Evaluating transferability of flow–ecology relationships across space, time and taxonomy

Abstract

Environmental flow assessments are becoming increasingly central to ecologically‐sustainable river management. Rigorous evaluations of flow–ecology relationships serve a vital role in guiding these assessments to meet targeted ecosystem objectives. However, limited resources and widespread environmental change are outpacing the ability to gain knowledge of species’ flow responses and assess environmental needs for rivers individually. Successfully transferring flow–ecology relationships across space and time would facilitate regional‐scale environmental flow assessments, yet the necessary contexts for such success remains a knowledge gap. Here, we leverage long‐term, multi‐species datasets across multiple river basins in southwestern United States as a case study to explore whether relationships between species abundances and hydrological conditions are transferable across space and time. Additionally, we evaluate the potential for ecological guilds based on fluvial dependence and life‐history strategies to facilitate the transfer of flow–ecology knowledge across taxonomic boundaries. Species varied in the spatial transferability of their flow–ecology relationships. Spatial transferability was similar when comparing a species’ flow–ecology relationships within a river basin versus across different river basins, although transferability was considerably greater across free‐flowing rivers compared to regulated rivers. Species’ flow–ecology relationships transferred through time just as well as across space. Ecological guilds defined according to fluvial dependence and life‐history strategies offered just as much potential for transferring flow–ecology knowledge among species as transferring within species across space or time. Our study provides insights into transferring flow–ecology knowledge to support effective, regional‐scale environmental flows. Further research into developing transferable flow–ecology relationships for a wide range of environmental predictors and biological responses across different spatial scales and flow regimes will enable us to keep pace with the increasing demand for science to inform sustainable river management.

Beyond the natural flow regime? Broadening the hydro‐ecological foundation to meet environmental flows challenges in a non‐stationary world

“…However, quantitative ecological responses to hydrologic alteration alone tend to be “noisy” and may have low general transferability (Poff & Zimmerman, ), although stratification by river type and careful selection of ecological metrics can enhance transferability (e.g. Chen & Olden, ). Other factors can themselves limit ecological response potential; therefore, including those factors more actively into e‐flows applications is needed and can improve hydro‐ecological predictions (Kennard, Olden, Arthington, Pusey, & Poff, ; King et al., ; McManamay, Orth, Dolloff, & Mathews, ).…”

Recent advances in environmental flows science and water management—Innovation in the Anthropocene

“…Their paper quantifies the response of the macroinvertebrate community in terms of traditional taxonomic indicators versus ecological traits along a velocity gradient. Chen and Olden () review numerous studies and convincingly demonstrate that trait guilds can provide a sound basis or “basic building block” for transferring flow–ecological relationships within and across river basins experiencing similar climatic and hydrological conditions. Their findings also support efforts to conserve species for which understanding of flow requirements is limited using similar “surrogate species” (Lindenmayer & Likens, ; Webb, Koster, Stuart, Reich, & Stewardson, ).…”

“…: Environmental flows describe the quantity, timing, and quality of freshwater flows and water levels necessary to sustain aquatic ecosystems which, in turn, support human cultures, economies, sustainable livelihoods, and well‐being. In this definition, “Aquatic ecosystems include rivers, streams, springs, riparian, floodplain and other wetlands, lakes, ponds, coastal waterbodies, including lagoons and estuaries, and groundwater‐dependent ecosystems.” Expand measurement of ecological responses to flow to reflect system dynamics: There is a need to move away from static hydrologic metrics and ecological endpoints (ecosystem states) towards a new suite of indicators (process rates, dynamic population models, state‐and‐transition models and species traits) that can help measure the success of environmental flows and broader water management (Bond et al., ; Chen & Olden, ; Monk et al., ; Poff, ; Wheeler et al., ). A complete understanding of biotic response to flow alteration, or to an environmental flow regime, requires information on how species (or trait guilds) respond over the short‐ to long‐term temporal spectrum, measured at the spatial scales needed for species to recruit, disperse and form meta‐population and assemblage structures (Poff, ).…”

Habitat‐specific invertebrate responses to hydrological variability, anthropogenic flow alterations, and hydraulic conditions

“…flow–ecology relationships) represents a key scientific process underpinning many e‐flow methodologies (Davies et al., ; Poff, ; Poff & Zimmerman, ; Tharme, ). Scientists now widely advocate the construction of flow–ecology relationships to guide the implementation of region‐wide e‐flow strategies, in part due to limited resources restricting the collection of detailed ecological and hydrological information on a river by river basis (Arthington, Bunn, Poff, & Naiman, ; Chen & Olden, ; Poff et al., ). As such, the functional properties of biotic communities are being increasingly utilised within flow–ecology relationships (e.g.…”