Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for Ambrosia pumila, 44238-44267 [E9-20499]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 74, Number 165 (Thursday, August 27, 2009)]
[Proposed Rules]
[Pages 44238-44267]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E9-20499]



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Part III





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 Ambrosia pumila (San Diego ambrosia); Proposed Rule

Federal Register / Vol. 74, No. 165 / Thursday, August 27, 2009 / 
Proposed Rules

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

[Docket No. FWS-R8-ES-2009-0054; 92210-1117-0000-B4]

50 CFR Part 17

RIN 1018-AW20


Endangered and Threatened Wildlife and Plants; Designation of 
Critical Habitat for Ambrosia pumila (San Diego ambrosia)

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), propose to 
designate critical habitat for Ambrosia pumila (San Diego ambrosia) 
under the Endangered Species Act of 1973, as amended (Act). In total, 
approximately 802 acres (ac) (324 hectares (ha)) of land are being 
proposed for designation as critical habitat. The proposed critical 
habitat is located in Riverside and San Diego Counties, California.

DATES: We will consider comments we receive on or before October 26, 
2009. We must receive requests for public hearings, in writing, at the 
address shown in the FOR FURTHER INFORMATION CONTACT section by October 
13, 2009.

ADDRESSES: You may submit comments by one of the following methods:
     Federal eRulemaking Portal: https://www.regulations.gov. Follow the instructions for submitting comments to 
Docket No. FWS-R8-ES-2009-0054.
     U.S. mail or hand-delivery: Public Comments Processing, 
Attn: FWS-R8-ES-2009-0054; Division of Policy and Directives 
Management; U.S. Fish and Wildlife Service; 4401 N. Fairfax Drive, 
Suite 222; Arlington, VA 22203.
    We will post all comments on https://www.regulations.gov. This 
generally means that we will post any personal information you provide 
us (see the Public Comments section below for more information).

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:

Public Comments

    We intend that any final action resulting from this proposed rule 
will be based on the best scientific and commercial data available and 
be as accurate and as effective as possible. Therefore, we request 
comments or information from the public, other concerned government 
agencies, the scientific community, industry, or other interested party 
concerning this proposed rule. We particularly seek comments 
concerning:
    (1) The reasons why we should or should not designate habitat as 
``critical habitat'' under section 4 of the Endangered Species of 1973, 
as amended (Act) (16 U.S.C. 1531 et seq.), including whether there are 
threats to the species from human activity, the degree of which can be 
expected to increase due to the designation, and whether that increase 
in threat outweighs the benefit of designation such that the 
designation is not prudent.
    (2) Specific information that may assist us in clarifying or 
identifying more specific primary constituent elements (PCEs). There is 
a lack of specific information available regarding what constitutes 
physical and biological features essential to the conservation of this 
species. Additionally, the available information does not identify a 
consistent pattern in specific life-history requirements and habitat 
types where Ambrosia pumila is found. For these reasons, the PCEs in 
this proposed rule are broad and based on our assessment of the 
ecosystem settings in which the species has most frequently been 
detected and our best assessment regarding its life history requisites. 
We specifically seek information that may assist us in defining those 
physical and biological features essential to the conservation of the 
species which may require special management considerations or 
protection, or in identifying specific areas outside the geographical 
area occupied by the species at the time it was listed that may be 
essential to the conservation of the species. In particular, answers to 
the following questions may be helpful to clarify or identify more 
specific PCEs of Ambrosia pumila habitat:
     Does the species reproduce via seed? If so, does the 
species rely on some aspect of its environment to trigger seed 
germination?
     What are the key factors determining why the species 
occupies the particular areas it occupies (but not other areas with the 
same habitat type)? For example, what role does proximity to waterways 
or vernal pools play?
    (3) The appropriateness of designating critical habitat for this 
species. If the broad essential physical and biological features 
proposed for Ambrosia pumila habitat cannot be defined more 
specifically, or we cannot reasonably identify essential habitat for 
this species based on our evaluation of information received, it may be 
difficult to identify specific areas as critical habitat for this 
species. This may be the case if specific information regarding what 
constitutes essential habitat for this species cannot be obtained, or 
if the data obtained suggest that the species can effectively carry out 
all necessary life functions in a range of habitat types and conditions 
(i.e., there may not be specific habitat features essential to the 
conservation of the species).
    (4) Specific information on:
     The amount and distribution of Ambrosia pumila habitat 
included in this proposed rule,
     What areas occupied at the time of listing that contain 
features essential for the conservation of the species should we 
include or exclude in the designation and why, and
     What areas not occupied at the time of listing are 
essential to the conservation of the species and why.
    (5) How the proposed critical habitat boundaries could be refined 
to more closely circumscribe the areas identified as essential. We also 
seek recommendations to improve the methodology used to delineate the 
areas proposed as critical habitat; especially comments regarding how 
we might more accurately estimate the additional surface area beyond 
the visible surface area covered by the aerial stems that we need to 
include for each occurrence of Ambrosia pumila in the critical habitat 
designation to ensure that habitat areas do not exclude unseen 
underground portions of A. pumila plants (see step number 4 in the 
Methods section below).
    (6) Land use designations and current or planned activities in the 
areas proposed as critical habitat and their possible impacts on the 
species and the proposed critical habitat.
    (7) Any probable economic, national security, or other relevant 
impacts of designating any area that may be included in the final 
designation. We are particularly interested in any impacts on small 
entities, and the benefits of including or excluding areas that exhibit 
these impacts.
    (8) Any issues with the exclusions being considered under section 
4(b)(2) of the Act as part of this proposed designation, or reasons why 
any proposed critical habitat not considered for exclusions should be 
excluded.
    (9) Any special management considerations or protections that the 
proposed critical habitat may require.
    (10) Whether we could improve or modify our approach to designating

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critical habitat in any way to provide for greater public participation 
and understanding, or to better accommodate public concerns and 
comments.
    (11) Whether the benefit of an exclusion of any particular area 
outweighs the benefit of inclusion under section 4(b)(2) of the Act, in 
particular for those areas covered by the Western Riverside County 
Multiple Species Habitat Conservation Plan (Western Riverside MSHCP), 
and Subarea Plans (City of San Diego and County of San Diego) under the 
San Diego Multiple Species Conservation Program (MSCP), and specific 
reasons why.
    (12) Whether the benefit of excluding the area proposed as critical 
habitat within the City of Oceanside in San Diego County (Subunit 4C) 
under section 4(b)(2) of the Act outweighs the benefit of including 
this area as critical habitat, and specific reasons why. The City of 
Oceanside is working on a Subarea Plan under the Northwestern San Diego 
County Multiple Habitat Conservation Plan (MHCP) in cooperation with 
the Service.
    Our final determination concerning critical habitat for Ambrosia 
pumila will take into consideration all written comments and comments 
received during a public hearing, should one be requested, and any 
additional information we receive during the public comment period. 
These comments will be included in the public record for this 
rulemaking. Our final determination will also incorporate all comments 
requested of peer reviewers and received during the comment period. 
Finally, our final determination concerning critical habitat will 
consider all written comments and any additional information we receive 
during the comment period for the draft Economic Analysis (DEA). On the 
basis of peer reviewer and public comments, we may, during the 
development of our final determination, find that areas within those 
proposed do not meet the definition of critical habitat, that some 
modifications to the described boundaries are appropriate, or that 
areas are not appropriate for exclusion under section 4(b)(2) of the 
Act.
    You may submit your comments and materials concerning this proposed 
rule by one of the methods listed in the ADDRESSES section.
    We will post your entire comment--including your personal 
identifying information--on https://www.regulations.gov. If you provide 
personal identifying information in addition to the required items 
specified in the previous paragraph, such as your street address, phone 
number, or e-mail address, you may request at the top of your document 
that we withhold this information from public review. However, we 
cannot guarantee that we will be able to do so.
    Comments and materials we receive, as well as supporting 
documentation we used in preparing this proposed rule, will be 
available for public inspection at https://www.regulations.gov, or by 
appointment, during normal business hours, at the U.S. Fish and 
Wildlife Service, Carlsbad Fish and Wildlife Office (see FOR FURTHER 
INFORMATION CONTACT).
    You may obtain copies of the proposed rule by mail from the 
Carlsbad Fish and Wildlife Office (see FOR FURTHER INFORMATION CONTACT) 
or by visiting the Federal eRulemaking Portal at https://www.regulations.gov.

Background

    It is our intent to discuss only those topics directly relevant to 
the designation of critical habitat in this proposed rule. This rule 
incorporates new information on the biology, distribution, and 
abundance of Ambrosia pumila that we did not discuss in the 2002 final 
listing rule for this species (67 FR 44372). For more information on A. 
pumila, refer to that final listing rule, which was published in the 
Federal Register on July 2, 2002.

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 failure of the Service 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, a proposed critical habitat designation to the Federal 
Register for publication on or before August 20, 2009, and submit a 
final critical habitat designation to the Federal Register for 
publication on or before August 19, 2010. In this proposed critical 
habitat rule, we reaffirm that determination of critical habitat for A. 
pumila is prudent. However, we may revisit our prudency determination 
following additional review and consideration of information we receive 
during the public comment period.

Species Description

    Ambrosia is a genus comprising 35 to 50 wind-pollinated annual and 
perennial plant species in the Asteraceae (sunflower) family. Members 
of this genus occur predominantly in the Western Hemisphere, especially 
North America. Species are generally found in arid or semiarid areas, 
while some are weeds of cultivated fields or strand species of Pacific 
and Caribbean beaches (Payne 1976, p. 169).
    Ambrosia pumila is a clonal herbaceous perennial. Individual stems 
are generally 5 to 30 centimeters (cm) (2 to 12 inches (in)) tall, but 
may grow to 50 cm (20 in), and are densely covered with short hairs. 
The leaves are two to four times pinnately divided into many small 
segments and are covered with short, soft, gray-white, appressed (lying 
flat on surface) hairs. The species has separate male and female 
flowers on the same plant (monoecious). The male flowers have no 
petals, are yellow to translucent, and are borne in clusters on 
terminal flower stalks. The female flowers have no petals and are 
yellowish-white. Female flowers are in clusters in the axils of the 
leaves below the male flower clusters (Nuttall 1840, pp. 344-345; Gray 
1882, p. 217; Munz 1935, p. 544; Keck 1959, p. 1103; Ferris 1960, p. 
148; Munz 1974, p. 112; Beauchamp 1986, p. 94; Payne 1993, p. 194). 
Female flowers produce a dry, single-seeded fruit called an achene. 
References to seeds in this document refer to the single-seeded fruits.
    Ambrosia pumila spreads vegetatively by means of slender, branched, 
underground root-like rhizomes from which new aboveground stems (aerial 
stems or ramets) arise each year (Nuttall 1840, p. 344; Munz 1974, p. 
112; Payne 1993, p. 194). This growth pattern results in numerous 
aerial stems interconnected by a system of rhizomes, called a clone. 
All aerial stems growing from the same root system are genetically 
identical and represent a single individual A. pumila plant (called a 
genet) (Harper 1977, p. 26). Growing rhizomes extend underground beyond 
the aboveground limit of the aerial stems into adjacent suitable 
habitat, allowing rhizomes of adjacent individuals to intermingle. The 
underground interconnections can break or disintegrate, resulting in 
aerial stems that are genetically identical but physically separate 
(McGlaughlin and Friar 2007, p. 319). The extent to which

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rhizomes are capable of spreading has been observed only in individuals 
translocated to previously unoccupied sites. For example, A. pumila 
individuals transplanted on the San Diego National Wildlife Refuge in 
January 2008 were documented to produce new stems several inches away 
within 10 months (by November 2008). Additionally, A. pumila 
individuals transplanted in 1997 to an unoccupied site at Pilgrim Creek 
just south of Marine Corps Base Camp Pendleton in San Diego County were 
documented to produce new stems up to 70 in (178 cm) from the original 
stems within 2 years (by 1999) (Johnson et al. 1999, p. 3).
    Because of the clonal nature of Ambrosia pumila's growth, it is not 
possible to directly determine the number of genetically distinct 
plants present in an area simply by counting stems (McGlaughlin and 
Friar 2007, p. 320). McGlaughlin and Friar's (2007, p. 323) analysis of 
clonality in A. pumila determined that the aerial stem-to-genet ratio 
is roughly 10-to-1 on average (about 1 genet for every 10 aerial stems 
counted in a patch (cluster of stems)). A patch constitutes a spatially 
distinct cluster of stems within an occurrence, whereas an occurrence 
constitutes a group of individuals separated from the next nearest 
group of individuals by a distance greater than or equal to 0.25 mile 
(mi) (0.40 kilometer (km)).

Habitat

    Ambrosia pumila occurs primarily on upper terraces of rivers and 
drainages (Beauchamp 1986, p. 94; Johnson et al. 1999, p. 1; 
McGlaughlin and Friar 2007, p. 321; California Natural Diversity 
Database data report for A. pumila 2008 (CNDDB 2008)); however, several 
patches of the plant occur within the watershed of a large vernal 
(ephemeral) pool in the Skunk Hollow preserve in Riverside County 
(Dudek 2003, p. P-326; CNDDB 2008). Within these areas, the species is 
found in open grassland of native and nonnative plant species, and 
openings in coastal sage scrub (Johnson et al. 1999, p. 1; Dudek 2000, 
p. 18; Dudek 2003, p. P-330; CNDDB 2008), and primarily on sandy loam 
or clay soils (Johnson et al. 1999, p. 1; Dudek 2000, p. 18; CNDDB 
2008; USDA 2008). The species may also be found in ruderal habitat 
types (disturbed communities containing a mixture of native and 
nonnative grasses and forbs) such as fire fuel breaks and edges of dirt 
roadways (Beauchamp 1986, p. 94; Payne 1993, p. 194; CNDDB 2008). 
Nonnative grassland and ruderal habitat types provide adequate habitat 
for A. pumila; however, nonnative plants can out-compete A. pumila 
plants for resources in some situations if not managed. Occurrences are 
disjunct (generally 1 or more miles (1.6 or more km) apart) and most 
locations have been subjected to disturbance such as nonnative plant 
invasion, mining activities, development, grading, and human 
encroachment on foot, horses, or vehicles (CNDDB 2008).
    It is unclear why Ambrosia pumila consistently occurs in areas near 
waterways such as upper terraces of rivers or other water bodies. The 
areas where the species is found do not necessarily provide high levels 
of soil moisture, and A. pumila is adapted to dry conditions (Keck 
1959, p. 1103; Munz 1974, p. 112; Dudek 2000, Appendix A; CNLM 2008, p. 
18). Additionally, Service biologists have observed green (that is, not 
desiccated) aerial stem shoots of A. pumila after small amounts of 
precipitation and after other vegetation in the observed area had 
desiccated. Ambrosia pumila may require periodic flooding for dispersal 
of seeds and roots dislodged during flooding, seed germination, or some 
other segment of its life cycle. Further, areas subject to periodic 
flooding appear to be less amenable to competing nonnative and native 
plants.

Life History

    The reproductive biology of Ambrosia pumila has not been studied to 
the same extent as the more common Ambrosia species, such as A. 
artemisiifolia (common ragweed) and A. trifida (giant ragweed) (Dudek 
2000, p. 16). Thus, little is known about its pollination system, seed 
production, seed dispersal, and germination (Dudek 2000, p. 16; Dudek 
2003, p. P-331; McGlaughlin and Friars 2007, p. 320).
    Aerial stems of Ambrosia pumila sprout from their underground 
rhizomes in early spring after winter rains, and flower between May and 
October (Keck 1959, p. 1103). Recently, however, Service biologists 
observed aerial stems sprouting under dry conditions in late fall 
(Folarin 2008, pers. comm.). The plants senesce after the growing 
season, leaving the root system in place from which new aerial stems 
may sprout when environmental conditions are appropriate (Keck 1959, p. 
1103).
    Ambrosia pumila is presumed to be wind-pollinated because most 
other species of Ambrosia are wind-pollinated, and because biological 
pollinators have not been observed visiting A. pumila flowers (Johnson 
et al. 1999, p. 4; Dudek 2000, p. 16; Dudek 2003, p. P-331). 
Alternatively, pollinator(s) of A. pumila may have been extirpated 
(Dudek 2003, p. P-331). The species is presumed to be capable of self-
pollination and of being self-fertile (i.e., self-compatible, where 
pollen from an individual plant can fertilize an ovule on the same 
plant, resulting in production of viable seed) because other species of 
Ambrosia are capable of self-pollination (Payne 1976, pp. 171-172). The 
configuration of the male flowers in relation to the female flowers 
also implies opportunity for self-pollination (Dudek 2000, p. 16). 
However, studies are needed to determine whether viable seed is 
produced through self-pollination in this species (Johnson et al. 1999, 
p. 4; Dudek 2000, p. 16; Dudek 2003, p. P-332; McGlaughlin and Friars 
2007, p. 329).
    Ambrosia pumila is thought to have limited sexual reproductive 
output due to low production of viable seed (Johnson et al. 1999, pp. 
1-5; Dudek 2000, pp. 16-17; Dudek 2003, pp. P-331-P-332). Low seed 
production in this species is inferred by the lack of fertile fruits on 
all but a few preserved A. pumila museum specimens (Wallace 1999, pers. 
comm.), and field observers have found seed production in A. pumila to 
be low (Dudek 2000, p. 17; Dudek 2003, p. P-332). Specific germination 
requirements of A. pumila seed are unknown. A 1998 germination study 
using 22 A. pumila seeds of unknown viability collected from 3 sites at 
Mission Trails Regional Park did not result in any germination of 
seedlings (Dudek 2000, Appendix B). The lack of germination could have 
been due to the seeds being nonviable or to inappropriate germination 
conditions. Regardless of what proportion of A. pumila seeds are 
viable, low seed production implies that little sexual reproduction is 
occurring in this species. Low levels of sexual reproduction is not an 
unusual condition in clonal plant species (Sackville et al. 1987, p. 
54). This reduced sexual reproduction may negatively impact the ability 
of the species to adapt to rapid environmental change or environmental 
change over the long term, which is especially deleterious to a rare 
species with disjunct occurrences such as A. pumila (Dudek 2000, p. 17; 
Dudek 2003, p. P-332).
    The dispersal strategy of Ambrosia pumila is unknown. Ambrosia 
pumila seeds lack structures that facilitate dispersal by wind or 
passing animals (Nuttall 1840, p. 344; Payne 1993, p. 194). The species 
may depend on periodic flooding of nearby waterways for dispersal of 
seeds and rhizomes that can produce new aerial stems (Dudek 2003, p. P-
332). The longevity of individual plants is also unknown,

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although plants with clonal growth patterns tend to be long-lived 
(Watkinson and White 1985, pp. 44-45; Tanner 2001, p. 1980). Finally, 
the longevity of seeds and potential for buried seed banks to develop 
in the soil is unknown.

Genetics

    Little is known about genetic diversity or genetic distribution of 
Ambrosia pumila across its range. McGlaughlin and Friar (2007) 
conducted a genetic study of A. pumila to address conservation and 
management of the species. They found that each population they 
examined contained multiple genetically distinct individuals, but no 
individuals that occurred in more than one population. Therefore, they 
concluded that in order to maintain a level of genetic diversity 
capable of responding to variable ecological conditions, conservation 
of the species should involve the protection and maintenance of as many 
populations of A. pumila as possible (McGlaughlin and Friar 2007, pp. 
319 and 329).

Geographic Range and Status

    Ambrosia pumila is distributed in southern California from 
northwestern Riverside County, south through western San Diego County, 
to northwestern Baja California, Mexico (CNDDB 2008). It is generally 
found at or below elevations of 1600 feet (ft) (487 meters (m)) in 
Riverside County, and 600 ft (183 m) in San Diego County (CNDDB 2008). 
When listed as endangered under the Act in 2002, 15 occurrences of A. 
pumila were known in the United States: 3 in Riverside County and 12 in 
San Diego County (67 FR 44372; July 2, 2002). As noted previously, the 
term ``occurrence'' as used in this proposed critical habitat rule is 
defined as one or more A. pumila plants more than 0.25 mi (0.40 km) 
from another individual or group of individuals (Bittman 2002, in 
litt.). More than 80 percent of the occupied sites identified in the 
final listing rule were concentrated in the following 6 areas:
     Near Alberhill about 2.1 mi (3.5 km) to the northwest of 
the Nichols Road site in Riverside County;
     Along Nichols Road in the City of Lake Elsinore, Riverside 
County;
     Near the Skunk Hollow vernal pool in southwestern 
Riverside County;
     Adjacent to State Route 76 in northern San Diego County;
     Mission Trails Regional Park, in the City of San Diego, 
San Diego County; and
     San Diego National Wildlife Refuge near the unincorporated 
community of Jamul in southern San Diego County.
    According to information used to develop the final listing rule (67 
FR 44372; July 2, 2002), roughly 44 ac (18 ha)) of habitat in San Diego 
County was occupied by this species in 12 occurrences. This habitat 
estimate only includes areas where A. pumila stems were found in the 5 
to 10 years prior to listing in 2002. Similar area estimate data were 
unavailable for the 3 occurrences in Riverside County.
    Since this species was listed, one occurrence was identified in 
Riverside County about 1 mile (1.6 km) south of Skunk Hollow along San 
Diego aqueduct, from a survey report (AMEC 2006, pp. 12-13; CNDDB 
2008), and one occurrence was identified in unincorporated San Diego 
County on the west side of State Route 76, south of Olive Hill Road 
(see ``Criteria Used to Identify Critical Habitat'' below). Also since 
listing, we determined that one occurrence, on the west side of 
Interstate 15 just north of Lake Hodges and south of Via Rancho Parkway 
in San Diego County, previously identified as extirpated or not viable 
in the final listing rule is now extant and viable.
    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, Mexico (Burrascano and Hogan 1996, p. 8). Two 
of these three occurrences were confirmed by David Hogan, formerly with 
the Southwest Center for Biological Diversity (now Center for 
Biological Diversity), and Cindy Burrascano of the California Native 
Plant Society (CNPS), San Diego Chapter (Burrascano and Hogan 1996, p. 
8). Although additional occurrences may have existed in Baja 
California, the species was not considered to be widespread at the time 
of listing due to the lack of appropriate habitat and impacts from 
agriculture and urban development, especially near the coast 
(Burrascano and Hogan1996, p. 8).
    All currently known occurrences are 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. Also, because the plants 
produce very few if any seeds, the ability of the plant to disperse 
into and colonize previously unoccupied areas is diminished. Since this 
species was listed, no additional occurrences were documented in 
Mexico; the occurrences along the west coast of Baja California between 
Cabo Colonet and the U.S.-Mexico border are rapidly disappearing due to 
recreational development and agriculture (Dudek 2003, p. P-330).

Critical Habitat

Background

    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 provisions of 
section 4 of 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 by the Secretary 
of the Interior that such areas are essential for the conservation of 
the species.
    Conservation, as defined under section 3 of the Act, means the use 
of all methods and procedures that are necessary to bring an endangered 
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 otherwise be 
relieved, may include regulated taking.
    Critical habitat receives protection under section 7 of the Act 
through the prohibition against Federal agencies carrying out, funding, 
or authorizing activities that result in the destruction or adverse 
modification of critical habitat. Section 7(a)(2) 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 the landowner. Where a landowner

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seeks or requests Federal agency funding or authorization for an 
activity 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 Federal 
action agency's and the applicant'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.
    To be considered for inclusion in a critical habitat designation, 
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 the 
physical and biological features are found laid out in the appropriate 
quantity and spatial arrangement essential to the conservation of the 
species. Under the Act and regulations at 50 CFR 424.12, we can 
designate as critical habitat areas outside the geographical area 
occupied by the species at the time it is listed only when we determine 
that those areas are essential for the conservation of the species and 
that designation limited to those areas occupied at the time of listing 
would be inadequate to ensure 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 proposed 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 dynamic, and species may move from one area to another 
over time. We recognize that climate change may cause changes in the 
arrangement of occupied habitat patches. Current climate change 
predictions for terrestrial areas in the Northern Hemisphere indicate 
warmer air temperatures, more intense precipitation events, and 
increased summer continental drying (Field et al. 1999, pp. 1-3; Hayhoe 
et al. 2004, p. 12422; Cayan et al. 2005, p. 6; Intergovernmental Panel 
on Climate Change 2007, p. 11). However, predictions of climatic 
conditions for smaller subregions such as California remain uncertain. 
It is unknown at this time if climate change in California will result 
in a warmer trend with localized drying, higher precipitation events, 
or other effects. Thus, the information currently available on the 
effects of global climate change and increasing temperatures does not 
make sufficiently precise estimates of the location and magnitude of 
the effects, so we are unable to determine what, if any, additional 
areas would be needed. However, we recognize that critical habitat 
designated at a particular point in time may not include all of the 
habitat areas that we may later determine are necessary for the 
recovery of the species. For these reasons, a critical habitat 
designation does not signal that habitat outside the designated 
critical habitat area is unimportant or may not be required for 
recovery of the species.
    Areas that are important to the conservation of the species, but 
are outside the critical habitat designation, will continue to be 
subject to conservation actions implemented under section 7(a)(1) of 
the Act. Areas that support populations are 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 information available at the time of 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, in determining which areas within the geographical area 
occupied by the species at the time of listing to propose as critical 
habitat, we consider the physical and biological features that are 
essential to the conservation of the species and that may require 
special management considerations or protection. Those features are the 
primary constituent elements (PCEs) laid out in the appropriate 
quantity and spatial arrangement for the 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 habitat specificity and characteristics 
of this species. Therefore, the PCEs for Ambrosia pumila are based on 
our assessment of the ecosystem settings in which the species has most 
frequently been detected.

Space for Individual and Population Growth and for Normal Behavior

Clonal Growth--Rhizome Spread and New Aerial Stems
    Individual Ambrosia pumila plants spread by underground rhizomes to 
produce a group of genetically identical aerial 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 investigating an intact, underground rhizome system.
    The extent and configuration of the visible portion (aerial stems) 
of A. pumila patches can change from one growing season to the next 
(Martin 2005, p. 3; City of San Diego 2008a, p.

[[Page 44243]]

1). For example, see Figure 4 in Martin 2005, in which patches of A. 
pumila are shown to change in shape and size (up to several square 
meters) from 2000 to 2005, 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 (Folarin 2008, pers. comm.)). These 
changes in patch size and shape are perhaps 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 occupied by the stems 
above ground at any given time, with aerial stems produced only where 
conditions are appropriate. Thus, to ensure that a habitat area does 
not exclude unseen underground portions of A. pumila plants, the area 
needs to include additional surface area beyond the visible surface 
area covered by the aerial stems.
Germination of Seeds and Spread of Seedlings
    It is unclear to what extent and with what frequency Ambrosia 
pumila reproduces by seed. Presuming at least low rates of sexual 
reproduction, space is needed for new plants to germinate, grow, and 
spread. However, 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 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 green (not desiccated) 
aerial stem shoots after small amounts of precipitation and after 
annual vegetation in the area had desiccated, 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 (Folarin 2008, pers. comm.). 
Additionally, we believe that periodic flooding may be necessary to 
some segment of the plant's life history (such as seed germination, 
dispersal of seeds and rhizomes) or to maintain some essential aspect 
of its habitat, because of the indicator that the plant is 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 (etiolation) and more 
slender compared to those in more open areas (Dudek 2000, p. 19), which 
also 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 
2008). These soil types likely are particularly conducive to the growth 
and persistence of A. pumila because it 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), and 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 seen no reports of data 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 whether this 
species reproduces via seed.

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

    As stated above under the ``Life History'' section, little is known 
about sexual reproduction in Ambrosia pumila. Because occurrences are 
consistently found on the upper terraces of rivers and other waterways, 
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, A. pumila may depend on floods to disperse 
rhizomes and seeds (Dudek 2003, p. P-332) and to create space for new 
stems by removing or limiting the growth of competitors.
    Presuming Ambrosia pumila is wind-pollinated, as discussed in the 
``Life History'' section above, the species requires sufficient airflow 
through inflorescences to pick up and carry pollen (McGlaughlin and 
Friars 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 in (30 cm) tall (McGlaughlin and Friars 2007, p. 329).
    Ambrosia pumila is presumed to be self-compatible (an individual 
can produce viable seed using 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 
Friars 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 
(flat or gently sloping areas of 0 to 42 percent slopes are typical for 
terraces on which A. pumila occurrences are found, near, but not 
directly adjacent to, the river channel) and other drainages in western 
Riverside County, western San Diego County, and northwestern Baja 
California (Beauchamp 1986, p. 94; Johnson et al. 1999, p. 1; 
McGlaughlin and Friar 2007, p. 321; CNDDB 2008). These areas are or 
have been associated with a natural flood disturbance regime. The 
species is primarily associated with 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 2008). 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;

[[Page 44244]]

CNDDB 2008). 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 2008). 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 2008).
    Occurrences in Riverside County are found at much higher elevation 
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, we are required to 
identify the known physical and biological features, called primary 
constituent elements (PCEs), within the geographical area occupied by 
Ambrosia pumila at the time of listing that are essential to the 
conservation of the species and which may require special management 
considerations or protection. Again, the physical and biological 
features are those PCEs laid out in a specific 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 traits of the habitat 
types in which the species is most often found. All areas we are 
proposing as critical habitat for A. pumila were occupied at the time 
the species was listed, occur within the species' historical geographic 
range, and contain physical and biological features 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 
have 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 on near (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 A. 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.
    With this proposed designation of critical habitat, we intend to 
conserve the physical and biological features that are essential to 
support the life-history functions that are the basis for the proposal. 
All units and subunits proposed in this rule 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 
A. pumila.
    We are soliciting public comment for information to help us more 
specifically identify PCEs and essential habitat for Ambrosia pumila. 
There is a lack of available information regarding what constitutes 
essential habitat for this species. Additionally, the available 
information does not identify a consistent pattern in specific life-
history requirements and habitat types where Ambrosia pumila is found. 
For these reasons, the PCEs in this proposed rule are broad and based 
on our assessment of the ecosystem settings in which the species has 
most frequently been detected and speculation regarding its life 
history. We specifically seek information that may assist us in 
defining those physical and biological features essential to the 
conservation of the species which may require special management 
considerations or protection, or in identifying specific areas outside 
the geographical area occupied by the species at the time it was listed 
that may be essential to the conservation of the species (see questions 
2 and 3 in the Public Comments section).

Special Management Considerations or Protection

    When designating critical habitat, we assess whether the physical 
and biological features within the geographical area occupied by the 
species at the time of listing contain features that are essential to 
the conservation of the species and that may require special management 
considerations or protection. All areas proposed for designation 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 Ambrosia pumila. 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.
    Researchers estimate 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 as much of 
its habitat has been impacted by human activities (Burrascano and Hogan 
1997, p. 7; Dudek 2000, p. 17; CNDDB 2008). A detailed discussion of 
threats to A. pumila and its habitat can be found in the final listing 
rule (67 FR 44372). The primary threats impacting the physical and 
biological features essential to the conservation of A. pumila that may 
require special management considerations or protection within the 
proposed critical habitat include, but are not limited to, the 
following (67 FR 44372):
     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 remove the PCEs by 
removing soil (by grading) and changing Ambrosia pumila habitat to 
urban land, which is unsuitable for the species.
     Soil compaction caused by the creation 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 on trails, implying that although the appropriate 
soil type might be present, soil compaction can alter the physical 
characteristics of the soil such that the soil can no longer support 
growth of the plant.

[[Page 44245]]

     Habitat alteration caused by nonnative plant species that 
may, if present in large enough numbers, change the plant community to 
the extent that A. pumila plants can no longer receive adequate 
sunlight and airflow.
     Alteration of hydrology 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 periodic flooding presumed 
necessary for the plant's persistence altogether, or change groundwater 
levels that could change the plant community to the extent that A. 
pumila plants can no longer receive adequate sunlight and airflow.
    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 hydrology and floodplain 
dynamics of waterways associated with A. pumila occurrences where 
feasible.
    The designation of critical habitat does not imply that lands 
outside of critical habitat do not play an important role in the 
conservation of Ambrosia pumila. 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 A. 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.

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, and areas 
outside of the geographical area occupied at the time of listing that 
are essential to the conservation of A. pumila, or both. All essential 
areas were occupied at the time of listing, as discussed below. As a 
result, we are not currently proposing any areas outside the 
geographical area presently occupied by A. pumila because we have 
determined that including only occupied areas in critical habitat is 
sufficient for the conservation of the species. In San Diego County, 
where the pattern of extirpated occurrences reflects a loss of 
occurrences from each of the watersheds in which the species occurs 
rather than a complete loss from those watersheds, the areas occupied 
at the time of listing include the known historical range of the 
species (CNDDB 2008). In Riverside County, the loss of an occurrence 
near the Riverside Airport reflects a loss to the geographical extent 
of the range in that county (Provance and Sanders 2001, p. 47).
    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 habitat specificity, 
characteristics, and breeding system. Additionally, data from different 
information sources at times conflict, further complicating the task of 
discerning the specific habitat requirements of the species. We used 
numerous sources of information, such as materials and data included in 
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 and 
presented in academic theses and agency reports; regional Geographic 
Information System (GIS) coverages for area calculations and mapping; 
and data collected in the field by Service biologists.
    We are proposing to designate critical habitat in areas that we 
determined were occupied by the species at the time of listing, and 
that contain the PCEs in the quantity and spatial arrangement to 
support life history functions essential to the conservation of the 
species. This includes two areas occupied by occurrences detected after 
Ambrosia pumila was listed. We have concluded that 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 near Santa Gertrudis Creek was found during a survey for a 
subtransmission line project in 2006 (AMEC 2006, p. 12). The occurrence 
at the intersection of State Route 76 and Olive Hill Road was found 
during a general survey for A. pumila in 2006 (CNDDB 2008). To our 
knowledge, the areas had not been surveyed for A. pumila previously, 
and we have no reason to believe the plant was imported or had 
dispersed into these areas from other areas after A. pumila was listed. 
The occurrences identified since listing likely were in existence for 
many years and were only recently detected due to increased awareness 
of this species.
    We are also proposing to designate critical habitat in some areas 
where A. pumila was thought to be extirpated or where, though extant, 
A. pumila was not considered viable at the time of listing. We 
conducted surveys of historical occurrences as part of the background 
research for this proposed rule. We found one documented occurrence 
area east of Lake Hodges in San Diego County that was thought to be 
extirpated or nonviable because the occurrence had not been seen since 
1999, and because records did not contain sufficient information to 
locate the occurrence site. Our survey found this site does contain a 
viable occurrence of A. pumila and meets the criteria set out in this 
rule for A. pumila critical habitat. The site was located after the 
species was listed and found to contain a large population of A. 
pumila. We are not proposing to designate any areas outside the 
geographical area occupied by the species at the time of listing, and 
all of the areas we are proposing to designate are currently occupied 
by the species. All units and subunits proposed contain the PCEs 
believed to be essential to the conservation of this species.

Methods

    As required by section 4(b)(1)(A) of the Act, we use the best 
scientific and commercial data available in trying to determine areas 
that contain the features that are essential to the conservation of 
Ambrosia pumila. We used the best scientific data available to select 
areas that we believe may possess those physical and biological 
features essential to the conservation of the species, and that may 
require special management considerations or protection.
    After identifying the PCEs, we followed these steps to delineate 
critical habitat:
    (1) We identified areas occupied by Ambrosia pumila at the time of 
listing as extant occurrences, where an occurrence is defined as an 
occupied habitat area separated by 0.25 mi (0.40 km) or more from the 
next nearest occupied habitat area.
    (2) We determined that due to the lack of specific information 
regarding the needs of the species, we are unable to identify specific 
areas outside the geographical area occupied by the species at the time 
it was listed that may be essential to the conservation of the species.

[[Page 44246]]

    (3) We removed all areas where the species occurs in habitat of low 
quality for growth and propagation (such as pavement areas or cracks 
within paved areas). Although occupied, we believe these occurrences 
are not capable of providing for the full life-history requirements of 
this species and are not likely to contribute to its long-term 
conservation; therefore, we did not consider these locations as 
containing essential features as habitat and did not include them in 
critical habitat.
    (4) To define an outer boundary for each patch that captures the 
existing underground rhizome system (which extends beyond the visible 
aerial stems of plants within each occurrence), we added the average 
distance between the visible (aerial stems) portions of each Ambrosia 
pumila patch and the next nearest patch to the limits of the visible 
portion of each patch. Using GIS data, we found the average distance 
between clusters of stems in adjacent patches to be approximately 1,181 
ft (260 m), and we added this distance to the visible outer limit of 
each occurrence to delineate the presumed expanse of the occurrence 
that also includes the underground rhizomes.
    (5) We removed any area within the outer boundary of an occurrence 
where habitat type was not grassland, ruderal, or coastal sage scrub.
    We describe how we implemented each of the steps above in detail 
below.
    (1) We identified all occurrences of Ambrosia pumila--those known 
to exist at the time of listing and those detected since 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) the California Natural 
Diversity Database occurrence data report for A. pumila and 
accompanying GIS records (CNDDB 2008, pp. 1-49); (3) the data from the 
Consortium of California Herbaria and accompanying Berkeley Mapper GIS 
records (Consortium of California Herbaria 2008, pp. 1-5); (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 internal species GIS 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). 
As discussed in detail earlier in this section, we consider all extant 
occurrences to have been in existence at the time of listing. We used 
these data to delineate GIS polygons around Ambrosia pumila 
occurrences.
    We reviewed the data that we compiled to ensure its accuracy. We 
checked each data point in our database to ensure that it represented a 
site documented by a herbarium voucher or observation of Ambrosia 
pumila and was not a duplicate voucher or observation of another 
occurrence in the database. Duplicates were removed from our 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 observations where the location could 
not be determined from available data or site visits.
    We then determined which areas are currently occupied. For areas 
where we have past occupancy data for Ambrosia pumila, we assumed the 
area remains occupied unless: (1) Three or more surveys for the species 
did not find A. pumila; (2) the site was significantly disturbed (for 
example, converted to development) since the last observation of the 
species at that location; or (3) specific location information for the 
site was lacking, and field surveys carried out in conjunction with 
this proposed critical habitat determination could not locate the 
occurrence.
    (2) We determined that there are no specific areas outside the 
geographical area occupied by the species at the time it was listed 
that are essential to the conservation of the species. Information 
found during the Service's research in connection with this proposed 
action indicated that the geographical area occupied by the species at 
the time it was listed provides sufficient resources for the 
conservation of the species. We do not have sufficient information 
regarding the specific needs of the species to determine if any 
unoccupied areas 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 pavement areas or cracks 
within paved areas). Although occupied, we did n