Incorporating food web dynamics into ecological restoration: a modeling approach for river ecosystems

Abstract

Restoration is frequently aimed at the recovery of target species, but also influences the larger food web in which these species participate. Effects of restoration on this broader network of organisms can influence target species both directly and indirectly via changes in energy flow through food webs. To help incorporate these complexities into river restoration planning, we constructed a model that links river food web dynamics to in-stream physical habitat and riparian vegetation conditions. We present an application of the model to the Methow River, Washington, USA, a location of on-going restoration aimed at recovering salmon. Three restoration strategies were simulated: riparian vegetation restoration, nutrient augmentation via salmon carcass addition, and side channel reconnection. We also added populations of nonnative aquatic snails and fish to the modeled food web to explore how changes in food web structure mediate responses to restoration. Simulations suggest that side channel reconnection may be a better strategy than carcass addition and vegetation planting for improving conditions for salmon in this river segment. However, modeled responses were strongly sensitive to changes in the structure of the food web. The addition of nonnative snails and fish modified pathways of energy through the food web, which negated restoration improvements. This finding illustrates that forecasting responses to restoration may require accounting for the structure of food webs, and that changes in this structure, as might be expected with the spread of invasive species, could compromise restoration outcomes. Unlike habitat-based approaches to restoration assessment that focus on the direct effects of physical habitat conditions on single species of interest, our approach dynamically links the success of target organisms to the success of competitors, predators, and prey. By elucidating the direct and indirect pathways by which restoration affects target species, dynamic food web models can improve restoration planning by fostering a deeper understanding of system connectedness and dynamics.

Dam removal: Listening in

“…; Bellmore et al . ; Foley et al ., ]. In turn, these holistic studies could inform the development of standardized metrics to be measured at all dam removal studies, increasing our ability to analyze responses across different removal types.…”

“…Stanley and Doyle [] discussed linking ecological models with geomorphic models to predict how ecosystem processes such as nutrient retention and cycling respond to dam removal. Models developed for other contexts that link food web dynamics to instream physical habitat conditions could be adapted to dam removal [ Doyle , ; Bellmore et al ., ]. These models may be useful for exploring how the complex linkages and feedbacks inherent within ecological systems may govern complex dam removal responses and may identify critical data gaps and uncertainties.…”

Hierarchical multi‐population viability analysis

“…We expected population growth to increase after high flows because of their potential to increase production (Bellmore et al. ) and available space (Dunham and Vinyard ). was centered and scaled on a per‐population basis so that it reflected deviations from each population's normal peak discharge.…”

A network model for primary production highlights linkages between salmonid populations and autochthonous resources

“…To date, there have been few comprehensive efforts to describe these two sources of energy for riverine food webs simultaneously (but see Bellmore et al. ), and thus, broad generalizations of the role of allochthonous vs. autochthonous resources for structuring river food webs remain elusive.…”

“…Despite gaps in knowledge, there is a pressing need for accurate estimates of aquatic production both at local scales and for entire stream networks, particularly within a river-restoration context. Firstly, restoration practitioners increasingly recognize that the success or failure of particular management strategies can depend on how system changes interact with or are mediated by the structure and function of biological communities (e.g., Power et al 1996, Bellmore et al 2017. Accordingly, Naiman et al (2012) provide a recent and compelling argument in favor for pursuing river restoration with an explicit 'food-web perspective' in mind.…”