Identifying non-reference sites to guide stream restoration and long-term monitoring☆
Graphical abstract
Introduction
The reference condition is considered by many as the standard or benchmark for ecological assessments, including measuring the outcomes of restoration projects (Stoddard et al., 2006, Hawkins et al., 2010). Clearly defined goals are essential to objectively guiding and measuring the success of restoration actions (Tear et al., 2005). Naturally, conservation goals and the metrics by which they are evaluated are typically based upon the selection of reference sites and the characteristics they possess. Even so, there continues to be disagreement on how best to evaluate a restoration project's success or failure (e.g., Palmer et al., 2005, Bernhardt et al., 2007, Brewer and Menzel, 2009, Morandi et al., 2014, Suding, 2011).
To aid in the process of reference selection, Stoddard et al. (2006) recommended some standard terminology for use in defining reference conditions. Stoddard et al. (2006) urge that the term “reference” be preserved for systems absent of human disturbance and then suggest terms for several alternative conditions, i.e. “minimally disturbed condition”, “historical condition”, “least disturbed condition”, and “best attainable condition”. While their terminology has been adapted by some, what constitutes an appropriate reference site remains an important yet unsettled issue, as evidenced by the focus of several recent major reviews (e.g., Dallas, 2013, Hawkins et al., 2010, Morandi et al., 2014) and research efforts (e.g., Feio et al., 2013, Kosnicki et al., 2014, Ode et al., 2016). The debate over defining “reference condition” stems, in part, from many regions across the globe having little or no populations of undisturbed sites for adequate representation in biological integrity analyses (Brewer and Menzel, 2009, Dallas, 2013, Feio et al., 2013, Kosnicki et al., 2014).
Regardless of how reference streams are defined, the main precept of the reference stream paradigm suggests that context is necessary to assess biophysical conditions at non-reference sites and interpret what those values mean relative to a given standard (Hawkins et al., 2010). Reference conditions, however, are not the only benchmark that provides context in interpreting the outcomes of ecological assessments (Brewer and Menzel, 2009). Streams of varying disturbance regimes, and the ecological communities they support, also provide additional dimensions in assessing the ecological status of a restoration project and understanding the nature of disrupted mechanisms (or processes) influencing ecological patterns. We term these systems “bearing streams”, as they provide a point of orientation that bears witness to the desired endpoint. “Bearing trees”, as defined by the US Department of Agriculture Forest Service, do not mark the true property corner, but bears witness to that location (USFS, 2013).In other words, they serve as a bearing and distance to the true property corner.
Bearing streams provide a point-of-reference rather than serve as the reference condition, as defined by Stoddard et al. (2006). Identifying both reference and disturbed streams in post-restoration monitoring (e.g., Violin et al., 2011) help to elucidate the impaired processes, and by doing so, they assist in appropriately setting goals and guiding restoration practices to achieve a given endpoint (Roni et al., 2008). In many cases, restoration occurs in areas of intense cumulative disturbance arising from multiple independent and interacting agents, all of which act upon the physiochemical and biological processes that shape the ecological community. Teasing apart the relative roles of each disturbance agent is a difficult, but necessary, step in guiding restoration practice; however, elucidating roles of disturbance is unlikely via direct comparison with reference sites lacking any disturbance. In situations where some disturbances can be ameliorated via restoration while others will remain active agents, selecting bearing streams impacted by individual disturbances may be advantageous in understanding disturbance-mediated processes, which only become evident after long-term monitoring.
A great deal of effort has been expended in identifying regional pools of reference streams to provide standards or benchmarks for biological assessments (Hughes et al., 1986, Whittier et al., 2007, Dallas, 2013: Lunde et al., 2013, Ode et al., 2016).Many of these studies utilize geospatial approaches to characterize landscape conditions and biological survey information to identify best representatives of reference conditions within a region. Developing reference standard criteria is completely appropriate for regional biological assessments, i.e. Indicators of Biological Integrity (Ode et al., 2016); however, these criteria are typically represented by hundreds of reference sites where biological information is available (e.g., Lunde et al., 2013) and not necessarily selected based on the specific physiochemical properties or anthropogenic disturbance regimes that approximate conditions at individual restoration sites. Indeed, restoration practices require very specific guidance to set realistic expectations and appropriate actions (Suding, 2011). Additionally, we suggest that non-reference sites help provide some of this guidance. Programs that monitor the effectiveness of restoration may arbitrarily select reference sites that either match pre-conceived preferences or are convenient (e.g., easily sampled, accessible, part of existing sampling regimes, etc). For example, the justification for selecting restoration comparison sites (reference or non-reference) is typically based on access or priority from social emphasis (e.g., Violin et al., 2011, Kondolf et al., 2008). To avoid human-generated biases, a comprehensive geographic approach to selecting reference and non-reference sites (i.e., bearing streams) is recommended, especially not limiting the selection to only sites biologically sampled.
Herein, we present a spatial framework as a 1st-step screening criteria to identify bearing streams (both reference and non-reference condition) to guide stream restoration. The framework is structured as a step-wise procedure that requires managers clearly define and revisit goals and objectives of restoration while also evaluating all potential streams that could approximate those goals. First, we provide a brief overview of the spatial framework and its elements. Then we apply the framework to a case study of East Fork Poplar Creek, the focus of a 30-year pollution remediation and biological monitoring program. Multi-dimensional impacts from large-scale chemical contamination and urbanization and the sheer complexity of the ecosystem present an ideal situation requiring the additional context of non-reference streams to isolate impaired physical and ecological mechanisms still at play in the stream.
Section snippets
Spatial framework
The proposed framework includes six main elements, which can be used to incrementally screen and reduce the potential number of bearing streams (Fig. 1). The elements are collectively drawn from our review of the literature related to: developing candidate reference sites (e.g., Hughes et al., 1986), lack of suitable reference sites (e.g., Dallas, 2013), understanding watershed disturbances to prioritize restoration efforts (e.g., Beechie et al., 2008), using typologies to infer reference
Case study
We applied the spatial framework to identify potential bearing streams for East Fork Poplar Creek (EFPC) Tennessee, a system impacted by substantial chemical contamination, channel alteration, and urbanization followed by intense remediation and pollution abatement efforts. For over 30 years, EFPC has been the focus of large-scale remediation efforts and a long-term biological monitoring program (Peterson, 2011, Loar et al., 2011), a sampling regimen that included reference streams as
Discussion
Our spatial framework identified both low-disturbance and non-reference sites to be used as comparisons to restoration sites in order to guide restoration actions or long-term monitoring. Rather than develop a substantive pool of reference sites within a region (e.g., Ode et al., 2016), our framework narrowed the selection of potential bearing streams down to a handful of sites that mirrored well-defined endpoints of disturbance regimes, physiochemical properties, and ecological conditions. For
Conclusions
We provided a framework to identify specific low-disturbance and non-reference sites as comparisons to restoration sites. Substantial literature exists on defining reference conditions (Hawkins et al., 2010, Dallas, 2013, Ode et al., 2016), prioritizing restoration actions (Bohn and Kershner, 2002, Beechie et al., 2008), or developing appropriate restoration endpoints (Palmer et al., 2005, Tear et al., 2005, Miller and Hobbs, 2007). In contrast, the scientific literature is deficient of
Acknowledgements
The study was authored by employees of UT-Battelleunder contract DE-AC05-00OR22725 with the US Department of Energy. This research was sponsored by the Environmental Compliance Department of the Y-12 National Security Complex and by the Oak Ridge National Laboratory's Environmental Protection Services Division's Water Quality Programs. We thank Allison Fortner and two anonymous reviewers for providing valuable comments on earlier versions of this manuscript.
References (94)
- et al.
Establishing aquatic restoration priorities using a watershed approach
J. Environ. Manag.
(2002) - et al.
History of mercury use and environmental contamination at the Oak Ridge Y-12 Plant
Environ. Pollut.
(2011) - et al.
Regional fish community indicators of landscape disturbance to catchments of the conterminous United States
Ecol. Indic.
(2013) - et al.
Novel ecosystems: implications for conservation and restoration
Trends Ecol. Evol.
(2009) - et al.
How is success or failure in river restoration projects evaluated? Feedback from French restoration projects
J. Environ. Manag.
(2014) - et al.
Long-term recovery of stream habitat structure and benthic invertebrate communities from in-stream restoration
Biol. Conserv.
(2002) - et al.
Identifying regional differences in threshold responses of aquatic invertebrates to land cover gradients
Ecol. Indic.
(2009) - et al.
The challenge of providing e-flow rules to sustain river systems
Ecol. Appl.
(2006) Reproductive guilds in fishes: a proposal and definition
J. Fish. Res. Board Can.
(1975)- et al.
Setting river restoration priorities: a review of approaches and a general protocol for identifying and prioritizing actions
N. Am. J. Fish Manag.
(2008)
Alternative stable states in ecology
Front. Ecol. Environ.
River restoration: the fuzzy logic of repairing reaches to reverse catchment scale degradation
Ecol. Appl.
Synthesizing U.S. river restoration efforts
Science
Restoring rivers one reach at a time: results from a survey of U.S. river restoration practitioners
Restor. Ecol.
Local habitat restoration in streams: constraints on the effectiveness of restoration for stream biota
Ecol. Manag. Restor.
Challenges and prospects for restoring urban streams: a perspective from the Pacific Northwest of North America
J. N. Am. Benthol. Soc.
A method for evaluating outcomes of restoration when no reference sites exist
Restor. Ecol.
Rural land-usetrends in the conterminous United States, 1950–2000
Ecol. Appl.
Physical and biological responses of streams to suburbanization of historically agricultural watersheds
J. N. Am. Benthol. Soc.
Stacking species distribution models and adjusting bias by linking them to macroecological models
Glob. Ecol. Biogeogr.
Macroinvertebrate assemblages associated with patterns in land use and water quality
Guidelines for Developing and Managing Ecological Restoration Projects
Ecological status assessment in Mediterranean rivers: complexities and challenges in developing tools for assessing ecological status and defining reference conditions
Hydrobiologia
The biological condition gradient: a descriptive model for interpreting change in aquatic ecosystems
Ecol. Appl.
Predicting spatial patterns of plant species richness: a comparison of direct macroecological and species stacking modelling approaches
Divers. Distrib.
Quantitative ecology and impact assessment
J. Environ. Manag.
A working guide to boosted regression trees
J. Anim. Ecol.
Fishes of Tennessee
Least disturbed condition for European Mediterranean rivers
Sci. Total Environ.
Long-term demographic responses of trout populations to habitat manipulation in six Colorado streams
Ecol. Appl.
Defining reference conditions for restoration of riparian plant communities: examples from California, USA
Environ. Manag.
The reference condition: predicting benchmarks for ecological and water-quality assessments
J. N. Am. Benthol. Soc.
Abrupt regime shifts in space and time along rivers and connected lake systems
Oikos
NHDPlus Version 2. NHDPlus Home
Using historical atlas data to develop high-resolution distribution models of freshwater fishes
PLoS ONE
Regional reference sites: a method for assessing stream potentials
Environ. Manag.
The data model concept in statistical mapping
Resource management plan for the Oak Ridge reservation
Spatial considerations for linking watershed land cover to ecological indicators in streams
Ecol. Appl.
Projecting cumulative benefits of multiple river restoration projects: an example from the Sacramento-San Joaquin River system in California
Environ. Manag.
Large-scale flow experiments for managing river systems
Bioscience
Defining the reference condition for wadeable streams in the Sand Hills subdivision of the Southeastern Plains ecoregion
Environ. Manag.
An Ecological Survey of White Oak Creek, 1950–1953. ORO-587
First Report on the Oak Ridge Y-12 Plant Biological Monitoring and Abatement Program for East Fork Poplar Creek. Y/TS-886
Twenty-five years of ecological recovery of East Fork Poplar Creek: review of environmental problems and remedial actions
Environ. Manag.
Identifying reference conditions and quantifying biological variability within benthic macroinvertebrate communities in perennial and non-perennial northern California streams
Environ. Manag.
Selenium bioaccumulation in fish exposed to coal ash at the Tennessee Valley Authority Kingston Spill Site
Environ. Toxicol. Chem.
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This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy.The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes.The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan(http://energy.gov/downloads/doe-public-access-plan).