Societal risk-to-life from natural hazards: Assessments, acceptability and actions at Whakaari/White Island and Piopiotahi/Milford Sound, Aotearoa/New Zealand

Conventional tourism risk-to-life analyses require data that are often unavailable, inaccurate or out-of-date. Thus tourist fatalities can occur where risk analyses have not been completed, as at Whakaari/White Island volcano, New Zealand in 2019, when 22 people on commercial tours died because of a sudden eruption. Even where risk analyses have been carried out (as at Piopiotahi/Milford Sound, New Zealand, a World Heritage Site where thousands of lives are endangered by coseismic landslide-triggered tsunami) unacceptable risks remain because (i) analyses can be misinterpreted, (ii) risk calculations change with time, and (iii) sociopolitical factors influence risk management decision-making. Herein we (i) develop a methodology for reconnaissance ("average") risk-to-life assessment, to indicate where more complete assessments are required, and (ii) test this against (a) the empirical acceptability of risks following a disaster and (b) a series of risk analyses where no disaster has yet occurred. We develop an “average” risk-to-life assessment for Whakaari/White Island, and compare its outcomes with existing risk analyses for Piopiotahi/Milford Sound. It agrees with post-event risk acceptability at Whakaari/White Island, and with pre-event risk analyses at Piopiotahi/Milford Sound. We update the “average” risk analysis for Piopiotahi/Milford Sound by incorporating vulnerabilities of cruise ships and improved hazard data - the societal risk-to-life is unacceptable by several orders of magnitude. The only feasible strategy for achieving acceptable risk is drastically reducing visitor numbers. Socio-economic considerations suggest that this may not be societally practicable, which calls into question the way in which risk is used in planning to reduce tourism fatalities.