Natural Disturbance and Post-Disturbance Management Effects on Selected Watershed Values

This extension note summarizes the key findings of the chapter entitled "A synthesis of the effects of natural disturbance and post-disturbance management on streamflow, stream temperature, suspended sediment, and aquatic invertebrate populations" of FORREX Series 28, which is an overview of the available research on the effects of climate change, natural disturbance (focused on wildfire and insect infestation), and post-disturbance management actions (primarily clearcut salvage harvesting) on key watershed processes and values. The scope of the synthesis was limited to the magnitude and timing of streamflow, stream temperature, suspended sediment, and aquatic invertebrate population dynamics. In general, the effects on hydrologic processes and watershed functions are greater following post-disturbance activities; climate change is anticipated to further negatively compound these natural disturbances. To maintain the resilience of watersheds(that is, the ability of natural systems to recover from perturbation), management activities should be designed to maintain natural hydrologic and ecosystem function wherever possible. Key considerations to maintain resilience include: planning management activities at the site, watershed and landscape scales, maximizing riparian overstory retention within 10 metres of streams, minimizing the introduction of fine sediments into surface water bodies, and monitoring the effects of disturbances and management interventions to support adaptive management. Using the best available information, along with advice from qualified watershed professionals, is key to ensuring effective management.