Reigniting healthy resilience: Using disturbance to overcome negative resistance and resilience

Abstract

‘Resistance’ and ‘resilience’ describe the capacity of ecosystems to withstand and recover from disturbance. Often linked to ecological health, these regularly underpin restoration goals. However, degraded ecosystems can also be resistant and resilient to disturbance (negative resistance and resilience) making their communities highly stable and thus restoration resistant. We investigated this post-restoration scenario (physical recovery without biological recovery) using a stream mesocosm experiment, demonstrating that presence of a persistent degraded community can hinder biological recovery. We propose degraded communities must first be destabilised to facilitate recovery, requiring understanding of how degraded communities are assembled. To detangle trait environment relationships, we conducted a meta analysis of New Zealand streams across both anthropogenic and natural disturbance gradients. Trait based ordination indicated different disturbance gradients shape communities along different axes of change, informing restoration by identifying disturbances which could disrupt existing trait environment relationships, displacing less desired taxa. We tested this theory in channel experiments, investigating how different community types responded to additional disturbance. Responses depended on disturbance history: novel disturbances incited the most community change. Thus, there is potential to overcome negative resistance and resilience by applying disturbance as a restoration tool to direct community recovery.