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Prioritizing management goals for stream biological integrity within the developed landscape context
Citation:
Beck, M., R. Mazor, S. Johnson, K. Wisenbaker, J. Westfall, P. Ode, R. Hill, C. Loflen, M. Sutula, AND E. Stein. Prioritizing management goals for stream biological integrity within the developed landscape context. Freshwater Science. The Society for Freshwater Science, Springfield, IL, 38(4):883-898, (2019). https://doi.org/10.1086/705996
Impact/Purpose:
Understanding the potential outcomes of management is critical where freshwater ecosystems may be constrained by human-related watershed stressors. This manuscript describes a statistical model to understand these constraints and to help prioritize streams for managing biological integrity in developed landscapes. Ranges of biological index scores that were expected relative to the observed landscape were predicted with a state-wide model that uses geospatial data from the US EPA’s StreamCat dataset. A case study is also described where regional managers were shown maps created from the landscape model to evaluate differences between observed and expected biological condition. From these maps, and expert input, stream reaches were prioritized for conservation, restoration, or additional monitoring. Maps showed that many streams were potentially limited in their potential for restoration because of constraints imposed by heavy development. In contrast, two underperforming streams in less-developed parts of the watershed were prioritized for restoration and three high-performing streams were prioritized for conservation. This manuscript provides a clear case study of how modeling of freshwater ecosystems with US EPA-produced data, such as StreamCat, can provide support for decision making by states and potentially provides a model for other states looking to conduct similar prioritizations.
Description:
Stream management goals for biological integrity may be difficult to achieve in developed landscapes where channel modification and other factors impose constraints on in-stream conditions. To evaluate potential constraints on biological integrity, we developed a statewide landscape model for California that estimates ranges of likely scores for a macroinvertebrate-based index that are typical at a site for the observed level of landscape alteration. This context can support prioritization decisions for stream management, like identifying reaches for restoration or enhanced protection based on how observed scores relate to the model expectations. Median scores were accurately predicted by the model for all sites in California with bioassessment data (Pearson correlation r = 0.75 between observed and predicted for calibration data, r = 0.72 for validation). The model also predicted that 15% of streams statewide are unlikely to achieve biological integrity, particularly for urban and agricultural areas in the South Coast, Central Valley, and Bay Area regions. We worked with a local stakeholder group from the San Gabriel River watershed (Los Angeles County, California) to evaluate how the statewide model could support local management decisions. To achieve this purpose, we created an interactive application, the Stream Classification and Priority Explorer (SCAPE), that compares observed scores with expectations from the landscape model to assign priorities. We observed model predictions that were consistent with the clear land use gradient from the upper to lower watershed, where potential limits to achieving biological integrity were more common in the heavily urbanized lower watershed. However, most of the sites in the lower watershed scored within their expected ranges, and were therefore given a low priority for restoration. In contrast, two low-scoring sites in the undeveloped upper watershed were prioritized for causal assessment and possible future restoration, whereas three high-scoring sites were prioritized for protection. The availability of geospatial and bioassessment data at the national level suggests that these tools can easily be applied to inform management decisions at other locations where altered landscapes may limit biological integrity.
URLs/Downloads:
DOI: Prioritizing management goals for stream biological integrity within the developed landscape context