An Approach for Assessing U.S. Gulf Coast Ecosystem Restoration A Gulf Research Program Environmental Monitoring Report (2022) / Chapter Skim
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3 Assessing Cumulative Effects of Restoration: Current and Emerging Approaches
3 Assessing Cumulative Effects of Restoration: Current and Emerging Approaches
Pages 59-88
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From page 59... ...
Restoration actions taken now will continue to affect the GoM Coast, and environmental changes and interacting stressors have the potential to confound future assessments of the effectiveness of these restoration efforts (Hobbs and Norton, 1996; Manning et al., 2006; Moreno-Mateos et al., 2020; Palmer et al., 2016)
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From page 60... ...
BOX 3.1 Definition of Cumulative Effects The cumulative effects of restoration, as defined in this report, are the collective additive, synergistic, and antagonistic effects of all restoration activities that occur within a setting defined by common or connected characteristics of hydrolo gy, geomorphology, ecology, ecological function, and biodiversity. Assessment of the cumulative effects of restoration may occur at various geographic scales, such as a wetland complex, bay, estuary, watershed, or the Gulf Coast itself.
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From page 61... ...
, the evaluation of cumulative effects may be less important. For all other restoration, the approaches are described in this chapter, which includes: • a detailed overview of antagonistic and synergistic effects of restoration actions; • a description of modes and pathways of several types of cumulative effects; • the use of hypotheses summarized by ecosystem conceptual models; • an introduction to multiple lines of evidence and causal criteria frameworks and in turn, a descrip tion of the various tools needed to develop multiple lines of evidence; • reflections on restoration planning and endpoints, including constraints; and • a case-study discussion of cumulative effects assessment in the annually occurring GoM hypoxic zone.
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From page 62... ...
The diagram indicates important effects occurring in restoration communities from both external and often less controllable sources, as well as from interactions among restoration types. WWTP refers to wastewater treatment plants; H20 refers to water loads; SLR refers to sea level rise; SAV refers to submerged aquatic vegetation; HABs refers to harmful algal blooms.
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From page 63... ...
. The potential for synergistic or antagonistic interactions has implications for designing the spatial configuration of large habitat restoration projects or suites of projects.
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From page 64... ...
Furthermore, net-beneficial interactions between nutrient reduction projects and habitat restoration projects were documented in Tampa Bay (Beck et al., 2019)
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From page 65... ...
Assessing Cumulative Effects of Restoration: Current and Emerging Approaches 65 Figure 3.3. A logic-flow diagram summarizing five altered effect pathways associated with enhanced freshwater inflows to Gulf estuaries.
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From page 66... ...
For example, one sequence of effects of enhanced freshwater flow indicates increased nutrient availability, leading to increased algal-induced turbidity, less submerged aquatic vegetation (SAV) production, less secondary production associated with diminished SAV community health, and, ultimately, reduced fisheries production.
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From page 67... ...
. The applications of HSHMs in the field of ecosystem restoration to date have been limited even though HSHMs provide an opportunity to increase the benefits gained through restoration projects and programs, given that the potential returns of all locations are not equal in light of events such as natural disasters (e.g., hurricanes)
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From page 68... ...
or processes outside of restored Basin (Robertson and Saad, 2021) sites, including interactions between restoration sites Space High spatial density of effects Nonpoint source phosphorus Multiple restoration projects are Mobile Bay or landbridge in Louisiana crowding management in Florida coastal waters implemented within the same (Gregory Steyer, presentation to the (Yang and Toor, 2018)
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From page 69... ...
. Further, developing a better understanding of the combination of drivers and stressors responsible for triggering HSHMs and ecosystem control points for a particular ecosystem could help to incorporate them in a predictive modeling framework for assessing the cumulative effect of restoration projects.
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From page 70... ...
" To help inform adaptive management of the trajectory, it can be valuable to consult the conceptual model that guided restoration design. Conceptual Models Conceptual models are graphical representations of interrelationships between drivers, pressures, stressors, restoration actions, and ecosystem response, based on one or a series of hypotheses (Gentile et al., 2001; Suter, 1999)
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From page 71... ...
. At regional and larger levels, the Chesapeake Bay Program and its partners have used conceptual models throughout the development and implementation of their action plan to help guide research, project implementation, and assessment of cumulative effects, as discussed in the following section (Linker et al., 2002, 2013; Shenk et al., 2012, 2013)
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From page 72... ...
; nutrient load reductions exhibit the strongest effects close to load-reduction locations; and season and location are also important, with high-salinity areas responding to small load reductions during the nutrient-limited summer season. The Chesapeake Bay Program uses a variety of models, from qualitative conceptual models to complex spatially explicit simulation models.
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From page 73... ...
The Chesapeake Bay example, discussed above, can be used to illustrate the concepts of multiple lines of evidence, causality, and thresholds. From the beginning of the Chesapeake Bay Program in the 1980s, extensive monitoring data analysis and various types of modeling, such as mass-balance models and largescale numerical models, were undertaken.
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From page 74... ...
Description of Seven Lines of Evidence for the Recovery of Aquatic Species through Habitat Restoration Data Summary Analysis Synthesis Evaluation Cumulative Effects Line of Evidence Monitored Indicators Analyses Causal Criteria † Category ‡ a. Research on Various Summarize advances in Plausibility, temporality, Indirect, time lags, Critical Ecological understanding cause– specificity, coherence, compounding Uncertainties effect associations; exposure pathway, iterative improvement of predictive performance the conceptual model b.
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From page 75... ...
As discussed in the Chesapeake Bay example, uncertainties are often acknowledged at the outset, during development of ecosystem conceptual models. They can also arise during project and program implementation, especially when things go wrong or there are unexpected outcomes (Ebberts et al., 2018)
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From page 76... ...
, and water quality models (Moriasi et al., 2015) -- have been used to examine alternative coastal restoration project designs, the impact of sea level rise on coastal ecosystems, water column characteristics, soil erosion potential and soil–water dynamics, movement of riverborne sediments, carbon flux dynamics in wetlands, and other hydrological and geomorphological processes (e.g., Brown and Pevey, 2019; Burchard et al., 2006; Hiatt et al., 2018; Leach et al., 2021; Passeri et al., 2015; Rogers et al., 2012; Wassmann et al., 2006)
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From page 77... ...
The results of many GoM restoration projects initiated after DWH for restoring coastal nursery habitats, such as oyster reefs, salt marshes, and seagrass meadows, are still under way or in the process of being analyzed, and in lieu of formal meta-analysis, a qualitative meta-analysis of interim reports could be informative. As an example, reports developed during the initial phase of the multi-State/EPA Chesapeake Bay Program (1978–1983)
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From page 78... ...
For example, a marsh restoration site can use a bird population model to examine the changes in species dynamics and individual traits before and after the restoration projects. Population models have been widely used in the GoM to project changes in plant or animal populations in response to types and severity of background trends, particularly in developing Gulf-wide or regional fisheries and endangered species management plans.
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From page 79... ...
. Because this additive function considers multiple restoration efforts in a particular geographic area, it can be a useful tool for assessing the cumulative effects of multiple restoration projects relative to a specific target function.
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From page 80... ...
MBNEP and partners intend to use the BCG for monitoring status and trends, communicat ing with the public, developing numeric criteria for conditions, tracking management effectiveness, and inform ing coastal restoration efforts (MBNEP CCMP, 2018; Vittor and Associates, 2019)
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From page 81... ...
. Data-driven modeling tools to assess cumulative effects of large-scale restoration projects need large amounts of data, whether field, simulated, climate, and other biophysical data; satellite-derived spatial or point data; or a combination of all data (Crisci et al., 2012; Goldstein and Coco, 2015; Vinuesa et al., 2020)
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From page 82... ...
These data-driven models can be valuable to analyze cumulative effects across multiple restoration projects at a variety of scales, provided sufficient training data are available at the initial stages. Although these models have not yet been widely adapted by researchers and restoration managers for large-scale cumulative impact assessment in the GoM, they have been increasingly popular for many types of ecosystem monitoring and predictions in the past decade, including wetland biomass, primary production, species dynamics, habitat suitability, and driver-response characterization studies (Huang et al., 2021; Michaels et al., 2019; O'Connell et al., 2021; Ridge et al., 2020; Shiu et al., 2020)
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From page 83... ...
. Planning by the DWH funding entities required the invention of systems for both prioritizing restoration projects and evaluating their outcomes, with many projects proposed at ecoregional (e.g., Chenier Plain)
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From page 84... ...
Traditionally, a selected restoration project yields projected benefits, or net ecosystem improvement (Thom et al., 2005) or net ecological gain (National Infrastructure Commission, 2021)
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From page 85... ...
Of course, this is only the preliminary funding and granting effort, and much more will be completed in the future, but it does illustrate the difficulties of scale and points to the necessity of explicitly determining an appropriate scale for cumulative effects assessment and the need to scale restoration efforts to a size appropriate for addressing the ecosystem problem. Further, a lack of evidence of cumulative effects at the regional scales does not necessarily point to a failure of individual restoration effects, but rather may be due to an insufficient relative scale of change.
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From page 86... ...
. This single annual measurement of the hypoxic zone is an indicator of cumulative effects of human and natural systems on water quality and ecosystem health across large scales and long time periods.
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From page 87... ...
Examples Relevant to Restoration Efforts to Reduce the Hypoxic Zone Compounding Multiple wetland restoration projects upstream can generate additive nutrient reductions. Triggers and Thresholds Once the temperature is warm enough, harmful algae blooms (HABs)
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From page 88... ...
The effort to maximize successful large-scale restoration efforts is a daunting task not only because of the normal complexities of these coastal ecosystems, but also because of trends in important chronic and acute influences on these ecosystems. As shown in the case studies, these complexities are present in the long-term and ongoing Chesapeake Bay Program and in the development of hypoxia in the GoM.
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