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Federal Register / Vol. 86, No. 103 / Tuesday, June 1, 2021 / Proposed Rules
Influencing Current Condition provides the baseline of woody vegetation encroachment, and rates derived from the literature were applied to this baseline to project new acres of encroachment. We then adjusted the projected number of new acres of encroachment using relative density calculations specific to each ecoregion to account for indirect effects.

Additionally, due to assumed differences in encroachment rates and tree densities we provide two projections for each of the Short-Grass/
CRP and Mixed-Grass Ecoregions East and West portions in the Northern DPS, largely based on current tree distribution and precipitation gradient.
We projected the extent of expected habitat loss due to encroachment of
woody vegetation at low, intermediate, and high levels of encroachment see the SSA report Service 2021, Appendix C for rationale behind assumed rates of change. Table 13 outlines the three levels of this projected habitat loss by ecoregion caused by future encroachment of woody vegetation over the next 25 years for the purpose of the SSA report.

TABLE 13PROJECTION OF IMPACTS FROM WOODY VEGETATION ENCROACHMENT INCLUDING BOTH DIRECT AND
INDIRECT EFFECTS AT THREE LEVELS AT YEAR 25 IN THE LESSER PRAIRIE-CHICKEN ECOREGIONS
Numbers may not sum due to rounding Projected impacts acres
Ecoregion Low
High
Short-Grass/CRPEast
Short-Grass/CRPWest
Mixed-GrassEast
Mixed-GrassWest
Sand Sagebrush

38,830
1,390
311,768
874
7,650

64,489
3,598
517,784
2,261
12,706

93,877
5,963
753,739
3,748
18,496

Northern DPS totals
Shinnery Oak Southern DPS

360,512
11,548

600,838
81,660

875,823
170,653

Rangewide Total

372,060

682,498

1,046,476

Roads and Electrical Distribution Lines Roads and electrical distribution lines are another important source of habitat loss and fragmentation. In our geospatial analysis for the current condition of the lesser prairie-chicken, we were able to quantify the area affected by roads, but no data were available to quantify the potential independent impacts of distribution lines on habitat loss and fragmentation. We acknowledge that some additional habitat loss and fragmentation will occur in the future due to construction of new roads and power lines, but we do not have data available to inform projections on how much and where any potential new development would occur.
Climate Change
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Intermediate
Future climate projections for this region of the United States indicate general trends of increasing temperatures and increasing precipitation extremes over the 21st century Karl et al. 2009, pp. 123128;
Kunkel et al. 2013, pp. 7375; Shafer et al. 2014, pp. 442445; Easterling et al.
2017, pp. 216222; Vose et al. 2017, pp.
194199. Average temperature has already increased between the first half of the last century 19011960 and present day 19862016, with observed regional average temperatures within the Southern Great Plains including Kansas, Oklahoma, and Texas
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increasing by 0.8 F 0.4 C and within the Southwest including Colorado and New Mexico increasing by 1.6 F 0.9
C Vose et al. 2017, p. 187. By midcentury 20362065, regional average temperatures compared to near-present times 19762005 are projected to increase by 3.64.6 F 2.02.6 C in the Southern Great Plains, and by 3.74.8 F
2.12.7 C in the Southwest, depending on future emissions. By latecentury 20712100, regional average temperatures are projected to rise in the Southern Great Plans by 4.88.4 F 2.7
4.7 C, and by 4.98.7 F 2.74.8 C
in the Southwest Vose et al. 2017, p.
197. Annual extreme temperatures are also consistently projected to rise faster than annual averages with future changes in very rare extremes increasing; by late century, current 1-in20 year maximums are projected to occur every year, while current 1-in-20
year minimums are not expected to occur at all Vose et al. 2017, pp. 197
198.
Projecting patterns of changes in average precipitation across these regions of the United States results in a range of increasing and decreasing precipitation with high uncertainty in overall averages, although parts of the Southwest are projected to receive less precipitation in the winter and spring Easterling et al. 2017, pp. 216218;
Wuebbles et al. 2017, p. 12. However,
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extreme precipitation events are projected to increase in frequency in both the Southern Great Plains and the Southwest Easterling et al. 2017, pp.
218221. Other extreme weather events such as heat waves and long duration droughts Cook et al. 2016, entire, as well as heavy precipitation, are expected to become more frequent Karl et al. 2009, pp. 124125; Shafer et al.
2014, p. 445; Walsh et al. 2014, pp. 28
40. The devastating dust bowl conditions of the 1930s could become more common in the American Southwest, with future droughts being much more extreme than most droughts on record Seager et al. 2007, pp. 1181, 11831184. Other modeling also projects changes in precipitation in North America through the end of this century, including an increase in dry conditions throughout the Central Great Plains Swain and Hayhoe 2015, entire.
Furthermore, the combination of increasing temperature and drought results in greater impacts on various ecological conditions water availability, soil moisture than increases in temperature or drought alone Luo et al.
2017, entire. Additionally, future decreases in surface top 4 inches 10
centimeters soil moisture over most of the United States are likely as the climate warms under higher scenarios Wehner et al. 2017, p. 231.

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