A global analysis on impact of conflicts on long-term greening trends

Abstract: Armed conflicts were and are still shaping the global terrestrial land surface and can have severe direct and indirect impacts on societies, economies and the environment. This study attempts to assess the impact of armed conflicts on vegetation on global and regional scale. Four aims were formulated to scrutinize the impact of conflicts based on 1) globally distributed conflicts involving events with more than 25 deaths, 2) types of conflicts, namely: state-based violence, non-state violence and one-sided violence, 3) regional examples: Rwanda and Afghanistan and 4) levels of conflict severity by death number: greater than 0, 25 and 100. The long-term impacts were analysed by calculating linear Normalised Difference Vegetation Index (NDVI) trends in locations hit by conflicts with respect to the incident date, using an ordinary least square model. To exclude climate influence on the vegetation, over the study period of 1982-2015, the global monthly 4km climate dataset TerraClimate was used to predict NDVI in a multiple linear regression for the periods after the conflicts. It was found that conflicts have neither positive nor negative significant overall impact on vegetation on a global scale (aim 1). Between the types of conflicts (aim 2) and the death number thresholds (aim 4) no significant differences could be identified. The Rwanda results, in contrast to the Afghanistan results (aim 3) showed a disproportional amount of negative NDVI slopes, but again the slopes where not significant. In conclusion, the analysis resulted only in insignificantly small trend changes, which leads to the assumption that on this scale, conflicts have no overall strong impacts on greening.