Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for Cirsium hydrophilum var. hydrophilum (Suisun thistle) and Cordylanthus mollis ssp. mollis (soft bird's-beak), 18518-18553 [07-1777]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 72, Number 70 (Thursday, April 12, 2007)]
[Rules and Regulations]
[Pages 18518-18553]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 07-1777]



[[Page 18517]]

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Part II





Department of the Interior





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Fish and Wildlife Service



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50 CFR Part 17



Endangered and Threatened Wildlife and Plants; Designation of Critical 
Habitat for Cirsium hydrophilum var. hydrophilum (Suisun thistle) and 
Cordylanthus mollis ssp. mollis (soft bird's-beak); Final Rule

Federal Register / Vol. 72, No. 70 / Thursday, April 12, 2007 / Rules 
and Regulations

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

1018-AU44


Endangered and Threatened Wildlife and Plants; Designation of 
Critical Habitat for Cirsium hydrophilum var. hydrophilum (Suisun 
thistle) and Cordylanthus mollis ssp. mollis (soft bird's-beak)

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Final rule.

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SUMMARY: We, the U.S. Fish and Wildlife Service (the Service), are 
designating critical habitat for Cirsium hydrophilum var. hydrophilum 
(Suisun thistle) and Cordylanthus mollis ssp. mollis (soft bird's-beak) 
under the Endangered Species Act of 1973, as amended (Act). In total, 
approximately 2,052 acres (ac) (830 hectares (ha)) fall within the 
boundaries of the critical habitat designation for C. hydrophilum var. 
hydrophilum in Solano County, California, and approximately 2,276 ac 
(921 ha) for C. mollis ssp. mollis in Contra Costa, Napa, and Solano 
Counties, California. Due to overlap of some units, the total area of 
critical habitat designation for both subspecies is 2,621 ac (1,061 
ha).

DATES: This rule becomes effective on May 14, 2007.

FOR FURTHER INFORMATION CONTACT: Field Supervisor, Sacramento Fish and 
Wildlife Office, 2800 Cottage Way, Sacramento, California 95825; 
telephone, 916-414-6600; facsimile, 916-414-6713. People who use a 
telecommunications device for the deaf (TDD) may call the Federal 
Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Role of Critical Habitat in Actual Practice of Administering and 
Implementing the Act (16 U.S.C. 1531 et seq.)

    Attention to and protection of habitat is paramount to successful 
conservation actions. The role that designation of critical habitat 
plays in protecting habitat of listed species, however, is often 
misunderstood. As discussed in more detail below in the discussion of 
exclusions under the Act section 4(b)(2), there are significant 
limitations on the regulatory effect of designation under the Act 
section 7(a)(2). In brief, (1) designation provides additional 
protection to habitat only where there is a Federal nexus; (2) the 
protection is relevant only when, in the absence of designation, 
destruction or adverse modification of the critical habitat would take 
place (in other words, other statutory or regulatory protections, 
policies, or other factors relevant to agency decision-making would not 
prevent the destruction or adverse modification); and (3) designation 
of critical habitat triggers the prohibition of destruction or adverse 
modification of that habitat, but it does not require specific actions 
to restore or improve habitat.
    Currently, only 485 species, or 37 percent of the 1,310 listed 
species in the United States under the jurisdiction of the Service, 
have designated critical habitat. We address the habitat needs of all 
1,310 listed species through conservation mechanisms such as listing, 
section 7 consultations, the section 4 recovery planning process, the 
section 9 protective prohibitions of unauthorized take, section 6 
funding to the States, the section 10 incidental take permit process, 
and cooperative, nonregulatory efforts with private landowners. The 
Service believes that it is these measures that may make the difference 
between extinction and survival for many species.
    In considering exclusions of areas proposed for designation, we 
evaluated the benefits of designation in light of Gifford Pinchot Task 
Force v. U.S. Fish and Wildlife Service, 378 F.3d 1059 (9th Cir 2004) 
(hereinafter Gifford Pinchot). In that case, the Ninth Circuit 
invalidated the Service's regulation defining ``destruction or adverse 
modification of critical habitat.'' In response, on December 9, 2004, 
the Director issued guidance to be considered in making section 7 
adverse modification determinations. This proposed critical habitat 
designation does not use the invalidated regulation in our 
consideration of the benefits of including areas. The Service will 
carefully manage future consultations that analyze impacts to 
designated critical habitat, particularly those that appear to be 
resulting in an adverse modification determination. Such consultations 
will be reviewed by the Regional Office or the California/Nevada 
Operations Office prior to finalizing to ensure that an adequate 
analysis has been conducted that is informed by the Director's 
guidance.
    To the extent that designation of critical habitat provides 
protection, that protection can come at significant social and economic 
cost. In addition, the mere administrative process of designation of 
critical habitat is expensive, time-consuming, and controversial. The 
current statutory framework of critical habitat, combined with past 
judicial interpretations of the statute, make critical habitat the 
subject of excessive litigation. As a result, critical habitat 
designations are driven by litigation and courts rather than biology, 
and made at a time and under a timeframe that limits our ability to 
obtain and evaluate the scientific and other information required to 
make the designation most meaningful.
    In light of these circumstances, the Service believes that 
additional agency discretion would allow our focus to return to those 
actions that provide the greatest benefit to the species most in need 
of protection.

Procedural and Resource Difficulties in Designating Critical Habitat

    We have been inundated with lawsuits for our failure to designate 
critical habitat, and we face a growing number of lawsuits challenging 
critical habitat determinations once they are made. These lawsuits have 
subjected the Service to an ever-increasing series of court orders and 
court-approved settlement agreements, compliance with which now 
consumes nearly the entire listing program budget. This leaves the 
Service with little ability to prioritize its activities to direct 
scarce listing resources to the listing program actions with the most 
biologically urgent species conservation needs.
    The consequence of the critical habitat litigation activity is that 
limited listing funds are used to defend active lawsuits, to respond to 
Notices of Intent (NOIs) to sue relative to critical habitat, and to 
comply with the growing number of adverse court orders. As a result, 
listing petition responses, the Service's own proposals to list 
critically imperiled species, and final listing determinations on 
existing proposals are all significantly delayed.
    The accelerated schedules of court-ordered designations have left 
the Service with limited ability to provide for public participation or 
to ensure a defect-free rulemaking process before making decisions on 
listing and critical habitat proposals, due to the risks associated 
with noncompliance with judicially imposed deadlines. This in turn 
fosters a second round of litigation in which those who fear adverse 
impacts from critical habitat designations challenge those 
designations. The cycle of litigation appears endless and is very 
expensive, thus diverting resources from conservation actions that may 
provide relatively more benefit to imperiled species.
    The costs resulting from the designation include legal costs, the 
cost

[[Page 18519]]

of preparation and publication of the designation, the analysis of the 
economic effects and the cost of requesting and responding to public 
comment, and in some cases the costs of compliance with the National 
Environmental Policy Act (NEPA; 42 U.S.C. 4371 et seq.). These costs, 
which are not required for many other conservation actions, directly 
reduce the funds available for direct and tangible conservation 
actions.

Background

    It is our intent to discuss only those topics directly relevant to 
the designation of critical habitat in this rule. For more information 
on Cirsium hydrophilum var. hydrophilum and Cordylanthus mollis ssp. 
mollis, refer to the final listing rule published in the Federal 
Register on November 20, 1997 (62 FR 61916), and the proposed critical 
habitat designation published in the Federal Register on April 11, 2006 
(71 FR 18456).

Previous Federal Actions

    On November 17, 2003, the Center for Biological Diversity and other 
environmental groups filed a lawsuit against the Service (Center for 
Biological Diversity, et al. v. Gale Norton, Secretary of the 
Department of the Interior, et al., CV 03-5126-CW), leading to a 
stipulated settlement and court order signed June 14, 2004. We agreed 
in the settlement to propose critical habitat for Cirsium hydrophilum 
var. hydrophilum and Cordylanthus mollis ssp. mollis by April 1, 2006, 
and to make a final designation by April 1, 2007. On April 11, 2006, we 
published the proposed critical habitat designation for the two plants 
in the Federal Register (71 FR 18456). For more information on previous 
Federal actions concerning C. hydrophilum var. hydrophilum or C. mollis 
ssp. mollis, refer to the proposed critical habitat designation 
published in the Federal Register on April 11, 2006 (71 FR 18456). This 
final rule complies with the settlement agreement.

Summary of Comments and Recommendations

    We requested written comments from the public on the proposed 
designation of critical habitat for Cirsium hydrophilum var. 
hydrophilum and Cordylanthus mollis ssp. mollis in the proposed rule 
published on April 11, 2006 (71 FR 18456) and again in a subsequent 
notice of availability (NOA) of a draft economic analysis published in 
the Federal Register on November 20, 2006 (71 FR 67089). We also 
contacted appropriate Federal, State, and local agencies; scientific 
organizations; and other interested parties and invited them to comment 
on the proposed rule.
    The first comment period on the proposed designation opened April 
11, 2006 and closed on June 12, 2006. During that time, we received six 
comments: three from peer reviewers, one from a California State 
agency, and two from private organizations and individuals. We received 
no comments during the second comment period, which covered both the 
proposed designation and the draft economic analysis, and was open from 
November 20, 2006, to December 20, 2006. In total, five commenters 
supported the designation of critical habitat for Cirsium hydrophilum 
var. hydrophilum and Cordylanthus mollis ssp. mollis and one opposed 
the designation. Comments received were grouped into general issues 
specifically relating to the proposed critical habitat designation, and 
are addressed in the following summary and incorporated into the final 
rule as appropriate. We did not receive any requests for a public 
hearing.

Peer Review

    In accordance with our policy published on July 1, 1994 (59 FR 
34270), we solicited expert opinions from three knowledgeable 
individuals with scientific expertise that included familiarity with 
the species, the geographic region in which the species occurs, and 
conservation biology principles. We received responses from all three 
of the peer reviewers. The peer reviewers generally concurred with our 
methods and conclusions regarding the critical habitat under 
consideration, and provided additional information, clarifications, and 
suggestions to improve the final rule. Peer reviewer comments are 
addressed in the following summary and incorporated into this final 
rule as appropriate.
    We reviewed all comments received from the peer reviewers and the 
public for substantive issues and new information regarding critical 
habitat for Cirsium hydrophilum var. hydrophilum and Cordylanthus 
mollis ssp. mollis. We address them in the following summary.

Peer Reviewer Comments

    1. Comment: The peer reviewers generally supported designation of 
the proposed areas and also argued for inclusion of additional areas. 
Two reviewers noted that sea levels are likely to rise in the 
foreseeable future, and that adjacent gently sloped terrestrial areas 
and additional higher-elevation marshlands should be designated as 
refugia.
    Our Response: Section 3(5)(A)(ii) does allow us to designate areas 
outside the geographical area occupied by the subspecies at time of 
listing if the Secretary of Interior determines that such areas are 
essential to the conservation of the subspecies. Identifying exactly 
which areas would be likely to become appropriate habitat for the 
plants, and how long such new habitat might last, would require a great 
many assumptions beyond those required to simply project a rise in sea 
level. Climate, rainfall, soil types, existing and planned roadways and 
development, and vegetation cover, both in the proposed area and in the 
watershed, are all confounding variables that could affect where (and 
for how long) appropriate habitat develops in the future. Given the 
speculative nature of such an undertaking, we do not consider the 
available evidence sufficient to support a finding that any particular 
unoccupied upland area is essential to the conservation of the 
subspecies. The Act includes procedures for modifying existing critical 
habitat designations as the need arises. We consider those procedures 
to be the appropriate and legally supportable means of coping with 
long-term habitat change.
    2. Comment: All three peer reviewers commented that we relied too 
heavily on designating known occupied sites, and not enough on choosing 
sites that would allow for population colonization and growth necessary 
to conserve the subspecies. Additional sites specifically suggested for 
Cirsium hydrophilum var. hydrophilum included Southampton Marsh (two 
reviewers) and the Denverton Slough area of Suisun Marsh. Additional 
sites suggested for Cordylanthus mollis ssp. mollis included the 
Huichica-Carneros area of San Pablo Bay, Denverton Slough, Antioch 
Bridge, Beldon's Landing, Bentley Wharf, Cullinan Ranch, Mare Island, 
Martinez, Petaluma Marsh, and San Antonio Creek Marsh. Additionally, 
one reviewer asked us to explain why the C. mollis ssp. mollis 
populations at Denverton Slough and Edith Point were not included in 
the designation, and another reviewer asked why proposed Unit 3 for C. 
mollis ssp. mollis did not include a nearby area that was occupied in 
the 1990s and that may still have a seedbank.
    Our Response: Our focus on known occupied sites is based on section 
3(5)(A) of the Act, which requires us to look first to sites within the 
geographical area occupied at the time of listing. In the case of 
Cirsium hydrophilum var. hydrophilum, only three sites are known to 
have been

[[Page 18520]]

occupied at the time of listing. We therefore had proposed designating 
an additional unoccupied site (Hill Slough Marsh) that we believed was 
essential to the conservation of the subspecies. In the absence of any 
planned reintroduction projects, Hill Slough Marsh was the only 
location we considered to be sufficiently likely to support a new 
occurrence in the foreseeable future. There were three reasons for 
this: (1) Hill Slough Marsh is the subject of an ongoing tidal marsh 
restoration project, and thus has already caught the attention of 
agencies capable of carrying out a reintroduction project; (2) the 
majority of the unit consists of the Hill Slough Wildlife Area, 
acquired by the California Department of Fish and Game (CDFG) to help 
meet the mandates of the Suisun Marsh Preservation Act of 1977 (Becker 
2001, p. 1); and (3) the unit is about 2 miles (mi) (3 kilometers (km)) 
from existing C. hydrophilum var. hydrophilum occurrences at Rush Ranch 
and Peytonia Slough Marsh, and so may support natural colonization by 
seeds from those locations. In contrast, the Denverton Slough area is 
roughly 5 miles (8 km) from the nearest occupied sites, while 
Southampton Marsh is about 12 mi (19 km). Although C. hydrophilum var. 
hydrophilum seeds have plumes conducive to wind dispersal, the seeds 
are relatively heavy and tend to detach from the plumes (Service 2005, 
p. 76). Chances of successful colonization are, therefore, likely to 
decrease rapidly with distance. C. hydrophilum var. hydrophilum seeds 
may also be dispersed by water (LCLA 2003, p. 49), but this is more 
conducive to dispersals of short distances along tidal channels than to 
dispersals across miles of sloughs and baywater. Although two peer 
reviewers pointed out that Southampton Marsh may have supported C. 
hydrophilum var. hydrophilum historically, numerous surveys for C. 
mollis ssp. mollis dating back to 1978 failed to document C. 
hydrophilum var. hydrophilum at the location (CNDDB 2006b, p. 9). We 
must therefore consider the site unoccupied, both now and at the time 
of listing. We do note, however, that our designation of Southampton 
Marsh as critical habitat for C. mollis ssp. mollis may incidentally 
help protect the area for the benefit of C. hydrophilum var. 
hydrophilum, should that subspecies successfully colonize the area in 
the future.
    In the case of Cordylanthus mollis ssp. mollis, we proposed only 
areas containing the features essential to the conservation of the 
subspecies (PCEs). Section 3(5)(A)(ii) of the Act allows us to include 
areas unoccupied at the time of listing only on a determination that 
such areas are essential for the conservation of the subspecies. 
Section 3(5)(C) of the Act further requires us to avoid including the 
entire area which can be occupied by the subspecies, except where 
additional area is essential to conservation of the subspecies. We 
interpret these provisions to mean that critical habitat must represent 
core habitat areas without which conservation would be extremely 
unlikely. Other important occupied habitat areas typically exist, but 
do not rise to the essential level of importance required for critical 
habitat designation. Such other areas still benefit from the 
protections afforded to the subspecies by the Act. Based on the best 
scientific information available to us at the time, we determined in 
the proposed designation that the other locations suggested by the peer 
reviewers for C. mollis ssp. mollis did not qualify as such core areas. 
Reasons included size of the area; size and persistence of the C. 
mollis ssp. mollis occurrence; and presence, quality, and extent of the 
listed PCEs. The C. mollis ssp. mollis occurrence left out of Unit 3 
consisted of a single plant observed in 1991. No plants were found at 
the site during a subsequent survey in 1993 (CNDDB 2006b, p. 13), and 
the habitat supporting that occurrence is separated from the unit by 
about a quarter mile of upland. Therefore, extending the unit bounds to 
include both occurrences did not meet the intentions of the Act.
    If in the future important new C. hydrophilum var. hydrophilum or 
C. mollis ssp. mollis occurrences are discovered or established in 
other areas, or if evidence becomes available showing that we 
miscalculated the conservation value of undesignated areas, there are 
provisions in the Act to amend the critical habitat designation to 
include those areas.
    3. Comment: All three peer reviewers argued against excluding any 
units based on expected protections from the Suisun Marsh Habitat 
Management, Preservation and Restoration Plan (SMHMP). Reasons offered 
included that the SMHMP is not sufficiently complete.
    Our Response: We agree that the SMHMP is not sufficiently complete. 
Although the draft Programmatic Environmental Impact Statement/Report 
(PEIS/R) was initially expected to be available for public review and 
comment in the fall of 2006, the expected completion date has been 
pushed back to June 2008 (Engle 2006, p. 2).
    4. Comment: One peer reviewer argued against excluding any units 
based on existing plans such as the Suisun Marsh Protection Plan. The 
peer reviewer stated: (a) the historic ranges of both plants extend 
beyond the Protection Plan boundaries; (b) some organizations with 
management responsibilities directly affecting the recovery of the 
plants are not parties to the Protection Plan; and (c) the Protection 
Plan has failed to prevent detrimental management decisions in the 
past.
    Our Response: We agree with the peer reviewer's conclusion. The Act 
allows the Secretary of Interior to exclude areas for which the 
benefits of exclusion outweigh the benefits of inclusion unless the 
Secretary determines that such exclusion will result in the extinction 
of the species (16 U.S.C. 1533(b)(2)). We have found nothing to 
indicate that designation of the units proposed within the Protection 
Plan's boundaries would negatively affect the Protection Plan. 
Additionally, our analysis of economic impacts indicates that costs 
likely to result from designation will be relatively low and will not 
unduly burden small businesses. We therefore expect the benefits of not 
designating critical habitat to be low. In contrast, the benefits of 
designation include: (1) the establishment of an additional layer of 
protection applicable to situations with a federal nexus; and (2) the 
calling of attention to each unit's importance for the conservation of 
the endangered plants. Accordingly, we do not find that the benefits of 
excluding lands within the bounds of the Suisun Marsh Protection Plan 
outweigh the benefits of including those lands.
    The definition of critical habitat also includes the requirement 
that designated areas may require special management considerations or 
protection (16 U.S.C. 1532(5)(A)(i)). We discuss the special management 
needs of the designated units in the Special Management Considerations 
section below, as well as in the description of each unit. While these 
threats may be ameliorated by existing protections such as the 
Protection Plan, special management may be necessary in any or all of 
the units despite the existing plan because the populations of both 
subspecies are low, the threats significant, and the knowledge of how 
best to avoid or ameliorate those threats lacking. Management decisions 
taken under the Protection Plan must balance numerous goals. 
Designation of critical habitat may provide additional protection by 
pointing out the specific habitat and habitat needs of these

[[Page 18521]]

endangered plants, thereby encouraging management decisions specific to 
those areas that are more beneficial to the listed plants. Accordingly 
we find that all units, including those subject to the Suisun Marsh 
Protection Plan, meet the definition of critical habitat in that they 
may require special management.
    5. Comment: A peer reviewer asked us to discuss our decision not to 
propose designation of habitat on land owned by the Concord Naval 
Weapons Station (CNWS), in light of the possibility of base closure and 
transfer of land management.
    Our Response: Our decision not to propose designation for 402 ac 
(163 ha) of land on the CNWS was based on section 4(a)(3)(B)(i) of the 
Act, which requires us to avoid designating Department of Defense (DOD) 
land that is subject to an Integrated Natural Resources Management Plan 
(INRMP) if that INRMP benefits the species in question. The Navy has 
indeed closed most of the base and is considering plans to transfer 
ownership of most CNWS lands (Hoge 2006, p. 1). Additionally, there is 
wording in the INRMP to suggest it may have expired in 2006 (USDN 2002, 
pp. abstract, ES-2, 1-8). However, management of the tidal portion of 
CNWS lands, which include the excluded Cordylanthus mollis ssp. mollis 
habitat, will be transferred to the Army, which will continue to carry 
out the terms of the INRMP (Rouhafza 2002, p. 1; Wallerstein 2006, p. 
1). The INRMP is intended to continue in effect indefinitely, but Navy 
and Army policy requires review of existing INRMPs every 5 years to 
keep them up to date. References to a working period ending in 2006 
likely were intended to refer to the date of first review. That review 
has been completed with no significant changes (Wallerstein 2006, p. 
1). Therefore, based on the approved INRMP and our obligations under 
section 4(a)(3)(B)(i) of the Act, we are finalizing our exemption of 
402 ac (163 ha) on CNWS.
    6. Comment: One peer reviewer asked why we were not including any 
Cordylanthus mollis ssp. mollis populations in ``diked, managed, and 
muted'' tidal marshes, given our earlier statement that ``diked and 
managed marshes account for approximately 14 percent'' of C. mollis 
ssp. mollis occurrences. Another peer reviewer pointed out that even 
natural tidal areas may be muted somewhat by natural features and yet 
still support C. mollis ssp. mollis, making our distinction of ``fully 
tidal'' versus ``diked, managed, and muted'' a false dichotomy. The 
third reviewer stated that diked and managed marshes account for less 
than 14 percent of C. mollis ssp. mollis occurrences. This reviewer 
indicated that muted tidal regimes can be detrimental to C. mollis ssp. 
mollis due to negative correlations with host plants and with seed 
predation (presumably depending on the degree of muting). This peer 
reviewer nevertheless noted several areas with somewhat muted tidal 
action that still support important occurrences. Areas with muted tidal 
regimes mentioned by the reviewers include Hill Slough Marsh (Unit 2), 
Point Pinole (Unit 3), and the exempted areas of Concord Naval Weapons 
Station.
    Our Response: We have updated the discussion of primary constituent 
elements (PCEs) to better indicate that Cordylanthus mollis ssp. mollis 
does not readily occur in diked wetlands, but can occur in muted tidal 
wetlands, and that chances of deleterious effects increase as tidal 
muting increases. For more information see the Primary Constituent 
Elements section below.
    7. Comment: A peer reviewer questioned the use of soil type and 
salinity as a PCE for C. mollis ssp. mollis, stating that a recent 
study (Rejmankova and Grewell 2003) indicated soil physical type and 
salinity were not predictive of C. mollis ssp. mollis occurrences, but 
that host community composition and vigor were predictive, as were 
canopy light and disturbance gaps.
    Our Response: We have changed the PCEs for Cordylanthus mollis ssp. 
mollis to reflect this.
    8. Comment: One peer reviewer noted the following discrepancies in 
the unit boundaries: (a) Table 2 for the Hill Slough unit mentions 85 
ac (34 ha) of private land that do not appear to be included on the 
map; (b) Unit 2b for Cirsium hydrophilum var. hydrophilum appears to 
include areas with diked wetlands and landfill; (c) Unit 1 for 
Cordylanthus mollis ssp. mollis includes a large permanent pond that 
does not constitute habitat for the subspecies, and in fact acts as a 
threat by creating a dispersal barrier for C. mollis ssp. mollis seeds 
and by serving as a propagule source for exotic invasive species; and 
(d) Unit 5 for C. mollis ssp. mollis includes a 22 ac (9 ha) Superfund-
listed landfill.
    Our Response: We have redrawn the maps and adjusted the tables to 
avoid the areas mentioned lacking PCEs. However, our sources do 
indicate 85 ac (34 ha) of private land are located in the northeastern 
portion of the Hill Slough unit (BIA 2001). This land is referred to in 
the economic analysis (p. 52) as part of the Lang Tule Ranch.
    9. Comment: One peer reviewer noted that the PCEs for Cirsium 
hydrophilum var. hydrophilum discuss the banks of tidal channels but 
could be interpreted as leaving out tidal channel beds, since such beds 
are typically below mean high water (MHW). He noted that tidal channel 
beds are extremely important hydrologically to the subspecies. He also 
disagreed with our reference in that PCE to the high water mark of 
natural tidal channels, stating ``there is generally no `high water 
mark' along a tidal channel edge unless it is lined with an artificial 
levee.'' Additionally, he defined the edge of ``upland ecotone'' (to 
which we refer in the first PCE for both plants) as ``extreme high 
water''.
    Our Response: Our intent was to include the tidal channel beds 
within the mapped bounds of each designated unit. We noted in the 
mapping section of the proposed rule that tidal channels are included 
in critical habitat in their entirety because they ``are essential for 
the conservation of the subspecies based on hydrologic processes, 
despite the fact that these plants do not normally grow within the 
banks of such channels and ponds'' (71 FR 18465). We have adjusted the 
wording of the PCEs so that they now clearly include the entire tidal 
channel within the bounds of each mapped unit. We have also removed 
mention of ``high water mark'' and upland ecotone, and have redefined 
the first PCE of both subspecies in terms of our official wetlands 
classification system (Cowardin et al 1977, p. 6).
    10.Comment: One peer reviewer noted that, in the section on 
Landscape Hydrology of Cirsium hydrophilum var. hydrophilum, we stated 
that the plants may typically occur along the banks of canals or 
ditches because of lowered soil and groundwater salinity. The peer 
reviewer termed this speculative, and suggested that the physical 
characteristics of the soil itself at those locations may provide a 
better explanation than salinity.
    Our Response: We have removed comments related to salinity and 
added the existence of tidal channels themselves as a PCE. We were not 
able to further characterize the specific characteristics of tidal or 
alluvial deposits sufficiently to indicate additional soil-based PCEs 
essential to the subspecies.

Comments from the State

    The CDFG provided the following comments concerning the proposed 
critical habitat designation for Cirsium hydrophilum var. hydrophilum 
and Cordylanthus mollis ssp. mollis.
    11. Comment: The CDFG acknowledged that the proposed areas

[[Page 18522]]

provide essential needs for the plants, and so concurred with the 
proposed designation as it pertains to CDFG lands.
    Our Response: We acknowledge and appreciate CDFG's concurrence.

Public Comments Regarding Potential Exclusions of Proposed Units

    12. Comment: We received one comment supporting designation of all 
units despite protections expected from the Suisun Marsh Habitat 
Management, Preservation and Restoration Plan (SMHMP). Another 
commenter argued that all units in the Suisun Marsh area should be 
excluded based on the sufficiency of existing and planned protections 
(SMHMP, Suisun Marsh Preservation Act, Federal endangered species 
designations) and on the costs likely to result from designation.
    Our Response: As discussed above in our response to comments 3 and 
4, based on our economic analysis, we do not consider the economic or 
other impacts of designation to rise to a level where the benefits of 
exclusion outweigh the benefits of inclusion. We also do not consider 
existing or planned management protections to rise to the level such 
that the benefits of exclusion would outweigh the benefits of inclusion 
for any of the units.
    13. Comment: One commenter argued that proposed Unit 2A for Cirsium 
hydrophilum var. hydrophilum should not be designated for three 
reasons: (a) it is not known to support C. hydrophilum var. hydrophilum 
occurrences; (b) it lacks fully tidal inundations and so does not have 
a necessary PCE; and (c) designation would result in an undue burden on 
the landowner's efforts to create an environmental easement on or near 
the property for the benefit of Lasthenia conjugens (Contra Costa 
goldfields), a federally threatened upland species.
    Our Response: Regarding the commenter's first point: Our procedure 
for mapping critical habitat units has been to include within each unit 
the entire extent of persistent emergent intertidal estuarine wetland 
above mean high water that supports the PCEs and that was occupied by 
the subspecies at the time of listing (except for Unit 1 for C. 
hydrophilum var. hydrophilum, which is unoccupied). We contacted a 
biologist involved in the conservation easement planning process for 
the area who provided us with a recent rare plants survey report and 
associated mapping information. Both the survey report and the 
biologist's observations at the site (Vollmar 2005a, p. 2, 3, 5; 
Huffman 2006, p. 1) indicate that the sloughs and area beneath the 
railroad connecting proposed unit 2A to proposed unit 2B are fully 
tidal and are not blocked by the Union Pacific railroad tracks 
separating the two proposed subunits. Since there is no intervening 
area that does not consist of persistent emergent intertidal estuarine 
wetland, we have combined the two proposed subunits into a single 
contiguous unit. That unit was occupied at the time of listing (CNDDB 
2006a, p.1), although the occupied portion was in the eastern half of 
the unit. Although the survey report did not note any C. hydrophilum 
var. hydrophilum in the western portion of the unit, it did confirm the 
presence of the PCEs for the subspecies in that area (Vollmar 2005a, p. 
5, 7, 18, Figure 9). The report added: ``While this species was not 
observed during field surveys, it may have been missed since it can be 
cryptic and areas where it might grow were difficult to access.'' 
(Vollmar 2005a, p. 18).
    Regarding commenter's second point: As discussed above, the survey 
report and biologist's observations at the site both indicate the 
general area of the commenter's concern is fully tidal (Vollmar 2005a, 
p. 2, 3, 5; Huffman 2006, p. 1).
    Regarding the commenter's third point: The survey report included 
detailed mapping information showing a western boundary of ``perennial 
brackish marsh'' that was somewhat to the east of our proposed unit 
bounds (Vollmar 2005a, Figure 9). We have adjusted the western bounds 
of Unit 2 accordingly, thereby removing some of the area referred to by 
the commenter from critical habitat designation. This should help 
address concerns regarding the potential for C. hydrophilum var. 
hydrophilum's critical habitat to interfere with the development of a 
conservation easement for Lasthenia conjugens, which is an upland 
species. Our economic analysis noted that significant economic impacts 
to private landholders were unlikely as a result of the designation of 
the area proposed as subunit 2A.

Summary of Changes From Proposed Rule

    In preparing this final critical habitat designation for Cirsium 
hydrophilum var. hydrophilum and Cordylanthus mollis ssp. mollis, we 
reviewed and considered comments from the public and peer reviewers on 
the proposed designation of critical habitat published on April 11, 
2006 (71 FR 18456). We received no comments on the draft economic 
analysis published on November 20, 2006 (71 FR 67089). As a result of 
comments received on the proposed rule and a reevaluation of the 
proposed critical habitat boundaries, we made changes to our proposed 
designation, as follows:
    We combined subunits A and B of Unit 2 for C. hydrophilum var. 
hydrophilum (Peytonia Slough Marsh) based on new information indicating 
that the two subunits are not hydrologically divided by the railroad 
tracks that cut between them. We also removed 18 ac (7 ha) of private 
land from the western edge of the unit based on mapping information 
provided by a recent biological survey of the area, and we removed 53 
ac (21 ha) of State land from the northeastern edge of what was 
originally subunit 2B, to exclude diked marsh and landfilled areas 
pointed out by a peer reviewer. We have updated the map and legal 
description for the unit accordingly.
    (2) We removed 23 ac (9 ha) of State land from the middle of the 
eastern portion of Unit 1 for C. mollis ssp. mollis (Fagan Slough 
Marsh) to exclude a large permanent pond and diked wetland pointed out 
by a peer reviewer. We have updated the map and legal description for 
the unit accordingly.
    (3) We removed 14 ac (6 ha) of State land from the northwestern 
portion of Unit 5 for C. mollis ssp. mollis (Southampton Marsh) to 
exclude a landfill pointed out by a peer reviewer. We have updated the 
map and legal description for the unit accordingly.
    (4) We changed the wording of the first PCE for both subspecies to 
apply the terms of our wetlands classification system (Cowardin et al 
1977, p. 6) and to better indicate that the seaward edge (defined on 
the marsh plain by mean high water) should be drawn directly across 
intervening tidal channels despite the fact that the beds of such 
channels are typically below mean high water. We also removed 
references to tidal channel migrations, based on a peer reviewer's 
assertion that such channels do not typically migrate.
    (5) We removed references to soil salinity in the second PCE for 
both subspecies, based on a peer reviewer's assertion that soil 
salinity is not predictive of C. mollis ssp. mollis occurrences within 
areas identified by PCE 1. Further review also showed that the soils on 
which both subspecies typically occur are actually strongly saline, not 
slightly-to-moderately saline as we stated in the proposed designation 
(USDA 1993, p. 194; NRCS 2005, Joice Series p. 1, Tamba Series p.1). 
Because essentially all the soils within the area supporting PCE 1 are 
strongly saline, the identification of soil salinity provided no 
further predictive value, and was removed for both subspecies.

[[Page 18523]]

    (6) We changed the wording of all the PCEs to focus on the specific 
physical or biological features essential to the subspecies, rather 
than on the areas containing those features.
    (7) We changed the second PCE for C. hydrophilum var. hydrophilum 
by removing reference to the high water mark of tidal channels (which, 
as a peer reviewer pointed out, is essentially the bank of the 
channel), and by identifying the tidal channels and tidally influenced 
ditches themselves as a PCE.
    (8) We added a third PCE for C. hydrophilum var. hydrophilum to 
address the threat posed by invasive Lepidium latifolium (perennial 
peppergrass), which appears to prevent seedling establishment of C. 
hydrophilum var. hydrophilum by growing very densely (CDWR 1999, p. 
171; Service 2005, p. 78).
    (9) Based on a peer reviewer's comments, we changed the third PCE 
for C. mollis ssp. mollis by removing references to canopy height and 
focused instead on canopy cover and germination openings.
    (10) We renumbered the fourth PCE for C. mollis ssp. mollis, making 
it the second PCE. We also rephrased the PCE to focus more on the 
rarity or absence of unsuitable host plants rather than on the presence 
of suitable host plants. The presence of suitable host plants is 
presumed by the canopy cover requirements of the third PCE.

Critical Habitat

    Critical habitat is defined in section 3 of the Act as: (i) the 
specific areas within the geographical area occupied by a species, at 
the time it is listed in accordance with the Act, on which are found 
those physical or biological features (I) essential to the conservation 
of the species and (II) that may require special management 
considerations or protection; and (ii) specific areas outside the 
geographical area occupied by the species at the time it is listed, 
upon a determination that such areas are essential for the conservation 
of the species. Conservation, as defined under section 3 of the Act, 
means to use and the use of all methods and procedures which are 
necessary to bring any endangered species or threatened species to the 
point at which the measures provided pursuant to the Act are no longer 
necessary. Such methods and procedures include, but are not limited to, 
all activities associated with scientific resources management such as 
research, census, law enforcement, habitat acquisition and maintenance, 
propagation, live trapping, and transplantation, and, in the 
extraordinary case where population pressures within a given ecosystem 
cannot be otherwise relieved, may include regulated taking.
    Critical habitat receives protection under section 7 of the Act 
through the prohibition against destruction or adverse modification of 
critical habitat with regard to actions carried out, funded, or 
authorized by a Federal agency. Section 7 requires consultation on 
Federal actions that are likely to result in the destruction or adverse 
modification of critical habitat. The designation of critical habitat 
does not affect land ownership or establish a refuge, wilderness, 
reserve, preserve, or other conservation area. Such designation does 
not allow government or public access to private lands. Section 7 is a 
purely protective measure and does not require implementation of 
restoration, recovery, or enhancement measures.
    To be included in a critical habitat designation, the habitat 
within the area occupied by the species at the time of listing must 
first have features that are essential to the conservation of the 
species. Critical habitat designations identify, to the extent known 
using the best scientific data available, habitat areas that provide 
essential life cycle needs of the species (areas on which are found the 
primary constituent elements, as defined at 50 CFR 424.12(b)).
    Habitat occupied at the time of listing may be included in critical 
habitat only if the essential features thereon may require special 
management considerations or protection. Thus, we do not include areas 
where existing management is sufficient to conserve the species. (As 
discussed below, such areas may also be excluded from critical habitat 
pursuant to section 4(b)(2) of the Act.) Areas outside of the 
geographic area occupied by the species at the time of listing may only 
be included in critical habitat if they are essential for the 
conservation of the species. Accordingly, when the best available 
scientific data do not demonstrate that the conservation needs of the 
species require additional areas, we will not designate critical 
habitat in areas outside the geographical area occupied by the species 
at the time of listing. However, an area that is currently occupied by 
the species, but which was not known at the time of listing to be 
occupied, will likely, but not always, be essential to the conservation 
of the species and, therefore, eligible for inclusion in the critical 
habitat designation.
    The Service's Policy on Information Standards Under the Endangered 
Species Act, published in the Federal Register on July 1, 1994 (59 FR 
34271), and Section 515 of the Treasury and General Government 
Appropriations Act for Fiscal Year 2001 (P.L. 106-554; H.R. 5658) and 
the associated Information Quality Guidelines issued by the Service, 
provide criteria, establish procedures, and provide guidance to ensure 
that decisions made by the Service represent the best scientific data 
available. They require Service biologists, to the extent consistent 
with the Act and with the use of the best scientific data available, to 
use primary and original sources of information as the basis for 
recommendations to designate critical habitat. When determining which 
areas are critical habitat, a primary source of information is 
generally the listing package for the species. Additional information 
sources include the recovery plan for the species, articles in peer-
reviewed journals, conservation plans developed by States and counties, 
scientific status surveys and studies, biological assessments, or other 
unpublished materials and expert opinion or personal knowledge. All 
information is used in accordance with the provisions of Section 515 of 
the Treasury and General Government Appropriations Act for Fiscal Year 
2001 (P.L. 106-554; H.R. 5658) and the associated Information Quality 
Guidelines issued by the Service.
    Section 4 of the Act requires that we designate critical habitat on 
the basis of the best scientific data available. Habitat is often 
dynamic, and species may move from one area to another over time. 
Furthermore, we recognize that designation of critical habitat may not 
include all of the habitat areas that may eventually be determined to 
be necessary for the recovery of the species. For these reasons, 
critical habitat designations do not signal that habitat outside the 
designation is unimportant or may not be required for recovery.
    Areas that support populations of Cirsium hydrophilum var. 
hydrophilum and Cordylanthus mollis ssp. mollis, but are outside the 
critical habitat designation, will continue to be subject to 
conservation actions implemented under section 7(a)(1) of the Act and 
to the regulatory protections afforded by the section 7(a)(2) jeopardy 
standard, as determined on the basis of the best available information 
at the time of the action. Section 7(a)(1) directs all other Federal 
agencies to utilize their authorities in furtherance of the purposes of 
the ESA by carrying out programs for the conservation of listed 
species. Federally funded or permitted projects affecting listed 
species outside their designated critical habitat areas

[[Page 18524]]

may still result in jeopardy findings in some cases. Similarly, 
critical habitat designations made on the basis of the best available 
information at the time of designation will not control the direction 
and substance of future recovery plans, habitat conservation plans, or 
other species conservation planning efforts if new information 
available to these planning efforts calls for a different outcome.

Primary Constituent Elements

    In accordance with section 3(5)(A)(i) of the Act and regulations at 
50 CFR 424.12, in determining which areas to designate as critical 
habitat within areas occupied by the species at the time of listing, we 
consider those physical and biological features (PCEs) that are 
essential to the conservation of the species, and that may require 
special management considerations and protection. These include, but 
are not limited to, space for individual and population growth and for 
normal behavior; food, water, air, light, minerals, or other 
nutritional or physiological requirements; cover or shelter; sites for 
breeding, reproduction, and rearing (or development) of offspring; and 
habitats that are protected from disturbance or are representative of 
the historic geographical and ecological distributions of a species.
    The specific PCEs required for Cirsium hydrophilum var. hydrophilum 
and Cordylanthus mollis ssp. mollis are derived from the biological 
needs of the two plants as described below and in the proposed critical 
habitat designation published in the Federal Register on April 11, 2006 
(71 FR 18456).

Cirsium hydrophilum var. hydrophilum: Space for Individual and 
Population Growth

    Cirsium hydrophilum var. hydrophilum appears to have been 
historically restricted to Suisun Marsh in Solano County, California 
(CDWR 1999, p. 171). Cirsium hydrophilum var. hydrophilum is only known 
to occur in persistent emergent intertidal estuarine wetland, from the 
landward edge of that habitat type down to the mean high water line 
(Service 2005, p. 22). A wetland is an area that is at least 
periodically saturated or covered by water of up to 6 feet (2 meters). 
An estuarine wetland is a wetland exposed at least occasionally to both 
ocean tides and freshwater runoff from the land. ``Intertidal'' means 
the area is occasionally flooded by tides, rather than being 
continuously submerged. ``Emergent'' indicates that the area is 
dominated by erect, rooted plants adapted to growth in saturated, low 
oxygen soils. Such areas are ``persistent'' when these plants normally 
remain standing at least until the beginning of the next growing season 
(Cowardin et al 1977, pp. 11, 18, 19, 35, 36). The landward limit of 
such a wetland is the highest point that is still occasionally flooded 
by tides (Cowardin et al 1977, p. 19). This wetland type extends down 
below mean high water, to the seaward limit of persistent emergent 
vegetation (Cowardin et al 1977, p. 18), but C. hydrophilum var. 
hydrophilum is not known from areas below the mean high water line. 
Within these limits, most C. hydrophilum var. hydrophilum plants grow 
along the banks of small natural tidal channels and tidally influenced 
ditches (CDWR 1999, p. 171; LCLA 2003, p. 19; Service 2005, p. 22; 
CNDDB 2006a, pp. 2, 3). Occurrences also exist on low-order floodplain 
unassociated with any water channel, but this is rare (LCLA 2003, p. 
19). The subspecies does not appear to thrive in diked wetlands (CDWR 
1999, p. 172), presumably because such wetlands become nonestuarine due 
to the lack of tidal inundations.
    Specific conditions for germination and growth of Cirsium 
hydrophilum var. hydrophilum are not known, but field observations 
suggest they are associated with small gaps or sparsely vegetated 
areas. Dense vegetative cover, particularly Lepidium latifolium 
(perennial peppergrass) restricts the establishment of the subspecies 
(CDWR 1999, p. 171; LCLA 2003, p 21).

Cirsium hydrophilum var. hydrophilum: Sites Providing Nutritional or 
Physiological Requirements

    Cirsium hydrophilum var. hydrophilum tends to grow along the banks 
of tidal channels and tidally influenced ditches (CDWR 1999, p. 171). 
Tidal channels are characterized as being open conduits that either 
periodically or continuously contain moving water (Cowardin et al 1977, 
p. 69). Such channels in an estuarine wetland would extend landward to 
the point where ocean-derived salts measure less than 0.5 percent 
during the period of average annual flow (Cowardin et al 1977, p. 18).

Cirsium hydrophilum var. hydrophilum: Sites for Reproduction

    Cirsium hydrophilum var. hydrophilum is a perennial plant that dies 
after flowering and bearing seeds. Its vegetative period is usually 1 
year, but if small vegetative plant size or unfavorable environmental 
conditions delay flowering, a plant may grow back from its central root 
crown after the winter, and thereby live for more than a year. 
Flowering occurs throughout the summer during most years and continues 
through the production of ripe seed heads (Service 2005, p. 75).
    Pollination ecology of Cirsium hydrophilum var. hydrophilum has not 
been studied to identify specific flower pollinators. Field 
observations at Rush Ranch indicate that several bee species may be 
important in pollinating the subspecies (LCLA 2003, pp. 39-40, 47; 
Service 2005, p. 75). The most common species observed gathering pollen 
at the ranch was the yellow-faced bumble bee (Bombus vosnesenskii) 
(LCLA 2003, pp. 39-40).
    Information on short- and long-distance seed dispersal for Cirsium 
hydrophilum var. hydrophilum is lacking, but streams and tidal flows 
have been shown to be important seed dispersal mechanisms in C. 
vinaceum (Sacramento Mountain thistle) and certain halophytic plants 
(Koutstaal et al. 1987, p. 226; Huiskes et al. 1995, p. 559; Craddock 
and Huenneke 1997, p. 215; LCLA 2003, p. 46). C. hydrophilum var. 
hydrophilum seeds float in water (LCLA 2003, p. 46), and also have 
plumes conducive to wind dispersal, but the seeds are relatively heavy 
and tend to detach from the plumes, making long distance wind dispersal 
less likely (Service 2005, p. 76).

Cirsium hydrophilum var. hydrophilum: Primary Constituent Elements

    Pursuant to our regulations, we are required to identify the known 
physical and biological features (primary constituent elements (PCEs)) 
essential to the conservation of Cirsium hydrophilum var. hydrophilum. 
All areas except for Unit 1 (Hill Slough Marsh) are currently occupied 
by C. hydrophilum var. hydrophilum. All of the critical habitat areas 
are within the subspecies' historic geographic range, and contain 
sufficient PCEs to support at least one of the plant's life history 
functions.
    Based on our current knowledge of the life history, biology, and 
ecology of Cirsium hydrophilum var. hydrophilum and the requirements of 
the habitat to sustain the essential life history functions of the 
subspecies, we have determined that the PCEs for Cirsium hydrophilum 
var. hydrophilum are:
    (1) Persistent emergent, intertidal, estuarine wetland at or above 
the mean high-water line (as extended directly across any intersecting 
channels);
    (2) Open channels that periodically contain moving water with 
ocean-derived salts in excess of 0.5 percent; and
    (3) Gaps in surrounding vegetation to allow for seed germination 
and growth.

[[Page 18525]]

Cordylanthus mollis ssp. mollis: Space for Individual and Population 
Growth

    Cordylanthus mollis ssp. mollis is somewhat more geographically 
widespread than C. hydrophilum var. hydrophilum, growing in tidal 
marshes of San Pablo Bay, as well as of Suisun Bay (CNDDB 2006b). As 
with C. hydrophilum var. hydrophilum, however, C. mollis ssp. mollis is 
restricted to persistent emergent intertidal estuarine wetland above 
the mean high water line (Ruygt 1994, p. 77). C. mollis ssp. mollis 
does not typically occur in diked wetlands without tidal action (CDWR 
1994, p. 50; Ruygt 1994, p. 77; Grewell et al. 2003, p. 32). Areas with 
muted tidal regimes can support the subspecies (CDWR 1999, p. 176), but 
increased tidal muting can constitute a threat to C. mollis ssp. mollis 
by increasing the prevalence of unsuitable host plants, and by changing 
the balance of seed production to seed predation maintained between the 
plant and seed-eating moths, such as various Saphenista species 
(Grewell 2004, pp. 115, 16; Grewell 2006, p. 3). The moth larvae burrow 
in the sediment during part of their life cycle, so reduced tidal 
flooding may improve their survivorship.

Cordylanthus mollis ssp. mollis: Sites Providing Nutritional or 
Physiological Requirements

    Cordylanthus mollis ssp. mollis thrives best under a partially open 
canopy that provides intermediate light levels (average 790 nanomols 
per square meter per second (nMol/m2/s)) at ground level during 
seedling emergence in the spring (Grewell et al. 2003, p. 31). The 
plant establishes fragile, parasitic root connections to its host 
plants by means of a specialized structure called a haustorium (Chuang 
and Heckard 1971, p. 218; Grewell et al. 2003, p. 8). These connections 
produce an extensive network of intertwined roots that provides the 
subspecies with part of its water and nutritional requirements to 
augment its growth. C. mollis ssp. mollis seedlings will attach to a 
wide range of host plants, but not all plants are suitable hosts. 
Nonnative winter annuals, such as Hainardia cylindrica (barbgrass) and 
Polypogon monspeliensis (annual rabbitsfoot grass), or native winter 
annuals, such as Juncus bufonius (toad rush), are not suitable hosts 
because they typically die before C. mollis ssp. mollis can flower and 
produce seeds (Grewell et al. 2003, pp. 77, 78; and Grewell 2004, pp. 
86, 107). Known suitable hosts include Distichlis spicata (salt grass), 
Sarcocornia pacifica (pickleweed), and Jaumea carnosa (marsh jaumea). 
Seedlings suffer increased mortality when they germinate near 
unsuitable hosts or in habitats with a low availability of suitable 
hosts (Grewell 2004, pp. 86, 107).

Cordylanthus mollis ssp. mollis: Sites for Reproduction

    Cordylanthus mollis ssp. mollis, an annual, regenerates from a 
persistent, dormant seed bank. The longevity of seed banks is unknown, 
but some populations fail to emerge for several years and then 
reappear, suggesting long-term viability of dormant seeds (Service 
2005, p. 97). The peak seed germination period occurs during the most 
frequent tidal inundations in areas of bare soil (CDWR 1994, p. 52; 
Ruygt 1994, p. 78). Accordingly, the presence of small gaps in the 
surrounding overstory are important to the germination success. Such 
gaps can be created by Cuscuta salina (salt marsh dodder), a parasitic 
plant (Grewell et. al. 2003, pp. 22, 31). Seed production can be 
significantly influenced by flower, fruit, and seed predation by 
lepidopteran larvae (caterpillars) (Ruygt 1994, p. 59; Grewell et al. 
2003, pp. 43-45).
    Cordylanthus mollis ssp. mollis is probably dependent on insects 
for successful pollination and reproduction. Ruygt (1994, p. 56) 
observed three bee species that were visitors to various C. mollis ssp. 
mollis populations in Napa and Solano Counties. Bumble bees (Bombus 
californicus) were the most frequent visitors seen foraging among 
flowers. The low number of potential pollinators at some locations 
suggests that the subspecies may rely to some degree on self-
pollination to fertilize flowers within larger populations (Ruygt 1994, 
p. 58). During a pollinator exclusion experiment, Ruygt (1994, p. 58) 
observed that several plants were able to produce seeds through self-
fertilization, but the viability of these seeds were not tested or 
compared to those for non-experimental plants. Grewell et al. (2003, 
pp. 37-39) observed five bee genera and one bee fly acting as potential 
pollinators at a recently reintroduced population of C. mollis ssp. 
mollis at Rush Ranch and a natural population at Hill Slough Marsh. 
Pre-dispersal predation of C. mollis ssp. mollis seeds by various 
moths, including Saphinista and Lipographis species, can also play a 
significant role in reproductive success (Grewell et al. 2003, p. 45). 
The influence of natural tidal regimes on Saphinista population levels 
is discussed above. Populations of these seed predators are also kept 
in check by various wasps of the Eumenidae and Vespidae families.
    Limited information exists on seed dispersal mechanisms for 
Cordylanthus mollis ssp. mollis. Seeds may disperse short distances 
from parent plants by tidal inundations or animals (Grewell et al. 
2003, pp. 89-90), but successful long distance dispersal by these or 
other events has not been documented. Stromberg and Villasenor (1986, 
p. 6) observed that most of the mature seed capsules remained closed on 
parent plants. They believed that the majority of the seeds were 
probably released from seed capsules after mature plants fell to the 
ground and decayed. This would likely result most often in seeds 
germinating directly beneath parent plants, but since the seeds can 
float (Ruygt 1994, p. 31), it would also provide opportunity for 
dispersal by tidal inundations.

Cordylanthus mollis ssp. mollis: Primary Constituent Elements

    Pursuant to our regulations, we are required to identify the known 
physical and biological features (PCEs) essential to the conservation 
of Cordylanthus mollis ssp. mollis. All areas designated as critical 
habitat for C. mollis ssp. mollis are occupied by the subspecies, are 
within the subspecies' historic geographic range, and contain 
sufficient PCEs to support at least one of the plant's life history 
functions.
    Based on our current knowledge of the life history, biology, and 
ecology of Cordylanthus mollis ssp. mollis, we have determined that the 
PCEs for Cordylanthus mollis ssp. mollis:
    (1) Persistent emergent, intertidal, estuarine wetland at or above 
the mean high-water line (as extended directly across any intersecting 
channels);
    (2) Rarity or absence of plants that naturally die in late spring 
(winter annuals); and
    (3) Partially open spring canopy cover (approximately 790 nMol/m2/
s) at ground level, with many small openings to facilitate seedling 
germination.
    This designation is designed for the conservation of areas 
supporting PCEs necessary to support the life history functions which 
were the basis for the proposal. In general, critical habitat units are 
designated based on sufficient PCEs being present to support one or 
more of the subspecies' life history functions. Each of the areas 
proposed in this rule have been determined to contain sufficient PCEs 
to provide for one or more of the life history functions of the two 
subspecies. Because not all life history functions require all the 
PCEs, not all critical habitat will uniformly contain all the PCEs.

[[Page 18526]]

Criteria Used To Identify Critical Habitat

    As required by section 4 of the Act, we use the best scientific 
data available in determining areas that contain the features that are 
essential to the conservation of Cirsium hydrophilum var. hydrophilum 
and Cordylanthus mollis ssp. mollis. The material included data in 
reports submitted during section 7 consultations and by biologists 
holding section 10(a)(1)(A) recovery permits; research published in 
peer-reviewed articles and presented in academic theses and agency 
reports; and regional Geographic Information System (GIS) coverages. 
With the partial exception of Hill Slough Marsh, we designated no areas 
outside the geographical area presently occupied by the subspecies. 
Hill Slough Marsh is designated for both C. hydrophilum var. 
hydrophilum and C. mollis ssp. mollis, but is only currently occupied 
by C. mollis ssp. mollis. The area is being designated critical habitat 
for C. hydrophilum var. hydrophilum because it contains the PCEs for 
the species and is required for its conservation due to the plants 
limited distribution. The Hill Slough Marsh has been identified as the 
single best area for restoration for C. hydrophilum var. hydrophilum 
and is the subject of on-going planning and restoration efforts.

Mapping

    After choosing general areas based on the above considerations, we 
mapped unit bounds to correspond with the contiguous areas supporting 
the listed PCEs, according to procedures listed in the Mapping section 
of the proposed rule (71 FR 18465; April 11, 2006). As discussed above 
(Summary of Changes From the Proposed Rule), we redrew some bounds in 
this final designation to account for changes to the PCEs, as well as 
for new information provided by peer reviewers and commenters.

Criteria Used to Identify Critical Habitat for Cirsium hydrophilum var. 
hydrophilum

    The tidally influenced habitat required for Cirsium hydrophilum 
var. hydrophilum survival has been greatly reduced from historical 
levels. Of the estimated 71,000 ac (29,000 ha) of tidal marsh habitat 
originally within the Suisun Marsh, only about 9,300 ac (3,800 ha) 
remained as tidal marsh in 1989 (Dedrick 1989, pp. 4, 7). Most of this 
area is backed by steep levees, allowing for little or no tidally 
influenced marsh habitat required for the subspecies as identified in 
the PCE section above. The distribution of C. hydrophilum var. 
hydrophilum has also been greatly reduced from historical levels. It 
was considered very common in Suisun Bay in the late 19th century (CDWR 
1999, p. 171). In 1975, the plant was deemed to be extirpated due to a 
15-year absence from known locations within the Suisun Marsh. Extensive 
survey work in 1993 identified two populations in the Suisun Marsh area 
and identified the Hill Slough area as containing habitat essential for 
the conservation of the subspecies (Grewell 1993).
    The population size of C. hydrophilum var. hydrophilum varies 
greatly from year to year. At the time of listing, the subspecies was 
known from two small areas totaling a few thousand plants occupying an 
area of less than one acre. Survey work done since the time of listing 
has identified an additional population within the same general area as 
the two at the time of listing. These three populations continue to be 
threatened by the same factors discussed in the listing determination: 
habitat loss, fragmentation, disruption to the hydrologic regime, 
invasive competition from nonnative plants, chronic and acute pollution 
from point and non-point sources, insect or pest outbreaks, and 
extended drought. Due to their small size, the populations are also 
subject to increased risk of extirpation from random anthropogenic or 
natural events.
    We have determined that, due to the limited availability of habitat 
for the subspecies, the limited distribution and small population size 
of the subspecies, and the subspecies' poor dispersal capabilities, the 
long-term conservation of this plant is dependent upon the protection 
of habitat supporting all three existing populations, including 
surrounding areas that may contain dormant seed banks and that support 
the PCEs of the subspecies. For the same reasons, the co