Sensitivity analysis of the recovery time for a population under the impact of an environmental disturbance

Abstract

Wildlife populations are often affected by natural or artificial disasters that reduce their vital rates leading to drastic fluctuations in population dynamics. We use a stagestructured matrix model to study the recovery process of a population given an environmental disturbance.We focus on the time it takes the population to recover to its pre-event level and develop general formulas to calculate the sensitivity and elasticity of the recovery time to changes in the initial population, vital rates, and event severity. Our results suggest that the recovery time is independent of the initial population size but it is sensitive to the initial structure. Moreover, the recovery time is more sensitive to reductions in vital rates than to the duration of the impact of the event. We explore an application of the model to the sperm whale population in Gulf of Mexico following a disturbance such as the Deepwater Horizon oil spill. Recommendations for Resource Managers • Understanding a population's recovery process following a disturbance is important formanagement and conservation decisions. • This study establishes a general framework that makes it possible to identify the key components in the recovery process. • When applied to a sperm whale population, the recovery time appears to be most sensitive to changes in survival. In addition, themagnitude of impact of a disturbance may have a greater impact on the recovery time than the duration of impact of the disturbance.