Impacts, effects, and food webs: Integrating science and conservation perspectives into non-native species management on the Channel Islands

Unanticipated outcomes from non-native species management programs provide compelling evidence that “restoration” will often not be a useful concept to base these programs on. From an objective ecological perspective these outcomes represent a range of interactions that reflects the complexity inherent in ecological systems. But from a values-based conservation perspective many outcomes have been undesirable. In addition, positive interactions between native and non-native species conflict with management policies that generally consider non-native species undesirable. A critical implication of the ecological perspective is that management of non-native species, especially where many have been present for long periods of time, is likely to send systems on unpredictable trajectories. This may lead to alternative ecosystem states and transitions, some of which may or may not meet “restoration” or “recovery” goals. Non-native species management programs would benefit greatly by: (1) conducting studies that are not focused exclusively on documenting “impacts”, but identifying the roles non-native species play within ecosystems; (2) using multi-trophic level conceptual models as a management program framework; (3) identifying the phase of the invasion process target species are in and linking this explicitly to likely management options; (4) planning and evaluating program outcomes from both conservation and ecological perspectives; and, (5) implementing monitoring programs several years before, during, and after management actions. This framework is especially important in the Channel Islands, where most management actions are, in one way or another, related to reducing or eliminating effects from non-native plants and animals.