Endangered and Threatened Wildlife and Plants; Final Rule Designating Critical Habitat for Ambrosia pumila (San Diego ambrosia), 74546-74604 [2010-29692]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 75, Number 229 (Tuesday, November 30, 2010)]
[Rules and Regulations]
[Pages 74546-74604]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-29692]



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Part V





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; Final Rule Designating 
Critical Habitat for Ambrosia pumila (San Diego ambrosia); Final Rule

Federal Register / Vol. 75 , No. 229 / Tuesday, November 30, 2010 / 
Rules and Regulations

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R8-ES-2009-0054; MO 92210-0-0009-B4]
RIN 1018-AW20


Endangered and Threatened Wildlife and Plants; Final Rule 
Designating Critical Habitat for Ambrosia pumila (San Diego ambrosia)

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Final rule.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), are 
designating critical habitat for Ambrosia pumila (San Diego ambrosia) 
under the Endangered Species Act of 1973, as amended. Approximately 783 
acres (317 hectares) are being designated as critical habitat for A. 
pumila in Riverside and San Diego counties, California.

DATES: This rule becomes effective on December 30, 2010.

ADDRESSES: The final rule, final economic analysis, and map of critical 
habitat will be available on the Internet at https://www.regulations.gov 
at Docket No. FWS-R8-ES-2009-0054. Supporting documentation we used in 
preparing this final rule will be 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, Suite 101, Carlsbad, CA 92011; telephone 760-431-9440; facsimile 
760-431-5901.

FOR FURTHER INFORMATION CONTACT: Jim Bartel, Field Supervisor, U.S. 
Fish and Wildlife Service, Carlsbad Fish and Wildlife Office, 6010 
Hidden Valley Road, Suite 101, Carlsbad, CA 92011; telephone 760-431-
9440; facsimile 760-431-5901. If you use a telecommunications device 
for the deaf (TDD), call the Federal Information Relay Service (FIRS) 
at (800) 877-8339.

SUPPLEMENTARY INFORMATION:

Background

    We intend to discuss only those topics directly relevant to the 
designation of critical habitat for Ambrosia pumila under the 
Endangered Species Act of 1973 (Act), as amended (16 U.S.C. 1531 et 
seq.), in this final critical habitat designation. For more information 
on the taxonomy, biology, and ecology of A. pumila, refer to the final 
listing rule published in the Federal Register on July 2, 2002 (67 FR 
44372), the proposed critical habitat designation published in the 
Federal Register on August 27, 2009 (74 FR 44238), and the Notice of 
Availability (NOA) of the draft economic analysis (DEA) published in 
the Federal Register on May 18, 2010 (75 FR 27690).

New Information on Species' Description, Life History, Ecology, 
Habitat, and Geographic Range and Status

    We received no new information pertaining to the description, life 
history, ecology, or habitat of Ambrosia pumila following the 2009 
proposed critical habitat designation (74 FR 44238, August 27, 2009). 
However, we did receive and analyze new information related to the 
distribution and status of A. pumila, which is described below.
Geographic Range and Status
    As described in the proposed rule, Ambrosia pumila is distributed 
in southern California from northwestern Riverside County, south 
through western San Diego County, to northwestern Baja California, 
Mexico (CNDDB 2010). It is generally found at or below elevations of 
1,600 feet (ft) (487 meters (m)) in Riverside County, and 600 ft (183 
m) in San Diego County (CNDDB 2010). Since publication of the proposed 
rule in the Federal Register on August 27, 2009 (74 FR 44238), we 
became aware of two additional occurrences of this species, both of 
which fall within the previously known geographic range of the species. 
One occurrence (Subunit 3B) is in the City of Temecula in Riverside 
County near the western end of 1st Street, just west of Murrieta Creek. 
This occurrence is believed to have been present at the time of listing 
because plants with clonal growth patterns tend to be long-lived 
(Watkinson and White 1985, pp. 44-45; Tanner 2001, p. 1980). Although 
stems may die and portions of the rhizome may disintegrate over time, 
except under extreme conditions, enough of the rhizome survives from 
one growing season to the next to support continued growth of an 
individual plant. Additionally, because the plants produce very few if 
any seeds, the ability of the plant to disperse into and colonize 
previously unoccupied areas is diminished. The second occurrence is 
located just west of Lake Hodges in the western portion of central San 
Diego County, on and adjacent to the west side of the Crosby National 
Golf Club. This occurrence was included in the listing rule, but was 
thought to have been possibly extirpated since the species was listed. 
This occurrence is now known to be extant.

Previous Federal Actions

    Ambrosia pumila was listed as an endangered species on July 2, 2002 
(67 FR 44372). Designation of critical habitat was found to be prudent 
in the proposed (64 FR 72993; December 29, 1999) and final listing 
rules, but was deferred due to budgetary constraints and higher listing 
priorities. The Center for Biological Diversity filed a complaint in 
the U.S. District Court for the Southern District of California on 
December 19, 2007, challenging the Service's failure to designate 
critical habitat for four endangered plants, including A. pumila 
(Center for Biological Diversity v. United States Fish and Wildlife, et 
al., Case No. 07- CV-2378 NLS). The April 11, 2008, settlement 
agreement stipulates that the Service shall submit a determination as 
to whether it is prudent to designate critical habitat for A. pumila, 
and if prudent, submit a proposed critical habitat designation to the 
Federal Register for publication by August 20, 2009, and submit a final 
critical habitat designation to the Federal Register for publication by 
before August 19, 2010. By order dated August 3, 2010, the district 
court approved a modification to the settlement agreement that extends 
to November 19, 2010, the deadline for submission of a final revised 
critical habitat designation to the Federal Register. The proposed 
critical habitat designation published in the Federal Register on 
August 27, 2009 (74 FR 44238).

Summary of Changes From Proposed Rule To Designate Critical Habitat

    In our 2009 proposed rule (74 FR 44247, August 27, 2009), we 
proposed approximately 802 acres (ac) (324 hectares (ha)) as critical 
habitat in 7 units with 8 subunits in Riverside and San Diego Counties, 
California. We reevaluated our data in conjunction with information 
received during the comment period and information obtained after the 
publication of the 2009 proposed rule. Based on this reevaluation, we 
changed our proposal to approximately 1,140 ac (461 ha) in 7 units, 
which collectively consist of 13 subunits (75 FR 27690, May 18, 2010). 
In this final critical habitat rule, we are designating approximately 
783 ac (317 ha) as critical habitat in 6 units with 13 subunits, 
reflecting the exclusion of approximately 329 ac (133 ha) based on 
consideration of relevant impacts under section 4(b)(2) of the Act. All 
land designated as critical habitat in this final rule was included in 
the 2009 proposed rule (74 FR 44247, August 27, 2009) or the Notice of 
Availability

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(NOA) for the Draft Economic Analysis (DEA) (75 FR 27690, May 18, 
2010). Changes between this designation and the 2009 proposed 
designation are described below and in Table 1.
    (1) In the proposed rule and the NOA, we considered lands covered 
under the Western Riverside County Multiple Species Habitat 
Conservation Plan (Western Riverside County MSHCP) in Subunits 1A and 
1B, Unit 2 and Subunit 3B for exclusion under section 4(b)(2) of the 
Act. We have analyzed each of the areas considered for exclusion under 
the Western Riverside County MSHCP and determined that the benefits of 
exclusion outweigh the benefits of inclusion of approximately 118 ac 
(48 ha) of land in Unit 2 covered by the Western Riverside County 
MSHCP. We also determined that exclusion of this area will not result 
in extinction of the species. Therefore, we excluded this area from 
this critical habitat designation under section 4(b)(2) of the Act. For 
a complete discussion of the benefits of inclusion and exclusion, see 
Exclusions Under Section 4(b)(2) of the Act section below.
    (2) In the proposed rule as modified by the NOA, we considered 
lands in Units 5A and 6 owned by or under the jurisdiction of the City 
of San Diego within the City of San Diego Subarea Plan under the 
Multiple Species Conservation Program (City of San Diego MSCP Subarea 
Plan) for exclusion under section 4(b)(2) of the Act. We have analyzed 
each of the areas considered for exclusion under the City of San Diego 
MSCP Subarea Plan and determined that the benefits of exclusion 
outweigh the benefits of inclusion of approximately 160 ac (65 ha) of 
land in Unit 6 covered by the City of San Diego MSCP Subarea Plan. 
Exclusion of this area will not result in extinction of the species. 
Therefore, we excluded this area from this critical habitat designation 
under section 4(b)(2) of the Act (see Exclusions Under Section 4(b)(2) 
of the Act section below).
    (3) In the proposed rule as modified by the NOA, we considered 
lands in Subunit 5B and Unit 7 (Subunits 7A, 7B and 7C) owned by or 
under the jurisdiction of the County of San Diego within the County of 
San Diego Subarea Plan under the MSCP (County of San Diego MSCP Subarea 
Plan) for exclusion under section 4(b)(2) of the Act. We have analyzed 
each of the proposed areas within the County of San Diego MSCP Subarea 
Plan area and determined that the benefits of exclusion outweigh the 
benefits of inclusion of approximately 52 ac (21 ha) of land in Subunit 
5B covered by the County of San Diego MSCP Subarea Plan that are 
conserved and managed under the Crosby at Rancho Santa Fe Habitat 
Management Plan. We also determined that exclusion of this area will 
not result in extinction of the species. Therefore, we excluded this 
area from this critical habitat designation under section 4(b)(2) of 
the Act (see Exclusions Under Section 4(b)(2) of the Act section 
below).
    (4) The boundaries of Subunits 4A, 4B, and 4C have been modified to 
remove habitat that is not suitable for Ambrosia pumila according to 
data received after the proposed rule was published, and to remove 
widened portions of State Route 76 where habitat is no longer suitable 
for A. pumila (see Criteria Used To Identify Critical Habitat section 
below).
    (5) To prepare final critical habitat maps, we overlay maps of 
those lands we are excluding from this critical habitat designation on 
polygons that are delineated using physical and biological features. 
This process often leaves small fragments of a proposed critical 
habitat unit or subunit that are not excluded but that, by themselves, 
may not be considered essential. We evaluated these areas and removed 
from the final designation habitat fragments remaining after areas are 
excluded that were not considered essential. As a result, the sum of 
the areas designated and excluded is slightly reduced in this final 
critical habitat designation compared to the size of the total proposed 
designation due to removal of small artifacts or fragments created by 
the exclusion process.

 Table 1--A Comparison of the Areas Identified as Containing Features Essential to the Conservation of Ambrosia
      pumila in the 2009 Proposed Critical Habitat Designation and This Final Critical Habitat Designation
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                                     2009 Proposed critical    Excluded under section      2010 Final critical
                                             habitat                   4(b)(2)                   habitat
             Location              -----------------------------------------------------------------------------
                                       Acres       Hectares      Acres       Hectares      Acres       Hectares
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Unit 1: Santa Ana River watershed.          112           45            0            0          112           45
Subunit 1A: Alberhill (Lake                  41           17            0            0           41           17
 Street)..........................
Subunit 1B: Nichols Road..........           70           29            0            0           70           29
Unit 2: Skunk Hollow Vernal Pool            118           48          118           48            0            0
 watershed........................
Unit 3: Santa Margarita River                77           31            0            0           77           31
 watershed........................
Subunit 3A: Santa Gertrudis Creek.           33           13            0            0           33           13
Subunit 3B: Murrieta Creek........           44           18            0            0           44           18
Unit 4: San Luis Rey River                  126           51            0            0           92           37
 watershed........................
Subunit 4A: Calle de la Vuelta....           30           12            0            0          15*            6
Subunit 4B: Olive Hill Road.......           35           14            0            0          23*            9
Subunit 4C: Jeffries Ranch........           40           16            0            0          33*           13
Subunit 4D: Gird/Monserate Hill...           21            9            0            0         21**            8
Unit 5: San Dieguito River                  294          119           52           21          249          101
 watershed--Lake Hodges...........
Subunit 5A: Lake Hodges East (Via            21            9            0            0           21            9
 Rancho Pkwy).....................
Subunit 5B: Lake Hodges West                279          113           52           21          228           92
 (Crosby Estates).................
Unit 6: San Diego River watershed--         198           80          160           65           38           16
 Mission Trails Regional Park.....
Unit 7: Sweetwater River watershed          215           87            0            0          215           87
Subunit 7A: Jamul Drive...........           39           16            0            0           39           16
Subunit 7B: San Diego National              133           54            0            0          133           54
 Wildlife Refuge..................
Subunit 7C: Steele Canyon Bridge..           44           18            0            0           44           18
                                   -----------------------------------------------------------------------------
    Total.........................        1,146          461          329          133          783          317
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Values in this table may not sum or may differ slightly from values in the proposed rule and NOA due to
  rounding.

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* Modified to remove habitat that is not suitable for Ambrosia pumila.
** This number is different than the number given in the NOA due to a typographical error in the NOA.

Critical Habitat

    Critical habitat is defined in section 3(5)(A) of the Act as:(1) 
The specific areas within the geographical area occupied by the 
species, at the time it is listed in accordance with the Act, on which 
are found those physical or biological features
    (a) essential to the conservation of the species and
    (b) which may require special management considerations or 
protection; and (2) 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(3) of the Act, means the 
use of all methods and procedures that are necessary to bring any 
endangered or threatened species to the point at which the measures 
provided under 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, transplantation, and--in the extraordinary case where 
population pressures within a given ecosystem cannot otherwise be 
relieved--regulated taking.
    Critical habitat receives protection under section 7(a)(2) of the 
Act through the prohibition against Federal agencies carrying out, 
funding, or authorizing the destruction or adverse modification of 
critical habitat. Section 7(a)(2) of the Act requires consultation on 
Federal actions that may affect 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 the government or public to access private 
lands. Such designation does not require implementation of restoration, 
recovery, or enhancement measures by private landowners. Where a 
landowner requests Federal agency funding or authorization for an 
action that may affect a listed species or critical habitat, the 
consultation requirements of section 7(a)(2) would apply, but even in 
the event of a destruction or adverse modification finding, the 
landowner's obligation is not to restore or recover the species, but to 
implement reasonable and prudent alternatives to avoid destruction or 
adverse modification of critical habitat.
    For inclusion in a critical habitat designation, the habitat within 
the geographical area occupied by the species at the time of listing 
must contain physical and biological features that are essential to the 
conservation of the species, and be included only if those features may 
require special management considerations or protection. 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; that is, areas on which are found the 
primary constituent elements (PCEs) laid out in the appropriate 
quantity and spatial arrangement essential to the conservation of the 
species. Under section 3(5)(A)(ii) of the Act, the Secretary can 
designate critical habitat in areas outside the geographical area 
occupied by the species at the time it is listed as critical habitat 
only when he/she determines that those areas are essential for the 
conservation of the species.
    Section 4 of the Act requires that we designate critical habitat on 
the basis of the best scientific and commercial data available. 
Further, our Policy on Information Standards Under the Endangered 
Species Act (published in the Federal Register on July 1, 1994 (59 FR 
34271)), the Information Quality Act (section 515 of the Treasury and 
General Government Appropriations Act for Fiscal Year 2001 (Pub. L. 
106-554; H.R. 5658)), and our associated Information Quality Guidelines 
provide criteria, establish procedures, and provide guidance to ensure 
that our decisions are based on the best scientific data available. 
They require our 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 we are determining which areas should be designated as 
critical habitat, our primary source of information is generally the 
information developed during the listing process for the species. 
Additional information sources may 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.
    Habitat is often dynamic, and species may naturally move within an 
area or from one area to another over time. Furthermore, we recognize 
that designation of critical habitat may not include all habitat areas 
that may eventually be determined necessary for recovery of the 
species, based on scientific data not now available. For these reasons, 
a critical habitat designation does not signal that habitat outside the 
designated area is unimportant or may not promote the recovery of the 
species. Federal activities that may affect areas outside of critical 
habitat are still subject to review under section 7 of the Act if they 
may affect Ambrosia pumila. The prohibitions of section 9 of the Act 
applicable to listed plant species also continue to apply both inside 
and outside of designated critical habitat.
    Areas that support occurrences of the species, but are outside the 
critical habitat designation, will continue to be subject to 
conservation actions we implement under section 7(a)(1) of the Act. In 
these areas, the species is also subject to the regulatory protections 
afforded by the section 7(a)(2) jeopardy standard, as determined on the 
basis of the best available scientific information at the time of the 
agency action. Federally funded or permitted projects affecting listed 
species outside their designated critical habitat areas 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 (HCPs), or other 
species conservation planning efforts if new information available to 
these planning efforts calls for a different outcome.

Physical and Biological Features

    In accordance with section 3(5)(A)(i) of the Act and regulations at 
50 CFR 424.12(b), in determining which areas occupied by the species at 
the time of listing to propose as critical habitat, we consider those 
physical and biological features that are essential to the conservation 
of the species that may require special management considerations or 
protection. We consider the physical and biological features to be the 
PCEs laid out in the appropriate quantity and spatial arrangement 
essential for the

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conservation of the species. The PCEs include, but are not limited to:
    (1) Space for individual and population growth and for normal 
behavior;
    (2) Food, water, air, light, minerals, or other nutritional or 
physiological requirements;
    (3) Cover or shelter;
    (4) Sites for breeding, reproduction, and rearing (or development) 
of offspring; and
    (5) Habitats that are protected from disturbance or are 
representative of the historical, geographical, and ecological 
distributions of a species.
    Little is known about the specific characteristics of Ambrosia 
pumila habitat. Therefore, the PCEs for this species are based on our 
assessment of the ecosystem settings in which the species has most 
frequently been detected. The physical and biological features 
essential to the conservation of A. pumila are derived from studies of 
this species' habitat, ecology, and life history as described below, in 
the Background section of the proposed critical habitat designation 
published in the Federal Register on August 27, 2009 (74 FR 44238), and 
in the final listing rule published in the Federal Register on July 2, 
2002 (67 FR 44372).

Space for Individual and Population Growth and for Normal Behavior

Clonal Growth--Rhizome Spread and New Aerial Stems
    Individual Ambrosia pumila plants spread by slender underground 
rhizomes to produce a group of genetically identical aerial (above-
ground) stems--a clone. Growing rhizomes extend underground beyond the 
extent of the aerial stems into adjacent suitable habitat, and rhizomes 
of adjacent plants likely intermingle to a degree. The distance 
rhizomes extend beyond the standing aerial stems is difficult to 
measure because of the difficulty in unearthing an intact rhizome 
system.
    The number and spatial distribution of the aerial stems of Ambrosia 
pumila patches can differ from one growing season to the next (Martin 
2005, p. 3; City of San Diego 2008a, p. 1). For example, a study that 
monitored A. pumila in 2000 and 2005 observed patches of A. pumila 
differing in shape and size (up to several square meters), with some 
patches not producing any stems in 2005 (some of the patches that did 
not produce stems in 2005 were observed to produce stems in 2008 
(Martin 2005, p. 8; A. Folarin 2008, pers. comm.)). Differences in 
patch size and shape may be due to differences in available moisture or 
competition from other plants (Martin 2005, p. 3; City of San Diego 
2008a, p. 1). Based on these and other observations, we conclude that 
the rhizome system of a group of A. pumila stems likely occupies a 
greater underground area than that occupied by the aerial stems at any 
given time, and aerial stems may be produced only when and where 
conditions are appropriate. Thus, habitat occupied by A. pumila extends 
beyond that seen to be occupied by the aerial stems, and area 
designated as critical habitat must extend beyond the area seen to be 
occupied by standing aerial stems to encompass the estimated limits of 
the underground rhizome system.
Germination of Seeds and Spread of Seedlings
    It is unknown to what extent and with what frequency Ambrosia 
pumila reproduces by seeds. Based on genetic studies described below, 
at least some low rate of sexual reproduction has occurred. We are not 
aware of any research that would provide the information needed to 
assess the species' germination and seedling needs.

Food, Water, Air, Light, Minerals, or Other Nutritional or 
Physiological Requirements

Water
    Specific water needs of the species are unknown. Ambrosia pumila is 
adapted to the dry conditions which occur annually throughout its range 
(Keck 1959, p. 1103; Munz 1974, p. 112; Dudek 2000, Appendix A; CNLM 
2008, p. 18). Service biologists have observed fresh (not desiccated) 
aerial stem shoots after small amounts of precipitation and after 
annual vegetation in the area had desiccated (A. Folarin 2008, pers. 
comm.), implying that either A. pumila requires less water than other 
grassland plants, that the underground perennial rhizome system has 
some capacity to store enough water to sustain growth, or both. 
Additionally, we believe that periodic flooding may be necessary at 
some stage of the plant population's life history (such as seed 
germination, dispersal of seeds and rhizomes) or to maintain some 
essential aspect of its habitat, because native occurrences of the 
plant are always found on river terraces or within the watersheds of 
vernal pools.
Light
    Ambrosia pumila is limited to open or low-growing plant 
communities, which implies that the species is not shade tolerant 
(Dudek 2000, pp. 18-19). Ambrosia pumila stems amid taller vegetation 
obtain adequate sunlight by growing taller and more slender compared to 
those in more open areas (Dudek 2000, p. 19), which implies the species 
is not shade tolerant.
Soil
    Ambrosia pumila is found primarily on sandy loam or clay soils 
including (but not limited to) the Placentia (sandy loam), Diablo 
(clay), and Ramona (sandy loam) series (Dudek 2000, Appendix A; CNDDB 
2010). Ambrosia pumila is rarely found growing on other substrate types 
(such as gravel).
    Chemical soil attributes and other abiotic and biotic 
characteristics have been measured and documented for Ambrosia pumila 
occurrences at Skunk Hollow (Riverside County), Mission Trails Regional 
Park, and San Diego National Wildlife Refuge (San Diego County) (Dudek 
2000, Appendix A; CNLM 2008, pp. 6-7, 12, and 18), including pH, 
percent organic matter, soil moisture, and elemental composition. These 
measurements did not provide consistent results across the range of the 
species; thus, we are unable to make generalizations as to needs of the 
species as far as soil attributes are concerned.
Temperature
    We have no information on the tolerance of Ambrosia pumila to 
climatic extremes. Temperature is thought to potentially play a role in 
inducing (or prohibiting) seed germination (Johnson 1999, p. 5), 
although there is limited information at this time as to how often this 
species currently reproduces via seed.

Sites for Breeding, Reproduction, or Rearing (or Development) of 
Offspring

    As stated in the ``Life History'' section of the proposed rule, 
little is known about the nature and frequency of sexual reproduction 
in Ambrosia pumila. Occurrences are consistently found on the upper 
terraces of rivers and other waterways; consequently, periodic flooding 
of these waterways likely plays or likely has played a role in the life 
history of the plant. For example, Johnson (1999, p. 5) postulated that 
A. pumila seeds may require soaking in flood waters or scarification as 
they are churned about with debris in flood waters to germinate. 
Additionally, floods may disperse A. pumila rhizomes and seeds (Dudek 
2003, p. P-332) and create space for new stems by removing or limiting 
the growth of competitors.
    Presuming Ambrosia pumila is wind pollinated, as discussed in the 
``Life

[[Page 74550]]

History'' section of the proposed rule, the species requires sufficient 
airflow through inflorescences to pick up and carry pollen (McGlaughlin 
and Friar 2007, p. 329). This is another reason (in addition to not 
being shade-tolerant) that A. pumila may require habitat containing 
primarily low-growing plants--low-growing plants do not block or 
dramatically reduce airflow to plants of A. pumila's stature, which is 
generally less than 12 inches (30 centimeters) tall (McGlaughlin and 
Friar 2007, p. 329).
    Ambrosia pumila is presumed to be self-compatible (an individual 
can produce viable seed with its own pollen), but this aspect of the 
species' reproductive strategy has not been well-examined. In a recent 
study, another Ambrosia species previously thought to be self-
compatible was found not to be self-compatible (Friedman and Barrett 
2008, p. 4). If A. pumila likewise is not self-compatible, genetically 
distinct individuals in close proximity to one another may be crucial 
to maintaining sexual reproduction in the species (McGlaughlin and 
Friar 2007, p. 329).

Habitats Protected From Disturbance or Representative of the 
Historical, Geographical, and Ecological Distributions of the Species

    Ambrosia pumila occurs most frequently on upper terraces of rivers 
with flat or gently sloping areas of 0 to 42 percent slopes. A. pumila 
occurrences are found near, but not directly adjacent to, the river 
channels and along other drainages in western Riverside County, western 
San Diego County, and northwestern Baja California, Mexico (Beauchamp 
1986, p. 94; Johnson et al. 1999, p. 1; McGlaughlin and Friar 2007, p. 
321; CNDDB 2008). These areas are or likely have been associated with a 
natural flood disturbance regime. The species is primarily associated 
with native and nonnative grassland and ruderal communities, and 
openings in coastal sage scrub (Johnson et al. 1999, p. 1; Dudek 2000, 
p. 18; Dudek 2003, p. P-330; CNDDB 2010). In Riverside County, A. 
pumila occurs in ruderal and nonnative grassland communities adjacent 
to creeks and other smaller drainages (for example, Temescal 
(Alberhill) Creek and Santa Gertrudis Creek) (Dudek 2003, p. P-326; 
CNDDB 2010). Ambrosia pumila also occurs in nonnative grassland 
community adjacent to and within the watershed of Skunk Hollow vernal 
pool in Riverside County (Dudek 2003, p. P-326; CNDDB 2010). In San 
Diego County, A. pumila is more often found adjacent to larger 
waterways (for example, San Luis Rey River, San Diego River, and 
Sweetwater River), although the species is also often found associated 
with smaller drainages and washes (CNDDB 2010).
    Occurrences in Riverside County are found further inland and at 
higher elevations than in San Diego County. For example, the occurrence 
at Skunk Hollow in Riverside County is 1,350 ft (411 m) above sea 
level, while the occurrences at Mission Trails Regional Park and San 
Diego National Wildlife Refuge in San Diego County are about 315 ft and 
360 ft (96 m and 110 m) above sea level, respectively (CNLM 2008, p. 
7)).
    The documented range of Ambrosia pumila in Mexico at the time of 
listing extended from Cabo Colonet south to Lake Chapala in north-
central Baja California. We have no information regarding additional 
occurrences in Mexico, or the physical and biological features 
essential to the conservation of the species there.

Primary Constituent Elements for Ambrosia pumila

    Under the Act and its implementing regulations at 50 CFR 424.12, we 
are required to identify the specific areas within the geographical 
area occupied by a species, at the time it is listed, on which are 
found those physical or biological features determined to be essential 
to the conservation of the species and that may require special 
management considerations or protection. The essential physical and 
biological features are those PCEs laid out in the appropriate spatial 
arrangement and quantity determined to be essential to the conservation 
of the species. Because not much is known about the specific needs and 
characteristics of this species, the PCEs are based on observed 
characteristics of the habitats in which the species is most often 
found. All areas designated as critical habitat for A. pumila were 
occupied at the time the species was listed, occur within the species' 
historical geographic range, and contain sufficient PCEs to support at 
least one life-history function.
    Based on the above needs and our current knowledge of the life 
history, biology, and ecology of Ambrosia pumila, and the 
characteristics of the areas where the species is known to occur, we 
identified two PCEs for A. pumila:
    1. Sandy loam or clay soils (regardless of disturbance status), 
including (but not limited to) the Placentia (sandy loam), Diablo 
(clay), and Ramona (sandy loam) soil series that occur near (up to 
several hundred meters from but not directly adjacent to) a river, 
creek, or other drainage, or within the watershed of a vernal pool, and 
that occur on an upper terrace (flat or gently sloping areas of 0 to 42 
percent slopes are typical for terraces on which Ambrosia pumila 
occurrences are found).
    2. Grassland or ruderal habitat types, or openings within coastal 
sage scrub, on the soil types and topography described in PCE 1, that 
provide adequate sunlight, and airflow for wind pollination.
    Based on our current knowledge of the needs of the species, we 
believe the need for space for individual and population growth and 
normal behavior is met by PCE 2, and areas for reproduction, water, 
light, and soil are provided by PCEs 1 and 2. These areas provide 
nutrients, moisture, and proximity to water features that provide 
periodic flooding presumed necessary for the plant's persistence.
    In designating this critical habitat, we intend to conserve the 
physical and biological features considered essential to support the 
life-history functions of the species. All units and subunits 
designated here as critical habitat contain sufficient PCEs in the 
appropriate quantity and spatial arrangement to provide for one or more 
of the life-history functions of Ambrosia pumila.

Special Management Considerations or Protection

    When designating critical habitat, we assess whether the occupied 
areas contain the physical and biological features that are essential 
to the conservation of the species, and whether these features may 
require special management considerations or protection. The area 
designated as critical habitat will require some level of management to 
address the current and future threats to the physical and biological 
features essential to the conservation of the species. In all units, 
special management will be required to ensure that the habitat is able 
to provide for the growth and reproduction of the species.
    Records indicate that Ambrosia pumila historically was known from 
over 50 locations in San Diego and Riverside counties, but the number 
of extant occurrences has been dramatically reduced because much of the 
species' habitat has been impacted by human activities (Burrascano and 
Hogan 1997, p. 7; Dudek 2000, p. 17; CNDDB 2010). A detailed discussion 
of threats to A. pumila and its habitat can be found in the final 
listing rule (67 FR 44372, July 2, 2002). The features essential to the 
conservation of A. pumila require special management

[[Page 74551]]

considerations or protection to reduce the following threats, among 
others:
     Habitat destruction caused by urban development, including 
highway and utility corridor construction and maintenance, highway 
expansion, and development of recreational facilities (such as golf 
courses and campgrounds). These activities can destroy the PCEs by 
removing or compacting soil, making habitat unsuitable for Ambrosia 
pumila.
     Soil compaction caused by the creation and use of trails 
by hikers, horses, and vehicles. Ambrosia pumila appears to be tolerant 
to some level of disturbance caused by trail creation and use; it is 
often found in the disturbed areas along margins of dirt trails. 
However, it is found less often in trailways, implying that although 
the appropriate soil type might be present, soil compaction can alter 
soil physical characteristics such that the soil can no longer support 
plant growth (PCE 1).
     Habitat alteration caused by invasion of nonnative plant 
species that may, if present in large enough numbers, change the plant 
assemblage or cover density to the extent that Ambrosia pumila plants 
can no longer receive adequate sunlight and airflow (PCE 2).
     Alteration of hydrological and floodplain dynamics, such 
as channelization and water diversions, (an additional threat not 
discussed in the listing rule), which can change the frequency of 
flooding in occupied areas or eliminate natural periodic flooding 
presumed necessary for the plant's long-term persistence (PCE 1).
    Special management considerations or protection are required within 
critical habitat areas to address these threats. Management activities 
that could ameliorate these threats include fencing Ambrosia pumila 
occurrences and providing signage to discourage encroachment by hikers, 
horses, and off-road vehicle users; control of nonnative plants using 
methods shown to be effective (for examples, see CNLM 2008); guiding 
the design of development projects to avoid impacts to A. pumila 
habitat; and restoring and maintaining natural hydrology and floodplain 
dynamics of waterways associated with A. pumila occurrences where 
feasible. These management activities will help protect the PCEs for 
the species by reducing soil compaction (PCE 1), lowering the density 
of nonnative plants thereby maintaining the appropriate community 
structure (PCE 2), and maintain periodic flooding of A. pumila habitat 
where possible (PCE 1).

Criteria Used To Identify Critical Habitat

    As required by section 4(b) of the Act, we used the best scientific 
and commercial data available in determining areas within the 
geographical area occupied at the time of listing that contain the 
features essential to the conservation of Ambrosia pumila. We are 
designating critical habitat in areas that we consider to have been 
occupied by the species at the time of listing and that continue to be 
occupied today, and that contain the PCEs laid out in the appropriate 
quantity and spatial arrangement essential to the conservation of the 
species (see the ``Geographic Range and Status'' section of the 
proposed critical habitat rule (74 FR 44241, August 27, 2009) for more 
information). We are not designating any areas outside the geographical 
range occupied at the time of listing. All units and subunits contain 
the PCEs of A. pumila habitat.
    We also reviewed available information that pertains to the habitat 
requirements of this species, although A. pumila has not been well-
studied and little is known about its breeding system or habitat 
requirements and characteristics. Additionally, some data from 
different information sources conflict, further complicating the task 
of discerning species' habitat requirements. We used sources of 
information, such as reports submitted to the Service during section 7 
consultations and other project reviews, and by biologists holding 
section 10(a)(1)(A) recovery permits; research published in peer-
reviewed articles; research presented in academic theses and agency 
reports; regional Geographic Information System (GIS) coverages; and 
data collected in the field by Service biologists.
    Ambrosia pumila was first detected after listing of the species in 
two of the areas we are designating as critical habitat. We concluded 
these areas were occupied at the time the species was listed because 
individuals of species with a clonal growth habit like A. pumila are 
usually long-lived (Watkinson and White 1985, pp. 44-45; Tanner 2001, 
p. 1980). The occurrence at the intersection of State Route 76 and 
Olive Hill Road in San Diego County (Subunit 4B) was found during a 
general survey for A. pumila in 2006 (CNDDB 2010). The occurrence near 
the intersection of State Route 76 and Gird Road in San Diego County 
(Subunit 4D) was mapped during a survey for a State Route 76 road 
widening project (GIS data provided to the Service by California 
Department of Transportation in 2009; USFWS 2008). To our knowledge, 
these two areas had not been adequately, if at all, surveyed for A. 
pumila prior to discovery, and we have no reason to believe the plant 
was imported, or had dispersed into these areas from other locations 
after listing because the plants produce very few if any seeds and, 
consequently, the ability of the plant to disperse into and colonize 
previously unoccupied areas is diminished. It is unlikely that the 
species would be able to disperse great distances and colonize new 
areas (see Index Map below). We believe that the occurrences identified 
since listing were in existence for many years and were only recently 
detected due to increased awareness of this species.
    We are also designating critical habitat in some areas where 
Ambrosia pumila was thought to be extirpated and where an occurrence 
exists that was not considered viable at the time of listing. We 
conducted surveys of historical occurrences as part of the background 
research for this rule. Based on information provided by a local 
biological consultant, we were able to verify one occurrence east of 
Lake Hodges in San Diego County that was previously thought to be 
extirpated because it had not been seen since 1999. During our 
development of the proposed rule, we were unable to verify this site 
because the available records contained minimal site location 
information. However, our recent survey (2009) of the site east of Lake 
Hodges in San Diego County found a viable, relatively large A. pumila 
occurrence and we determined this site meets the definition of critical 
habitat (see criteria below). All units and subunits contain the 
physical and biological features believed to be essential to the 
conservation of this species.
    As required by section 4(b)(1)(A) of the Act, we used the best 
scientific and commercial data available in trying to determine areas 
that contain the physical and biological features that are essential to 
the conservation of Ambrosia pumila, and that may require special 
management considerations or protection.
    After identifying the PCEs, we followed these steps to delineate 
critical habitat:
    (1) We identified all extant, natural occurrences of Ambrosia 
pumila, which consist of those known to exist at the time of listing, 
and those subsequently detected that we believe existed at the time of 
listing. We compiled data from the following sources to create our 
database of A. pumila occurrences: (1) Data used in the 2002 listing 
rule for A. pumila (67 FR 44372, July 2, 2002); (2)

[[Page 74552]]

the current CNDDB element occurrence data report for A. pumila and 
accompanying GIS references (CNDDB 2010, pp. 1-50); (3) data from the 
on-line Consortium of California Herbaria and accompanying Berkeley 
Mapper GIS records (Consortium of California Herbaria 2010); (4) the 
Western Riverside County Multiple Species Habitat Conservation Plan 
(Western Riverside County MSHCP) species GIS database; and (5) the 
Carlsbad Fish and Wildlife Office's (CFWO) internal GIS species 
database, which includes the species data used for the San Diego 
Multiple Species Conservation Program (MSCP) and the San Diego Multiple 
Habitat Conservation Plan (MHCP), reports from section 7 consultations, 
and Service observations of A. pumila (CFWO internal species GIS 
database). We used these data to delineate GIS polygons around A. 
pumila occurrences.
    First, we reviewed the data that we compiled to ensure its 
accuracy. We checked each data point to ensure it represented a site 
documented by a herbarium voucher or reported observation of Ambrosia 
pumila and was not a duplicate occurrence in the database. Any 
duplicates detected were removed from the database. Secondly, we 
checked each data point to ensure that it was correctly mapped. Data 
points that did not match the description for the original herbarium 
collection or observation were remapped in the correct location, if 
possible. We removed occurrences where the location could not be 
determined from available data or site visits. Third, we determined 
occupancy status. For areas where we have past occupancy data for A. 
pumila, we assumed the area remained occupied unless: (1) Multiple 
surveys for the species did not find A. pumila; (2) the site was 
significantly disturbed (for example, developed) since the last 
observation of the species; or (3) records lacked specific location 
information, and field surveys carried out in conjunction with this 
critical habitat determination could not locate the occurrence.
    (2) We determined there are no specific areas outside the 
geographical area occupied by Ambrosia pumila at the time it was listed 
that are essential for the conservation of the species. Information 
obtained during the Service's research in connection with this action 
indicates that the geographical area occupied by the species at the 
time it was listed provides sufficient resources for the conservation 
of the species. For example, McGlaughlin and Friar (2007, p. 329) 
conducted an analysis of genetic diversity within and among populations 
of A. pumila and determined that the existing occurrences could support 
recovery of the species. We do not have sufficient information 
regarding the specific needs of the species to determine if any areas 
outside the geographical area occupied by Ambrosia pumila at the time 
it was listed are essential for the conservation of the species.
    (3) We removed areas where Ambrosia pumila occurs in habitat of low 
quality for growth and propagation (such as paved areas, or relatively 
small urban lots surrounded by residential development and continuously 
subjected to impacts of urbanization such as mowing or foot and vehicle 
traffic). For example, we did not include one occurrence in the City of 
El Cajon on a site composed of two residential lots less than half an 
acre in size, one mowed and landscaped, the other with highly disturbed 
and compacted soil. Although occupied, we did not consider these 
locations for critical habitat because they likely do not contribute to 
the long-term conservation of the species. We made this determination 
using site descriptions in the CNDDB, satellite imagery, and by talking 
with Service biologists, other researchers, and land managers familiar 
with the areas in question.
    (4) Using data from studies that mapped the aerial stems of 
Ambrosia pumila, we estimated the distance the rhizome system likely 
extends beyond aerial stems clusters by calculating the average 
distance between aerial stems clusters within a CNDDB occurrence 
polygon. An occurrence is defined by CNDDB as an occupied habitat area 
separated by 0.25 mi (0.40 km) or more from the next nearest occupied 
habitat area. Using this method we estimated the average distance of 
underground rhizome expansion beyond the above-ground aerial stems as 
approximately 1,181 ft (260 m). Therefore, we expanded the outer 
boundary of the above-ground extent of each CNDDB occurrence polygon by 
1,181 ft (260 m) to account for the underground rhizome system 
extending beyond the area occupied by visible stems. We believe this 
distance adequately captures the extent of individual occurrences.
    (5) We removed any areas within the boundary mapped in step (4) 
above where vegetation type was not grassland, ruderal, or coastal sage 
scrub, using the vegetation types in our GIS database and personal 
observations by Service biologists and other researchers or land 
managers.
    When determining the critical habitat boundaries, we made every 
effort to map precisely only the areas that contain the PCEs and 
provide for the conservation of Ambrosia pumila. However, we cannot 
guarantee that every fraction of critical habitat contains the PCEs due 
to the mapping scale we use to identify critical habitat boundaries. We 
made every attempt to avoid including developed areas such as lands 
underlying buildings, paved areas, and other structures that lack PCEs 
for A. pumila. The scale of maps prepared under the parameters for 
publication within the Code of Federal Regulations may not reflect the 
exclusion of such developed areas. Any developed structures and the 
land under them inadvertently left inside critical habitat boundaries 
shown on the maps of this final critical habitat designation are 
excluded by text in this rule and are not designated as critical 
habitat. Therefore, Federal actions involving these lands would not 
trigger section 7 consultation with respect to critical habitat and the 
requirement of no adverse modification unless the specific actions may 
affect the species or PCEs in adjacent critical habitat.

Critical Habitat Designation

    We are designating 783 ac (317 ha) of critical habitat for Ambrosia 
pumila in 6 units that include 13 subunits. The critical habitat areas 
outlined in Table 2 and described below constitute our best assessment 
of areas occupied at the time of listing that contain the PCEs laid out 
in the appropriate quantity and spatial arrangement essential to the 
conservation of the species that may require special management 
considerations or protection. We are not designating any areas outside 
the geographic area occupied by the species at the time of listing 
because we determined that occupied lands within the species' known 
geographical range are sufficient for the conservation of A. pumila. 
Each unit and subunit include suitable habitat that will allow for 
population growth and growth of individual plants represented by aerial 
stems and the associated rhizome system.

[[Page 74553]]



                        Table 2--Area Estimates (Acres) (Hectares) and Land Ownership for Ambrosia pumila Final Critical Habitat
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Federally owned land       State or local       Privately-owned land         Total area
   Unit : Unit name (CNDDB element occurrence   ------------------------  government-owned land -----------------------------------------------
                         number)                                                 ------------------------
                                                             Acres     Hectares      Acres     Hectares      Acres     Hectares      Acres     Hectares
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                    RIVERSIDE COUNTY
--------------------------------------------------------------------------------------------------------------------------------------------------------
Unit 1: Santa Ana River watershed.......................  ..........  ..........          26          11          85          35         112          45
1A. Alberhill (58)......................................  ..........  ..........          23          10          18           7          41          17
1B. Nichols Road (44)...................................  ..........  ..........           3           1          67          27          70          29
Unit 3: Santa Margarita River watershed.................  ..........  ..........           8           3          69          28          77          31
Subunit 3A: Santa Gertrudis Creek.......................  ..........  ..........           8           3          25          10          33          13
Subunit 3B: Murrieta Creek..............................  ..........  ..........  ..........  ..........          44          18          44          18
    Subtotal:...........................................  ..........  ..........          34          14         154          62         189          76
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                    SAN DIEGO COUNTY
--------------------------------------------------------------------------------------------------------------------------------------------------------
Unit 4: San Luis Rey River watershed....................  ..........  ..........          17           7          75          30          92          37
4A. Calle de la Vuelta (43).............................  ..........  ..........           1           0          14           6          15           6
4B. Olive Hill Road (16)................................  ..........  ..........          16           6           8           3          23           9
4C. Jeffries Ranch (45).................................  ..........  ..........           0           0          33          13          33          13
4D. Gird/Monserate Hill (n/a)...........................  ..........  ..........           1           0          20           8          21           8
Unit 5: San Dieguito River watershed....................  ..........  ..........         129          52         121          49         249         101
5A. Lake Hodges East (Via Rancho Pkwy) (14).............  ..........  ..........          16           6           5           2          21           9
Subunit 5B: Lake Hodges West (Crosby Estates)...........  ..........  ..........         113          46         115          47         228          92
Unit 6: San Diego River watershed--Mission Trails         ..........  ..........           6           3          32          13          38          15
 Regional Park..........................................
Unit 7: Sweetwater River watershed......................         146          59          13           5          57          23         215          87
Subunit 7A: Jamul Road..................................  ..........  ..........           3           1          36          15          39          16
7B. SDNWR (48)..........................................         118          48  ..........  ..........          15           6         133          54
7C. Steele Canyon Bridge (34)...........................          28          11          10           4           6           2          44          18
                                                         -----------------------------------------------------------------------------------------------
    Subtotal............................................         146          59         164          67         284         115         594         240
                                                         -----------------------------------------------------------------------------------------------
        Total...........................................         146          59         199          81         438         178         783         316
--------------------------------------------------------------------------------------------------------------------------------------------------------
Values in this table may not sum due to rounding.

Critical Habitat Units

    Presented below are brief descriptions of all subunits included in 
the final critical habitat designation and reasons why they meet the 
definition of critical habitat for Ambrosia pumila. The subunits are 
listed in order geographically north to south and east to west.

Unit 1: Santa Ana River Watershed

    Unit 1 is located in western Riverside County and consists of two 
subunits totaling approximately, 26 ac (11 ha) of State or local 
government-owned land, and 85 ac (35 ha) of private land for a total of 
approximately 112 ac (45 ha) (values do not sum due to rounding).
Subunit 1A: Alberhill
    Subunit 1A is located near Alberhill, north of Lake Elsinore and 
just west of Interstate Highway 15 in Riverside County, California. 
This subunit is near the northern base of Alberhill Mountain, and near 
the intersection of Lake Street and Temescal Canyon Road. Subunit 1A 
consists of approximately 23 ac (10 ha) of County-owned land, and 18 ac 
(7 ha) of privately owned land for a total of approximately 41 ac (17 
ha). The approximately 23 ac (10 ha) of County-owned land in Subunit 1A 
are conserved and currently managed by the Western Riverside County 
Regional Conservation Authority; transfer of ownership by the County of 
Riverside to the Western Riverside County Regional Conservation 
Authority is planned for the near future. This conserved area is not 
yet receiving active management. This subunit was occupied at the time 
of listing and remains occupied and, like all other extant occurrences, 
we also believe this subunit is essential to the conservation of this 
species because of its contribution to the genetic diversity of the 
species (McGlaughlin and Friar 2007, p. 329; see Genetics section of 
the proposed rule (74 FR 44241, August 27, 2009)). Subunit 1A contains 
the physical and biological features essential to the conservation of 
Ambrosia pumila, including sandy loam or clay soils located on an upper 
terrace of a water source, which provide nutrients, moisture, and 
potentially periodic flooding presumed necessary for the plant's 
persistence (PCE 1); and coastal sage scrub vegetation, which allows 
adequate sunlight and airflow for A. pumila (PCE 2). The PCEs in this 
subunit require special management considerations or protection to 
address threats from nonnative plant species in situations where 
nonnative species are outcompeting A. pumila for resources, and from 
human encroachment and development. Please see the Special Management 
Considerations or Protection section of this rule for a discussion of 
the threats to A. pumila habitat and potential management 
considerations.
Subunit 1B: Nichols Road
    Subunit 1B is located about 2.1 mi (3.5 km) southeast of Subunit 1A 
(Alberhill), on the north and south sides

[[Page 74554]]

of Nichols Road, in Riverside County, California. This subunit is near 
the southeastern base of Alberhill Mountain, just west of Durant Road 
and Temescal Creek. Subunit 1B consists of approximately 3 ac (1 ha) of 
State or local government-owned land, and 67 ac (27 ha) of privately 
owned land for a total of approximately 70 ac (29 ha) (values do not 
sum due to rounding). No lands in Subunit 1B are conserved or managed 
for biological resources. This subunit was occupied at the time of 
listing and remains occupied, and is essential to the conservation of 
this species because this subunit (along with Subunit 1A) represents 
the northernmost occurrences of this species, which is geographically 
situated to potentially assist this species expand its range northward. 
Like all other extant occurrences, this subunit is also essential to 
the conservation of this species because of its contribution to the 
genetic diversity of the species (McGlaughlin and Friar 2007, p. 329; 
see Genetics section of the proposed rule (74 FR 44241, August 27, 
2009)). However, due to impacts from unauthorized grading and disking, 
and a permitted road realignment project, Ambrosia pumila within this 
subunit may be in imminent danger of extirpation. Subunit 1B contains 
physical and biological features that are essential to the conservation 
of A. pumila, including sandy loam or clay soils located on an upper 
terrace of a water source, which provide nutrients, moisture, and 
periodic flooding presumed necessary for the plant's persistence (PCE 
1), and ruderal habitat type, which allows adequate sunlight and 
airflow for A. pumila (PCE 2). The physical and biological features 
essential to the conservation of the species in this subunit may 
require special management considerations or protection to address 
threats from nonnative plant species in situations where nonnative 
species are outcompeting A. pumila for resources, and from activities 
(grading, construction, human encroachment) that occur in the area. 
Please see the Special Management Considerations or Protection section 
of this rule for a discussion of the threats to A. pumila habitat and 
potential management considerations.

Unit 3: Santa Margarita River Watershed

    Unit 3 is located in western Riverside County and consists of two 
subunits totaling approximately, 8 ac (3 ha) of State or local 
government-owned land, and 69 ac (28 ha) of private land for a total of 
77 ac (31 ha).
Subunit 3A: Santa Gertrudis Creek
    Subunit 3A is located about 1 mile (1.6 km) southwest of Unit 2, 
along the San Diego Aqueduct, south of the intersection of Chandler and 
Suzi Roads and north of Santa Gertrudis Creek in Riverside County. 
Subunit 3A consists of approximately 8 ac (3 ha) of State-owned land 
and 25 ac (10 ha) of privately owned land for a total of approximately 
33 ac (13 ha). No lands in Subunit 3A are conserved or managed for 
biological resources. This unit was occupied at the time of listing and 
remains occupied, and like all other extant occurrences, is essential 
to the conservation of this species because of its contribution to the 
genetic diversity of the species (McGlaughlin and Friar 2007, p. 329; 
see Genetics section of the proposed rule (74 FR 44241, August 27, 
2009)). Subunit 3A contains physical and biological features that are 
essential to the conservation of Ambrosia pumila, including sandy loam 
or clay soils located on an upper terrace of a water source, which 
provide nutrients, moisture, and periodic flooding presumed necessary 
for the plant's persistence (PCE 1), and ruderal habitat type, which 
allows adequate sunlight and airflow for A. pumila (PCE 2). The 
physical and biological features essential to the conservation of the 
species in this unit may require special management considerations or 
protection to address threats from nonnative plant species in 
situations where nonnative species are outcompeting A. pumila for 
resources, human encroachment, and utility maintenance activities. 
Please see the Special Management Considerations or Protection section 
of this rule for a discussion of the threats to A. pumila habitat and 
potential management considerations.
Subunit 3B: Murrieta Creek
    Subunit 3B is located in the City of Temecula in southwestern 
Riverside County, California. This subunit is near the western end of 
1st Street, just west of Murrieta Creek. Subunit 3