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.