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Federal Register / Vol. 86, No. 243 / Wednesday, December 22, 2021 / Proposed Rules
would respond to the changing conditions. We used the best available data and models to project out 30 years into the future i.e., 2050.
We chose this timeframe based on the subspecies life span and observed cycles in population abundance, as well as the time period where we could reasonably project certain land use changes and urbanization patterns relevant to the pygmy-owl and its habitat. The majority of the projections of urbanization and population growth within the geographic range of the pygmy-owl extend to 2050. Since urbanization and development are some of the primary drivers of habitat loss and fragmentation, we extended our analysis only as far as we could reasonably project these changes and the species response to those changes.
Additionally, the average lifespan of a pygmy-owl is 3 to 5 years. Thus, over a 30-year timeframe, we would expect eight to ten generations of pygmy-owls to be produced which should be adequate to assess the effects of both threats and conservation actions.
Because the primary avenue through which pygmy-owls move across the landscape is through the dispersal of juveniles, it can take multiple generations to provide adequate exchange of individuals to elicit detectable change at the population group and analysis unit scale. Including multiple generations of pygmy-owls also allows adequate time to account for lags in demographic factors resulting from changes in environmental conditions.
Therefore, this number of generations is sufficient to assess the effective levels of resiliency, redundancy and representation. Monitoring of pygmyowl occupancy and productivity also indicates that, at least in Arizona and northern Sonora, 30 years was an adequate time period to document abundance cycles driven by climate conditions. Monitoring in both Arizona and northern Sonora from the mid1990s to present showed a period of decline in occupancy and productivity, primarily due to drought, followed by an increase in productivity and occupancy during years of better precipitation such that abundance and occupancy recovered to nearly the original levels Flesch et al. 2017, p. 12;
Service 2021, entire. For more information on the models and their projections, please see the SSA report Service 2021, entire.
Under Scenario 1 continuation of current trends, we projected there would be no significant changes to the rate of habitat loss and fragmentation within the subspecies range. For this scenario, we considered that climate
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change would track Representative Concentration Pathway RCP 4.5, which is one of four alternative trajectories for carbon dioxide emissions set forth by the International Panel on Climate Change. Specifically, RCP4.5 is an intermediate scenario where carbon dioxide emissions continue to increase through the mid-21st century, but then decline. This scenario would result in atmospheric carbon dioxide levels between 580 and 720 parts per million ppm between 2050 and 2100 and would represent an approximately 2.5
C increase in global mean temperature relative to the period 18611880 IPCC
2014, p. 9. We also considered that conservation efforts that are currently underway, such as captive rearing, would continue to be limited in their efficacy, due to limited resources and the continued efforts to identify appropriate and effective methodologies and protocols. Additionally, climate change will continue to affect the suitability of conditions at release sites for captive-reared pygmy-owls, potentially limiting the effectiveness of pygmy-owl releases.
Under these conditions, we do not anticipate that any of the factors used to evaluate resiliency would improve and, in fact, vegetation intactness would be reduced due to continued development.
Northeastern Mexico is projected to maintain its current level of high pygmy-owl abundance because significant changes to habitat conditions are not expected. Because of this, the northeastern Mexico analysis unit is expected to maintain a moderate level of population resiliency under this scenario. Conditions in the Arizona analysis unit would continue to decline due to continued habitat fragmentation and climate change, and resiliency would remain low. Resiliency in the remaining three analysis units, northern Sonora, western Mexico, and Texas, would decline due to continued loss of cactus ferruginous pygmy-owl habitat, reduced habitat intactness, and a reduction in cover and prey availability for cactus ferruginous pygmy-owls.
Overall, current levels of population redundancy and representation would be maintained rangewide because all analysis units would remain occupied;
however, representation within each analysis unit would likely decline at the population-group scale.
Under Scenario 2 worsening or increased effects scenario, we projected increased rates of habitat loss and fragmentation leading to a decline in pygmy-owl habitat conditions. For this scenario, we considered that climate change would track RCP8.5, which is the highest greenhouse gas emission
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scenario. Under this scenario, atmospheric carbon dioxide concentrations are projected to exceed 1,000 ppm between 2050 and 2100 and would represent a 4.5 C increase in global mean temperature IPCC 2014, p.
9. We also considered that conservation efforts that are currently underway would not be effective or would not be implemented.
Increased habitat loss and fragmentation would result in the greatest effect to overall resiliency through a reduction in abundance and occupancy of pygmy-owls. Increased development and urbanization would result in a permanent loss of habitat.
Indirect effects to vegetation and prey availability as a result of climate change would also be expected. Due to increased habitat fragmentation, such as agricultural development, as well as a reduction in vegetation health from drought, resiliency in the western Mexico analysis unit is projected to decline. Under this scenario, climate change and increased habitat fragmentation from urbanization and agricultural development lead to the loss of some population groups within the Texas, Arizona, and northern Sonora analysis units. The resultant decline would decrease representation and redundancy within these analysis units.
In particular, the Texas and Arizona analysis units would become more vulnerable to extirpation because of low pygmy-owl abundance and occupancy driven by reduced habitat quality as a result of drought and high levels of habitat fragmentation from ongoing urbanization and agricultural development. Genetic representation would be reduced through the loss of population groups or analysis units and the subsequent reduction of gene flow.
Overall, there would be a reduction in resiliency, representation, and redundancy within most analysis units and the likelihood of maintaining longterm viability would be considerably reduced.
Under Scenario 3 improving or reduced effects scenario, we project that habitat loss and fragmentation would continue, but at a reduced rate.
For this scenario, we considered that climate change would track RCP4.5, and conservation efforts that are currently underway would be effective. We did not include other planned conservation efforts in this scenario because we are not aware of any that would significantly influence the viability of the species.
Despite effective conservation actions in portions of the range, the viability of pygmy-owl populations would continue to decline within all five analysis units
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