Development of a regional framework for
fish and wildlife restoration in the Columbia River Basin
A PROPOSED SCIENTIFIC FOUNDATION
FOR THE RESTORATION OF FISH AND WILDLIFE
IN THE COLUMBIA RIVER BASIN
document 98-16 | July 7, 1998
The role of the scientific foundation
The scientific foundation provides a broad, scientific basis for
developing and evaluating fish and wildlife recovery strategies. In this
sense, the foundation represents the kind of conceptual foundation called
for by the Independent Scientific Group in their report, Return to the
River. By stating an explicit conceptual foundation, there is a clear
basis for decisions and a scientific starting point for future
investigation.
The scientific foundation draws from three major scientific reports on
the Columbia River and its fish and wildlife: the Independent Scientific
Group's Return to the River, the National Research Council's Upstream:
Salmon and Society in the Pacific Northwest, and the scientific reports of
the Interior Columbia Basin Ecosystem Management Project (ICBEMP) . The
scientific principles proposed here also draw from the technical aspects
of the Multi-Year Implementation Plan prepared by the regional Fish and
Wildlife Managers and Wy-Kan-Ush-Mi-Wa-Kush-Wit: The Spirit of the Salmon,
prepared by the Columbia River Treaty Indian Tribes. The scientific
foundation distills from these and other sources a set of general
principles about ecosystems, and then discusses important ecological
patterns and interactions in the Columbia River Basin.
The scientific foundation described here has two major parts. Part I
provides the scientific principles--a set of broad, scientifically based
statements concerning the relationship between organisms, including
humans, and their ecosystems. These provide an explicit set of general
principles to guide development of specific strategies and actions. In
Part II of the scientific foundation, these principles are applied to a
description of the Columbia River as an ecosystem. This description also
draws heavily from the previously mentioned scientific reports and other
sources. As the framework process moves forward, it is intended that Part
II will continue to be developed. A third part of the scientific
foundation, a set of analytical tools based on Parts I and II, remain to
be developed. It is hoped that these can be derived largely from existing
analytical tools.
The scientific foundation does not represent a series of political
judgments, nor does it dictate the course of fish and wildlife recovery in
the Columbia River Basin. Policy makers set policies and goals, determine
the nature of recovery programs and how to finance them. The foundation
informs these judgments, however, by depicting the scientific principles
and ecological setting for recovery efforts. Rather than being the result
of political debate, the principles reflect the weight of scientific
evidence encompassed in the three reports. Thus, the foundation is
developed through scientific synthesis and peer review.
The scientific foundation directly addresses how we use many of the
conventional tools of fish and wildlife management. For example, the
principles could apply to the use of transportation or artificial
production of salmon and other fish species. Principles such as the
relationship between fish and their ecosystems (Principle 1), the role of
biological diversity (Principle 5) and the use of technology in ecosystem
management (Principle 8) could help the region determine roles for these
techniques and describe procedures for how they should be used.
Part I. The Scientific Principles
This section describes scientific principles organized around the
following questions: 1) What is the relationship between species of
interest and their ecosystems?, 2) What characteristics of ecosystems
affect management programs?, 3) How do we define the ecosystem?, 4) How do
fish and wildlife accommodate environmental variation?, 5) How do
ecosystem conditions develop?, and 6) How does the nature of ecosystems
affect natural resource management?
Principle 1: The abundance and productivity of fish and wildlife
species reflect the conditions of their ecosystems.
Discussion: Intuitively, we can appreciate the relationship between
plants, animals and their environment. Farmers know that the health and
productivity of their crops and livestock reflect the quality of the soil,
water, weather and other conditions. In like manner, the health and
productivity of species in natural ecosystems reflect the conditions they
encounter over the course of their life cycle. The characteristics of
plants and animals are closely tuned to the physical and biological
conditions of their environment and the variation in these conditions over
time and space. Life histories, physical characteristics and diversity of
individual species are shaped by physical and biological interactions.
Farmers try to maintain optimal conditions for a select group of species
through their entire life. However, in natural ecosystems, these
conditions develop and are maintained by processes related to geology,
hydrology and natural selection.
Because of this close relationship between species and their
ecosystems, goals for individual species, such as salmon, resident fish or
wildlife, are achieved by allowing the ecosystem to develop in a manner
consistent with the biological needs of the target species. Change in the
ecosystem, either natural or human-induced, will affect the abundance and
viability of fish and wildlife species. Sustainability, harvest,
mitigation or other goals require management of human impacts to achieve,
maintain or restore ecological functions. Ecosystem management means
management of human impacts to allow the ecosystem to develop
characteristics that are consistent with the biological needs of important
species.
Implications: Making progress toward goals for fish and wildlife
species requires certain ecosystem conditions. Traditional management has
tended to isolate species from their environment in much the same way that
a farmer isolates livestock from the natural environment. The intent has
been to develop a protected corridor within controllable parts of the life
cycle. This ignores the role of biological and physical factors of the
ecosystem in shaping individuals, populations and species through natural
selection. For salmon, the reality has been that, although large numbers
of individuals are released into the system and protected through their
freshwater phase, fewer and fewer fish return to spawn. This principle
stresses the need to shift our focus to the development of compatible
ecosystem conditions that support productive and diverse species. Rather
than attempting to engineer the biological system to accommodate human
activities, these activities must be engineered to operate within the
biological system.
Principle 2. Natural ecosystems are dynamic, evolutionary and
resilient.
Discussion: Agriculture arose out of the human desire to eliminate the
variation inherent in natural ecosystems. To increase yields and eliminate
cycles of feast and famine, farmers attempt to manage an ecosystem (the
farm) to provide optimal conditions for crops and livestock. Farmers
control the environment to minimize natural variation from drought, pests
or other factors. Livestock and crops are selected to provide consistent
characteristics.
Many fishery management actions are designed to achieve a stable and
predictable yield from a highly dynamic system. Hatcheries were conceived,
in part, to smooth out natural variation in fish populations and to
sustain harvest over time. Fisheries management often has emphasized
predictability of abundance to encourage economically viable fisheries.
Hatchery production and fish passage measures are timed and engineered to
provide a predictable fish migration with minimal impact on human uses of
the river.
The agricultural model is at odds with the management of species that
spend a large part of their lives in ecosystems where human control is
limited. Even if fish are protected in hatcheries or by other means for
some portion of their lives, it is their ability to survive and reproduce
in the natural system that determines success. Species in natural systems
must contend with many different human and natural conditions.
Natural ecosystems are dynamic and constantly change in response to
internal and external factors . For many ecosystems, change is an
essential feature. Floods structure aquatic habitat and fires structure
terrestrial habitats. Many human actions seek to moderate or eliminate
these factors that structure biological systems.
However, while change is characteristic, ecosystems also have a certain
stability. Ecosystems evolve in the sense that they show describable, if
not precisely predictable, patterns of development over time . Forests,
for example, show patterns of succession characterized by the change from
pioneer to mature species. A forest, like other ecosystems, may appear
stable when we observe it at one time, but it evolves and changes when we
observe it at a broader time frame.
Ecosystems accommodate disturbance and change. Disturbance can occur as
a result of natural processes such as fire, climate change or geological
events, or as a result of human actions. Depending on the degree of
perturbation, the system may eventually resemble its previous condition
once the disturbance dissipates. However, larger impacts can fundamentally
change the ecosystem. The system is usually not destroyed but instead
shifts into a new configuration. Different species may be favored and new
biological and physical interactions may develop.
Implications: A management program that focuses on specific species
within ecosystems should anticipate change. This principle encourages a
departure from futile attempts to manage for constant yields and eliminate
variation. Consideration of the impacts of human actions on specific
species should occur within the context of natural ecological variation.
Management programs need to anticipate change and include evaluation
mechanisms that permit adaptation over time.
Principle 3. Ecosystems are structured hierarchically .
Discussion: Ecosystems are like Russian dolls that can be opened to
find a smaller doll within. Each doll may contain a smaller doll but also
be contained within a larger doll. In a like manner, an ecosystem is
composed of smaller scale ecosystems and is also a component of a
larger-scale ecosystem. However, while each doll is a discrete entity,
ecosystems are a continuum from the large-scale to the small-scale.
Ecosystems range in size from the microbial to the entire biosphere of the
earth. At any point on this continuum, the ecosystem reflects the behavior
of smaller scale components and is constrained by the larger-scale system.
Scale in this sense refers to both geographic and time dimensions.
Large-scale ecosystems address larger chunks of space and generally
fluctuate at lower frequencies relative to smaller-scale ecosystems. By
analogy to a camera lens, we can zoom in to consider fine scale details
and pan out to consider the ecosystem as a whole. For example, a
pool/riffle ecosystem operates at relatively short time frames and
involves a relatively small geographic area. It is contained within a
larger stream ecosystem that is itself contained within the overall
watershed . Each time we zoom out from the pool/riffle ecosystem we
consider larger steps of time and space. Ecological characteristics at any
level reflect the characteristics of smaller scale systems and contribute
to the characteristics of larger scale systems. To solve large-scale
problems on the order of the Columbia River Basin, we need to filter out
smaller-scale data. On the other hand, questions concerning small-scale
components (e.g. watersheds) cannot be addressed by looking at large scale
data appropriate to the entire basin.
Implications: This principle provides an ecologically based way to
structure fish and wildlife recovery. A recovery program must first define
the ecosystem at the point in the ecological continuum appropriate to the
problem. We may bound an ecosystem at different places depending on the
questions we ask. The ecosystem at that point reflects the characteristics
of the features nested within, and it is also constrained within the
context of larger systems. Consideration of the ecosystem in isolation
provides an incomplete picture.
For example, recovery of a particular salmon population under the
Endangered Species Act might focus on delisting criteria of the population
in its natal watershed. Achievement of those delisting criteria is
affected by smaller scale habitat conditions, species interactions and
other factors nested within the watershed. At the same time, the watershed
is affected by factors acting at the scale of the Columbia River Basin and
by even larger scale regional climatic factors. Focusing narrowly on what
is required to increase survival of the population at one life stage in
isolation is incomplete without consideration of smaller scale factors
within the watershed and larger scale constraining factors outside the
watershed.
Framework elements developed at any level need to be consistent with
elements developed at larger and smaller scales. Goals set at the level of
the Columbia River Basin need to constrain goals at the watershed level.
Regional goals collect and reflect goals set at the watershed level.
Similarly, the scientific foundation at the watershed level needs to be
consistent with the scientific foundation for the basin as a whole.
Because the Columbia River is a system of nested elements, there needs to
be a logical consistency in policy, science and action as we zoom in or
pan out to address problems at different scales.
Principle 4. Ecosystems are defined relative to specific
communities of plant and animal species.
Discussion: The dimensions, relevant components and condition of the
ecosystem can be identified with respect to specific species of interest
and their associated biological communities. The ecosystem of snail
populations in the upper Snake River is quite different from the ecosystem
of endangered salmon populations in the same river. Each species interacts
with different physical and biological elements. Likewise, the relative
condition (or "health") of the Columbia River ecosystem with
respect to walleye may be quite different than its condition relative to
native salmonids .
Species do not exist as isolated elements of the physical habitat.
Instead, they interact closely with other species and the environment to
form a system. Their ability to survive, reproduce and evolve depends not
only on the hydrology, geology and climate, but also on interactions with
other individuals and species through competition, predation and natural
selection. These interactions select and develop healthy, robust
populations.
Because of this, ecosystems and their conditions are defined in
relation to a community or assemblage of interacting species rather than
by individual species. The dimensions and elements of the ecosystem with
respect to a population of Bull Trout, for example, includes the
interacting community of aquatic and terrestrial plant and animal species
that collectively define the conditions needed for success of the
population.
The community of plants and animals in which a species coexists changes
through its life cycle, particularly for highly migratory species such as
most salmonids. As an organism moves through different life stages, the
scale of the ecosystem that concerns managers may change. At the
egg-to-emergent-fry stage of bull trout in the Flathead Lake system, for
example, the scale of physical and biological interactions is quite small.
It may focus on small tributaries and concern interstitial gravel flow,
sediment, temperature and interactions with other fry and with predatory
species. On the other hand, when we view the adult stage, a much larger
scale and a much different set of physical and biological factors --
perhaps the whole of Flathead Lake -- might be relevant. It is the
continuum of habitat and biological interactions integrated across the
life cycle of the biological community of concern that defines the
conditions needed to meet goals for individual species.
Implications: Defining the ecosystem with respect to a distinct
community of interacting species allows us to identify and quantify the
ecological conditions needed to address the goals of specific species of
interest. The physical and biological needs of the community provide a
composite index of the conditions needed to meet goals for specific
individual species.
For example, achieving goals for a specific salmon population listed
under the Endangered Species Act requires not only certain water quality,
sediment and other habitat characteristics, but also the aquatic and
terrestrial conditions needed to allow development of a compatible
community of plant and animal species. A plan for delisting the species
might describe these conditions at several scales to address the entire
life cycle. Because actions at one scale are nested within larger scale
systems, a continuum of needed physical and biological interactions can be
developed that encompasses the entire life cycle of a species.
Principle 5. Biological diversity accommodates environmental
variation.
Discussion: The physical and biological template of the environment
shapes species and populations. Variation in biological characteristics
helps species cope with the range of environmental variation in their
ecosystems. A more biologically diverse species has a greater range of
possible solutions to the challenges posed by variation in the
environment. Within the spectrum of populations that comprises a species (chinook
salmon in the Columbia River, for example) there is a variation in
survival of different populations as the environment shifts over time. As
some populations suffer under an environmental extreme such as an El Nino
condition, others fare better. The species survives, bolstered by its
ability to respond to the shifting environment . Generally speaking,
greater diversity in species and populations leads to greater ecological
stability.
Biological variation is a function of life history traits, behavior and
physical features. Within salmon, for example, populations differ in
regard to migration and spawning times, size of individuals, coloration,
growth and maturation rates and many other factors. In many cases, these
traits have a genetic basis and so reflect natural selection by the
environment. Short and long-term variation in the environment shifts the
impacts of natural selection resulting in variation in the array of traits
over time.
Implications: Human actions can reduce biological variation.
Confronting a dynamic and complex ecosystem, we try to simplify and
constrain it to make it more compatible with our needs. For example, fish
passage measures in the Columbia River focus on a narrowed migration
period to minimize cost and impact on other human uses of the river.
Hatchery practices may select for traits that favor domestication over
traits favoring survival in the wild. Harvest practices concentrate on
fish of certain sizes, ages or behaviors. The complexity of many natural
habitats has been simplified by stabilizing banks or by eliminating
floods.
If we accept that diversity within species enhances the ability of the
species to sustain itself productively over time, then we should manage
our activities to allow natural expression of biological diversity. While
diversity can be quantified, determination of the "proper" level
of biological diversity is likely not possible, partly because it shifts
and varies over time in response to natural selection by the environment.
The challenge is to manage human activities to minimize our impacts on
selection and allow diversity to develop accordingly.
Principle 6. Ecosystem conditions develop primarily through
natural processes.
Discussion: On a farm, ecological conditions are carefully controlled
to optimize conditions for the narrow community of crops and livestock
favored by the farmer. Maintenance of this artificial ecosystem requires
input of energy, water and sweat to create conditions that often contrast
with natural conditions. So, for example, rice and other exotic crops can
be grown in naturally arid environments.
In contrast, natural ecosystems are created, altered and maintained
primarily by natural processes operating at a range of scales encompassing
the entire life history of species of interest. Habitats develop in
response to the local hydrology, geology and climate. Species and
communities in turn develop to match the template provided by the physical
and biological conditions. Human actions that constrain or alter these
habitats have a biological consequence: native species and populations are
lost and non-native species proliferate. Management of ecosystems to
achieve goals for specific species implies allowing normal ecological
processes to operate and develop an appropriate environment.
Implications: Natural ecosystems cannot be managed in the sense that we
manage the artificial environment of the farm. They develop through
natural processes and react to outside constraints including the impact of
human actions. Attempts to engineer these conditions have generally been
unsuccessful . Ecosystem management more often involves managing human
impacts on the ecosystem than managing the natural environment to force it
into a particular configuration.
Take, for example, efforts to create fish habitat in streams using
in-steam flow structures. This is based on observations that productive
streams for native species have certain characteristics such as the ratio
of pools and riffles. Streams impacted by logging or grazing often lose
these characteristics. Considerable effort and money has been spent to
place log or rock structures to create pools and rip-rap to stabilize
banks. In almost all cases, these efforts have failed to provide habitat
over the long-term.
This principle stresses that the needed conditions would develop
naturally if we moderate the constraints on the system. Instead of
spending money on unsuccessful efforts to engineer a river based on a
mental picture of a productive river, managers would develop and enforce
land use practices to moderate the effects of logging or grazing that
ultimately caused the river to deteriorate.
Principle 7. Ecological management is adaptive and experimental.
Discussion: The complexity and variability of ecosystems argues for the
idea that ecological management is inherently experimental. Our knowledge
of ecosystem functions is incomplete. We can describe the structure and
nature of ecosystems in some ways, but important details elude us. More
importantly, we have only recently begun to appreciate the Columbia River
as an ecosystem. For most of this century we have thought of the Columbia
River as a machine that can be adapted to meet our needs. Ready solutions
structuring human activities in a highly developed system like the
Columbia River have not been developed. Finally, as has been emphasized in
these principles, ecosystems vary over time. What is key to recovery of
species today may not be so important in the future as the system shifts
in some largely unpredictable fashion.
Adaptive management - the use of management experiments to investigate
biological problems -- provides a model for experimental management.
However, management of ecosystems presents special challenges to adaptive
management. Ecosystem level experiments may be impractical, infeasible or
pose equity questions . We may be unwilling to experiment with beleaguered
fish and wildlife populations. Under these circumstances there may be less
opportunity for large-scale management experiments, and more need for
directed experimentation and research. Nevertheless, an explicit, directed
approach to learning is essential. Experimental management does not mean
passive "learning by doing", but, rather a directed program
aimed at understanding key ecosystem dynamics and the impacts of human
actions.
Implications: This principle argues for management that constantly
experiments and probes to better understand the ecosystem. Ecosystem
management is likely to require the development of new measuring tools. To
the standard indices of abundance of important fish and wildlife species,
ecosystem management calls for new indicators of success such as
development of normal trophic structure, biological diversity and species
conservation status. What is critical to fish and wildlife restoration in
one decade may not be critical in the next as the ecosystem shifts in
response to internal or external factors. As we learn about ecosystems,
new strategies may be indicated. However, in order to provide relevant
information regarding these factors, monitoring and evaluation need to be
built into management programs from the ground up.
Principle 8. Human actions can be key factors structuring
ecosystems.
Discussion: Humans are a key biological component of ecosystems. Like
other organisms, humans structure and control their ecosystems to enhance
their own needs. In some ecosystems, human impacts are pervasive and act
as major factors controlling and structuring the environment. However,
unlike other organisms, we can consciously control our actions to allow
needed ecological conditions to develop. While our actions may be unique
in the scale of impact on ecological systems, the method of interaction is
not; ecological principles apply to human interactions with ecosystems as
much as they do to the interactions of fish and wildlife species and the
ecosystem.
It is a reasonable assumption that for most species, the ecological
conditions that are most conducive to their long-term survival and
productivity are those under which they evolved. Human actions in the
Columbia River have shifted ecosystems away from their pre-development
conditions with negative impacts for most native species. Some changes are
irreversible. New species have been introduced and permanent changes have
been made to the landscape. Even with complete cessation of human
activities, these ecosystems would not return to their previous condition.
However, human impacts on ecosystems can be managed to move the system to
a state that is more compatible with the needs of other species. It is
simply a question of the type of environment in which we choose to live
and how much we are willing to limit our actions to achieve these
objectives.
Implications: These scientific principles suggest ways to view our role
in ecosystems. In highly developed ecosystems like the Columbia River,
human actions and technology will continue to dominate the system.
However, those actions can be managed in a manner consistent with the
needs of other species. Fish hatcheries, for example, will likely continue
to support some fish populations. Appreciation of the fact that the
success of species reflects the condition of their ecosystems (principle
1) leads to the conclusion that hatcheries are unlikely to be an adequate
substitute for lost habitat. Hatcheries, however, may augment natural
production in the context of functioning ecosystems. Recognizing the
importance of biological diversity (principle 5) counsels against
practices that narrow the range of biological traits in a population. If
ecological conditions develop primarily through natural processes
(principle 6), then developing conditions needed by specific species is
more a matter of relaxing human impacts on land and water rather than
attempting to engineer alternative environments.
Part II. The Columbia River as an Ecosystem
This section describes the ecology of the Columbia River Basin at a
high level of generality, in a manner that is consistent with the
scientific principles. Much of the material is drawn from Upstream, Return
to the River, the Interior Columbia Basin Ecosystem Management Project (ICBEMP)
scientific reports and other sources. As a landscape-level assessment,
this summary is intended to provide a sense of ecological context and
pattern in which the scientific principles can be applied. It will
continue to be developed as a part of the framework development process.
1. The natural system
The Columbia River Basin covers an area of 259,000 square miles. The
lands in the Basin are highly diverse. They range from the Pacific Ocean
on the west to the continental divide in the Rocky Mountains on the east.
Elevations range from sea level to over 13,000 feet. The topography has
been shaped by regional geological forces ranging from continental edge
folding in the Rocky Mountains, flood basalt on the Columbia River Plateau
and volcanism and folding in the Cascade Mountains. This has resulted in a
large range of biological zones ranging from alpine, to high desert to
coastal rainforests.
Within this vast area climate patterns are determined by regional
processes interacting with topographic features. Moist air from the
Pacific Ocean moves east until it encounters the Cascade Mountains. Much
of the moisture is dropped on the west side of the Cascades producing a
temperate rain forest, while the area east of the Cascades is arid. Within
these extremes, the type and distribution of vegetation varies with
elevation, soils, long-term precipitation patterns and climate. Forested
vegetation ranges from the spruce-hemlock dominated coastal rainforest to
the dry interior Douglas fir and Ponderosa pine zones. Grasslands,
shrublands and woodlands dominate the basalt plateaus. The area is drained
by the Columbia River and its tributaries. The Basin is, for the most
part, sparsely populated with the majority of the population concentrated
in urban areas west of the Cascade Mountains.
Over 43,000 species of macroorganisms are estimated to occur in the
Basin and over 17,000 species are known to occur. Microorganisms, critical
to ecosystem health and function, probably number at least several hundred
thousand species. This diversity of species results from the extensive
habitat types, topography and geologic and climatic events that have
shaped the region.
The river systems in the Basin form a complex, dynamic gradient from
the headwaters to the mouth encompassing terrestrial as well as aquatic
features. Along this gradient, flora and fauna are distributed according
to the requirements of each stage in their life cycle. These watershed
have four critical habitat types: riverine (the open river), riparian (the
terrestrial area adjacent to the river), hyporheic (the network of
underground habitats associated with the flow of water through sediments
of the river and flood plain beds) and terrestrial uplands. The drainage
system forms a longitudinal continuum of habitats from the headwaters to
the river mouth. Riparian and hyporheic habitats form a lateral continuum
linking the river and the terrestrial uplands. Four aquatic habitat
variables are key: water quality (temperature, dissolved oxygen,
turbidity, nutrients, and environmental contaminants); properties of flow
(velocity, turbulence and discharge); geological and topographic features
(stream width and depth, bedrock type, landform, streambed roughness,
particle size, riffle and pool frequency and floodplain characteristics);
and cover (shading, interstitial hiding places, undercut banks and ledges,
woody debris and aquatic vegetation).
Within the aquatic areas, salmonids (anadromous and resident) play an
important role in maintaining ecosystem integrity. Juvenile salmonids move
within watersheds to take advantage of diverse food sources that change
with the seasons. When they migrate to the ocean, anadromous salmon feed
on marine organisms for several years and grow to mature size. In a
similar manner, adfluvial resident salmonids move between stream and lake
habitats over the course of their life cycles. When they return to their
natal streams as adults, these salmonids move nutrients from marine to
freshwater systems and, in the case of adfluvial species, within
freshwater habitats. Spawned-out carcasses are consumed by a wide variety
of terrestrial animals forming a linkage between aquatic and terrestrial
environments. They also nurture aquatic plants, bacteria, fungi, stream
substrate, and other fish. Thus, salmonids play a key role in nutrient
cycling and ecosystem productivity.
Species are organized genetically along a continuum ranging from the
species to the individual. Within this continuum, populations, demes and
other features can be discerned. Both Upstream and Return to the River
suggested that salmon, at least, be viewed as metapopulations rather than
as isolated stocks. Other anadromous and resident fish population as well
as wildlife may also be structured into metapopulations. Upstream explains
the metapopulation concept as follows:
Natural environmental fluctuations, including major disruptions caused
by geological activity, can cause the extinction of local populations.
Because homing* is not perfect, fish that stray from nearby streams can
replenish those populations. Strays are more likely to re-establish a
population if the environment in the new stream is similar to that in the
stream where they hatched. Thus, strays into tributaries in the same major
river system or into nearby streams are more likely to succeed than those
that stray into very different environments. This network of local
populations (know as metapopulation) provides a balance between local
adaptation and the evolutionary flexibility that results from exchange of
genetic material among local populations. . . . It likely also explains
why artificial attempts to re-establish populations from a captive
broodstock have often failed - too often, the gene pool of the broodstock
has had reduced variation or has been derived from a population adapted to
a different environment. The metapopulation structure provides a balance
between local adaptation and evolutionary flexibility; therefore,
maintaining a metapopulation structure with good demographic distribution
should be a top management priority to sustain salmon populations over the
long term. Many of the committee's recommendations are based on this
crucial conclusion.
While this description refers specifically to anadromous salmonids, it
can be rather easily extended to include resident fishes and wildlife as
well.
Return to the River and ICBEMP referred to recent studies suggesting
that salmonid metapopulations may have core-satellite structures:
Core populations occupy high quality habitat and are generally large,
productive populations that are less susceptible to extinction than the
smaller satellite populations. Core populations also can serve as
important sources of colonists to sustain populations whose abundance has
been severely depleted, i.e., the "rescue effect." Thus, core
populations can buffer metapopulations against environmental change and
contribute to the resiliency of regional salmonid production .
The core for maintaining and restoring much of the biological diversity
associated with fishes still exists. Conservation and restoration of
important habitats for key salmonids could provide habitat for associated
species and will sustain important processes that influence structure and
function within these systems.
2. The Columbia River Ecosystem.
The Columbia River ecosystem begins in tiny headwater streams, most of
which arise in the Rocky and Cascade mountain ranges. In their natural
state, these headwater streams are often heavily shaded by riparian
vegetation that provides organic input to the stream and maintains cool
water temperatures. These streams are home to a variety of native salmonid
and non-salmonid fishes, while the riparian areas provide habitat for many
wildlife species. Riparian areas grade into terrestrial uplands that
support other wildlife species. These systems are extremely susceptible to
habitat change, especially the destruction of the riparian area through
grazing and other agricultural practices. This begins a series of
environmental changes that cascade downstream through the rest of the
ecosystem. Water temperatures rise, water tables may be lowered and mosses
and other aquatic plants may intrude. Alteration of riparian and
terrestrial habitats results in loss of native plant and animal species
while favoring many non-native species. The headwater streams collect into
larger tributaries that flow to the mainstem Columbia and Snake rivers.
Although still important, the influence of riparian areas decreases as the
size of the stream increases. The condition of the tributary streams and
rivers reflects the collective upstream conditions in the headwater
streams as well as local factors. The tributary streams provide spawning
and rearing habitat for stream-type spring chinook salmon below anadromous
barriers, and for a variety of other salmonid and non-salmonid fishes
throughout the basin. As a result of agriculture, logging, mining and
urbanization, suitable habitat for many native species in the tributaries
now exists only in isolated pockets that likely have fragmented the
natural population structure. As with the headwater areas, riparian and
upland watershed areas support a variety of wildlife species.
The mainstem Columbia and Snake rivers provide spawning, rearing and
migrational habitat for anadromous salmonids, sturgeon and other species.
The quality of the mainstem as a migrational corridor for adult and
juvenile fish has been greatly reduced by development of hydroelectric
projects. Before development, the Columbia's mainstem was also an
important spawning area for chinook salmon. Alluvial reaches of the river
- floodplain areas and gravel-cobble bedded mainstem segments like the
Hanford Reach - may be especially important to salmon production because
this is where habitat diversity and complexity with respect to salmon are
greatest. Salmon with ocean-type life histories, primarily fall and summer
returning fish, spawn and rear in these areas and historically may have
been the most important contributors to the river's salmon productivity.
These populations spawned in the mainstems of the Snake and Columbia
Rivers and in the lower portions of the larger tributary rivers. With the
exception of the Hanford Reach and a few other locations, most of this
mainstem habitat was destroyed as a result of development of the
hydroelectric system.
Mainstem river reaches also provided important habitat for resident
fish and wildlife species. The demarcation between areas accessible to
anadromous fish has been moved downstream considerably by the construction
of Chief Joseph Dam on the Columbia River and Hells Canyon Dam on the
Snake River. Above these points, other human actions have changed the
ecosystem to the point that it is less supportive of many native species
of fish and other aquatic flora and fauna. Most of the natural riparian
habitats on the mainstem were inundated by the construction of the dams,
resulting in considerable loss to terrestrial wildlife and other riparian
dependent species.
With respect to anadromous salmonids, the Columbia River ecosystem
expands to include large areas of the northeast Pacific Ocean. Pacific
salmon spend most of their lives in the ocean, where they grow to
maturity. Conditions affecting the survival of salmon leaving the Columbia
River vary greatly in regard to both time and space. Change occurs
annually, at multiple year intervals such as El Nino events, and over
decadal or longer scales. The impact of these natural cycles can mask the
impact of human-induced changes in the freshwater environment.
3. Effects of human development
Development over the last 150 years has blocked, degraded and
fragmented a significant part of the basin's fish and wildlife habitat,
eliminated important populations through over-harvest, and narrowed a good
deal of biological diversity. The ICBEMP reports state:
The composition, distribution and status of fish within the Basin are
different than they were historically. The overall changes are extensive
and in many cases irreversible?Even with no further habitat loss, the
apparent fragmentation and isolation may place remaining populations of
key salmonid species at risk. Much of the native ecosystem has been
altered but core areas remain for rebuilding and maintaining functioning
native aquatic ecosystems.
Development in the Basin has altered flows, temperatures, sediment
loads, reduced riparian areas and caused other physical changes.
Consequently, the aquatic ecosystem no longer supports the same species of
fish, macroinvertebrates and aquatic plants. The ecosystem has adapted to
the changed physical and biological conditions to produce a new ecosystem
characterized by many non-native species. A number of non-charismatic
species of fish and macroinvertebrates have likely been lost. For
anadromous fish, passage mortality in migration corridors (largely due to
dams) has meant weak and diminished populations in much of the highest
quality remaining habitat. Almost complete loss of mainstem spawning and
rearing habitat eliminated a major component of the anadromous salmon run
to the river. Mainstem habitats provide a critical role in linking
habitats and in maintaining the complex life histories of other species as
well. For example, resident salmonids that retain migratory life history
patterns such as bull-trout, redband trout, Yellowstone cutthroat and
westslope cutthroat trout may move repeatedly between small rivers and
headwater streams. Loss of riparian habitat disrupted important migratory
corridors for many terrestrial species as well.
In recent historic time native grasslands, shrublands, intact riparian
areas and natural forest ecosystems have declined in total area and
shifted in distribution due to agriculture and urbanization. Many of the
native species of fungi, lichen, plants, invertebrates and vertebrates
associated with these habitats have also declined and/or shifted in
distribution. Vertebrate species associated with these declines include
large predators, habitat specialists (e.g. cavity nesting species),
aquatic mammals, amphibians and migratory fish. Vegetation types that have
increased include mid and early successional forests, juniper-sage
shrublands, disturbed riparian areas and exotic plant communities. While
few if any vertebrate has become extinct, some wide ranging carnivores
have greatly decreased in abundance and distribution and become locally
extirpated.
The ICBEMP reports states that native fishes and other aquatic fauna
throughout the Columbia River Basin are on the decline. They characterize
the situation as follows:
Chinook and sockeye salmon in the Snake River are listed as endangered
under the Endangered Species Act. Bull trout, once widely distributed in
central Oregon, Idaho, and western Montana, warrant protection.
Genetically pure populations of Yellowstone cutthroat trout are limited to
a fraction of their historical stream habitat in the upper Snake River
drainage. Only a small portion the historic range of westslope cutthroat
trout in Idaho and Montana still sustains genetically pure populations.
Redband trout within the Basin are poorly understood, but many subbasins
appear to contain genetically unique strains that have declined
concomitant with habitat degradation. Such changes in salmonid populations
may be indicative of broad declines in other aquatic resources such as
stream habitats and riparian areas in the Columbia River basin?
Pacific salmon are either endangered or extirpated from about
two-thirds of their historic range. Many locally-adapted populations have
been lost because of dams and habitat loss. Remaining wild populations
have been modified to an unknown degree by fishing, interbreeding with
hatchery fish, and habitat modifications. Many resident salmonids and
other fishes have been similarly impacted.
Fragmentation and destruction of habitat can disrupt regional
metapopulation organization, leading to the collapse of core populations
and isolation of remaining populations. In turn, this may significantly
reduce population persistence and stability. Contemporaneous land use,
mainstem, estuary, harvest and ocean problems create the prospect of
"synchronous" extinctions of entire metapopulations. Such
factors may have shifted most Columbia River metapopulations from a
core-satellite structure to a situation in which extinction rates are
consistently greater than recolonization rates. As many stabilizing core
populations have become extinct, recolonization is limited, local
populations are increasingly isolated, and the entire population moves
toward extinction. It should be noted again that, while the above
hypothesis is focused on Pacific salmon, it is applicable to many other
aquatic and terrestrial species as well.
Development has blocked large areas of the basin to salmon. Before any
water resource development, over 163,000 square miles of the 260,000
square mile basin (in the U. S. and Canada) were accessible to salmon.
Today, only 73,000 square miles are accessible. Of all salmon and
steelhead habitat in the basin, 55% of the area and 31% of the stream
miles have been eliminated by dam construction. The ecosystem in the areas
blocked to salmon has been significantly altered by the loss of anadromous
stocks that provided a significant nutrient base to the aquatic ecosystem.
The ripple effect of this to the prey base and other ecological functions
has impacted both resident fish and wildlife species.
The decline of ocean-type life histories among Columbia River salmon
(summer and fall chinook) has contributed significantly to the overall
decline of chinook salmon in the river. The Hells Canyon hydroelectric
complex, for example, eliminated about 80% of the spawning habitat of
Snake River fall chinook. Summer temperature and other barriers in the
migration corridor eliminated many ocean-type populations. Extant
populations that survive in the remaining intact portions of the river
such as the fall chinook population spawning in the Hanford Reach, could
serve as focal points for restoration efforts. Significantly, despite
elimination of almost all the mainstem habitat and the fact that these
fish are heavily impacted by commercial fisheries, the ocean-type fall
chinook surviving in the only remaining free-flowing stretch of the
Columbia River remain the largest and apparently most robust salmon
population in the river. It is the largest naturally spawning population
of chinook salmon in the Columbia River and continues to support the only
remaining commercial fishery in the river.
Fall chinook were also abundant in the John Day and perhaps other
reaches of the river, and could form other core areas. Remnant populations
of fall chinook also occur in the lower mainstems of most major subbasins,
in the Snake River below Hell's Canyon and in the tailraces of some
mainstem dams.
Apart from the Hanford Reach, naturally-spawning salmon are limited to
remnant spring and summer chinook populations in headwater streams where
high quality habitat is still available. In various tributary basins,
excessive summer temperatures in lower rivers are the cumulative result of
watershed-wide habitat degradation. In addition to establishing suitable
mainstem migrational habitat, restoration of these populations may require
development of tributary habitat to reconnect these habitat pockets and
allow re-establishment of a normal population structure.
Ocean phenomena, which have received less consideration in salmon
management until recently, may have a great deal to do with the status of
salmon populations. Because salmon spend the majority of the lives in the
ocean, cycles and changes in ocean productivity exercise considerable
control over year-to-year abundance of salmon. Ignoring these factors
creates the risk of falling into misconceptions about population status,
making mistakes in management (e.g., overharvest) and misunderstanding the
effects of changes in freshwater habitat, which can be masked or
exacerbated by ocean factors.
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