Using Natural Disturbance and Portfolio Concepts to Guide Aquatic–Riparian Ecosystem Management

Abstract

The U.S. Forest Service and other federal land managers are responsible for maintaining the productivity of aquatic–riparian ecosystems, the associated native biota, and the ecosystem services they provide. These public lands are important sources of water, recreation opportunities, and habitat for a suite of animals and plants, including many that are protected under the Endangered Species Act. To meet these challenges and responsibilities, recent science suggests modifying practices to provide a broader array of habitat, biological conditions, and ecosystem functions than are associated with traditional management approaches. We suggest that by linking approaches based on natural disturbance and portfolio concepts, managers can achieve a robust strategy and desired outcomes more reliably and cost effectively. Locally complex habitat conditions created by natural disturbances provide the template for biological diversity to play out if provided enough time. Accordingly, natural disturbance regimes play an important role in creating and sustaining habitat and biological complexities on the landscape, suggesting that, to the extent possible, management actions should emulate natural disturbance processes at appropriate spatial and temporal scales. In concert with this approach, the portfolio effect (i.e., diversity that mitigates risk) provides justification for promoting connected heterogeneous habitats that reduce the risk of synchronous large‐scale population and ecosystem collapse. In this article, we describe how disturbance and portfolio concepts fit into a broader strategy of conserving ecosystem integrity and dynamism and provide examples of how these concepts can be used to address a wide range of management concerns. Ultimately, the outcome for populations, habitats, and landscapes depends on how well environmental change is understood, the degree to which change is appropriately addressed by natural resource managers, and solutions that allow populations and ecosystems to persist in the presence of and be resilient to a growing scope of human influences.

Brook trout (Salvelinus fontinalis) movement and survival after removal of two dams on the West Branch of the Wolf River, Wisconsin

“…We suggest that relatively mobile fish may represent important conduits for utilisation and colonisation of newly accessible habitats and gene flow, even if these fish represent a small component of the overall population. Moreover, in the future, maintaining connectivity may become even more important as the climate continues to change and areas of thermal refugia become more important (Penaluna et al, ). In conclusion, our results indicate that assessing the ecological effects of dam removals may require long‐term evaluations to determine whether objectives related to fish habitat use, reproductive success, genetic diversity and abundance have been met.…”

“…Inductance values on all loops were within the range that the ATC box will effectively tune (24-102 µH). The antenna was tuned using a tuning indicator, which adjusts the frequency resonated by the loop allowing for maximum read range (Oregon RFID, 2009). Each week, a dummy PIT tag was passed through the gate or loop at various locations to confirm functionality and tag detections.…”

Forgotten Legacies: Understanding and Mitigating Historical Human Alterations of River Corridors

“…Disturbance refers to natural processes initiating renewal or change (Penaluna et al, ). Disturbances include relatively infrequent events such as valley or continental‐scale glaciation, which have recurrence intervals of tens to hundreds of thousands of years; moderately frequent events with recurrence intervals of decades to millennia, such as extreme floods or severe wildfires; and relatively frequent events that recur approximately every year, such as seasonal snowmelt or rainfall peak flows.…”

Historical Perspectives and a New U.S. Forest Service Strategy for Fish and Aquatic Stewardship

“…Their work has produced crucial insights into the importance of watershed integrity, natural disturbance regimes, habitat complexity and connectivity, and gene flow for the long‐term viability of aquatic species (Penaluna et al. , this issue). In recent years, USFS scientists have created user‐friendly tools to organize, analyze, and share information about fish habitat and associated watershed characteristics to improve the cost effectiveness of investments in aquatic stewardship (Isaak et al.…”