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Conservation science is tasked with quantifying the relative importance of multiple threats to endangered species, both to determine if cumulative disturbances exceed sustainable levels and to guide effective recovery plans. In so doing, the first axiom is that the most severe threats of extinction should be abated while the addition of new hazards is stopped. Accordingly, endangered Southern Resident killer whales are a conservation reliant species requiring ongoing protection because they live in a degraded environment that can no longer sustain them. All available evidence confirms the present level of human caused disturbances is more than the whales can tolerate.

Optimistically, the current threats exposing the population to extinction and preventing recovery could be moderated but not eliminated. Rarely understood but critically important, multiple stressors that are moderated are still cumulative. Combined and acting synergistically, even mitigated multiple stressors would likely remain significantly higher than all the disturbances whales coevolved with and progressively adapted to over millennia.

Experiencing almost no population growth, Southern Residents have remained at a population size of less than 100 individuals for the last four decades, with an average of 85 individuals in the last decade. The population now stands at 76 individuals. At present, nutritional stress associated with reduced abundance and availability of the whales’ primary prey, Chinook salmon, is the most important negative influence affecting population wellbeing. Any future conditions that increase noise, reduce food, or expose individuals to random death, will significantly increase the risk of extinction. If any of these threats combine, extinction of the Southern Residents within the next century is probable.