesses. Chen says that access to credit is a commonly proposed policy lever for incentivizing migration in the face of climate risk. But in their models, when they increased access to credit, 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. So, what can be done to inform and support residents who are faced with the multi-faceted push, pull, and mooring influences on migration at a household scale?  

“Decision-makers seeking to affect migration outcomes around SLC should consider individual-level adaptive behaviors and motivations that evolve through time," says Chen. “As well as the potential for unintended behavioral responses.”