## 5 Discussion  
This paper aimed to explore the potential impacts of long-term and short-term environmental changes on population redistribution. Crop production and water resources, which are closely related to human living conditions, were selected as environmental change factors. Some related studies showed that short-term environmental shocks have different effects than long-term processes, typically resulting in temporary and short-distance population movements [58]. In some poor countries, because people lack sufficient resources for supporting migration, displaced people often have to return to their hometowns, and some people remain stationary [59]. Migration due to short-term environmental shocks is difficult to predict and observe [58]. In this paper, short-term environmental shocks, as measured by consecutive years below median crop yield (ConsecLowField) and consecutive years below median water flow (ConsecLowFlow), were not found to be correlated with population redistribution. It is possible that population redistribution is not affected by short-term environmental shocks or that demographic data do not capture temporary population movements.  
Some studies yielded conflicting results about the impacts of long-term environmental change on population redistribution. Large-scale population displacement caused by drought was observed in some countries in Africa, Latin America, and the Middle East [60]. However, in some poor counties, such as Mali in the mid-1980s, due to the lack of adequate resources to support migration, migration declined relative to past levels [61]. Furthermore, [PERSON] found that temperature rise gradually reduced international migration in some poor countries [62]. By using Mexico and Ethiopia as case studies, employing two different model datasets, considering two decades, and considering Pop and Built-up as control variables, it was found that crop yield deviation was significantly correlated with population redistribution at the country level. However, there was no consistent significant correlation between water flow deviation and population redistribution. Long-term environmental changes tended to result either in migration, which is generally perceived as being voluntary and predominantly economically motivated, or in immobility [58]. Reduced crop production means the deterioration of livelihoods for people, especially farmers. Economic losses from environmental change might have a more direct impact on people's migration decisions than short-term environmental shocks.  
Analysis at the local level of the relationship between crop yield deviation and population redistribution in Mexico and Ethiopia revealed spatial heterogeneity. The main factor causing population redistribution in Mexico was population migration, whereas the natural population growth rate in the country was low. In the face of the challenges imposed by environmental change, migration was a common response. As one of the least developed countries in the world, Ethiopia is characterized by a high population growth rate. Because it is difficult to obtain enough resources to support migration, environmental change may also result in immobility [61; 63]. The notion of \"trapped\" populations was used to describe those who are not able to migrate even if they wish to do so. Immobility may be a forced choice [58].