Crop vulnerability to tephra fall in volcanic regions: field, experimental and modelling approaches.Approximately 800 million people populate areas within 100 km of a potentially active volcano. Since the beginning of human settlements, communities in volcanically active regions have enjoyed various benefits from volcanic eruptions, notably the occurrence of volcanic soils with outstanding agricultural capabilities. However, these populations are also exposed to the potentially disastrous impacts of volcanic hazards, of which tephra fall produced during explosive activity is the most frequent and widespread, affecting areas of up to several tens to hundreds of thousands km². Agriculture is the economic sector most impacted by tephra emissions during explosive volcanic activity, posing serious threats to agricultural activities and rural livelihoods. Crops are particularly vulnerable to tephra, with impacts ranging from reduced yields to total destruction. Although the detrimental effect of tephra on vegetation has long been recognised, our current understanding of crop vulnerability to tephra suffers from a significant deficit in knowledge. This situation is rooted in limited data availability and poor descriptions of the intertwined volcanic and non-volcanic factors dictating the level of tephra damage to crops. As a result, our capacity to inform appropriate risk reduction, management, and long-term recovery strategies in regions exposed to volcano-related hazards is limited. In this PhD research, we have identified the main impact mechanisms explaining crop production loss after exposure to tephra and their governing factors. We have also generated a new database that can underpin the development of quantitative tools for describing crop vulnerability to tephra. These results will aid in the development of more robust risk assessment methodologies for crops subjected to the tephra hazard. Jury members:Prof. Pierre DELMELLE, Supervisor Prof. Patrick BOGAERT, Supervisor Prof. Emmanuel HANERT, Chairperson Prof. Xavier DRAYE, Secretary Dr. Benjamin BERNARD, Instituto Geofisico-EPN, Equator Dr. Sébastien BIASS (Université de Genève, Switzerland) |