[Federal Register Volume 61, Number 26 (Wednesday, February 7, 1996)]
[Notices]
[Pages 4722-4725]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-2639]
[[Page 4721]]
_______________________________________________________________________
Part IV
Department of the Interior
Fish and Wildlife Service
Department of Commerce
National Oceanic and Atmospheric Administration
_______________________________________________________________________
Policy Regarding the Recognition of District Vertebrate Population;
Notice
Federal Register / Vol. 61, No. 26 / Wednesday, February 7, 1996 /
Notices
[[Page 4722]]
DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
Policy Regarding the Recognition of Distinct Vertebrate
Population Segments Under the Endangered Species Act
AGENCIES: Fish and Wildlife Service, Interior; National Marine
Fisheries Service, NOAA, Commerce.
ACTION: Notice of policy.
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SUMMARY: The Fish and Wildlife Service and the National Marine
Fisheries Service (Services) have adopted a policy to clarify their
interpretation of the phrase ``distinct population segment of any
species of vertebrate fish or wildlife'' for the purposes of listing,
delisting, and reclassifying species under the Endangered Species Act
of 1973, as amended (16 U.S.C. 1531 et. seq.) (Act).
ADDRESSES: The complete record pertaining to this action is available
for inspection, by appointment, during normal business hours at the
Division of Endangered Species, U.S. Fish and Wildlife Service, in Room
452, Arlington Square Building, 4401 North Fairfax Drive, Arlington,
Virginia.
FOR FURTHER INFORMATION CONTACT: E. LaVerne Smith, Chief, Division of
Endangered Species, U.S. Fish and Wildlife Service at the above address
(703/358-2171), or Russell Bellmer, Chief, Endangered Species Division,
National Marine Fisheries Service, 1335 East-West Highway, Silver
Spring, Maryland 20910 (301/713-1401).
SUPPLEMENTARY INFORMATION:
Background
The Endangered Species Act of 1973, as amended (16 U.S.C. 1531 et.
seq.). (Act) requires the Secretary of the Interior or the Secretary of
Commerce (depending on jurisdiction) to determine whether species are
endangered or threatened. In defining ``species,'' the Act as
originally passed included, ``* * * any subspecies of fish or wildlife
or plants and any other group of fish or wildlife of the same species
or smaller taxa in common spatial arrangement that interbreed when
mature.'' In 1978, the Act was amended so that the definition read ``*
* * any subspecies of fish or wildlife or plants, and any distinct
population segment of any species of vertebrate fish or wildlife which
interbreeds when mature.'' This change restricted application of this
portion of the definition to vertebrates. The authority to list a
``species'' as endangered or threatened is thus not restricted to
species as recognized in formal taxonomic terms, but extends to
subspecies, and for vertebrate taxa, to distinct population segments
(DPS's).
Because the Secretary must ``* * * determine whether any species is
an endangered species or a threatened species'' (section 4(a)(1)), it
is important that the term ``distinct population segment'' be
interpreted in a clear and consistent fashion. Furthermore, Congress
has instructed the Secretary to exercise this authority with regard to
DPS's ``* * * sparingly and only when the biological evidence indicates
that such action is warranted.'' (Senate Report 151, 96th Congress, 1st
Session). The Services have used this authority relatively rarely; of
over 300 native vertebrate species listed under the Act, only about 30
are given separate status as DPS's.
It is important in light of the Act's requirement to use the best
available scientific information in determining the status of species
that this interpretation follows sound biological principles. Any
interpretation adopted should also be aimed at carrying out the
purposes of the Act (i.e., ``* * * to provide a means whereby the
ecosystems upon which endangered species and threatened species depend
may be conserved, to provide a program for the conservation of such
endangered species and threatened species, and to take such steps as
may be appropriate to achieve the purposes of the treaties and
conventions set forth in subsection (a) of this section'' (section
2(b)).
Available scientific information provides little specific
enlightenment in interpreting the phrase ``distinct population
segment.'' This term is not commonly used in scientific discourse,
although ``population'' is an important term in a variety of contexts.
For instance, a population may be circumscribed by a set of
experimental conditions, or it may approximate an ideal natural group
of organisms with approximately equal breeding opportunities among its
members, or it may refer to a loosely bounded, regionally distributed
collection of organisms. In all cases, the organisms in a population
are members of a single species or lesser taxon.
The National Marine Fisheries Service (NMFS) has developed a Policy
on the Definition of Species under the Endangered Species Act (56 FR
58612-58618; November 20, 1991). The policy applies only to species of
salmonids native to the Pacific. Under this policy, a stock of Pacific
salmon is considered a DPS if it represents an evolutionarily
significant unit (ESU) of a biological species. A stock must satisfy
two criteria to be considered an ESU:
(1) It must be substantially reproductively isolated from other
conspecific population units; and
(2) It must represent an important component in the evolutionary
legacy of the species.
This document adopts an interpretation of the term ``distinct
population segment'' for the purposes of listing, delisting, and
reclassifying vertebrates by the U.S. Fish and Wildlife Service (FWS)
and NMFS. The Services believe that the NMFS policy, as described
above, on Pacific salmon is consistent with the policy outlined in this
notice. The NMFS policy is a detailed extension of this joint policy.
Consequently, NMFS will continue to exercise its policy with respect to
Pacific salmonids
The Services' draft policy on this subject was published on
December 21, 1994 (59 FR 65885) and public comment was invited. After
review of comments and further consideration, the Services adopt the
policy as issued in draft form.
Summary of Comments and Recommendations
The Services received 31 letters from individuals and organizations
commenting on the draft policy. In addition, since publication of the
draft policy, the National Academy of Sciences, National Research
Council (NRC), has published a report titled ``Science and the
Endangered Species Act,'' prepared by a committee appointed by the
Academy at the request of several members of Congress. This report in
part examines the definition of ``species'' under the Act, and endorses
the recognition of scientifically identified evolutionary units for
conservation purposes. It discusses the recognition of DPS's in terms
of ``distinctiveness,'' which is consistent with the concept of
``discreteness'' as presented in the draft policy except that it would
not recognize an international political boundary to delimit a DPS. The
committee noted that: ``Although there can be good policy reasons for
such delineations, there are not sound scientific reasons to delineate
species only in accordance with political boundaries.'' The Services
agree that the inclusion of international boundaries in determining
whether a population segment is discrete is sometimes undertaken as a
matter of policy rather than science. Although the committee
[[Page 4723]]
expressed the belief that application of a distinctiveness test
(analogous to the standard of discreteness in the policy) would
adequately carry out the congressional instruction that the authority
to address DPS's be exercised sparingly, the Services continue to
believe that a judgement regarding the significance of any unit found
to be discrete is necessary to comply with congressional intent.
Respondents presented a wide range of opinion regarding the
recognition of DPS's. Some argued that the draft policy would be too
restrictive and make it difficult or impossible to protect important
elements of biodiversity; others maintained that the draft was not
restrictive enough and would allow the Services to extend protection to
entities never intended to be eligible for protection under the Act. A
few respondents questioned the need for any policy framework and
advocated case-by-case determinations of the eligibility of entities
for listing under the DPS provision. The Services continue to believe
that the Act will be best administered if there is a general policy
framework governing the recognition of DPS's that can be disseminated
and understood by the affected public.
Several respondents questioned the relationship of the draft policy
to the NMFS policy regarding salmonids. The Services believe that the
NMFS policy for salmonids is consistent with the general policy
outlined in this notice, although the salmonid policy is formulated
specifically to address the biology of this group. Several respondents
also questioned the use of qualifying words such as ``significant'' or
``markedly'' in the policy. The Services intended these words to have
their commonly understood senses. At the time any distinct population
is recognized or not recognized the reasons for which it is believed to
satisfy or not satisfy the conditions of the policy will be fully
explained.
Several respondents maintained that a policy of this nature
required adoption under rulemaking procedures of the Administrative
Procedure Act. The Services disagree, and continue to regard the policy
as non-regulatory in nature. Specific recommendations advanced by
respondents are paraphrased and responded to below.
Only Full Species are Genetically Distinct From one Another, and
Listing Should Only be Extended to These Genetically Distinct Entities.
Restricting listings to full taxonomic species would render the
Act's definition of species, which explicitly includes subspecies and
DPS's of vertebrates, superfluous. Clearly, the Act is intended to
authorize listing of some entities that are not accorded the taxonomic
rank of species, and the Services are obliged to interpret this
authority in a clear and reasonable manner.
The Services Should Focus on Genetic Distinctness in Recognizing a
Distinct Population Segment. Conversely, Some Respondents Believed
There Should be No Requirement That a DPS be Genetically Differentiated
or Recognizable for it to be Protected Under the Act
There appears to be a diversity of understanding regarding the
purposes of the Act, with some individuals viewing it as directed
almost exclusively toward the conservation of unique genetic resources
while other individuals emphasize its stated intention of conserving
ecosystems. This diversity of viewpoints is reflected in comments
addressing the role to be played by genetic information in the draft
policy. The Services understand the Act to support interrelated goals
of conserving genetic resources and maintaining natural systems and
biodiversity over a representative portion of their historic
occurrence. The draft policy was intended to recognize both these
intentions, but without focusing on either to the exclusion of the
other. Thus, evidence of genetic distinctness or of the presence of
genetically determined traits may be important in recognizing some
DPS's, but the draft policy was not intended to always specifically
require this kind of evidence in order for a DPS to be recognized. The
ESU policy of NMFS also does not require genetic data before an ESU can
be identified. Thus in determining whether the test for discreteness
has been met under the policy, the Services allow but do not require
genetic evidence to be used. At least one respondent evidently
understood the draft policy to require that genetic distinctness be
demonstrated before a DPS could be recognized, and criticized the draft
on that basis. As explained above, this was never intended.
The Elements Describing Reasons for Considering a Population Segment
Significant Should be Laid Out Comprehensively, Rather Than Presented
as an Open-Ended Set of Examples as in the Draft Policy
The Services appreciate the need to make a policy on this subject
as complete and comprehensive as possible, but continue to believe that
it is not possible to describe in advance all the potential attributes
that could be considered to support a conclusion that a particular
population segment is ``significant'' in terms of the policy. When a
distinct population is accepted or rejected for review pursuant to a
petition or proposed for listing or delisting, the Services intend to
explain in detail why it is considered to satisfy both the discreteness
and significance tests of the policy.
In Assessing the Significance of a Potential Distinct Population
Segment, the Services Should Focus on its Importance to the Status of
the Species to Which it Belongs. Alternatively, the Services Should
Emphasize the Importance of a Potential DPS to the Environment in Which
it Occurs
Despite its orientation toward conservation of ecosystems, the
Services do not believe the Act provides authority to recognize a
potential DPS as significant on the basis of the importance of its role
in the ecosystem in which it occurs. In addition, it may be assumed
that most, if not all, populations play roles of some significance in
the environments to which they are native, so that this importance
might not afford a meaningful way to differentiate among populations.
On the other hand, populations commonly differ in their importance to
the overall welfare of the species they represent, and it is this
importance that the policy attempts to reflect in the consideration of
significance.
International Boundaries are not Appropriate in Determining That a
Population is Discrete in the Draft Policy; Political Boundaries Other
Than Those Between Nations may be Appropriate in Some Cases to Delimit
DPS's
The Services recognize that the use of international boundaries as
a measure of discreteness may introduce an artificial and non-
biological element to the recognition of DPS's. Nevertheless, it
appears to be reasonable for national legislation, which has its
principal effects on a national scale, to recognize units delimited by
international boundaries when these coincide with differences in the
management, status, or exploitation of a species. Recognition of
international boundaries in this way is also consistent with practice
under the Convention on International Trade in Endangered Species of
Wild Fauna and Flora, which is implemented in the United States by the
Act. Recognition of other political boundaries, such as State lines
within the United States, would appear to lead to the recognition of
[[Page 4724]]
entities that are primarily of conservation interest at the State and
local level, and inappropriate as a focus for a national program. The
Services recognize, as suggested in some comments, that infra-national
political boundaries offer opportunities to provide incentives for the
favorable management of species if they were used as a basis for
recognizing discrete entities for delisting or for exclusion from a
listing. Particularly when applied to the delisting or reclassification
of a relatively widespread species for which a recovery program is
being successfully carried out in some States, recognition of State
boundaries would offer attractive possibilities. Nevertheless, the Act
provides no basis for applying different standards for delisting than
those adopted for listing. If the Services do not consider entities for
listing that are not primarily of conservation interest at a national
level, they must also refrain from delisting or reclassifying units at
this level.
Complete Reproductive Isolation Should be Required as a Prerequisite to
the Recognition of a Distinct Population Segment
The Services do not consider it appropriate to require absolute
reproductive isolation as a prerequisite to recognizing a distinct
population segment. This would be an impracticably stringent standard,
and one that would not be satisfied even by some recognized species
that are known to sustain a low frequency of interbreeding with related
species.
The Services Should Emphasize Congress' Instruction to use Their
Authority to Dddress DPS's ``Sparingly''
The Services believe that application of the policy framework
announced in this document will lead to consistent and sparing exercise
of the authority to address DPS's, in accord with congressional
instruction.
The Occurrence of a Population Segment in an Unusual Setting Should not
be Used as Evidence for its Significance
The Services continue to believe that occurrence in an unusual
ecological setting is potentially an indication that a population
segment represents a significant resource of the kind sought to be
conserved by the Act. In any actual case of a DPS recognized in part on
this basis, the Services will describe in detail the nature of this
significance when accepting a petition or proposing a rule.
The Authority to Address DPS's Should be Extended to Plant and
Invertebrate Species
The Services recognize the inconsistency of allowing only
vertebrate species to be addressed at the level of DPS's, and the
findings of the NRC committee also noted that such recognition would be
appropriate for other species. Nevertheless, the Act is perfectly clear
and unambiguous in limiting this authority. This policy acknowledges
the specific limitations imposed by the Act on the definition of
``species.''
The Services Should Stress Uniqueness and Irreplaceability of
Ecological Functions in Recognizing DPS's
The Services consider the Act to be directed at maintenance of
species and populations as elements of natural diversity. Consequently,
the principal significance to be considered in a potential DPS will be
the significance to the taxon to which it belongs. The respondent
appears to be recommending that the Services consider the significance
of a potential DPS to the community or ecosystem in which it occurs and
the likelihood of another species filling its niche if it should be
extirpated from a particular portion of its range. These are important
considerations in general for the maintenance of healthy ecosystems,
and they often coincide with conservation programs supported by the
Act. Nevertheless, the Act is not intended to establish a comprehensive
biodiversity conservation program, and it would be improper for the
Services to recognize a potential DPS as significant and afford it the
Act's substantive protections solely or primarily on these grounds.
Congress did not Intend to Require That DPS's be Discrete. In a Similar
Vein, Congress did not Require That a Potential DPS be Significant to
be Considered Under the Act
With regard to the discreteness standard, the Services believe that
logic demands a distinct population recognized under the Act be
circumscribed in some way that distinguishes it from other
representatives of its species. The standard established for
discreteness is simply an attempt to allow an entity given DPS status
under the Act to be adequately defined and described. If some level of
discreteness were not required, it is difficult to imagine how the Act
could be effectively administered or enforced. At the same time, the
standard adopted does not require absolute separation of a DPS from
other members of its species, because this can rarely be demonstrated
in nature for any population of organisms. The standard adopted is
believed to allow entities recognized under the Act to be identified
without requiring an unreasonably rigid test for distinctness. The
requirement that a DPS be significant is intended to carry out the
expressed congressional intent that this authority be exercised
sparingly as well as to concentrate conservation efforts undertaken
under the Act on avoiding important losses of genetic diversity.
A Population Should Only be Required to be Discrete or Significant, but
not Both, to be Recognized as a Distinct Population Segment
The measures of discreteness and significance serve decidedly
different purposes in the policy, as explained above. The Services
believe that both are necessary for a policy that is workable and that
carries out congressional intent. The interests of conserving genetic
diversity would not be well served by efforts directed at either well-
defined but insignificant units or entities believed to be significant
but around which boundaries cannot be recognized.
Requiring That a DPS be Discrete Effectively Prevents the Loss of Such
a Segment From Resulting in a Gap in the Distribution of a Species.
Essentially, if Distinct Populations are Entirely Separate, the Loss of
One Has Little Significance to the Others
If the standard for discreteness were very rigid or absolute, this
could very well be true. However, the standard adopted allows for some
limited interchange among population segments considered to be
discrete, so that loss of an interstitial population could well have
consequences for gene flow and demographic stability of a species as a
whole. On the other hand, not only population segments whose loss would
produce a gap in the range of a species can be recognized as
significant, so that a nearly or completely isolated population segment
could well be judged significant on other grounds and recognized as a
distinct population segment.
The Services Lack Authority to Address DPS's of Subspecies
The Services maintain that the authority to address DPS's extends
to species in which subspecies are recognized, since anything included
in the taxon of lower rank is also included in the higher ranking
taxon.
[[Page 4725]]
The following principles will guide the Services' listing,
delisting and reclassification of DPS's of vertebrate species. Any
proposed or final rule affecting status determination for a DPS would
clearly analyze the action in light of these guiding principles.
Policy
Three elements are considered in a decision regarding the status of
a possible DPS as endangered or threatened under the Act. These are
applied similarly for addition to the lists of endangered and
threatened wildlife and plants, reclassification, and removal from the
lists:
1. Discreteness of the population segment in relation to the
remainder of the species to which it belongs;
2. The significance of the population segment to the species to
which it belongs; and
3. The population segment's conservation status in relation to the
Act's standards for listing (i.e., is the population segment, when
treated as if it were a species, endangered or threatened?).
Discreteness: A population segment of a vertebrate species may be
considered discrete if it satisfies either one of the following
conditions:
1. It is markedly separated from other populations of the same
taxon as a consequence of physical, physiological, ecological, or
behavioral factors. Quantitative measures of genetic or morphological
discontinuity may provide evidence of this separation.
2. It is delimited by international governmental boundaries within
which differences in control of exploitation, management of habitat,
conservation status, or regulatory mechanisms exist that are
significant in light of section 4(a)(1)(D) of the Act.
Significance: If a population segment is considered discrete under
one or more of the above conditions, its biological and ecological
significance will then be considered in light of Congressional guidance
(see Senate Report 151, 96th Congress, 1st Session) that the authority
to list DPS's be used `` * * * sparingly'' while encouraging the
conservation of genetic diversity. In carrying out this examination,
the Services will consider available scientific evidence of the
discrete population segment's importance to the taxon to which it
belongs. This consideration may include, but is not limited to, the
following:
1. Persistence of the discrete population segment in an ecological
setting unusual or unique for the taxon,
2. Evidence that loss of the discrete population segment would
result in a significant gap in the range of a taxon,
3. Evidence that the discrete population segment represents the
only surviving natural occurrence of a taxon that may be more abundant
elsewhere as an introduced population outside its historic range, or
4. Evidence that the discrete population segment differs markedly
from other populations of the species in its genetic characteristics.
Because precise circumstances are likely to vary considerably from
case to case, it is not possible to describe prospectively all the
classes of information that might bear on the biological and ecological
importance of a discrete population segment.
Status: If a population segment is discrete and significant (i.e.,
it is a distinct population segment) its evaluation for endangered or
threatened status will be based on the Act's definitions of those terms
and a review of the factors enumerated in section 4(a). It may be
appropriate to assign different classifications to different DPS's of
the same vertebrate taxon.
Relationship to Other Activities
The Fish and Wildlife Service's Listing and Recovery Priority
Guidelines (48 FR 43098; September 21, 1983) generally afford DPS's the
same consideration as subspecies, but when a subspecies and a DPS have
the same numerical priority, the subspecies receives higher priority
for listing. The Services will continue to generally accord subspecies
higher priority than DPS's.
Any DPS of a vertebrate taxon that was listed prior to
implementation of this policy will be reevaluated on a case-by-case
basis as recommendations are made to change the listing status for that
distinct population segment. The appropriate application of the policy
will also be considered in the 5-year reviews of the status of listed
species required by section 4(c)(2) of the Act.
Effects of Policy
This guides the evaluation of distinct vertebrate population
segments for the purposes of listing, delisting, and reclassifying
under the Act. The only direct effect of the policy is to accept or
reject population segments for these purposes. More uniform treatment
of DPS's will allow the Services, various other government agencies,
private individuals and organizations, and other interested or
concerned parties to better judge and concentrate their efforts toward
the conservation of biological resources at risk of extinction.
Listing, delisting, or reclassifying distinct vertebrate population
segments may allow the Services to protect and conserve species and the
ecosystems upon which they depend before large-scale decline occurs
that would necessitate listing a species or subspecies throughout its
entire range. This may allow protection and recovery of declining
organisms in a more timely and less costly manner, and on a smaller
scale than the more costly and extensive efforts that might be needed
to recover an entire species or subspecies. The Services' ability to
address local issues (without the need to list, recover, and consult
rangewide) will result in a more effective program.
Author/Editor: The editors of this policy are Dr. John J. Fay of
the Fish and Wildlife Service's Division of Endangered Species, 452
ARLSQ, Washington, DC 20240 (703/358-2105) and Marta Nammack of the
National Marine Fisheries Service's Endangered Species Division,
1335 East-West Highway, Silver Spring, Maryland 20910 (301/713-
2322).
Authority: The authority for this action is the Endangered
Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).
Dated: February 1, 1996.
John G. Rogers,
Acting Director, Fish and Wildlife Service.
Dated: February 1, 1996.
Nancy Foster,
Deputy Assistant Administrator for Fisheries, National Marine Fisheries
Service.
[FR Doc. 96-2639 Filed 2-6-96; 8:45 am]
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