Ruapehu 1995-96


As a result of a less than 5 mm (0.2 in) ashfall on the Rangitaiki Plain (Taupo) during the 1995 Ruapehu eruption, approximately 2,000 ewes and lambs (2.5% of the area's sheep population) were killed by eating ash-affected pastures. Autopsies of the dead animals suggest fluorine poisoning or pregnancy toxaemia as the cause of death. Three Ayrshire dairy cows died at Atiamuri in June 1996. It was reported that they had stopped eating and showed signs of lethargy after swallowing quantities of ash; toxic levels of fluorine were found in the dead animals' blood. The Department of Conservation also reported the death of a number of wild deer in the Kaimanawa Ranges, located downwind from Ruapehu, following the two largest October 1995 eruptions (possibly up to 5% of the sika deer population). Livestock losses from the eruption of Ruapehu in 1995 were greatest in lactating ewes, grazing short pasture.

During the eruption, ashfall of 2 mm on pastoral land elevated soil sulfur levels and lowered soil pH by 0.2-0.3 units compared to pre-eruption values. One benefit was the reduction in sulfur requirement in annual fertilizer applications for many farms.