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Federal Register / Vol. 86, No. 109 / Wednesday, June 9, 2021 / Rules and Regulations
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that the entire Southeast was under conditions ranging from abnormally dry to moderate drought or severe drought. These data are from the first week in September, which as noted above is a very sensitive time for drought to be affecting both species.
Tributaries in the Neuse River basin had consecutive drought years in the period 20052012, indicating sustained stress on the species over a long period of time. Amphibians and fish have limited refugia from disturbances such as droughts and floods, and they are completely dependent on specific water temperatures to complete their physiological requirements. Changes in water temperature lead to stress and increased mortality, and also increase the likelihood of extinction for both species. Increases in the frequency and strength of storm events, which are caused by climate change, alter stream habitat, either directly via channelization or clearing of riparian areas or indirectly via high streamflows that reshape the channel and cause sediment erosion. The large volumes and velocity of water, combined with the extra debris and sediment entering streams following a storm, stress, displace, or kill Neuse River waterdogs and Carolina madtoms.
Synergistic Effects In addition to individually impacting the species, it is likely that several of the above summarized risk factors are acting synergistically or additively on both species. The combined impact of multiple stressors is likely more harmful than a single stressor acting alone. For instance, effects of sedimentation and predatory fishes on large aquatic salamanders have been found, in which larvae were more affected by predatory fishes and adults were more affected by sedimentation, suggesting that persistence of salamanders was especially threatened in streams with both stressors Lowe et al. 2004, pp. 164, 167170. As an example, within Carolina madtom and Neuse River waterdog habitat, there are 182 miles of impaired streams in the Middle Neuse MU. They have low benthicmacroinvertebrate scores, low dissolved oxygen, and low pH, and they contain Escherichia coli also known as E. coli.
There are 9 major and 272 minor discharges within this MU, along with 287 dams, almost 4,000 road crossings, and droughts recorded for 3 consecutive years in 20082010. If a small, but improperly installed, culvert at a road crossing prevents fish from moving up or downstream, the fish would not be able to escape to deeper areas of the stream during droughts. Similarly, a
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discharge into a stream has more impact on aquatic species if there are no precipitation events immediately following to help flush the system.
These combinations of stressors on the sensitive aquatic species in this habitat likely impact both species more severely than any one factor alone.
We note that, by using the SSA
framework to guide our analysis of the scientific information documented in the SSA reports, we have not only analyzed individual effects on the species, but we have also analyzed their potential cumulative effects. We incorporate the cumulative effects into our SSA analysis when we characterize the current and future condition of the species. Our assessment of the current and future conditions encompasses and incorporates the threats individually and cumulatively. Our current and future condition assessment is iterative because it accumulates and evaluates the effects of all the factors that may be influencing the species, including threats and conservation efforts.
Because the SSA framework considers not just the presence of the factors, but to what degree they collectively influence risk to the entire species, our assessment integrates the cumulative effects of the factors and replaces a standalone cumulative effects analysis.
Conservation Actions The Service and State wildlife agencies are working with numerous partners to provide technical guidance and offer conservation tools to meet both species and habitat needs in aquatic systems in North Carolina. Land trusts are targeting key parcels for acquisition; Federal, State, and university biologists are surveying and monitoring species occurrences; and there has been increased interest in efforts for captive propagation and species population restoration via augmentation, expansion, and reintroduction efforts, especially for the Carolina madtom. However, some of these programs are in their infancy, and currently none provides species-level protection at a scale such that the species would not warrant listing under the Act.
Future Scenarios For the purpose of this assessment, we define viability as the ability of the species to sustain populations in the wild over time. To address uncertainty associated with the degree and extent of potential future stressors and their impacts on species requisites, resiliency, redundancy, and representation were assessed using four plausible future scenarios. These
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scenarios were based, in part, on the results of urbanization and climate models that predict changes in habitat used by the Carolina madtom and the Neuse River waterdog. We developed scenarios by eliciting expert information on two main stressors, urbanization and climate change, that will impact the species in the future. The models that were used to forecast both factors projected 50 years into the future. Using the best available data to forecast plausible future scenarios allows the Service to determine if a species may become an endangered species in the foreseeable future. Relatively long species life spans, well-developed downscaled climate models specific to the region, and adequate human population growth data available for the Southeast region provide some confidence in the range of outcomes predicted over 50 years. Beyond that timeframe, there is too much uncertainty in threats that will be occurring on the landscape and how the species may respond to those threats.
For more detailed information on these models and their projections, please see the SSA reports Service 2021ab, chapter 5.
In the first scenario, the Status Quo scenario, factors that influence current populations of the Carolina madtom and the Neuse River waterdog were assumed to follow current trends over the 50-year time horizon. Climate models predict that, if emissions continue at current rates, the Southeast will experience an increase in low flow drought events IPCC 2013, p. 7. Likewise, this scenario assumed the business as usual BAU pattern of urban growth, which predicts that urbanization will continue to increase rapidly Terando et al. 2014, p. 1. This continued growth in development means increases in impervious surfaces, increased variability in streamflow, channelization of streams or clearing of riparian areas, and other negative effects explained above under Development and Pollution. The Status Quo scenario also assumed that current conservation efforts would remain in place but that no new actions would be taken.
In the second scenario, the Pessimistic scenario, factors that negatively influence Neuse River waterdog and the Carolina madtom populations get worse; reflecting Climate Model representative concentration pathway RCP 8.5
Wayne 2013, p. 11, effects of climate change are expected to be magnified beyond what is experienced in the Status Quo scenario. These predicted effects include extreme heat, more
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