[Federal Register Volume 71, Number 124 (Wednesday, June 28, 2006)]
[Proposed Rules]
[Pages 36745-36752]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-10138]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AU58


Endangered and Threatened Wildlife and Plants; Withdrawal of the 
Proposed Rule To List the Flat-Tailed Horned Lizard as Threatened

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule; withdrawal.

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SUMMARY: We, the Fish and Wildlife Service (Service), have determined 
that the proposed listing of the flat-tailed horned lizard (Phrynosoma 
mcallii) as a threatened species under the Endangered Species Act (Act) 
of 1973, as amended, is not warranted and, thus, we withdraw our 
November 29, 1993, proposed rule (58 FR 62625). As stated in our 
January 3, 2003, withdrawal of the proposed rule to list the species as 
threatened (68 FR 331), we have made this determination because threats 
to the species as identified in the November 29, 1993, proposed rule 
are not significant, and available data do not indicate that the 
threats to the species and its habitat, as analyzed under the five 
listing factors described in section 4(a)(1) of the Act, are likely to 
endanger the species in the foreseeable future throughout all or a 
significant portion of its range. The analyses and conclusions 
contained in the January 3, 2003, withdrawal (68 FR 331) are 
incorporated herein by reference subject to the revisions contained in 
this notice. In this revised withdrawal, we have re-examined the lost 
historical habitat of the flat-tailed horned lizard in relation to our 
January 3, 2003, withdrawal of the proposed listing rule and have 
determined that the lost historical habitat is not a significant 
portion of the flat-tailed horned lizard's range and does not result in 
the species likely becoming endangered in the foreseeable future 
throughout all or a significant portion of its range.

ADDRESSES: Supporting documentation for this rulemaking is available 
for public inspection, by appointment, during normal business hours at 
the U.S. Fish and Wildlife Service, Carlsbad Fish and Wildlife Office, 
6010 Hidden Valley Road, Carlsbad, CA 92011.

FOR FURTHER INFORMATION CONTACT: Jim Bartel, Field Supervisor, at the 
above address (telephone, 760-431-9440, or fax, 760-431-9624).

SUPPLEMENTARY INFORMATION:

Background

    Information on the biology and ecology of this species, factors 
affecting the species, and current conservation measures applicable to 
this species can be found in the January 3, 2003, withdrawal of the 
proposed listing rule (68 FR 331). This document primarily contains 
information relevant to the current and historical range of this 
species and the issue of the significance of the lost habitat. We also 
address the status of several projects and ongoing actions as they 
relate to the flat-tailed horned lizard and provide an update on 
several of the actions outlined in the 1997 Flat-Tailed Horned Lizard 
Conservation Agreement (see ``Summary of Comments and Recommendations'' 
section).
    The flat-tailed horned lizard is most commonly found in sandy flats 
and valleys within creosote (Larrea tridentata) and white bursage 
(Ambrosia dumosa) plant associations or series (Turner et al. 1980; 
Muth and Fisher 1992; Foreman 1997). This series is generally found on 
alluvial fans and upland slopes with well-drained soils that often have 
a pavement surface (Sawyer and Keeler-Wolf 1995), but flat-tailed 
horned lizards are usually found in areas with windblown sand deposits. 
The flat-tailed horned lizard is endemic to the northern Sonoran Desert 
in southern California, southwestern Arizona, and adjoining portions of 
northwestern Sonora and Baja California Norte, Mexico (Turner and 
Medica 1982). Within California, the flat-tailed horned lizard 
currently ranges in the Colorado Desert portion of the Sonoran Desert, 
from the Coachella Valley (the northernmost extent of its range), south 
along both sides of the Imperial Valley. On the west side of the 
Imperial Valley, the species ranges into the Borrego Valley, Ocotillo 
Wells area, West Mesa, and Yuha Basin. On the east side of Imperial 
Valley, the species occurs in the Bureau of Land Management (BLM) Dos 
Palmas Area of Critical Environmental Concern (ACEC), but predominantly 
occurs in East Mesa and in areas adjoining the Algodones Dunes (i.e., 
Imperial Sand Dunes, Glamis Sand Dunes). In Arizona, the flat-tailed 
horned lizard is found in the Yuma Desert portion of the Sonoran 
Desert, south of the Gila River and west of the Gila and Butler 
Mountains (Rorabaugh et al. 1987). The flat-tailed horned lizard is 
patchily distributed at varying densities throughout its range, and 
although the species was once recorded at 1,706 feet (ft) (520 meters 
(m)) above sea level, it is more commonly found below 820 ft (250 m) in 
flat areas or areas with gentle slopes (Turner et al. 1980).
    The range of the flat-tailed horned lizard extends into Mexico from 
the international border in the Yuha Basin in California, south along 
the west side of Laguna Salada in Baja California; and from the 
international border in the Yuma Desert in Arizona, south and east 
through the Pinacate Region to the sandy plains around Puerto Penasco 
and Bahia de San Jorge, Sonora (Johnson and Spicer 1985, Gonzales-
Romero and Alvarez-Cardenas 1989).
    Most of the range of the flat-tailed horned lizard in California 
and Baja California Norte is in the Salton Trough, a low-lying 
depression that is an extension of the Gulf of California. The lowest 
areas of the Salton Trough are below sea level and are protected from 
inundation from the ocean by the Colorado River delta. The geological 
record indicates that, as the Colorado River meandered across its river 
delta, it would periodically flow into the Salton Trough and form Lake 
Cahuilla in the bottom of the Trough. Over time,

[[Page 36746]]

the river would again flow into the Gulf of California, and Lake 
Cahuilla would evaporate (Waters 1983). As a result of dams, 
channelization, and water usage, such flooding no longer occurs.
    As discussed in the January 3, 2003, withdrawal of the proposed 
listing rule (68 FR 331), the range of this species in the United 
States has been analyzed by Hodges (1997) and the range of the species 
in the United States and Mexico has been analyzed by Johnson and Spicer 
(1985). The 2003 revision of the 1997 Flat-tailed Horned Lizard 
Rangewide Management Strategy (herein referred to as the 2003 Rangewide 
Management Strategy) is the most recent analysis of the species' range 
in the United States and Mexico (FTHL-ICC 2003).
    Hodges (1997) estimated that the flat-tailed horned lizard 
historically (prior to agricultural or urban development of either the 
Coachella or Imperial Valleys) occupied up to 2,419,200 acres (ac) 
(979,037 hectares (ha)) in Arizona and California. Approximately 51 
percent (1,243,339 ac (503,161 ha)) of the historical habitat 
identified by Hodges remains in the United States, with about 140,300 
ac (56,770 ha) in Arizona and 1,103,040 ac (446,390 ha) in California 
(Hodges 1997). Hodges (1997) included the Salton Sea as historical 
habitat. However, we noted in the January 3, 2003, withdrawal that the 
Salton Sea area could arguably be considered ephemeral historical 
habitat, present or absent at times, as the area changed through time 
as a result of intermittent flooding and drying. At that time we did 
not consider the effect of the larger Lake Cahuilla. We estimated that 
if the area now occupied by the Salton Sea was not considered 
historical habitat, then, using Hodges' (1997) numbers, approximately 
57 percent of historical habitat remains in the United States. Hodges' 
(1997) analysis did not include current or historical habitat for this 
species in Mexico.
    Johnson and Spicer (1985) analyzed the current range and threats to 
the species in the United States and Mexico at that time. They 
estimated that in 1981 approximately 59 percent of the species' range 
occurred in Mexico (569,578 ac (230,500 ha)), with the majority of the 
range in Mexico occurring in the state of Sonora (492,975 ac (199,500 
ha)). Johnson and Spicer (1985) also estimated that 50 percent of the 
species' habitat in California, Arizona, and Baja California Norte and 
14 percent of the species' habitat in Sonora was in danger of 
conversion to agriculture or urban development and/or degradation due 
to factors such as off-highway vehicle recreation. Overall, 21 percent 
of the species' habitat throughout its range was considered in danger 
of being lost or degraded (Johnson and Spicer 1985).
    The 2003 Rangewide Management Strategy contained updated 
information on the current and historical range of the species in the 
United States and Mexico and made available data on historical and 
current range in geographic information system (GIS) format (FTHL-ICC 
2003). We analyzed the GIS data used in the 2003 Rangewide Management 
Strategy and estimated the size of the historical and current ranges. 
We estimated the extent of historic Lake Cahuilla by using a GIS 
digital elevation model and the estimated elevation the lake reached. 
We estimated the historical range of the flat-tailed horned lizard in 
the United States and Mexico to be 4,875,624 ac (1,973,095 ha).

Previous Federal Actions

    On November 29, 1993, we published in the Federal Register a 
proposed rule to list the flat-tailed horned lizard as a threatened 
species pursuant to the Act (58 FR 62624). On May 16, 1997, in response 
to a lawsuit filed by the Defenders of Wildlife to compel us to make a 
final listing determination on the flat-tailed horned lizard, the 
District Court in Arizona ordered the Service to issue a final listing 
decision within 60 days. A month after the District Court's order, 
seven State and Federal agencies signed the Flat-Tailed Horned Lizard 
Conservation Agreement (referred to herein as the 1997 Conservation 
Agreement) to implement a Flat-tailed Horned Lizard Rangewide 
Management Strategy to protect the flat-tailed horned lizard on Federal 
lands. Pursuant to the 1997 Conservation Agreement, cooperating parties 
agreed to take voluntary steps aimed at ``reducing threats to the 
species, stabilizing the species'' populations, and maintaining its 
ecosystem.''
    On July 15, 1997, we published in the Federal Register a final 
decision to withdraw the proposed rule to list the flat-tailed horned 
lizard as a threatened species (62 FR 37852). We based the withdrawal 
on three factors: (1) Population trend data did not conclusively 
demonstrate significant population declines; (2) some of the threats to 
the flat-tailed horned lizard habitat were misunderstood previously; 
and (3) we believed that the recently approved ``conservation agreement 
w[ould] ensure further reductions in threats.''
    Six months following our withdrawal of the proposed listing rule, 
the Defenders of Wildlife filed a lawsuit challenging our decision. On 
June 16, 1999, the District Court for the Southern District of 
California granted summary judgment in our favor upholding our decision 
not to list the flat-tailed horned lizard. However, on July 31, 2001, 
the Ninth Circuit Court of Appeals reversed the lower court's ruling 
and directed the District Court to remand the matter back to us for 
further consideration in accordance with the legal standards outlined 
in its opinion. The case was remanded back to the Service because (1) 
the withdrawal did not expressly consider whether the flat-tailed 
horned lizard is likely to become an endangered species within the 
foreseeable future in a significant portion of its range; and (2) the 
withdrawal did not ``address the lizard's viability in a site-specific 
manner with regard to the putative benefits of the Conservation 
Agreement.''
    On October 24, 2001, the District Court ordered the Service to 
reinstate the previously effective proposed listing rule within 60 
calendar days and, thereafter, commence a 12-month statutory time 
schedule for a final listing decision, and render our final listing 
determination in compliance with the mandate of the Ninth Circuit 
Court's order. Accordingly, we published a notice in the Federal 
Register on December 26, 2001, announcing the reinstatement of the 
November 29, 1993, proposed rule to list the flat-tailed horned lizard 
as threatened and the opening of a 120-day public comment period on the 
reinstated proposed rule (66 FR 66384).
    On January 3, 2003, we again published in the Federal Register a 
decision to withdraw the November 29, 1993, proposed rule to list the 
flat-tailed horned lizard as a threatened species (68 FR 331). The 
Service found the lizard to be in danger of extirpation in the 
Coachella Valley; however, we determined that the Coachella Valley is 
not a significant portion of the species' range. We concluded in the 
January 3, 2003, withdrawal that the flat-tailed horned lizard 
populations on either side of the Imperial Valley/Salton Sea and in 
Arizona were not likely to become endangered in the foreseeable future 
and that listing the species was not warranted.
    The Tucson Herpetological Society and other environmental 
organizations and individuals filed a lawsuit challenging our January 
3, 2003, withdrawal. On August 30, 2005, the U.S. District Court for 
the District of Arizona set aside our withdrawal of the proposed rule 
to list the flat-tailed horned lizard as a threatened species on the 
grounds that our withdrawal violated the Act because it failed to

[[Page 36747]]

determine whether the lost historical habitat for the flat-tailed 
horned lizard was a significant portion of the range for this species. 
With this exception, all other aspects of the January 3, 2003, 
withdrawal were upheld by the District Court.
    On November 17, 2005, the District Court ordered the Service to 
submit for publication in the Federal Register by November 23, 2005, or 
as soon thereafter as was practicable, a notice advising the public 
that the January 3, 2003, withdrawal was vacated and that the November 
29, 1993, proposed listing rule was reinstated. On December 7, 2005, we 
published a notice in the Federal Register vacating the January 3, 
2003, withdrawal and restoring proposed status to the flat-tailed 
horned lizard (70 FR 72776).
    The November 17, 2005, order limited the scope of the remand to 
specifically address whether the lost historical habitat is a 
significant portion of the range for the flat-tailed horned lizard. The 
Court further required the Service to publish a determination in the 
Federal Register by April 30, 2006, as to whether the lost historical 
habitat of the flat-tailed horned lizard constitutes a significant 
portion of the species' range based on the best scientific and 
commercial data available. On March 2, 2006, we published a notice 
announcing the reopening of a 14-day public comment period on the 
November 29, 1993, proposed rule to list the flat-tailed horned lizard 
under the Act (71 FR 10631). To ensure the public was provided with an 
adequate opportunity to comment on the matters identified by the Court, 
the parties filed a Joint Stipulation with the Court on March 28, 2006, 
to allow for an additional public comment period. On March 29, 2006, 
the Court granted our request for an extension of the April 30, 2006, 
deadline, and ordered us to submit the new final listing determination 
for the flat-tailed horned lizard to the Federal Register on or before 
the date 6 weeks after the close of the second comment period. The 
second comment period was opened from April 21, 2006 to May 8, 2006 (71 
FR 20637). This withdrawal of the November 29, 1993, proposed listing 
rule complies with the Court's August 30, 2005, and November 17, 2005, 
orders.
    For your convenience, here is a list of the primary Federal 
Register documents pertaining to the proposed listing of the flat-
tailed horned lizard as threatened:

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             Action                     Date             FR citation
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Proposed rule to list the flat-  November 29, 1993.  58 FR 62624
 tailed horned lizard as
 threatened.
Withdrawal of proposed rule....  July 15, 1997.....  62 FR 37852
Reinstatement of proposed rule;  December 26, 2001.  66 FR 66384
 reopening of comment period.
Withdrawal of proposed rule....  January 3, 2003...  68 FR 331
Reinstatement of proposed rule.  December 7, 2005..  70 FR 72776
Reopening of comment period....  March 2, 2006.....  71 FR 10631
Reopening of comment period....  April 21, 2006....  71 FR 20637
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Summary of Comments and Recommendations

    During both public comment periods on the December 7, 2005 
reinstatement of the proposed rule to list, we requested all interested 
parties to submit information pertaining to the flat-tailed horned 
lizard's lost historical habitat. We requested this information to make 
a reexamination based on the best scientific and commercial data 
currently available. We also reopened the comment period to admit into 
the record the 2003 revision of the Flat-tailed Horned Lizard Rangewide 
Management Strategy. During the public comment periods, we received 
written comments from a total of 29 entities. Nineteen entities 
advocated listing of the species, 5 entities advocated not listing the 
species, and 5 entities did not advocate either decision.
    As stated previously, in its November 17, 2005 Order, the Court 
ordered that ``on remand the agency need only address the matters on 
which the court's August 30, 2005 Order * * * found the January 3, 2003 
Withdrawal unlawful, which may summarily be identified as whether the 
lizard's lost historical habitat renders the species in danger of 
extinction in a significant portion of its range.'' We received two 
comments directly related to the issue of the flat-tailed horned 
lizard's lost historical habitat. However, for informational purposes, 
we have also provided responses to comments on other substantive issues 
as well. Similar comments are grouped together.
    Comment 1: One commenter stated that there does not appear to be 
strong scientific evidence to establish the extent of the historical 
range of the lizard. The commenter stated that claims that east 
Imperial County and west Yuma County were historically occupied by 
flat-tailed horned lizards are unsupportable. The commenter indicates 
that the present range seems adequate to prevent the extinction of this 
species.
    Our Response: Delineation of historical habitat is retrospective 
and not testable in the way that other scientific models are. However, 
based on knowledge of habitat preference for the species, early 
descriptions of habitat before development, and early museum records, a 
reasonable and defensible theoretical estimation of the broad-scale 
historical range of the species is possible. While there are a number 
of records of flat-tailed horned lizards from the Imperial Valley and 
the Yuma Valley in areas that are now developed, locality records do 
not fully delineate the theoretical range of the flat-tailed horned 
lizard. Historical museum records are summarized in Funk (1981).
    Comment 2: One commenter stated that the habitat destroyed by human 
mediated processes and no longer available for the flat-tailed horned 
lizard in the Imperial, Coachella, and Yuma valleys was significant to 
the species from a metapopulation dynamics perspective because the 
availability of large, continuous patches of potentially available 
habitat provides areas for species to persist as resources (i.e. food, 
water, and habitat) shift geographically over time.
    Our Response: We interpreted the commenter's statements to pertain 
to the importance of maintaining large-scale metapopulation dynamics 
between populations in the Imperial, Coachella, and Yuma valleys. 
Metapopulation dynamics refers to the process exhibited when local 
populations become extirpated in response to local conditions but are 
later recolonized by adjacent patches.
    We acknowledge that large-scale metapopulation dynamics and gene 
flow have been disrupted by the loss of connectivity between 
populations in these areas; however, this loss of connectivity 
endangers primarily Coachella Valley populations because the other 
populations are large enough to be self-sustaining. We recognized the 
precarious status and possibility of extinction of the flat-tailed 
horned

[[Page 36748]]

lizard in the Coachella Valley in the January 3, 2003, withdrawal, 
further acknowledging that if the Coachella Valley populations go 
extinct, there is no connectivity for repopulation from other areas 
(e.g., Imperial Valley). However, we determined that the Coachella 
Valley populations are not a distinct vertebrate population segment and 
that the Coachella Valley is not a significant portion of the species' 
range.
    Relevant to the importance of maintaining large-scale 
metapopulation dynamics between Imperial and Yuma Valley populations, 
most of the intermittent and permanent habitat that has been lost due 
to human mediated processes (e.g., urbanization and agriculture) was 
lost early in the 20th century. This lost habitat is not considered 
significant because of its small size relative to the entire range and 
because this area has been lost for nearly a century and the flat-
tailed horned lizard has persisted in these areas.
    As discussed in detail in the January 3, 2003, withdrawal of the 
proposed listing rule (68 FR 331), the available data concerning 
population abundance, trends, and threats do not suggest, outside the 
Coachella Valley, that flat-tailed horned lizard populations are 
declining in any of the geographic areas, or that because of this 
habitat loss and degradation the species is likely to become endangered 
within the foreseeable future throughout all or a significant portion 
of its range. As discussed below, recent estimates of population sizes 
in several management areas in the Imperial Valley (Ocotillo Wells 
Research Area, West Mesa, Yuha Basin, and East Mesa) and Yuma Valley 
(Yuma Desert Management Areas) since the January 3, 2003, withdrawal of 
the proposed listing rule indicate that, overall, no large decline in 
population size has occurred between 2003 and 2005 in areas for which 
we have more than one year of data.
    Therefore, we do not believe the lost habitat is significant to the 
species from a large-scale metapopulation perspective, because 
populations in the Imperial and Yuma valleys appear to be large enough 
to be self-sustaining despite the loss of habitat between these valleys 
that occurred early in the 20th century.
    Comment 3: Several commenters stated that this species needs the 
protection of the Endangered Species Act.
    Our Response: As stated in our January 3, 2003, withdrawal of the 
proposed rule to list the species as threatened (68 FR 331), we have 
made this determination because threats to the species as identified in 
the November 29, 1993, proposed rule are not significant, and available 
data do not indicate that the threats to the species and its habitat, 
as analyzed under the five listing factors described in section 4(a)(1) 
of the Act, are likely to endanger the species in the foreseeable 
future throughout all or a significant portion of its range.
    Also, we have determined, as discussed in this notice, that the 
lost historical habitat does not render the species in danger of 
extinction throughout all or a significant portion of its range. 
Commenters did not provide new information or data during either 
comment period on additional threats not already considered in the 
January 3, 2003, withdrawal.
    Comment 4: Several commenters noted the impacts to the flat-tailed 
horned lizard that would be associated with the construction of the 
proposed Yuma Area Service Highway.
    Our Response: The Yuma Area Service Highway has been discussed at 
many Arizona Interagency Coordinating Committee (ICC) meetings. Arizona 
ICC members met repeatedly with Arizona Department of Transportation 
(DOT) engineers to ensure compliance with the 2003 Rangewide Management 
Strategy. The Arizona DOT already had long-term plans to construct this 
highway when the 1997 Conservation Agreement was signed. Therefore, the 
western border of the Yuma Desert Management Area was defined as the 
edge of the right-of-way of the future Yuma Area Service Highway. Until 
the highway is built, the lands under jurisdiction of the signatories 
of the Conservation Agreement will be managed as part of the Yuma 
Desert Management Area. The highway, as proposed, would destroy 623 ac 
(252 ha) of flat-tailed horned lizard habitat and isolate 3,734 ac 
(1,511 ha) from the Yuma Desert Management Area. Thus, the Yuma Area 
Service Highway shrinks the 131,000-ac (53,000-ha) Yuma Desert 
Management Area by a relatively small amount. It is our understanding 
from the Arizona members of the ICC that Arizona DOT intends to pay 
compensation for 4,277 ac (1,731 ha) of flat-tailed horned lizard 
habitat impacted or isolated by the project and that fencing will be 
installed to deter lizards from crossing the pavement where they may be 
subject to mortality because of traffic.
    Comment 5: Several commenters noted that the Bureau of Reclamation 
plans to construct a new reservoir, the All American Canal Drop 2 
reservoir, on East Mesa in flat-tailed horned lizard habitat.
    Our Response: The All American Canal Drop 2 reservoir, proposed for 
construction in Imperial County, California, was discussed extensively 
at the flat-tailed horned lizard ICC meetings. The 621-acre (251-ha) 
reservoir, as proposed, will be built on the site formerly used for the 
Brock Ranch Experimental Research Station and will be adjacent to, but 
outside the boundaries of the 115,300-acre (46,660-ha) East Mesa 
Management Area. A map released by the Bureau of Reclamation (BOR) 
showed that half of the reservoir would be within the boundaries of the 
East Mesa Management Area. However, according to the BLM, that map was 
in error. The input canal from the Coachella Canal to the Drop 2 
reservoir will cross BLM land in the East Mesa Management Area, along 
the southern boundary, and will directly impact 295 ac (119 ha) in the 
Management Area. The input canal will also isolate two small areas of 
the Management Area; however, these areas are of limited value to flat-
tailed horned lizards. The first area is 120 ac (49 ha) in the 
southeast corner of the Management Area that is already highly impacted 
by off-highway vehicle (OHV) activity. The second area is 320 ac (129 
ha) on private land that is currently an abandoned jojoba farm and not 
suitable habitat for flat-tailed horned lizards. It is our 
understanding from BLM staff that all areas impacted, including the 
areas to be isolated, will be compensated for by BOR at the ratio 
dictated by the 2003 Rangewide Management Strategy. Since this 
Management Area is not fenced, the location of the input canal will 
benefit the Management Area by creating a barrier that will discourage 
illegal OHV activity. The amount of habitat impacted will fall below 
the 1 percent of Federal lands allowed by the 2003 Rangewide Management 
Strategy.
    Comment 6: Several commenters pointed out plans for geothermal 
plants in flat-tailed horned lizard habitat.
    Our Response: It is our understanding from BLM staff that several 
applications for geothermal leases in the West Mesa Management Area and 
the Ocotillo Wells State Vehicle Recreation Area have been submitted. 
At this point in time, the construction of geothermal plants is 
speculative. A lease allows a project applicant to evaluate the site 
for geothermal energy. If it is then suitable, the applicant and the 
BLM must go through the National Environmental Policy Act (NEPA) 
process prior to constructing the geothermal facilities. The NEPA 
requires the Federal agencies to consider the environmental impacts, 
including impacts to listed and sensitive

[[Page 36749]]

species, of their proposed actions and reasonable alternatives to those 
actions.
    Comment 7: Several commenters noted the proposal for a large solar 
energy plant in flat-tailed horned lizard habitat in Imperial Valley.
    Our Response: The solar plant was originally proposed to be built 
in the West Mesa Management Area, but because of the 2003 Rangewide 
Management Strategy the BLM asked that it be moved out of the West Mesa 
Management Area and the project proponents agreed. According to the 
BLM, the current proposed site is on BLM land, is not within any 
Management Area occupied by the flat-tailed horned lizard, and 
compensation for any flat-tailed horned lizard lost habitat will be 
applied, if applicable.
    Comment 8: Several commenters noted the extensive Border Patrol 
activity in flat-tailed horned lizard habitat.
    Our Response: The Border Patrol is not a signatory of the 1997 
Conservation Agreement; however, the ICC works with them on 
conservation issues. In California, new Border Patrol agents are 
educated on the impacts to biological and archaeological resources by 
driving off-road. Recently, an educational video paid for by flat-
tailed horned lizard compensation funds was distributed to Border 
Patrol offices and they agreed to show the video to all existing agents 
as well as incorporate it into the training for new agents. It is our 
understanding that the ICC intends to continue working with the Border 
Patrol to minimize impacts to flat-tailed horned lizard and its habitat 
associated with the performance of their duties along the border.
    Comment 9: Several commenters stated that the 1997 Conservation 
Agreement and Rangewide Management Strategy are not working.
    Our Response: Progress toward the goals of the 1997 Rangewide 
Management Strategy was evaluated during the 2003 revision of the 
Rangewide Management Strategy and yearly in annual reports. Some of the 
progress made includes the following: Between 1997 and 2003, surface 
disturbance was kept well below the 1 percent cap in each of the five 
Management Areas. Designation of the Management Areas has occurred and 
the 2003 Rangewide Management Strategy has become an official part of 
the BLM California Desert Conservation Area plan. The Management Areas 
comprise 485,000 ac (196,273 ha) or 758 square miles (1,963 square 
kilometers) of presumably the best flat-tailed horned lizard habitat on 
Federal lands. Compensation funds have been collected for projects in 
flat-tailed horned lizard habitat and will continue to be collected. 
These funds have been used to purchase private lands within Management 
Areas.
    As outlined in the 1997 Conservation Agreement, research and 
monitoring for this species have been funded. Research on basic biology 
such as significant predators, home range size, diet, and reproduction 
has been conducted since the 1997 Conservation Agreement was signed. 
Research on impacts such as edge effects and OHV effects has also been 
conducted. Studies have also been conducted, or are planned, on the 
efficacy of mitigation measures such as relocation of lizards from 
project sites and use of under-highway culverts by this species. 
Methods to monitor this species, such as scat counts, mark-recapture, 
presence/absence, trapping webs, distance sampling, and occupancy 
estimation have been tested for this species, and population estimates 
have been obtained for four Management Areas and the Research Area. 
Based on these actions as well as others not explicitly mentioned 
above, we believe that the 1997 Conservation Agreement is helping to 
conserve the flat-tailed horned lizard and its habitat.

Summary of Factors Affecting the Species

    Section 4 of the Act (16 U.S.C. 1531 (et seq.) and the regulations 
(50 CFR part 424) that implement the listing provisions of the Act set 
forth the procedures for adding species to the Federal list of 
endangered and threatened species. They provide that a species may be 
determined to be endangered or threatened if one or more of the 
following five factors are met:
    A. The present or threatened destruction, modification, or 
curtailment of its habitat or range.
    B. Overutilization for commercial, recreational, scientific, or 
educational purposes.
    C. Disease or predation.
    D. The inadequacy of existing regulatory mechanisms.
    E. Other natural or manmade factors affecting its continued 
existence.
    As stated above, the November 17, 2005, Court Order limited the 
scope of the remand to specifically address whether the lost historical 
habitat is a significant portion of the range for the flat-tailed 
horned lizard. (See the January 3, 2003, withdrawal of the proposed 
listing rule [68 FR 331] for the full discussion of the five factors 
and their application to the flat-tailed horned lizard.) Therefore, the 
sole purpose of this withdrawal is to reexamine and expand upon our 
previous discussions of the five factors in order to address whether 
the lost historical habitat is a significant portion of the range for 
the flat-tailed horned lizard. The analysis in this document will 
primarily reflect lost historical habitat as a component of factor A 
because factor A requires an analysis of whether the curtailment of a 
species' habitat or range is a threat to its continued existence.

Historical and Current Range, and Temporal Baseline

    We consider the 2003 Rangewide Management Strategy to be the best 
scientific and commercial information available on the historical and 
current range of the species. The 2003 Rangewide Management Strategy 
builds on previous information on the range of the species (i.e., 
Johnson and Spicer 1985; Hodges 1997) and bases the delineation of 
historical and current range on the presence of suitable habitat, known 
localities, and elevation (flat-tailed horned lizards have rarely been 
found above 750 ft in elevation). As stated above, we analyzed the GIS 
data used in the 2003 Rangewide Management Strategy, which depicted the 
approximate current and historical distribution of the flat-tailed 
horned lizard. We also used GIS to estimate the extent of historic Lake 
Cahuilla, which was subtracted from the current and historical range of 
the species. We used our analysis to estimate the historical range of 
the flat-tailed horned lizard in the United States and Mexico to be 
4,875,624 ac (1,973,095 ha).

Temporal Baseline

    In the memorandum of support for the District Court order of August 
30, 2005, the Court ``found that the Service had failed to satisfy the 
Ninth Circuit's mandate in a prior phase of this case, by failing to 
examine whether lost historical habitat constituted a `significant 
portion' of the species' range.'' In citing the Ninth Circuit, the 
District Court noted that the Service `has discretion to choose the 
point in time at which to examine the range because neither the Ninth 
Circuit nor the [Endangered Species Act] provide `a temporal baseline 
for assessing a species' total range' * * *. The point in time must be 
sometime in the past, however, and cannot be the current range.'' In 
identifying the lost historical habitat for the flat-tailed horned 
lizard, we determined it was appropriate to consider the available 
recorded historical information.

[[Page 36750]]

Lake Cahuilla

    Lake Cahuilla is an important consideration in determining the 
historical range of the flat-tailed horned lizard. From prehistoric 
times to the formation of the current-day Salton Sea, Lake Cahuilla 
intermittently filled a portion of the Salton Trough. Thus, the lakebed 
was intermittent habitat for the flat-tailed horned lizard. Lake 
Cahuilla completely filled and evaporated 4 times between 700 to 1580 
AD (Waters 1983). At other times, spring floods on the Colorado River 
would partially fill the trough. During the 1800s, reported episodes of 
inundation occurred in 1828, 1840, 1849, 1852, 1859, 1862, 1867, and 
1897 (Littlefield 1966). A flood in 1891 created a water body of 
approximately the same surface area as the current Salton Sea (Sykes 
1914). The 2003 Rangewide Management Strategy, in discussing the 
historical range of the flat-tailed horned lizard, states: ``The Salton 
Basin [Salton Trough] had been subjected to frequent inundation from 
the Colorado River even prior to the accidental flooding from 1905 
through 1907, and it is questionable whether this area can be 
considered historic habitat.'' Flat-tailed horned lizards were likely 
killed during floods as the water rushed into the basin and 
recolonization occurred as the water evaporated.
    Even when the lake was dry, a large portion of the dry lakebed was 
likely unsuitable habitat for flat-tailed horned lizards. The lowest 
point of the trough was covered in a thick deposit of salt left behind 
when the water evaporated (Free 1914), which was likely devoid of plant 
and animal life. This area is now covered by the Salton Sea. Desert 
sinks and playas like the Salton Trough are typically inhabited by a 
salt-tolerant community dominated by Atriplex (saltbush) species 
(Baldwin et al. 2002). In the saltiest and wettest parts of a desert 
sink, Atriplex is replaced by more salt-tolerant plants such as 
pickleweed (Salicornia), iodine bush (Allenrolfea), and seepweed 
(Suaeda). Parish (1914) defined the ``Salton Sink'' as the area between 
the shoreline of Lake Cahuilla and the then-shrinking Salton Sea. He 
characterized the vegetation within the Salton Sink as the Atriplex 
zone, because of the domination by Atriplex in the sink. ``Of this 
general flora of the Colorado Desert the xerophytic vegetation of the 
Sink is a part, differentiated mainly by the great preponderance of 
Atriplex spp. in its composition, so that it may be fittingly 
denominated the Atriplex zone'' (Parish 1914, p. 89). Creosote, a 
typical habitat associate for flat-tailed horned lizards, was 
characterized as ``frequent in arid soil throughout the Sink, but 
scattered and seldom dominant'' (Parish 1914, p. 109). Parish described 
white bursage, another typical habitat associate for flat-tailed horned 
lizards, as ``frequent in detrital soil and occasional in light 
alluvium. [Locations:] Mecca, Caleb, Durmid, Westmorland.'' He 
described detrital soils as primarily occurring on the northeast margin 
of the Sink. Thus, the lakebed of Lake Cahuilla was not the typical 
creosote-bursage habitat association as has been described for this 
species (Turner and Medica 1982, Turner et al. 1980, FTHL-ICC 2003).
    The Atriplex community in the lakebed was, at best, likely marginal 
habitat for flat-tailed horned lizards. Flat-tailed horned lizards have 
been found in association with Atriplex in the Dos Palmas area and San 
Sebastian Marsh area, but a mark-recapture plot in desert sink scrub 
with no sand in the Dos Palmas ACEC found no flat-tailed horned lizards 
(Mark Massar, Wildlife Biologist, BLM, Palm Springs, pers. comm. 2005). 
The area surrounding San Sebastian Marsh is in the lakebed of Lake 
Cahuilla and mirrors the vegetation associations described by Parish 
(1914) with areas of Atriplex, iodine bush, and mesquite, but the San 
Sebastian Marsh area has yielded very few flat-tailed horned lizards 
(FTHL-ICC 2003). Turner et al. (1980) recognized that the lakebed 
appeared to be lesser quality habitat: ``In Imperial County, habitats 
above the old shoreline of Lake Cahuilla are better than those below 
the shoreline, possibly because soils above the old shoreline tend to 
be sandier.''
    The first known historical record of a flat-tailed horned lizard 
from the lakebed of Lake Cahuilla was collected near the present-day 
city of Calexico (Klauber 1932). Other flat-tailed horned lizards were 
collected early in the 20th century near the present-day cities of 
Westmorland and Holtville and from the edges of the Salton Sea (Klauber 
1932; Funk 1981; Turner et al. 1980). These areas are now urban or 
agricultural areas. Turner and others (1980), noting the few flat-
tailed horned lizards found in association with Atriplex, suggested 
they may represent dispersing individuals. In most cases, flat-tailed 
horned lizard populations in Atriplex habitat appear to be sparse. The 
exception to this rule may be the high densities of flat-tailed horned 
lizards found associated with Atriplex in the Coachella Valley (FTHL-
ICC 2003). However, the windblown sand preferred by flat-tailed horned 
lizards is found in adequate amounts in the Coachella Valley Preserve 
(Barrows 1996). The San Sebastian Marsh and Dos Palmas areas described 
above have little windblown sand. Parish (1914) describes the soils of 
the southern part of the sink (south of the current-day Salton Sea) as 
``loams of very fine compact grain * * * with very small percentages of 
sand. They are permeable by water only to a slight degree.'' No 
information has been found on the amount of wind-deposited sand that 
was present in the lakebed. Free (1914) alludes to accretion dunes in 
the lakebed that may have been good flat-tailed horned lizard habitat. 
But Parish (1914), describing the vegetation of the Imperial Valley, 
reported ``wide expanses absolutely devoid of a single plant save in 
the infrequent furrows and channels which constitute the drainage 
system.''
    The precise proportion of the lakebed that historically was 
habitat, and the quality of that habitat, is difficult to accurately 
determine. We do not know the precise proportions of specific plant 
communities that were present in the Salton Sink. We do not know the 
patterns of windblown sand deposition. Despite the difficulty in 
accurately determining historic conditions in the dry lakebed, we 
believe that it contained only a limited amount of suitable habitat, 
most of which is likely to have been marginal at best. Thus, even if 
the lakebed were considered historical habitat, it would not be 
significant to the species.
    Additionally, recent work on the genetics of the flat-tailed horned 
lizard suggests that gene flow across the lakebed between the east and 
west sides of the Salton trough was low even before the current 
fragmentation due to development and agriculture (Mulcahy et al. 2006). 
The authors state: ``* * * suggesting that there has not been 
substantial gene flow across the Imperial Valley since the drying of 
Lake Cahuilla. Although historic localities exist in the Imperial 
Valley, genetic differences suggested limited gene flow across this 
region prior to human development.''

Lost Habitat

    As discussed above, the area of the historical range periodically 
inundated by Lake Cahuilla was not important to the long-term viability 
of the flat-tailed horned lizard because this area was frequently 
unavailable and likely contained little quality habitat. Much of the 
area within the former Lake Cahuilla lakebed likely was not only 
intermittent, but low-quality habitat for the flat-tailed horned 
lizard, particularly the central salt deposit and saltier, less sandy 
portions of the Atriplex community. Thus, we determined this area 
should not be considered part of the species'

[[Page 36751]]

historical habitat. The remainder of this analysis considers the 
historical habitat outside the area of the former Lake Cahuilla to be 
the appropriate baseline for assessing the species' total range. Using 
our estimate that the former Lake Cahuilla was 1,309,409 ac (529,899 
ha) based on a 39 ft (12 m) shoreline (Waters 1983) calculated with a 
GIS digital elevation model, the baseline for assessing the species' 
range (which excludes the former Lake Cahuilla) was approximately 
4,875,624 ac (1,973,095 ha). Below we describe the significance of lost 
habitat within this delineated historical habitat (outside the area of 
the former Lake Cahuilla).
    Approximately 1,103,201 ac (446,450 ha) have been lost, nearly 
entirely within two areas: the Coachella Valley, and Mexicali and Yuma 
areas. In the January 3, 2003, withdrawal, we determined that the 
Coachella Valley, including its lost associated habitat, is not a 
significant portion of the range. Near Mexicali, agriculture extends 
from Mexicali south to near the Gulf of California and east to the 
Colorado River. This block of lost habitat is contiguous (across the 
Colorado River) with the block of lost habitat in the Yuma area. The 
block of habitat that encompasses northeastern Baja California Norte 
and southwestern Arizona is the largest block of lost habitat.
    These habitat areas were likely converted to agriculture early in 
the 20th century, similar to that described for the Imperial Valley 
(Imperial Irrigation District 2002). The lost habitat is not 
significant because of its small size relative to the entire range and 
because this area has been lost to agriculture for nearly a century and 
the flat-tailed horned lizard has persisted. Since the early 20th 
century, the species has persisted on East Mesa and West Mesa, and in 
the Yuha Basin over many generations. Flat-tailed horned lizards rarely 
live more than 4 years in the wild and can reproduce in their first or 
second year (FTHL-ICC 2003). If the median generation time is 2 years, 
then more than 25 generations of flat-tailed horned lizards have come 
and gone since most of the habitat conversion to agriculture production 
took place. This continued persistence over a span of nearly 100 years 
is a strong indication that the species will continue to persist into 
the foreseeable future despite the loss of historical habitat.
    We do not expect additional conversion of flat-tailed horned lizard 
habitat to agriculture in the future in the Imperial Valley and 
elsewhere along the Colorado River given the existing limitations on 
the availability of water for irrigation (Imperial Irrigation District 
2002). In fact, a recent water transfer agreement with San Diego 
required some fields to remain fallow (unirrigated); therefore, 
agricultural use may even decrease in this area (Imperial Irrigation 
District 2006).
    Though the lost habitat is situated between the Arizona-Sonora and 
California-Baja California Norte populations, the Colorado River 
already isolated these populations to some degree. The lost habitat of 
the flat-tailed horned lizard in the United States and Mexico is not 
viable for flat-tailed horned lizards in the foreseeable future. Much 
of this habitat has been permanently lost due to urbanization and/or 
flooding of the Salton Sea. Habitat lost due to agricultural uses may 
be restored in certain cases in the future, though most agricultural 
fields are isolated from existing flat-tailed horned lizard populations 
by irrigation canals like the Coachella Canal, Highline Canal, and All-
American Canal. We do not anticipate any significant amount of 
previously lost habitat could become viable habitat in the future.
    In sum, we believe the lost habitat does not represent a 
significant portion of the range of the flat-tailed horned lizard 
because the lost habitat was lost decades ago and the species has 
persisted. Most of the lost habitat was lost early in the century and 
that lost habitat was not significant enough to lead to the species' 
extirpation within intact habitat through edge effects or 
fragmentation. There were no attributes or specific uses of the lost 
habitat by flat-tailed horned lizards that made it any more significant 
than any other habitat. For example, a significant part of a range for 
a species might be a breeding ground or lek site, but there is nothing 
of the sort for flat-tailed horned lizards. Additionally, as discussed 
in detail in the January 3, 2003, withdrawal of the proposed listing 
rule (68 FR 331), the available data concerning population abundance, 
trends, and threats do not suggest, outside the Coachella Valley, that 
flat-tailed horned lizard populations are declining in any of the 
geographic areas, or that because of this habitat loss and degradation 
the species is likely to become endangered within the foreseeable 
future throughout all or a significant portion of its range. Recent 
estimates of population sizes have been conducted in the West Mesa, 
Yuha Basin, East Mesa, and the Yuma Desert Management Areas and 
Ocotillo Wells Research Area since the January 3, 2003, withdrawal of 
the proposed listing rule (Young et al. 2004; Hollenbeck, Environmental 
Scientist, California Department of Parks and Recreation, pers. comm. 
2005; Grant 2005). Overall, no large decline in population size 
occurred between 2003 and 2005 in areas for which we have more than one 
year of data (Grant 2005, Hollenbeck, Environmental Scientist, 
California Department of Parks and Recreation, pers. comm. 2005).

Finding

    On January 3, 2003 (68 FR 331), the Service issued a decision to 
withdraw the proposal to list the flat-tailed horned lizard. The Tucson 
Herpetological Society and other environmental organizations and 
individuals filed a lawsuit to challenge our decision. The U.S. 
District Court for the District of Arizona upheld our decision with the 
exception that we had failed to consider whether the lost historical 
range of the flat-tailed horned lizard constituted a significant 
portion of the range. This notice addresses this issue.
    We reviewed the best scientific and commercial data available and 
determined that the lost habitat is not a significant portion of the 
species range, and does not render the species likely to become 
endangered within the foreseeable future throughout all or a 
significant portion of its range. We conclude that the lost habitat is 
not significant because the species has persisted despite a large 
amount of habitat loss in the early 20th century, the species remains 
viable throughout most of its current extant range, and there were no 
particular attributes of the lost habitat that made it any more 
significant than any other part of the range. Therefore, based on the 
above reasoning and the reasoning presented in the January 3, 2003 
withdrawal of the proposed rule to list the flat-tailed horned lizard 
(68 FR 331), we have determined that the flat-tailed horned lizard is 
not likely to become in danger of extinction in the foreseeable future 
throughout all or a significant portion of its range.

[[Page 36752]]

References Cited

    A complete list of all references cited is available at the 
Carlsbad Fish and Wildlife Office (see ADDRESSES above).

Author

    The primary author of this document is the Carlsbad Fish and 
Wildlife Office (see ADDRESSES above).

Authority

    The authority for this action is section 4(b)(6)(B)(ii) of the 
Endangered Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).

    Dated: June 20, 2006.
Marshall Jones, Jr.,
Acting Director, U.S. Fish and Wildlife Service.
 [FR Doc. E6-10138 Filed 6-27-06; 8:45 am]
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