Short- and long-term evacuation of people and livestock during a volcanic crisis: lessons from the 1991 eruption of Volcán Hudson, Chile

Human and livestock evacuation during volcanic crises is an essential component of volcanic risk management. This study investigates the evacuation of human and livestock populations from areas impacted by ashfall from the 1991 Hudson eruption, Patagonia. The eruption was one of the largest in the 20 century resulting in significant impacts on rural communities in affected areas, including the evacuation of people and livestock. In the short-term (<3 months), evacuation of people from farms and rural towns was driven primarily by ashfall and ash storm impacts on public health and essential services. Severe impacts on livestock and the inability to restore vegetation growth following pasture burial, also meant pastoral farming became unsustainable in the short term. This resulted in evacuation of farms for usually <1, but up to 4 years following the ashfall and subsequent intense ash-storms. In areas of very heavy ashfall (>1 m) or where agricultural systems were stressed (from drought and long-term low commodity prices) many farms were abandoned, resulting in permanent migration of the farm population. Farms and farmers under pressure from marginal economic returns were the least likely to cope with the ‘shock’ of the ashfall. The financial capacity of farmers was important in their resilience and ability to return once conditions improved, although emotional attachment to the land sometime outweighed financial considerations. Evacuation of livestock in areas affected by ash falls was undertaken by many farmers, but it was not very successful or economically justifiable. Access for livestock trucks to the impacted area was difficult due to a poor road network, ashfall and snow induced blockage, and remobilised ash inhibiting visibility. The lack of reliable records of livestock populations inhibited evacuation and efforts to supply supplementary feed to the remaining livestock. The very poor condition of livestock prior to the eruption and burial of feed following the eruption often made evacuation uneconomic as well as reducing livestock resilience to cope with the eruption and transport impacts. The lack of capacity within the local livestock market and lack of available grazing land for the influx of transported livestock were also key failings of the evacuation effort.