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CONSERVATION CONFLICTS BETWEEN SPECIES 111
6
Conservation Conflicts Between Species
Plants and animals are linked to other organisms in ecosystems in a variety of ways, so it is inevitable that
conflicts will arise when attempts are made to protect individual species of plants or animals. Part of the charge
presented to the Committee on Scientific Issues in the Endangered Species Act was to consider the severity of
conflicting conservation needs when more than one species is listed1 in the same geographical area and provide
recommendations for resolving these conflicts.
INTERACTIONS OF SPECIES IN NATURE
To evaluate the potential problem of conservation conflicts between listed species, two fundamental
ecological principles must be considered. The first principle is that organisms are components of networks in
which they interact. This principle has significant implications in planning for survival and recovery of
endangered species. If a management strategy does not account for the important relationships and interactions
embodied in networks, then unexpected or untoward results can be expected (Holt and Talbot, 1978; Walker,
1989; Pickett et al. 1992; Fiedler et al., 1993; Franklin, 1993; Orians, 1993). For example, management of the
New Jersey Pine
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1Not all the species discussed in this chapter are listed under the ESA, but the cases illustrate the kinds of conservation
conflicts that could occur between listed species.
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CONSERVATION CONFLICTS BETWEEN SPECIES 112
Lands without consideration of certain rare herbs in the successions of pitch pine lowland or Atlantic white cedar
swamp communities results in the decline in density of herb populations and their extirpation from many sites
(Little, 1977; 1979). Likewise, managing Pennsylvania forests for high densities of white-tailed deer to support
sporting interests inhibits tree regeneration in some stands and eliminates many shrub and herb species from the
understory of the majority of forest stands (Marquis et al., 1975), although if hunting were prohibited, the
problem would get worse.
Management or planning for recovery of endangered species in ignorance of the networks in which they
exist is scientifically untenable. In situations where two or more endangered species are present, taking account
of any network that includes them both (or all) should enhance the chances of optimizing the persistence and
recovery of all species.
The second fundamental principle of ecology that is relevant to potential conflicts among listed species is
that species are parts of spatial and temporal mosaics. The spatial dimension is cast in terms of mosaics because
both natural and human-modified landscapes are conspicuously patchy (Pickett and White, 1985; Kolasa and
Pickett, 1991; McDonnell and Pickett, 1993). This principle implies that the networks of interaction in which
species exist have a spatial component.
The important ecological characteristics of mosaics for conservation of endangered species are that the
resources, interactions, and constraints of endangered species can originate in the mosaic in components other
than the current location of the listed entity (Risser, 1985). Although it is difficult to learn about the important
ecological fluxes between patches that affect listed species, neglecting such fluxes can result in failures to
preserve targeted species (Saunders et al., 1991; Tyser and Whorley, 1992).
Taken together, the two fundamental principles described above suggest improvement in endangered
species management. Management that views each species as an entity by itself, with no or little attention to the
network of interactions, is likely to produce faulty protection strategies. Likewise, neglecting the larger spatial
context in which species exist may well miss key forces that are needed to maintain the species. Taking these
two principles into account in planning for management of listed species can provide a basis for assessing the
potential for species conflicts and mitigating them effectively. Without considering networks and spatial
contexts, species conflicts are relegated to ad hoc solutions on a crisis footing.
The committee has found few well-documented cases in which management practices focusing on
particular species protected under the Endangered Species Act have resulted in direct conflict between
conservation needs for the species. Such situations likely will increase, however, as more species are listed and
as species and their networks become better understood. A sample of a few specific cases demonstrates how
manage
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CONSERVATION CONFLICTS BETWEEN SPECIES 113
ment practices directed solely at single species might present such problems.
NORTHERN GOSHAWK AND MEXICAN SPOTTED OWL
Potential conflicts arise between the northern goshawk and the Mexican spotted owl, two species of avian
predators, when the U.S. Forest Service attempts to manage habitat for one or the other in areas where both
species occur. In the case of the Mexican spotted owl, current management favors comparatively large, dense
stands of closed canopy forest. However, guidelines for the northern goshawk require a much more varied forest
condition, with major areas of low stand density, open canopies, and numerous forest openings. In addition, the
Fish and Wildlife Service postulates that with more openings in the forest (i.e., forest fragmentation), the
Mexican spotted owl will be increasingly susceptible to avian predation (Fed. Reg. 58:14269). Thus, such habitat
manipulation might increase direct loss to the listed species through predation by the northern goshawk (see Box
6-1).
WINTER-RUN CHINOOK SALMON AND DELTA SMELT
Another example involves the endangered winter-run chinook salmon and the threatened delta smelt, two
species of fish that occur where the Sacramento and San Joaquin rivers meet in the Central Valley region of
California (see Box 6-2). The 1992 Central Valley Improvement Act (Title 34 of P. L. 102-575) contains a series
of provisions that dictate water use and contracting for the Central Valley Project, as well as mitigation and
restoration activities that will benefit the threatened fish species in the area. Revenues from water users and other
direct beneficiaries of the water project are to pay for the restoration costs.
Some of the provisions call for measures that will benefit both the winter-run salmon and the delta smelt.
For example, Provision 4 calls for the improvement of screens and fish-recovery facilities at the Tracy pumping
plant. Benefits to the delta smelt will accrue because of reduced entrainment (destruction of fish or larvae at the
intake mechanisms of diversion facilities such as those in the delta (Fed. Reg. 59:816)). These measures will also
protect the stronger-swimming salmon. Likewise, Provision 7 states that the Central Valley Project must comply
with all applicable flow standards that apply to it, including any new regulations that might be imposed. Such
regulations should benefit both species. Furthermore, the recent federal listing of water-quality standards for the
Sacramento and San Joaquin rivers, the San Francisco Bay, and the delta region (Fed. Reg. 59:810-852) and the
recent critical habitat listing for the delta smelt (Fed.
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CONSERVATION CONFLICTS BETWEEN SPECIES 114
Reg. 59:852-861) attempt to restore the important areas of the drainage system to historic salinity levels.
BOX 6-1 NORTHERN GOSHAWK AND MEXICAN SPOTTED OWL
The northern goshawk, the largest member of the genus Accipiter, is a forest habitat generalist that
uses a variety of forest types, forest ages, structural conditions, and successional stages (Reynolds et al.,
1992). The northern goshawk listed as a ''sensitive species" by the Southwest Region of the Forest Service
because of concerns that its populations and reproduction may be declining in this region due in part to
forest changes caused by historic timber harvest patterns.
In response to concern for this species, the Forest Service has developed and adopted a set of
management recommendations for the northern goshawk in the southwestern United States (Reynolds et
al., 1992). However, rather than focusing solely on the goshawk, these recommendations are designed to
provide habitat for many of the goshawk's prey species, such as the American robin (Turdus migratorius),
band-tailed pigeon (Columba fasiata), mourning dove (Zenaida macroura), blue grouse (Dendragapus
obscurus, hairy woodpecker Picoides villosus), northern flicker Colaptes auratus), red-naped sapsucker
(Sphyrapicus nuchalis ), Williamson's sapsucker (Sphyrapicus thyroideus), Steller's Jay (Cyanocitta
stelleri), chipmunks (Tamias spp.), golden-mantled ground squirrel (Citellus lateralis), red squirrel
(Tamiasciurus hudsonicus ), tassel-eared squirrel (Sciurus aberti), and cottontails (Syvilagus spp.).
Management for these species will result in a quite varied forest condition, with openings and low density
forest occurring fairly commonly.
The Mexican spotted owl (Strix occientalis lucida) was listed as a threatened species on March 16,
1993 (Fed. Reg. 58:14248-14271). This medium-sized owl is found in central Colorado and Utah south
through Arizona, New Mexico, and western Texas, primarily in canyons and areas with steep slopes. It is
believed to be threatened owing to loss and modification of its forest habitat due to timber harvest and fire
and increased predation due to habitat fragmentation. When found in forested habitats, the Mexican
spotted owl is believed to prefer areas wit high canopy closure, high stand density, and a multilayered
canopy for its nesting, roosting and foraging sites (Ganey et al., 1988; Ganey and Balda, 1989; Fletcher,
1990). Great horned owls ( Bubo virginianus) and red-tailed hawks (Buteo jamaicensis) have been
identified as possible predators, and goshawks as probable predators, of the Mexican spotted owl (Skaggs,
1990).
In one case, however, a provision of the Central Valley Improvement Act might benefit one of the
threatened species and have an adverse effect on the other. Provision 14 calls for modification of the flow and
control structures at the Delta Cross Channel; it is primarily for the benefit of striped bass, a popular nonnative
sport fish. This provision might benefit the winter-run salmon, because it will reduce the amount of water entering
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CONSERVATION CONFLICTS BETWEEN SPECIES 115
BOX 6-2 CHINOOK SALMON AND DELTA SMELT
Four races of chinook salmon (Oncorhynchus tshawytscha) inhabit the Sacramento River system. The
winter-run race migrates upstream in the winter. Although it was previously abundant in this drainage
system, population sizes have declined drastically, from an estimated 117,808 individuals in 1969 to 341 in
1992/93 (FWS, 1992). This race is now listed as endangered on the Federal Endangered Species List
(Fed. Reg. 59:13836). Adults migrate as far up the Sacramento River as possible in the winter, with
spawning as early as mid-April, reaching a peak in June, and then declining through the summer until
August. Eggs are incubated for 40-60 days followed by an additional 2-4 weeks for the newly hatched fry
on gravel substrate. Incubation must occur in cool water temperatures (43-58°F), although incubation
occurs during the hottest time of the year. Migration of the juveniles begins after a short period of growth,
with juveniles migrating to the lower river up to a year after the beginning of spawning of their cohort.
The delta smelt (Hypomesus transpacificus) is endemic to the Sacramento-San Joaquin River estuary.
The entire species is listed as threatened on the Federal Endangered Species List (Fed. Reg. 58:12863).
Compared with salmon, the smelt has a short life span. Spawning occurs primarily from December to
March. Eggs hatch 10-12 days after fertilization into larvae that drift downstream with the river current. By
one year of age the fish are sexually mature, with mating of a cohort continuing into the summer of the year
after hatching. Although the biology of this species is not known in detail, it appears that adults die soon
after spawning. The delta smelt is associated with well-oxygenated, very cold water. It also appears that
hard substrates and submerged rocks are needed for successful spawning
Two major water projects, the Central Valley Project (CVP) and the State Water Project (SWP), and
many smaller diversions affect these species both in the Sacramento-San Joaquin delta and the
Sacramento River (for the winter-run chinook salmon). These water diversions can entrain fish along the
diverted flows as well as reduce flows downstream. Flow diversions and impoundment storage behind
dams can greatly alter flows, flow pattern, and seasonality. Flows also affect movement of fish, particularly
larvae of delta smelt and striped bass. In addition, flows play a major role in the location of highly
productive areas for phytoplankton and zooplankton. An "entrapment" or "null" zone that provides important
nursery habitat for delta smelt and striped bass is typically formed in Suisun Bay downstream of the delta.
During drought years, this zone occurs in the channel of the delta much closer to the CVP and SWP water
intakes than in normal years. During such periods, entrainment is expected to be increased. In addition,
production of prey organisms is expected to decrease because of the smaller size of the delta channels.
An additional problem associated with the major water projects is increased predation by fish-eating
predators, including adult striped bass, which use features of the major intakes to prey on smaller fish.
Such predation is considered to be one of the major sources of loss associated with the SWP.
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CONSERVATION CONFLICTS BETWEEN SPECIES 116
the central delta while increasing the San Joaquin and Mokelumne rivers flows to the pumps. Delta smelt
will be adversely affected, however, because they will be in these waters at the times of reduced flows, and
entrainment at the Tracy pumping plant might increase. Moreover, striped bass are probably predators of the
smelt, so this action could result in increased mortality of the smelt. Another provision, Provision 18, advocates
restoration of the striped bass fishery, which would also have an adverse effect on the delta smelt due to
increased predation (see Box 6-2).
It is apparent that the Central Valley Improvement Act attempts to correct many problems that the Central
Valley Project causes for threatened and endangered fish and that, in some cases, actions will benefit all of the
species involved. However, in some situations, management techniques that are most beneficial to one
threatened species adversely affect the other. In this system, the situation is complicated by the presence of a
third species, striped bass, that is being considered because of public interest. Tradeoffs will have to be evaluated
in each case to determine what measures should be implemented. For example, additional flow releases without
additional pumping after delta smelt spawning could benefit that species by carrying eggs and larvae past the
pumps to Suisun Bay where the best rearing habitats occur during normal flow years.
Other actions affecting these species include the water-quality standards set by the U.S. Environmental
Protection Agency to protect the delta. Those standards (Fed. Reg. 59:810-852) will result in increased flows and
decreased pumpings, which should help normalize salt levels and provide larger quantities of water to facilitate
migration conditions and rearing. In addition, the State Water Resource Control Board is under federal court
mandate to impose standards and regulations as well. Such judicial and regulatory actions have resulted in
pumping restrictions at the State Water Project and Central Valley Project to reduce losses of winter-run salmon
and delta smelt. Nevertheless, it is unclear whether these actions will be able to help both species, or if one will
still suffer at the expense of the other.
BACHMAN'S SPARROW AND RED-COCKADED WOODPECKER
Management decisions designed to improve conditions for a threatened or endangered species may
inadvertently affect dozens of nontarget species found in the same habitats. Possible effects on nontarget species
are rarely assessed before implementation of management actions. It will become increasingly important to
develop tools to assess the effect of proposed management strategies on a wide variety of organisms as federal
agencies and others put increased emphasis on management for biodiversity.
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CONSERVATION CONFLICTS BETWEEN SPECIES 117
Several research groups are developing population simulation models linked to Geographical Information
System (GIS) maps that capture some of the complexity of real-world landscapes and allow simultaneous
consideration of the responses of many different species to management proposals. This approach requires, at a
minimum, a good understanding of the habitat requirements of the species of interest, and a realistic landscape
map that shows the locations of current and future suitable habitat as a function of management decisions. More
recent versions of these models also require detailed information on habitat-specific demography and dispersal
behavior.
Liu (1992) and Liu et al. (1995) give one example of the use of such models to forecast how management
plans largely designed for one endangered species might affect a nontarget species. Liu et al. (1995) used a
mobile animal populations model (Pulliam et al., 1992) (Chapter 5) to determine how the Bachman's sparrow
(Aimophila aestivalis), a declining species of management interest in the southeastern United States, might
respond to a management strategy largely designed to favor populations of the endangered red-cockaded
woodpecker (Picoides borealis) (see Box 6-3).
The results of such models are useful in a variety of ways. In the particular case discussed, the model
allowed alternative cutting and thinning plans to be explored, at least some of which allowed larger populations
of sparrows, as well as woodpeckers, to be maintained. Models of this sort can also incorporate economic
considerations (Angelstam, 1992; Liu et al., 1994) and might prove useful in future attempts to balance
ecological and economic goals. However, caution must be exercised in using models of this sort for management
decisions, because the models are not yet fully quantified or tested against field results. A prudent use of such
models would be in the context of adaptive ecosystem management. Here, the models would be used to generate
testable hypotheses, and forest-management practices would be used as an experiment to test the model
predictions.
MARINE MAMMALS AND SALMONIDS
The effect of predation by marine mammals on salmonids has been controversial since at least the 19th
century (Merriam, 1901). In 1899, the president of the California Board of Fish Commissioners proposed to kill
"10,000 of the 30,000 [California sea lions, Zalophus californianus, and Steller's sea lions, Eumatopias stelleri]
that now infest our harbor entrances and contiguous territories" to reduce their alleged depredations on salmon.
Merriam pointed out that there probably weren't even 10,000 sea lions on the coast. He described the work of
L.L. Dyche, who examined the stom
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CONSERVATION CONFLICTS BETWEEN SPECIES 118
achs of 25 sea lions and found mainly octopus and squid, but no fish, and he argued against killing sea lions.
Bonnot (1928) described the killing of sea lions in great detail; they were hunted in Oregon for bounties, in
California for their penises and testicles (known as "trimmings") and for various other purposes along the coasts,
including to prevent them from eating fish. Adult sea lions were killed with guns and landmines, and pups by
drowning them in weighted sacks (Bonnot, 1928).
BOX 6-3 BACHMAN'S SPARROW AND RED-COCKADED WOODPECKER
Although formerly much more widespread, Bachman's sparrow populations have disappeared from
much of the historic range and are now restricted mostly to the southeastern coastal plain, where they can
be found both in mature pine forest and in some early successional habitats. The species is found in
habitats with a dense ground cover of grasses and forbs aid relatively open understory with few shrubs
(Dunning and Watts, 1990) Mature pine forests (over 80 years old) managed for the red-cockaded
woodpecker usually provide adequate habitat for Bachman's sparrow, particularly if the understory is
burned periodically. The species is also relatively common in the young (15 years old) successional pine
stands that follow clearcutting. Intermediate-age pine stands (approximately 6-80 years old) are not suitable
for Bachman's sparrow, presumably because the relatively closed canopy prevents a dense ground layer
vegetation from forming.
Liu et al. (1994) developed a MAP model to study Bachman's sparrow responses to current and
proposed forest management plans on the Savannah River Site (SRS), a large region of pine forest in
South Carolina managed by the U.S. Forest Service for timber production and wildlife conservation. The
Forest Service has developed a 50-year operations plan for the SRS that considers the habitat
requirements of over 42 plant and animal species of management concern. However, most of the specific
management practices described in the operation plan are aimed at improving habitat for the endangered
red-cockaded woodpecker. Using the operation plan, Liu and coworkers projected future habitat conditions
at SRS to determine how the proposed management practices would impact the Bachman's sparrow, a
species that is not a target of most of the specified management strategies. According to these
researchers, the forest-management practices proposed in the operation plan would have a strong effect
on the Bachman's sparrow. The model simulations suggested that, in the long run, the sparrow would
benefit from the changes because, under the plan, the acreage of mature pine forest of the sort suitable for
the red-cockaded woodpecker and Bachman's sparrow would increase substantially. However, the
simulations suggest that the sparrow might decline precipitously during the first few decades of operation of
the plan because of decline in the availability of early successional habitat.
Fish predation by sea lions has received attention again recently, largely because of its high visibility in one
location: the Hiram M. Chittenden locks in Ballard (a section of Seattle). The Chittenden (or Ballard) locks
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CONSERVATION CONFLICTS BETWEEN SPECIES 119
were completed in 1917 as part of a project of the U.S. Army Corps of Engineers to allow ship traffic between
Puget Sound and Lake Washington (Willingham, 1992). Previously, the lake had drained through the Black
River, which flowed into the Cedar and Green rivers and then into Puget Sound. The current drainage into Puget
Sound is through the Lake Washington Ship Canal, Lake Union, and the Ballard locks. Steelhead trout
(Oncorhynchus mykiss) migrated through Lake Washington to spawn in its tributaries before 1917; they do so
today. The runs consist of wild and hatchery fish, but the hatchery program has been discontinued recently
(Fraker, 1994). Although some people believed the current runs were derived from hatchery fish, genetic
analysis indicates that they are probably descendants of the original wild runs (Fraker, 1994).
Lake Washington steelhead are winter-run fish, returning to the fresh water to spawn from December to
April. As the fish enter the ship canal below the locks, some of them are captured and eaten by California sea
lions. The first observation of such predation was made in 1980; by the mid-1980s there were as many as 60 sea
lions in the area around the locks and more than 50% of the returning steelhead were being eaten. (Between 51%
and 65% were taken each year up to 1992, except for 1985-1986 (15%) and 1986-1987 (41%), when predator-
control efforts had some success.) The number of fish in the run that escaped to spawn, which ranged from 474
to 2,575 fish from 1980-1981 to 1985-1986, declined to 184 fish in 1992-1993 (Fraker, 1994) and to 70 in
1993-1994 (NMFS and WDFW, 1995).
It is clear that sea lions have affected the Lake Washington steelhead run, but they are not entirely
responsible for its recent decline. Cooper and Johnson (1992) found that steelhead had declined generally since
1985. They considered the following items to be possible contributing factors: competition for food with other
salmon, in particular, 8 billion hatchery salmon released since the late 1980s; authorized and unauthorized drift-
net fisheries (probably not currently a factor); predation by birds and mammals; and large-scale environmental
changes.
Predation by marine mammals is probably not a major factor in the current decline of salmon in general.
Anadromous salmonids and marine mammals coexisted for thousands of years before the current declines in
salmonids, and California and Steller sea lions were much more abundant in the first half of the 19th century—a
time when salmon were also abundant—than later. And marine mammals do not normally specialize on
salmonids; they eat a wide variety of prey items, determined by what is available and how easy it is to catch
(Gearin et al., 1988; Fraker, 1994; Olesiuk, 1993). Finally, the Ballard locks area provides a local concentration
of fish in space and time, and they have few refuges there, and sea lions congregate there in large numbers
(Fraker, 1994).
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CONSERVATION CONFLICTS BETWEEN SPECIES 120
However, many marine-mammal populations are increasing, at least partly because of the protections of the
Marine Mammal Protection Act (MMPA). California sea lions now number more than 100,000 (Fraker, 1994).
Other human activities, combined with increasing marine-mammal populations, could cause increasing
problems, especially in areas where the fish congregate, as in the case of the steelhead at Ballard. If the Lake
Washington steelhead were listed as endangered or threatened under the Endangered Species Act, the conflict
would be brought into sharper focus by the requirements of the Endangered Species Act and the MMPA. Indeed,
the MMPA was amended in 1994 to allow the killing of marine mammals under particular circumstances, and
Washington state has filed a petition to remove sea lions from the Ballard locks and kill them if all other methods
to keep them from eating steelhead fail (NMFS and WDFW, 1995).
CONCLUSIONS
We have been able to document only these and a few other cases of conflicting conservation needs resulting
from management plans targeted toward individual species. It is possible that this low number stems from
several factors: lack of knowledge of the networks of which threatened and endangered species are part; the fact
that comparatively few species are currently listed and that recovery plans for even fewer have been formulated;
and the inadvertent protection for other listed species under some current recovery plans. We expect, however,
that the potential for such conflicts will rise as ecologies of listed species become better known, more recovery
plans are formulated, and habitat for conserving endangered species becomes more constricted.
The greatest potential for conflicts in protecting species and for management of individual species under
current policies will arise in situations in which habitat reductions—especially extreme reductions—themselves
are the causes of endangerment and the habitats of listed species are largely overlapping. Resolution of such
conflicts will have to be made on a case by case basis. A process should be devised that will facilitate such
resolutions using analyses of risk and recovery as outlined in Chapter 8.
The most effective way to avoid conflicts resulting from individual management plans is to maintain large
enough protected areas for listed species to allow the existence of mosaics of habitats and dynamic processes of
change within these areas. In addition to and as part of this strategy, multispecies plans should be devised that
ensure the maintenance of habitat mosaics and ecological networks. Habitat (in the broadest sense) thus plays a
crucial role in protecting individual target species and, ultimately, in reducing the need for listing additional
species.
The Fish and Wildlife Service has prepared a number of packages list
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CONSERVATION CONFLICTS BETWEEN SPECIES 121
ing multiple species in the same ecosystems, and it has agreed in a recent judicial settlement "to direct each
region, where biologically appropriate, to use a multi-species, ecosystem approach to their listing responsibilities
under the ESA" (settlement agreement, The Fund for Animals v. Lujan, Civ. No. 92-800, December 15, 1992).
This is an important directive whose implementation and oversight warrant priority. Key questions should be
addressed as the initiative moves forward: Are listing resources best deployed to advance the policy? To what
degree have staff and consulting resources been arranged to optimize cooperative work across taxa? To what
extent have the FWS and National Marine Fisheries Service made a special effort to identify widespread species
presenting great potential for conflict, but also for conflict resolution? Finally, should the National Biological
Service (NBS) be an important vehicle for ensuring that these questions can be answered in the affirmative?
RECOMMENDATIONS
Because of the interactions of plants and animals with other organisms in their environments, the most
effective way to avoid conflicts resulting from individual management plans of co-occurring endangered species
is to maintain large enough protected areas for listed species to ensure the presence of habitat mosaics and to
allow for the dynamic processes of change that will inevitably occur within such areas. As part of this strategy,
multispecies plans (e.g., habitat conservation plans; see Chapter 4) should be devised that ensure habitat mosaics
and ecological networks are maintained.
When the available habitat is insufficient to avoid conflicts, the analysis of options will have to be done
separately for each situation. In most cases, long-term results are more important than short-term ones. In the
example of Bachman's sparrow and the red-cockaded woodpecker (Box 6-3), both birds would benefit in the
long term under the Forest Service's plan, despite short-term declines in the sparrow's population. Other
considerations would be whic126h species is most likely to suffer irreversible harm if its needs are not fully
addressed, the taxonomic level of the populations involved (e.g., a full species is probably more important than a
distinct population segment), and ecological considerations (e.g., would the loss of one species have a greater
effect on the ecosystem than the loss of the other?).
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