Deciphering climate-induced displacement in Somalia: A remote sensing perspective

impact. The environmental indicators were viewed as casual indicators, while non-environ- mental features measured the effect these causes had on the local population that ultimately leading to migration. Methodological approaches for each environmental indicator were developed and explained in detail. Agricultural drought indicator (ADI) A methodology was developed for ADI, drawing on the cause-effect relationship for agricul- tural drought. This relationship posits that a shortage of precipitation leads to a soil moisture deficit, which in turn results in a reduction of vegetation productivity (see Fig 6). The method- ology combines anomalies of precipitation (SPEI-1 and SPEI-3), soil moisture (e.g., SMI) and vegetation stress (e.g., NDVI). Here is how NDVI calculated in this study: NDVI ¼ NIRðband 8Þ Redðband 4Þ NIRðband 8Þ þ Redðband 4Þ ð1Þ • SPEI-1 and SPEI-3: to identify the precipitation deficit. • SMI anomaly: to identify soil moisture anomalies. • NDVI anomaly: characterise the subsequent effect of soil water stress on crops. As illustrated in Table 2, a rainfall deficit (watch level) causes a reduction of the soil mois- ture (warning level), and a water deficit in the ground, leading to vegetation stress. This stress results in a reduction of NDVI values (alert level) which ultimately impacts agricultural pro- duction and could lead to food insecurity. The ADI developed for this study is a type of Com- bined Drought Indicator (CDI) derived by combining the SPEI, Soil Moisture Index anomaly

(SMIa), and NDVI anomaly (NDVIa). SMIa is derived from anomalies of the SMI archive data Fig 6. Mosaic of Agricultural Drought (ADI) map of the study area in Somalia with 20m resolution in September 2017. The extent coordinates for AOI: 41, 0.3 to 47, 5.4. https://doi.org/10.1371/journal.pone.0304202.g006 PLOS ONE Deciphering Climate-induced Displacement in Somalia: A Remote Sensing Perspective PLOS ONE | https://doi.org/10.1371/journal.pone.0304202 August 9, 2024 9 / 27