Je veux savoir à propos de…

12572

Federal Register / Vol. 86, No. 41 / Thursday, March 4, 2021 / Proposed Rules
jbell on DSKJLSW7X2PROD with PROPOSALS

aquifer groundwater overdraft will become more severe as recharge declines and groundwater pumping increases Meixner et al. 2016, p. 135.
For the purposes of our analysis, we chose two Representative Concentration Pathways, RCP 4.5 and RCP 8.5 IPCC
2014, p. 8 to assess future condition of the Arizona eryngo. These climate scenarios were incorporated into our future scenarios of the status of the Arizona eryngo in the SSA report.
Summary of water lossIn summary, water loss has caused the extirpation of two of six known populations of the Arizona eryngo and has affected the current viability of all extant populations. Both extant U.S.
populations are exposed to water loss through groundwater withdrawal, and one of these La Cebadilla is also exposed to spring diversion.
Groundwater withdrawal, particularly when exacerbated by climate change, is a primary threat to the survival of the Arizona eryngo at Lewis Springs and La Cebadilla. Less is known about water loss associated with the two populations in Mexico, but spring diversion is proposed at one site supporting the Arizona eryngo, and it is likely that the species is vulnerable to groundwater withdrawal. Drought and warming as a result of climate change affects all populations, particularly when combined with groundwater withdrawal and diversion.
Change in Vegetation at Cienegas The invasion of vegetation that reduces full sun conditions poses a threat to the Arizona eryngo. Changes in vegetation at cienegas are primarily from fire suppression, introduction of nonnative plant species, decreased flood events, and changes in hydrology and climate. Prior to the arrival of European settlers, burning of cienegas by indigenous people was frequent enough to exclude most woody plants e.g., hackberry Celtis spp., buttonbush Cephalanthus spp., cottonwood Populus spp., ash Fraxinus spp., and willow Salix spp. and suppress bulrush from cienegas and to promote growth of native grasses Davis et al.
2002, p. 1; Cole and Cole 2015, p. 32.
Extant cienegas now have less diversity of annual and disturbance-adapted native understory species and an increase in native woody, clonal, and nonnative plants Stromberg et al. 2017, p. 10. As water levels in cienegas decrease, woody plants invade without regular disturbance e.g., fires, floods to the system Huxman and Scott 2007, p.
1. Shifts from herbaceous wetland vegetation to more deeply rooted riparian trees have been well
VerDate Sep<11>2014

18:38 Mar 03, 2021

Jkt 253001

documented at wetlands with lowered water tables Stromberg et al. 2019, p.
9. These woody plants shade out Arizona eryngo and cause water level declines in cienegas through increased evapotranspiration, particularly in the summer Johnson et al. 2016, p. 83.
Invasive, nonnative plants e.g., giant reed, Johnsongrass are of concern because they often quickly colonize an area and aggressively compete with native species such as the Arizona eryngo for sunlight, water, and nutrients. Giant reed is a fast-growing, tall up to 6 meters m 20 feet ft, perennial, hydrophytic water-loving grass that grows in riparian areas, streams, irrigation ditches, and wetlands. It is an aggressive invader that rapidly spreads into a thick monoculture that outcompetes and shades out other vegetation Frandsen 1997, p. 245; DiPietro 2002, p. 9. Giant reed is fire-adapted and resprouts from extensive underground rhizomes even after very hot fires that kill native vegetation DiPietro 2002, p. 9.
Additionally, it uses large amounts of water, thereby reducing the amount of water available for native vegetation DiPietro 2002, p. 10.
Johnsongrass is a fast-growing, tall, invasive perennial grass that thrives in a variety of environments and climates Peerzada et al. 2017, p. 2. It mostly grows at moist sites e.g., irrigation canals, cultivated fields, field edges, pastures, and in Arizona, it is known as a riparian weed in the Sonoran and Chihuahuan Deserts. Johnsongrass impacts the growth of native plants; it is difficult to control and has become resistant to herbicides, particularly glyphosate Peerzada et al. 2017, p. 2.
At three of four cienegas supporting the Arizona eryngo Lewis Springs, La Cebadilla, and Ojo Vareleno, an increase in woody vegetation and nonnative plant species has been documented. This vegetation is outcompeting the Arizona eryngo for sunlight and space, likely causing a decrease in population size and extent at these sites. At Lewis Springs, Johnsongrass is aggressively invading and appears to be suppressing Arizona eryngo, particularly in the drier areas of the wetlands Li 2019, entire; Simms 2019, entire. Johnsongrass has been present at this site since at least 2009.
In the drier areas of the wetlands, baccharis is encroaching and appears to be suppressing Arizona eryngo; no Arizona eryngo plants have been found growing in the understory of baccharis Li 2019, entire; Simms 2019, entire. At La Cebadilla, aerial imagery indicates that mesquite Prosopis spp. is invading the cienega, and cottonwood
PO 00000

Frm 00023

Fmt 4702

Sfmt 4702

also appears to be shading out Arizona eryngo Fonseca 2019, entire. Arizona ash Fraxinus velutina trees are invading the cienega and shading out Arizona eryngo as well Li 2020b, p. 3.
At Ojo Vareleno, many nonnative plant species also occur, with a particularly aggressive invasion of giant reed Sanchez Escalante et al. 2019, pp. 9
10.
In summary, nonnative Johnsongrass and giant reed are likely to continue to aggressively invade Lewis Springs and Ojo Vareleno. These nonnative plant species may contribute to the near-term extirpation of Arizona eryngo populations at these sites. Woody vegetation encroachment at La Cebadilla and Lewis Springs is also likely to continue, further degrading habitat conditions.
Direct Harm and Mortality Livestock, such as cattle and horses, and native herbivores both invertebrate and vertebrate may cause harm or mortality to Arizona eryngo plants through trampling, herbivory, or uprooting. Because mature plants have large, fibrous leaves, cattle are more likely to consume young plants at an early growth stage. As discussed above, cattle are present at Rancho Agua Caliente, and trespass cattle and horses could enter Lewis Springs and trample, consume flowers, and reduce the seedbank of the Arizona eryngo. To our knowledge, no livestock are present at La Cebadilla or Ojo Vareleno. At the Agua Caliente reintroduction site in Arizona, javelina uprooted and killed young plants, and gophers ate young reintroduced plants Fonseca 2018, p. 1;
Li 2019, p. 6.
Many invertebrates have been observed on Arizona eryngo plants at La Cebadilla and Lewis Springs Stromberg et al. 2019, p. 8; Li 2019, p. 2; Simms 2019, p. 1. Some of these invertebrates may be floral herbivores, but they do not appear to be of concern for the species viability.
In summary, while herbivory and trampling may harm individual Arizona eryngo plants and the seedbank, they are not significant threats to the species.
Summary Our analysis of the past, current, and future influences on the needs of the Arizona eryngo for long-term viability revealed that there are two that pose the greatest risk to future viability: Water loss groundwater withdrawal and water diversion and invasion of nonnative and woody plant species, both of which are exacerbated by drought and warming caused by climate change.
Water loss reduces the availability of
E:FRFM04MRP1.SGM

04MRP1