A synthesis of the effects of multiple stressors on a long-lived vertebrate population to inform effective conservation efforts

Ecological restoration focuses on the recovery of impacted wildlife populations, but the actions that caused the injury cannot always be reversed. Modelling the cumulative risk from multiple stressors helps predict the benefit of reducing other activities that can be managed. We synthesize diverse data from a bottlenose dolphin population that suffered long-lasting health effects following the 2010 Deepwater Horizon oil spill. We demonstrate how results from health assessments, analysis of scarring from traumatic injury as a function of health status and epigenetic age analysis could be integrated to inform a model for the population consequences of multiple stressors. We use the model to simulate management scenarios involving the reduction of other stressors beyond oil exposure. Chronic health effects continue more than 10 years post-spill, and scar prevalence indicates that oiled animals may also be more likely to get struck by vessels. Moreover, chronic effects of entanglements are evidenced in individuals’ epigenetic patterns. Simulated scenarios suggest that the reduction of lethal vessel strikes could have accelerated population recovery if implemented promptly after the spill, but could still be beneficial. The assessment of combined effects and the targeted reduction of stressors that can feasibly be managed can support effective conservation efforts.