Effect of border policy on exposure and vulnerability to climate change

Abstract

Migration may be increasingly used as adaptation strategy to reduce populations' exposure and vulnerability to climate change impacts. Conversely, either through lack of information about risks at destinations or as outcome of balancing those risks, people might move to locations where they are more exposed to climatic risk than at their origin locations. Climate damages, whose quantification informs understanding of societal exposure and vulnerability, are typically computed by integrated assessment models (IAMs). Yet migration is hardly included in commonly used IAMs. In this paper, we investigate how border policy, a key influence on international migration flows, affects exposure and vulnerability to climate change impacts. To this aim, we include international migration and remittance dynamics explicitly in a widely used IAM employing a gravity model and compare four scenarios of border policy. We then quantify effects of border policy on population distribution, income, exposure, and vulnerability and of CO₂ emissions and temperature increase for the period 2015 to 2100 along five scenarios of future development and climate change. We find that most migrants tend to move to areas where they are less exposed and vulnerable than where they came from. Our results confirm that migration and remittances can positively contribute to climate change adaptation. Crucially, our findings imply that restrictive border policy can increase exposure and vulnerability, by trapping people in areas where they are more exposed and vulnerable than where they would otherwise migrate. These results suggest that the consequences of migration policy should play a greater part in deliberations about international climate policy.

Keywords: border policy; climate change impacts; integrated assessment models; migration; shared socioeconomic pathways.

Fig. 1.

Effect of border policies on per capita income after remittances. Shown are results in the 16 FUND regions over the period 2015 to 2100 for SSP2 (middle of the road) coupled to RCP4.5. (Top Left) Per capita income levels for current borders. (Top Right) Relative change for more open borders compared to current borders. (Bottom Left) Relative change for closed borders compared to current borders. (Bottom Right) Relative change for borders closed between Global North and Global South compared to current borders.

Fig. 2.

Effect of border policies on migrants’ exposure and vulnerability: change in damages/GDP ratio—quantifying exposure and vulnerability—in percentage point, experienced by migrants leaving each of the 16 FUND regions. Shown are results for 2100, for all five SSP narratives coupled to relevant RCP. Each symbol represents a migrant flow from the region considered toward one of the other 15 regions, for a given border policy. Symbol sizes are proportional to migrant flow sizes. Symbol shapes and colors represent border policies; the closed borders scenario, incurring no migrants, is not featured.

Fig. 3.

Effect of border policies on world ${\text{CO}}_2$ emissions in megatons ${\text{CO}}_2$ (Left) and global average temperature increase in degrees Celsius (Right). Colors illustrate all five SSP narratives coupled to relevant RCP. Symbol shapes represent border policies.

Fig. 4.

Including international migration dynamics in the FUND IAM. Dashed arrows refer to preexisting links between FUND components. We add the migration component (yellow) and link it to other components as described by the solid arrows. Blue arrows relate to population dynamics, while turquoise arrows illustrate income dynamics.

Fig. 5.

The five narratives of the SSPs and their embedded assumptions on international migration. (Left) Reprinted from ref. , with permission from Elsevier. (Right) Data from ref. .

Fig. 6.

Matrix of relevant combinations of development scenarios (SSP) and climate scenarios (RCP). Combinations shaded in blue are selected for the upcoming IPCC Assessment Report. Combinations also outlined in yellow are the ones used in this study. Reprinted from ref. , which is licensed under CC BY 3.0. Source for Coupled Model Intercomparison Project Phase 6 (CMIP6) data: ref. .