Models in the penstocks: putting theory to work for river conservation

Background/Question/Methods

Basic ecological understanding grounds proactive river conservation. Approaches such as invasive species biocontrol, dam removal, and protected area design draw on conceptual expectations regarding consumer-resource interaction, metapopulation dynamics in fragmented habitat, and niche dimensions. As quantitative expressions of these ideas, models provide virtual laboratories to test management alternatives, evaluate climate scenarios and target data collection.

I describe the ongoing development of models designed to improve strategic conservation by enhancing the representation of spatiotemporally complex ecological processes in river environments. Working across a range of mechanistic detail and spatiotemporal scales, my colleagues and I have initiated the construction of several tools focused on the question of how global change will affect riparian vegetation dynamics.

As part of a larger environmental flow needs assessment, a regional scale implementation of the ELOHA framework addresses the influence of altered flows on native cottonwood (Populus sp.) establishment within particular fluvial geomorphic settings.  Transition matrix approaches enable the evaluation of population dynamics and age class structure relative to the life history traits of native versus invasive species subject to varying levels of flooding. Floodplain-scale individual-based simulations permit climate and management scenario analyses relative to the interaction of abiotic drivers (e.g. flood scour, groundwater decline, heat stress, etc.) and biotic controls (e.g. exploitative competition for establishment sites, herbivory by biocontrol agents) of stand composition within a local community. 

Results/Conclusions

Although they differ in their mode of implementation, these approaches all emphasize the importance of hydrogeomorphic variability in structuring fluvial ecosystems, a broadly relevant factor across models of various biological response patterns.  This work also illustrates three research priorities for the refinement of applied models at the population/community scale: better integration of evolutionary forces, socioeconomic drivers and reciprocal feedbacks between physical and biological processes. I will discuss these models’ specific assumptions and conclusions while describing the plans for their continued development in the larger context of the ecological theory informing conservation in flowing waters.