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il
Chapter 10
Beyond the Endangered Species Act
This chapter explores the ability of the Endangerec! Species Act to fulfill! its purpose and how it
might be complemented by other activities. In its drafting of the act, Congress clearly recognized the
importance of habitats and ecosystems, because species-enciangerect and otherwise-cannot survive
without them. To protect those habitats and ecosystems will require more than the ESA alone can
provide, and that is also a topic of this chapter. The act's protections have helpecl listed species in many
cases, although some species continue to become extinct. Ecosystem-leve! planning and management
offer promise for aciciressing the conservation needs of a wider array of species than the traditional
species-orientec! approach and shouts! be viewer! as valuable complements to the ESA.
IS THE ESA WORKING?
Is the Endangered Species Act working? Critics of the act and its defenclers clebate this question
as reauthorization looms. Not surprisingly, the answers differ depending on how the poser is affected by
the act's provisions. To answer the question, we need to return to the objectives of the ESA as they are
described in the act. Section 2(b) of the ESA states that the purposes of the act are "to provide a means
whereby the ecosystems upon which endangered! species and threatened species clepenc! 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) ofthis section." The essential questions are:
.
.
Do the ESA's protections reduce the likelihood of species extinction?
Has the ESA successfully promoted species recovery?
Are the ecosystems upon which threatened and endangered species depend being
conserved?
REDUCING EXTINCTION
The difficulty with conclusively establishing extinction is manifest in several ways. First is the
nherent problem of proving negative facts. No matter how many times species searches Anal nothing,
there is always a chance that the object might appear. The black-footed ferret is a prime example.
Hundreds of surveys were conducted! throughout its historic range before it reappeared at Meeteetse,
Wyoming, several years after the last known field population in South Dakota failed from view.
Second, information on an organism's status might be scanty because little effort has been taken
to find and study it. In addition, finding rare species often requires specialized survey techniques that are
not systematically applied, or the methods used might simply be inappropriate if little is known about the
species. Finally, we may not have long enough time-series data or be looking in the right places (Taylor,
1993:witness the proliferation of several threatened or endangered! annual plants following heavy rains
that broke the recent several-year drought in California's San Joaquin Valley. Hoover's woolly-star
155
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Science and the Endangered Species Act
(Eriastrum hoover)) has been found in so many locations where it was formerly unknown or thought to
be extirpated that resource agencies may soon submit a delisting petition (L. Sastaw, U.S. Bureau of
Land Management, pers. comma..
Although not conclusive, the comparison of rates of extinction between listed and candidate
species, especially when remedial actions are clearly identifiable and feasible, indicates that the ESA
helps to retard extinctions. Recovery actions encouraged by the ESA and supported by agency funding
have helped to rescue several species from precarious status. A recent fact-sheet furnished by the Fish
and Wildlife Service (FWS) Office of Endangered Species provides 30 ESA success stories. Several of
them appear on the list of top 20 U.S. threatened and endangered animal species and top 20 plant species
in order of federal and state expenditures for recovery in 1989 (CEQ, 1990), including several high-
visibility symbols of the ESA's appeal, such as the bald eagle, grizzly bear, American peregrine falcon,
whooping crane, southern sea otter, black-footec} ferret, and California condor. Although the FWS does
not yet consider those species to be recovered, their chances for long-term survival have improved
greatly. Others on the list that received substantial funding, such as the Puerto Rican parrot, would have
fared much worse if not for strong intervention (Snyder et al., 1987), the recent damage caused by
hurricane Andrew notwithstanding. Also, a recent GAO report (GAO, 1994) concludes that the National
Wildlife Refuge system is contributing to the recovery of endangered species.
Combined with the mandates for federal agencies to avoid jeopardy and the ban on taking listed
species, the affirmative steps provided in the ESA are helping to ease the risk to other species too. The
status of the Utah prairie dog, piping plover, Oregon silver-spot butterfly, Aleutian Canada goose, Gila
trout, greenback cutthroat trout, least Bell's vireo, California least tern, Virginia big-eared bat, red wolf,
small whoried pagonia and several others have improved greatly from the time of listing (FWS, 1990),
although they are not out of danger. Others, such as the Florida panther, are still struggling despite
intensive efforts to stabilize the remaining population. Without the protections and recovery actions
required by the ESA, there is a strong, but hard-to-prove, possibility that most, if not all, of these and
many other species would be closer to extinction than they are today. It is not possible to evaluate from
available information whether any candidate species have improved without actions compelled by the
act.
REC OVERY SUCCESS
In December 1990, the FWS published its first report to Congress on the endangered and
threatened species recovery program. That report was prepared to meet a requirement in the 1988
amendments to the ESA, which were intended to improve recovery programs. Several provisions were
enacted in response to public perceptions that the recovery planning and implementation process was not
working very well (Fitzgerald ant! Meese, 1986; Clark and Harvey, 1988; GAO, 1988; Culbert and Blair,
1989).
The amendments provided for public involvement in recovery planning through review and
commenting opportunities on draft recovery plans. Every 2 years, FWS and National Marine Fisheries
Service (NMFS) are to report to Congress on the status of recovery planning and implementation efforts.
The resource agencies must set up systems for monitoring the status of recovered and delisted species.
States are encouraged to use Section 6 funds to monitor the status of candidate species, and recovery
expenditures must be reported annually. Congress tried to make recovery plans more useful by requiring
them to identify site-specific management actions to achieve recovery goals, to estimate the time needed
for recovery assuming sufficient funds are available for i~nple~nentation, to estimate costs required for
successful implementation, and to set measurable recovery criteria that enable FWS and NMFS to
evaluate recovery success.
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Beyond the Endangered Species Act
According to FWS (1992), recovery is the process by which the clecline of an endangered or
threatener! species is arrester! or reversed, and threats to its survival are neutralize~i. The goal of the
process is to achieve sufficient self-sustaining wild populations of listec! species to ensure their survival
in nature.
157
FWS aims to (1) identify ecosystems ant! organisms facing the greatest degree of threat, (2)
determine steps necessary to reduce or eliminate the threats, ant! (3) apply the resources available to the
highest priority recovery tasks. Restoration to the point where species can be delistec! is the ultimate
objective, although removal from the list is not a reasonable measure of short-term success (FWS, 1992~.
FWS asserts that a more realistic metric of recovery efforts is the number of species whose decline has
been arrested and the population stabilized.
The recovery process starts with development of a recovery plan. The purpose is to develop
species-specif~c recovery goals; identify needled biological information, including the status of the
species; anti set forth management tasks required to recover the species. FWS maintains that
coordination among fecleral, state, and local agencies; academic researchers; conservation organizations;
private individuals; anti major lane! users might be the most essential ingredient for the development ant!
implementation of an effective recovery program. The agency further states that it emphasizes
cooperation and teamwork among all involved parties.
As clescribe(i in Chapter 4, the resource agencies had approved 411 recovery plans covering 5 13
species as of March 1993 54% ofthe 956 U.S. species listed et that time. The percentage of species
having approved recovery Glans has dronneri somewhat from 1990. when 352 out of 581 listed species
O ~ ~ ~ 1 ~ ~ ~ ~
(61%) were coverer! (FWS, 19901. This is probably attributable to recent accelerated listing actions ant!
agency preoccupation with several manpower-intensive listing and recovery efforts (J. Bartell, FWS,
pers. comma.. Chapter 4 also describes FWS's recovery backlog, which is likely to expand in future
years as the pace of listings increases in response to the recent settlement over Category 1 candidates and
"warranteci but preclucled" species.
Because most recovery plans were prepared before the 1988 amendments were passed, we only
recently are beginning to see the effects of the new requirements. In April 1993,80 species had revised
plans that were intended to comply with the 1988 amendments; another 63 species tract draft first plans or
ciraft revised plans.
FWS broke out the listed species covered in its 1990 (581 species) and 1992i (711 species)
reports to Congress into the following groups:
1990
Improving
Stable
Declining
Extinct
Unknown
57 (9.8%)
181 (31.2%)
219 (37.7%)
11 (1.9%)
113 (19.4%)
1992
69 (9.7%)
201 (2X.3%)
232 (32.6%)
14 (2.0%)
195 (27.4%)
These results are interpreter! differently by various observers even within the environmental
community. Some are encouraged (Irvin, 1993) by the number of species stabilized or improving, while
others lament the lack of recovery plans for many species and the high numbers known to be declining or
whose status is unknown. Critics of the ESA point to the low numbers of clelistings due to successful
recovery an(l the high costs requires! to get there for many others (Desiclerio, 1993~. Only six
species have been clelisted due to successful recovery: the Palau dove, Palau owl, Palau flycatcher, the
The latest information available to the committee.
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Science and the Endangered Species Act
RycIberg milk-vetch, the Atlantic coast population of the brown pelican, and the gray whale. Several
recoveries (or improvements in status) happened because more individuals were found after the species
were listed. For example, the upgrading of the formerly endangered snail Carter of Tennessee (a fish,
Percina tanasi) was largely due to the discovery of acIclitional populations in different rivers from where
it was originally discovered (Etnier ant! Starnes, 19931. In other cases, progress toward recoveries might
have been due at least in part to actions unrelatec! to the ESA, such as the banning of DDT.
Expenditures for recovery have increaser! in recent years, although they are far less than needled
to attain recovery goals for the bulk of listed species (DOI, 1990; Jackson, 1992~. FWS's budget for
recovery programs was $10.4 million in FY 1990 and $39.7 million in FY 1995, although acIditional
funds were available from other state and fecleral agencies. FWS estimates that approximately $177
million was spent for endangered-species conservation programs in 1991 (FWS, 1992), but other funding
approaches or even exceeds that figure: for example, the Bonneville Power Administration (BPA)
estimated that its 1994 expenditures on salmon conservation (inclucling some stocks listed as endangered
under the ESA) in the Columbia River basin amounted to about $350 million, of which about $300
million was clue to lost power revenues (NRC, 19951. The importance of these numbers is not easy to
interpret: the BPA expenditure was 1 % of its 1994 revenues. That portion of the U.S. budget would be
about $ 10 billion per year.
Another concern is that what the FWS means by stable, improving, or cleclining is unclear. This
lack of precision mirrors reservations expressed by Rohif (1991) about the absence of clearly stated
threshoIcts to define differences among threatened, endangered! ant! secure (recovered) species. Although
these categories are qualitative designations, they are not very useful in comparing species trends,
because no measurable criteria are used to define them, as discussed in Chapter S. For example, what
percentage change in population size over what period constitutes a decline or improvement? Within
what range of variation around a midpoint must a population remain to be considered stable? For how
long? If the population size remains constant for several years but it is above or below the numbers
when it was listed, is this consiclered stable or floes it constitute a trend in either direction? It is not
apparent that calling a species stable allows someone to distinguish between species still at critically low
levels and that are be more abundant and less at risk. Chapter ~ offers guidance and encouragement to
the FWS to assign measurable criteria to these groupings in future reports.
The committee concludes that although the ESA has undoubtedly protected some species from
extinction, the overall effectiveness of recovery plans cannot be quantified at this time. In part, this is
because recovery plans can take a long time to work or to fail, especially where long-livecl species are
concerned In acIdition, as mentioned elsewhere, many recovery plans are
implemented only after long clelays, and often not at all.
PROTECTION OF ECOSYSTEMS
Although it is clear that the ESA has resulted in the protection of some ecosystems on which
endangered species depend, our ability to quantify the contribution the FWS and NMFS regulatory
programs make in protecting them is limitecI. Lacking effective metrics, we are left to compare the
relative advantages and disadvantages of species-by-species ~nanagement so common in the listing an(l
recovery programs with more regional ecosystem-oriented efforts. Although the purpose of the act is in
part to protect ecosystems on which threatened and enclangered species (lepen(l, public support and
congressional appropriations are more clearly linked with the neec! to protect individual species having
broaci social or cultural significance (RohIf, 19911. Traclitional approaches sometimes have been
necessitated by the urgent need to save certain species dangerously close to extinction during the early
years of the act's tenure.
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Beyond the Endangered Species Act
159
The historic focus of the FWS ant! NMFS regulatory programs on saving individual species is
acknowleclgecl by the agencies (FWS, 1990~. Listings have occurred mostly on a species-by-species
schedule with some exceptions, including plants from rare communities in Hawaii, Florida, and Puerto
Rico. Recent litigation settlement agreements committing FWS to act on several hundred candidate
species provide that FWS will use a multispecies, ecosyste~n-based approach for listing proposals and
critical habitat designation when biologically appropriate. Also, habitat conservation planning, although
selclom used in practice, has the potential to be effective in protecting ecosystems anti has relaizec! that
potential in a few cases (Chapter 4~.
With recovery protocols for 5 13 species contained in 41 1 plans, about one quarter of approved
plans act cress multiple species. Without reviewing each plan, the committee collie not tell how many of
those preparer! for more than one species try to meet con non ecosystem objectives. Examples of
recovery plans that feature an ecosystem perspective include Ash Meadows (five animals and seven
plants), Maui-Molokai forest bircis (seven species), and California Channel Island species (FWS, 1990~.
Plan development is uncler way for six plants and four animals in the San loaquin Valley of California,
where collaborators are trying to take a landscape view covering several biological community types and
a multitude of competing land uses. On February 23, 1994, FWS released a ciraft recovery plan for
aquatic species in the Snake River. The draft plan included 16 fish taxa anti 42 mollusks (including five
listed snails).
Because listings and recovery plans concentrate on individual species does not mean that the
ecosystems where they play constituent roles are not being protected. Indeed, if it (lid not protect
ecosystems, at least to some degree, the ESA would be less controversial than it is, because that
protection inclucles a prohibition of some economic activities. Perhaps the best-known example is the
limitations on forest harvest to protect the northern spotted owes ecosystem. Even where the ESA has
led to incomplete or even no protection of an ecosystem, it has focused attention on the nature and
biological siginificance of many ecosystems.
Unless the populations are being artificially maintained, recovery success depends on proper
consideration of how the species interacts with surrounding biotic anti physical environmental factors.
Self-sustaining wild populations require sufficient natural habitat, including food, water, shelter,
movement corridors, and the many other features essential for survival and reproduction (Morrison et al.,
1992~. As discussed above, about 4% of listed species have already recoverer! or are close enough to
downlisting or recovery thresholds for the FWS to take acI~ninistrative action. By clef~nition, if the
species are recovered, enough ecosystem-level values must be present to ensure long-term persistence.
The question is whether a broader, more systematic look at the recovery needs of multiple species would
improve the performance of FWS's recovery program.
In adclition to programs under the Enclangerecl Species Act, other fe(leral agencies have lancl-
management authorities and responsibilities, ant} their activities some under Congressional
mandates inclucle land acquisition, wildlife management, ~nanagement of parks and wilderness areas,
protection of wetIancis, and prevention of environmental pollution. These activities also result in
protection of ecosystems; the responsible agencies include tile National Park Service, the Bureau of Lanc!
Management, the Army Corps of Engineers, the Forest Service, the Natural Resources Conservation
Service (formerly the Soil Conservation Service), the Environmental Protection Agency, and the Bureau
of Reclamation.
THE FUTURE: BEYOND THE ENDANGERED SPECIES ACT
The ESA anti other existing programs will not by themselves prevent all future extinctions of
species in the Unitecl States. It appears to the committee that Congress inten(lect the ESA to be a safety
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Science and the Endangered Species Act
net to protect endangered species, ant! the committee concludes that that is its proper role.
However and this is not entirely the fault of the ESA species often will be in serious trouble by the
time they receive ESA protection. The director ofthe Fish and Wicilife Service, Mollie Beattie, holds a
similar view. She said (as quoted by the Jackson Hole News, February 8, 1995~: "The Endangered
Species Act is . . . a law that plays in when local planning and zoning, state fish anti wildlife efforts, the
Clean Water Act, and Clean Air Act haven't worked. It is the emergency room of conservation policy."
If species extinctions are to be prevented, a broader management approach will be neecled to complement
the ESA's protections. A few thoughts on that broader approach-ecosystem management are
appropriate here.
The goal of an ecosystem-based approach to ~nanaging natural resources is to maintain biological
diversity by recognizing the value of protecting an array of biological communities and habitat types
within a larger landscape context (Hunter, 19904. Ecosyste~n-focused programs are probably most useful
when individual elements of biological communities are not in so much trouble that they need narrowly
targeted management efforts.
Using an ecosystem perspectives for endangered species conservation planning offers several
advantages. First, species needs are viewed in the context of surrounding land uses, rather than within
the limits of their currently occupied habitat. Because surrounding land uses and the distribution of
habitat patches among them can strongly influence species welfare (Hunter, 1990), resource managers
can identify future opportunities and constraints.
Seconcl, the complexity of the problems facing ~nanagers who develop and implement strategies
for conservation of endangered species requires new concepts (LaRoe, 1993~. The expecter! rapid pace
of new listings coupled with funcling limitations places a premium on approaches that address the needs
of different species simultaneously. Recently developed tools, such as advances in remote sensing,
population-viability-analysis models, ciecision-analysis methods (see Chapter S), and geographic
information systems increase our ability to analyze complex problems involving interactions among
diverse influences and the implications of various possible solutions. Gap analysis (Scott et al., 1987)
can provide a process to identify areas of high biological diversity or those containing several protected!
species with overlapping ranges. It can also be used to develop a coarse overview of resource status and
land uses across political boundaries. Additional management approaches related to ecosystem
management show promise Thev include the fc~llc~wing:
· Reconstruction or rehabilitation of ecosystems. Restoration ecology is a growing discipline.
Many ecosystems functions have been improved or restored by such activities, and reconstruction or
rehabilitation of ecosystem functioning holds much promise for the protection of endangered species. It
is not usually possible to return an ecosystem to some prior pristine condition, however. Many
ecosystems have been so altered! that it is difficult to decide what prior condition we might want to return
to. The trajectory taken by the ecosystem to get to its current condition is not retraceable in the way that
a highway is, because many events occur in an ecosystem's history that are not precisely reversible.
Genetic variability is lost; evolution occurs; exotic species are introduced; human populations in the
region increase, and people develop dependence on a variety of modern technologies, cultures, and
economic systems; and other natural and anthropogenic environmental changes affect the range of
biophysical ant! socioeconomic possibilities for future states of the system. In brief, the past provides
opportunities for the future but also constrains it. Thus, attempts to rehabilitate ecosystem functioning
should keep these constraints in mind, so that inappropriately high expectations are not generated.
~ Mixed management plans. Oidren, resource managers manage areas either for protection of
2 See discussion of ecosystem management in Chapter 9.
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Beyond the Endangered Species Act
biota or for human use. It is increasingly difficult to keep people and the effects of their activities
separate from wildlife sanctuaries. Although such sanctuaries (e.g., national parks, wilderness areas,
wildlife refuges, marine sanctuaries) are indispensable for protecting endangereci species, greater
attention needs to be paid to cieveloping mixecI-use areas. These would be urban recreation areas or
resiclential and commercial clevelopments adjacent to untra~nmeleci areas clesignec! to improve
opportunities for wilcIlife while maintaining opportunities for human activities. Although the value of
this approach is becoming increasingly recognized, its development is still in the early stages.
· (cooperative management. various experiences with cooperative management the sharing
of planning ant! decision making by various government and nongovernment groups have had some
success. To some clearee. habitat conservation glans represent an example of this approach. but it is
~. ~_ _ , .
_ ~ · ~ r · · · ~1 ~ ~
161
(A ~ 1 ~ ~ At. ,& ~
likely that cooperative management will be necessary in cases where the strict requirements of the
Enciangerect Species Act have not yet been applied. It is important to inclucie the major interested parties
without having so many interests involved that consensus is clifficult to reach.
· Reviser! economic accounting. Too often, economic calculations underlying public and
private decision making are incomplete. Often, they cover too short a time span, and they often exclucle
nonmarket values. A short-term loss might turn into a long-term gain: for example, losing an economic
activity today might provide opportunities for greater economic activities of different types at some time
in the future. Again, the valiclity of expanding economic accounting to cover longer periods and to
inclucle nonmarket values is becoming more widely recognized but it is still in the early stages of
development.
SCIENCE, POLICY, AND THE ESA
This committee was asked to review the scientific aspects of the ESA ant! it has done so. It has
not uncovered any major scientific issue that seriously hinders the implementation of the act, although its
review has suggested several scientific improvements. Many of the conflicts and disagreements about
the ESA do not appear to be based on scientific issues. Instead, they appear to result because the act in
the committee's opinion designed as a safety net or act of last resort is called into play when other
policies and management strategies or their failures, or human activities in general, have led to the
endangerment of species and populations. In some cases, policies anti programs have been based on
sound science, but other factors have prevented them from working. The committee lions not see any
likelihood! that those endangerments will soon cease to occur or that the ESA can or shouic! be expected
to prevent them from occurring. It therefore concludes that any coherent, successful program to prevent
species endangerments and to protect the nation's biological diversity is going to require more
enlightened commitments on the part of all major parties to achieve success.
To conserve natural habitats, approaches must be developed that rely on cooperation and
innovative procedures; examples provided for by the ESA are habitat conservation plans anti natural
community consecration planning. But those are only a beginning. Many other approaches have been
discusser! in various fore. They include cooperative management (sharing decision-making authority
among several governmental an(l nongovernmental groups), transfer of development credits, mitigation
banks, tax incentives, and conservation easements.
An analysis of these and other policy and management options is beyond this committee's
charge, but sound science alone will not lead to successful prevention of many species extinctions,
conservation of biological diversity, and reducer! economic and social uncertainty and disruption. But
sound science is an essential starting point. Combined with innovative and workable policies, it can help
to solve these and related problems.
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Science and the Endangered Species Act
REFERENCES
CEQ (Council on Environmental Quality). 1990. 21st Annual Report. U. S. Government Printing
Office, Washington, D.C.
Clark, T. W. ant! A. H. Harvey. 1988. Implementing Endangered Species Recovery Policy: Learning as
We Go. Endangered Species Aviate 5: 35-42.
Culbert, R. and R. B. Blair. 1989. Recovery Planning and Endangereci Species. Enciangered Species
Update 6: 2-8.
Desiderio, M. 1993. The ESA: Facing Hard Truths and Advocating Responsible Reform. Natural
Resources anti Environment 8: 37, 41-42.
DOI (United States Department of the Interior) Office of the Inspector General. 1990. Audit Report:
The Endangered Species Program, U.S. Fish en c! Wildlife Service. Washington, D.C.
Etnier, D. A., and W. C. Starnes. 1993. The Fishes of Tennessee. University of Tennessee Press,
Knoxville.
Fitzgerald, J. and G. M. Meese. 1986. Saving Endangered Species, Amending the Implementing the
Endangered Species Act. Defenclers of Wildlife, Washington, D. C.36 pp.
FWS (Fish and Wildlife Service). 1990. Report to Congress, Enciangerect ant! Threatened Species
Recovery Program. U. S. Government Printing Office.
FWS (Fish ant! Wildlife Service). 1992. Report to Congress, Endangered and Threatened Species
Recovery Program. U. S. Government Printing Office.
GAO (General Accounting Office). 1988. Endangered Species Management Improvements Could
Enhance Recovery Programs. U. S. General Accounting Office, Washington, D.C.
GAO (General Accounting Office). 1994. National WilcIlife Refuge System: Contributions Being Macle
to Endangerec! Species Recovery. U. S. General Accounting Office, Washington, D.C.
Hunter, M. L. 1990. Wildlife, Forests, and Forestry, Principles of Managing Forests for Biological
Diversity. Regents/Prentice Hall, Englewood Cliffs, New Jersey. 370 pp.
Irvin, W. R. 1993. The Endangered! Species Act: Keeping Every Cog ant! Wheel. Natural Resources and
Environment 8: 36,38-40, 76.
Jackson, T. C. 1992. All creatures great ant! small. Legal Tines (December 7, 1992~:20-23.
LaRoe, E. T. III. 1993. Implementation of an Ecosystem Approach to Enclangere(i Species
Conservation. Endangered Species Update 10: 3-6.
Morrison, M. L., B. G. Marcot and R. W. Mannan. 1992. Wildlife-Habitat Relationships, Concepts and
Applications. University of Wisconsin Press, Madison, Wisconsin. 343 pp.
NRC (National Research Council). 1995. Upstream: Salmon and Society in the Pacific Northwest.
National Acaclemy Press, Washington, DC.
RohIf, D. I. 1991. Six Biological Reasons Why the Endangerec] Species Act Doesn't Work - And What
to Do About It. Conservation Biology 5: 273-282.
Scott, J. M. B. Csuti, J. D. Jacobi and J. E. Estes. 1987. Species Richness. Bioscience 39: 782-788.
Snyder, N. F. R., J. W. Wiley, and C. B. Kepler. 1987. The Parrots of Luquillo: Natural History and
Conservation of the Puerto Rican Parrot. Western Foundation of Vertebrate Zoology, Los
Angeies, CA.384 pp.
Taylor, R. Jr 1993. Biological Uncertainty in the Endangered Species Act. Natural Resources and
Environment 8: 6-9, 58-59.
Taylor, S. 1993. Practical Ecosystem Manage~ner~t for Plants and Animals. Endangered Species Update
10: 26-29.
Representative terms from entire chapter:
species act
