Review of the Edwards Aquifer Habitat Conservation Plan Report 2 (2017) / Chapter Skim
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3 Ecological Modeling
3 Ecological Modeling
Pages 49-72
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From page 49... ...
The model results will help the Applicants develop alternative approaches or possible mitigation strategies, if necessary." The ecological models should be able (1) "to predict specific ecological responses of the Comal and San Marcos Springs/River ecosystems and associated Covered Species to various envi onmental factors, both natural and anthropogenic"; r (2)
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From page 50... ...
NRC (2015) discussed the basic design of the FD model, including the decision to develop an individual-based model, and it opined on several precursors to the model, such as the habitat suitability analyses done for FD, Texas wild rice, and the Comal Springs riffle beetle (CSRB)
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From page 51... ...
The EAA has now provided a scientifically sound foundation on the way to developing a generalized ecosystem-based conceptual model. The process of developing the FD and SAV models, and the associated con
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From page 52... ...
It is hoped that the conceptual models produced to date, and their further expansion to the overall ecosystem, will not only serve to guide devel opment of the predictive models, but will provide a powerful integrative communication tool for the overall HCP and better coordinate the diverse expertise found across EAA's multiple advisory committees and contractors, particularly in cases where differences in opinion, interpretation, and under tanding might be prevalent. In addition, the conceptual and predic s tive ecological models should be used to evaluate the minimization and mitigation (M&M)
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From page 53... ...
ECOLOGICAL MODELING 53 FIGURE 3-1 Generalized frameworks developed by the EAA providing conceptual linkages between potential forcing factors and important response variables for fountain darter and submersed aquatic vegetation abundances. SOURCE: Adapted from BIO-WEST, 2015.
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From page 54... ...
The RRWG's response ("Done") made it clear that they did not see the value of continuing work on the habitat suitability analysis for FD given their focus on developing the mechanistic ecological model.
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From page 55... ...
That is, page 4-38 of the HCP states that "In 2010, the EARIP held workshops involving a multi-disciplinary team of biologists to develop influence diagrams regarding the impacts on fountain darters, Texas wild rice, and the Comal Springs riffle beetle. These species were believed to be good indicator species for the impacts on other Covered Species." There appears to be disagreement about whether the CSRB is an indicator species, particularly because assumptions about CSRB behavior during low flows (retreating into subterranean habitat)
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From page 56... ...
The ideas and concepts for designing scenarios apply to both the FD and SAV models, as well to ecological models in general. Then, a set of possible scenarios specific to the FD model are provided to illustrate the types of questions that could be addressed once the model is deemed management-ready.
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From page 57... ...
How do two consecutive years of 1 percent chance droughts within 20 years of historical conditions of flow affect the long-term (20-year) average annual population abundance of adult fountain darter?
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From page 58... ...
. The questions should also be informed by the types and needs of the management actions being considered under the Habitat Conservation Plan.
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From page 59... ...
With such a model, no other changes would be needed to test scenarios about how flow affects growth rates and population dynamics. Different time series of flows can be input to the model, and the predicted population dynamics can be compared.
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From page 60... ...
Examples of stochastic effects relevant to the FD model include the occurrence of drought conditions, variation in spring flows from year to year, and fluctuations in abundances of predators. Common sources of uncertainty are the use of laboratorybased measurements to estimate model parameters, use of multiple field studies that occurred in different time periods, and inability to specify unique formulations of processes in the model because alternative formulations result in equally valid fits to the available data.
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From page 61... ...
What sources of stochasticity are represented? Is uncertainty kept track of, including uncertainty in the data used to define the scenarios and from the outputs of other models that are used as input to the fountain darter model?
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From page 62... ...
should be clearly stated. Explanations for Predicted Results The power of using ecological models is that, not only can state variable or aggregate predictions (such as population abundance)
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From page 63... ...
. Example Fountain Darter Model Scenarios Some example sets of simulations are provided to illustrate the types of questions the FD model could be used to address.
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From page 64... ...
Each M&M measure can then be viewed as affecting certain life stages and processes, at certain times during the year, and in certain spatial areas. How well the M&M measures match up with sensitive life stages, processes, seasons, and areas can guide monitoring to ensure a high likelihood of detecting local responses to management actions.
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From page 65... ...
The SAV model that would allow for dynamic and spatially explicit responses of SAV to management actions is not yet operational. Rather, the FD model presently uses observed SAV maps and switches them every six months in simulations to match the historical progression of the observed maps.
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From page 66... ...
Shorter-term predictions are typically more influenced by the state of the population at the time of stress, whereas long-term predictions are influenced by the density-dependence in the model. General Suggestions Regarding SAV Model Scenarios As mentioned previously, the SAV model is not yet far enough along in its development for detailed suggestions regarding scenarios.
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From page 67... ...
A guiding question behind such a series of simulations might be "how many consecutive years of drought or low flow protection measures can the system withstand? " One of the strengths of the SAV model will be its ability to evaluate M&M measures and help to inform associated adaptive management decisions.
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From page 68... ...
The conceptual diagrams produced to date for the FD and SAV ecological models will help to guide further development of whole-system conceptual models. This collection of conceptual models will provide a communication tool for the HCP, will aid in coordination of the diverse expertise found across EAA's multiple advisory committees and contractors, and will serve an important function, along with the predictive ecological models, to evaluate the appropriateness and efficacy of the M&M measures.
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From page 69... ...
Edwards Aquifer Habitat Conservation Plan Contract No.
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From page 70... ...
2016. Evaluation of the Predictive Ecological Model for the Edwards Aquifer Habitat Conservation Plan: An Interim Report as Part of Phase 2.
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From page 71... ...
2015. Comal Springs Riffle Beetle Occupancy Modeling and Population Estimate within the Comal Springs System, New Braunfels, Texas.
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