Linking River Management to Species Conservation Using Dynamic Landscape‐scale Models

Abstract

Efforts to conserve stream and river biota could benefit from tools that allow managers to evaluate landscape-scale changes in species distributions in response to water management decisions. We present a framework and methods for integrating hydrology, geographic context and metapopulation processes to simulate effects of changes in streamflow on fish occupancy dynamics across a landscape of interconnected stream segments. We illustrate this approach using a 482 km 2 catchment in the southeastern US supporting 50 or more stream fish species. A spatially distributed, deterministic and physically based hydrologic model is used to simulate daily streamflow for sub-basins composing the catchment. We use geographic data to characterize stream segments with respect to channel size, confinement, position and connectedness within the stream network. Simulated streamflow dynamics are then applied to model fish metapopulation dynamics in stream segments, using hypothesized effects of streamflow magnitude and variability on population processes, conditioned by channel characteristics. The resulting time series simulate spatially explicit, annual changes in species occurrences or assemblage metrics (e.g. species richness) across the catchment as outcomes of management scenarios. Sensitivity analyses using alternative, plausible links between streamflow components and metapopulation processes, or allowing for alternative modes of fish dispersal, demonstrate large effects of ecological uncertainty on model outcomes and highlight needed research and monitoring. Nonetheless, with uncertainties explicitly acknowledged, dynamic, landscape-scale simulations may prove useful for quantitatively comparing river management alternatives with respect to species conservation. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.

Effects of streamflow reductions on aquatic macroinvertebrates: linking groundwater withdrawals and assemblage response in southern New Jersey streams, USA

“…These findings are highly consistent with the results of other studies that point to changes in streamflow as being a significant driver of changes in assemblage structure and function (e.g. Poff and Allan 1995, Clausen and Biggs 1997, Pusey et al 2000, Bunn and Arthington 2002, Freeman et al 2012. In this study, however, FAMs were developed that predict potential changes in aquatic-macroinvertebrate assemblages relative to changes in streamflow derived from a series of simulated groundwater-withdrawal scenarios.…”

“…Leonard and Orth 1988, Van Winkle et al 1998, Railsback et al 2009); however, recent efforts have strived to develop flow-response models that have broader applicability (e.g. Armstrong et al 2011, Freeman et al 2012, Murphy et al 2012. For this study, the development of empirical FAMs at the basin scale may have broader regional transferability to other streams in the New Jersey Pinelands that respond similarly to groundwater withdrawal because they are underlain by a common aquifer (i.e.…”

States and rates: Complementary approaches to developing flow‐ecology relationships

“…For example, Freeman et al. () applied stream fish colonisation and extinction rates estimated in response to seasonal flow events (Peterson & Shea, ) to simulate annual changes in species‐specific occurrences and assemblage richness for flow time series that reflected different water‐withdrawal levels, at a spatial scale (10 2 –10 4 km 2 ) relevant to local water management decisions. Importantly, ecologists and stakeholders can also use monitoring data to compare measured ecological responses to those predicted given alternative flow‐ecology relations and, over time, narrow uncertainty about flow effects (Peterson & Freeman, ).…”

Causes and consequences of habitat fragmentation in river networks

“…Most existing models of the effects of fragmentation on biological communities are equilibrial, so we know little about the pace at which biodiversity responds to fragmentation (but see Refs. and ). It will be necessary to understand the dynamics of change, as well as the ultimate effects of fragmentation, if we are going to manage fragmented river networks effectively.…”