Forecasting High Resolution Migration in Nigeria Under Different Climate Scenarios

Abstract

Existing research indicates that most climate-induced migration occurs and will continue to occur within rather than between nations. This can be harder to track than international migration but is crucial for understanding how climate change influences population trends, urbanization, and public health. Internally displaced people can have unique health, economic, and social challenges for which governments will need to prepare as climate change alters the distribution of undesirable or uninhabitable land. In this research, a gravity model was fit with past population, precipitation, and temperature trends to forecast population distributions in Nigeria to 2100 under different climate scenarios. The base gravity model is trained on 1km2 gridded population changes from WorldPop between 2000-2010. This model uses unique parameters for urban and rural cells to capture general urbanization trends based on each cell’s distance from urban spaces and the population of urban spaces within the country. The error in each cell of the population forecast from this first stage of the model is used to fit a model that predicts error from percentage changes of average temperatures, maximum temperatures, and precipitation changes of the same period. This model creates a cell-specific scalar to the population distribution forecast from the first stage based on that cell’s unique climate factors and how they affect the desirability to live there. Using Coupled Model Intercomparison Projects 6th iteration (CMIP6) data for future temperature and precipitation, population distributions were forecasted to 2100 under Shared Socioeconomic Pathway (SSP) 2-4.5 and SSP 5-4.5 scenarios. SSP 2-4.5 and SSP5-8.5 represent a “middle of the road” effort with respect to climate adaptation and mitigations and an improved technologies but continued high fossil fuel greenhouse gas (GHG) emissions scenario, respectively. The results show that under the higher emissions scenario Nigeria urbanizes faster as climate change reduces the desirability of rural areas, particularly those in the east. Western cities in Nigeria have 2-3 times the population weights in 2100 under a higher emissions future compared to lower emissions future. The implications of this research are that Nigeria may have different population distributions with unique needs in the future depending on how global policies do or do not reduce greenhouse gas emissions. Higher urbanization will not only mean a reduction in agricultural workforce but also denser cities and a higher population of urban migrants who may have unique health, education, and economic needs. Understanding what populations may look like in the future under different climate scenarios will be important for government planning to best support the Nigerian population.