Incorporating aquatic ecology into decisions on prioritization of road decommissioning

Roads provide increased access to lands rich in natural resources and beauty, but they can also damage those lands and the ecological values therein. In particular, much interest has been focused on the hydrologic and geomorphic changes in roaded watersheds and their effects on aquatic ecosystems (Lee et al., 1997; Dunham and Rieman, 1999; also see papers in Luce and Wemple, 2001). As a consequence, most public land management agencies and some private forest land managers are closing and rehabilitating roaded areas to restore forest productivity and improve watershed function. The decision to decommission or to retain a road is complex and often controversial and involves many issues, including aquatic ecosystem health. While some controversy may be inevitable, managers and specialists given the task of selecting roads to decommission need scientific, ecologically-based criteria to guide their decisions. Existing guidance, however, is limited primarily to descriptions – and occasionally models – of how roads alter stream hydrology, geomorphology, and ecology. Little guidance exists on the effectiveness of road decommissioning and alternative treatments. Coherent strategies for road system management and closure that consider potentially conflicting objectives and opportunities in multiple use and ecological management would be useful (Rieman et al., 2000). Setting priorities for road closure and decommissioning is not a new practice, and a variety of strategies have been used. While watershed restoration may be a primary motivation, other strategies may emerge where, for example, wildlife or recreation concerns predominate. The most common priority is the ‘problem’ roads that yield substantial mass wasting or severe surface erosion. Such roads represent a small fraction of most road systems, and many such roads have already been decommissioned. Some proponents of road decommissioning strongly favor prioritizing streamside roads that directly contribute surface erosion, constrain the channel, and reduce shading. Others note that roads in the riparian corridor often have lower gradients than midslope roads and drain to more stable ground so they may represent less of a potential problem. Yet others support a strategy that would reduce road density by decommissioning as much of the road system as financially, practically, and politically feasible. Dead-end ridgetop and short spur roads supporting management of individual stands and recently constructed roads are common targets. In some cases, sediment modeling has been used to support prioritization for road closures and decommissioning. This is often in response to the goal of managing basin-wide sediment yields to be within prescribed limits, such as those prescribed by state’s criteria and the Federal Clean Water Act. Despite the obvious rationale for managing and closing roads, there is no common framework for prioritizing management alternatives. Evaluating and prioritizing alternative road management strategies will be difficult, given the diverse nature of watersheds, aquatic ecosystems, and specific effects of roads. However, we believe there are some fundamental principles that can inform a more thoughtful strategy, including the following: