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Endangered and Threatened Species of the Platte River 8 CONCLUSIONS AND RECOMMENDATONS In the previous chapters, the Committee on Endangered and Threatened Species in the Platte River Basin has explored science and its application for policy on the central and lower Platte River. The committee presents here its responses to the series of questions (reviewed in Box 1-2) included in its charge. In this chapter, for each question, we state our conclusions and the primary sources of evidence leading to them. To reach its conclusions, the committee considered the extent of the data available for each question and whether the data was generated according to standard scientific methods that included, where feasible, empirical testing. The committee also considered whether those methods were sufficiently documented and whether and to what extent they had been replicated, whether either the data or the methods used had been published and subject to public comment or been formally peer-reviewed, whether the data were consistent with accepted understanding of how the systems function, and whether they were explained by a coherent theory or model of the system. To assess the scientific validity of the methods used to develop instream-flow recommendations, the committee applied the criteria listed above, but focused more directly on the methods. For example, the committee considered whether the methods used were in wide use or generally accepted in the relevant field and whether sources of potential error in the methods have been or can be identified and the extent of potential error estimated. The committee acknowledges that no one of the above criteria is decisive, but taken together they provide a good sense of the extent to
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Endangered and Threatened Species of the Platte River which any conclusion or decision is supported by science. Because some of the decisions in question were made many years ago, the committee felt that it was important to ask whether they were supported by the existing science at the time they were made. For that purpose, the committee asked, in addition to the questions above, whether the decision makers had access to and made use of state-of-the-art knowledge at the time of the decision. The population viability analysis (PVA) developed by the committee was constrained by the short study period. It did not include systematic sensitivity analyses and did not base stochastic processes and environmental variation on data from the Platte River region. A more thorough representation of environmental variation in the Platte River could be developed from regional records of climate, hydrology, disturbance events, and other stochastic environmental factors. Where records on the Platte River basin itself are not adequate, longer records on adjacent basins could be correlated with records on the Platte to develop a defensible assessment of environmental variation and stochastic processes. In addition, a sensitivity analysis could demonstrate the effects of wide ranges of environmental variation on the outcomes of PVAs. In its analysis, the committee did not consider methods and techniques that are under development by researchers such as the new SEDVEG model. SEDVEG is being developed, but is not yet completed or tested, by USBR to evaluate the interactions among hydrology, river hydraulics, sediment transport, and vegetation for application on the Platte River. The committee did not consider USGS’s in-progress evaluation of the models and data used by USFWS to set flow recommendations for whooping cranes. The committee did not consider any aspects of the Environmental Impact Statement that was being drafted by U.S. Department of the Interior (DOI) agencies related to species recovery, because it was released after the committee finished its deliberations. The Central Platte River recovery implementation program proposed in the cooperative agreement by the Governance Committee also was not evaluated, because it was specifically excluded from the committee’s charge. The committee’s experience with data, models, and explanations led us to the identification of three common threads throughout the issues related to threatened and endangered species. First, change across space and through time is pervasive in all natural and human systems in the central and lower Platte River. Change implies that unforeseen events may affect the survival or recovery of federally listed species. Land-use and water-use changes are likely in the central and lower Platte River region in response to market conditions, changing lifestyles, shifts in the local human population, and climate change; such changes will bring about pressures on wildlife populations that are different from those observed today. For example, riparian vegetation on the central Platte River has changed because of both natural and anthropogenic impacts. Regardless of its condition and
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Endangered and Threatened Species of the Platte River distribution before European settlement in the middle 1800s, the riparian forest of the central Platte River was geographically limited from the middle 1800s to the first decades of the 1900s. At the time of the first aerial photography of the river in 1938, extensive sandbars, beaches, and braided channels without extensive forest cover were common in many reaches of the central Platte. Between the late 1930s and the middle to late 1960s, woodland covered increasing portions of the areas that had previously been without trees. By the late 1990s, clearing of woodlands had become a major habitat-management strategy to benefit whooping cranes that desire open roosting areas with long sight lines. Whooping cranes have used the newly cleared areas, but the overall effects of clearing on the crane population and on the structure of the river are not completely known. As with most habitat-management strategies in the central Platte River, there has been no specific monitoring to assess the success of clearing. Unintended effects remain to be investigated. From a planning and management perspective, stable conditions are desirable so that prediction of outcomes of decisions can be simplified; but stability is rare, especially in the Platte River Basin. Explanations of existing hydrological, geomorphologic, and biological conditions and predictions of future conditions that fail to discern and accommodate change are not likely to be successful. Science can inform decision makers about expected outcomes of various choices, but prediction of the outcomes is likely to be imprecise because of ecosystem variability. Management choices therefore must include some flexibility to deal with the inevitable variability and must be adaptive, continually monitoring and adjusting. The conditions our parents would have seen in these ecosystems a half-century ago were not the conditions we see now, and present conditions are not likely to be the ones our children or grandchildren will see. A second thread identified by the committee is that one’s view of an ecosystem depends on the temporal and spatial scales on which it is examined. The variability in scale of processes in smaller drainage basins nested within larger ones is obvious, but most natural systems have a similar nested hierarchical structure. The groups of birds and fish that use the Platte River Basin are a fraction of the larger, more widely distributed population, so conditions along the river affect only a portion of each population at any time. Loss of the subpopulations that use the Platte River might not damage the entire population if there were no losses elsewhere—something that Platte River managers cannot assume. The concentration of listed species along the central Platte indicates the importance of the river, despite the fact that the birds can be found elsewhere in Nebraska during migration or nesting periods. The river is important from a management perspective because it contains all the habitat features that are included in the regulatory definitions of critical habitat.
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Endangered and Threatened Species of the Platte River The river supplies the needs of an assemblage of species in addition to serving the needs of single species. Climate also operates on a series of hierarchical scales. Regional climate in the central and northern Great Plains evinces a variety of changes that depend on the time scale used for analysis. Over a period of 5 or even 10 years, we do not see the complete range of temperature and rainfall conditions likely to be experienced over a century. Decades-long drought or wet periods are likely to be important in species survival and recovery, so short-term observations of less than a few years cannot illuminate the expected conditions that a recovery effort must face. The various scales of scientific analysis with respect to threatened and endangered species in the Platte River Basin imply that decisions based on science should also recognize scale. Decisions concerning the Platte River Basin that are based on short-term multiyear data and a local perspective are not likely to benefit the long-term (multidecadal) viability of a species that operates on a continental or intercontinental scale. The costs of efforts to recover threatened or endangered species are often most obvious on a local scale, but the benefits are much more widely distributed. The third thread is that water links the needs of human, wildlife, and habitat more than any other ecological process. Many of the risks to threatened and endangered species, and all the comprehensive solutions to the problem of recovery, require a refined understanding of hydrological processes. The hydrological system of the Platte River is highly interconnected, so solutions to the species issues that attempt to protect commodity values of water must also be interconnected, particularly between surface water and groundwater. Climatic changes create a changing backdrop for the more important human-induced changes in the hydrology of the basin. The committee is firmly convinced that upstream storage, diversion, and distribution of the river’s flow are the most important drivers of change that adversely affect species habitat along the Platte River. COMMITTEE’S FINDINGS 1. Do current central Platte habitat conditions affect the likelihood of survival of the whooping crane? Do they limit (adversely affect) its recovery? Conclusions: The committee concluded that, given available knowledge, current central Platte habitat conditions adversely affect the likelihood of survival of the whooping crane, but to an unknown degree. The Platte River is important to whooping cranes: about 7% of the total whooping crane population stop on the central Platte River in any one year, and many, if not all, cranes stop over on the central Platte at some point in their lifetimes. Population viability analyses show that if mortality were to
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Endangered and Threatened Species of the Platte River increase by only 3%, the general population would likely become unstable. Thus, if the cranes using the Platte River were eliminated, population-wide effects would be likely. Resources acquired by whooping cranes during migratory stopovers contribute substantially to meeting nutrient needs and probably to ensuring survival and reproductive success. Because as much as 80% of crane mortality appears to occur during migration, and because the Platte River is in a central location for the birds’ migration, the river takes on considerable importance. The committee concluded that current habitat conditions depend on river management in the central Platte River, but the population also depends on events in other areas along the migratory corridor. If habitat conditions on the central Platte River—that is, the physical circumstances and food resources required by cranes—decline substantially, recovery could be slowed or reversed. The Platte River is a consistent source of relatively well-watered habitat for whooping cranes, with its water source in distant mountain watersheds that are not subject to drought cycles that are as severe as those of the Northern Plains. There are no equally useful habitats for whooping cranes nearby: the Rainwater Basin dries completely about once a decade, and the Sandhills are inconsistent as crane habitat, while the Niobrara and other local streams are subject to the same variability as the surrounding plains. Future climatic changes may exacerbate conflicts between habitat availability and management and human land use. If the quality or quantity of other important habitats becomes less available to whooping cranes, the importance of the central Platte River could increase. Primary Sources of Scientific Information: The basis of the above conclusion is published documents that were available to other researchers and the public including the original listing document and recovery plan for the species and a review of knowledge about the cranes by the Interstate Task Force on Endangered Species (EA Engineering, Science and Technology, Inc. 1985). Other important contributions to knowledge include Allen (1952) and Austin and Richert (2001). The committee also reviewed and discussed critical comments presented in open sessions and written testimony exemplified by Lingle (G. Lingle, unpublished material, March 22, 2000) and Czaplewski et al. (M.M. Czaplewski et al., Central Platte Natural Resource District, unpublished material, August 22, 2003) that was critical of the research conducted by DOI agencies. 2. Is the current designation of central Platte River habitat as “critical habitat” for the whooping crane supported by existing science? Conclusions: An estimated 7% of the wild, migratory whooping crane population now uses the central Platte River on an annual basis and many, if not all, cranes stop over on the central Platte at some point in their
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Endangered and Threatened Species of the Platte River lifetimes. The proportion of whooping cranes that use the central Platte River and the amount of time that they use it are increasing (with expected inter-annual variation). The designation of central Platte River migratory stopover habitat as critical to the species is therefore supported because the birds have specific requirements for roosting areas that include open grassy or sandy areas with few trees, separation from predators by water, and proximity to foraging areas such as wetlands or agricultural areas. The Platte River critical habitat area is the only area in Nebraska that satisfies these needs on a consistent basis. However, some habitats designated as critical in 1978 appear to be largely unused by whooping cranes in recent years, and the birds are using adjacent habitats that are not so designated (Stehn 2003). Habitat selection (to the extent that it can be measured) on multiple geographic scales strongly suggests that Nebraska provides important habitat for whooping cranes during their spring migration. Riverine, palustrine, and wetland habitats serve as important foraging and roosting sites for whooping cranes that stop over on the central Platte River. Whooping cranes appear to be using parts of the central Platte River that have little woodland and long, open vistas, including such areas outside the zone classified as critical habitat. In some cases the cranes appear to be using areas that have been cleared of riparian woodland, perhaps partly explaining their distribution outside the critical habitat area. Primary Sources of Scientific Information: The basis of the committee’s conclusion is published documents that were available to other researchers and the public including the original listing document, recovery plan, and declaration of critical habitat; and information in Howe (1989) and Austin and Richert (2001). The committee also considered commentary that was critical of the research conducted by DOI agencies exemplified by open sessions and written testimony presented by Lingle (G. Lingle, unpublished material, March 22, 2000), EA Engineering, Science and Technology, Inc. (1985) and Czaplewski et al. (M.M. Czaplewski et al., Central Platte Natural Resources District, unpublished material, August 22, 2003). 3. Do current central Platte habitat conditions affect the likelihood of survival of the piping plover? Do they limit (adversely affect) its recovery? Conclusions: Reliable data indicate that the northern Great Plains population of the piping plover declined by 15% from 1991 to 2001. The census population in Nebraska declined by 25% during the same period. Resident piping plovers have been virtually eliminated from natural riverine habitat on the central Platte River. No recruitment (addition of new individuals to the population by reproduction) has occurred there since 1999. The
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Endangered and Threatened Species of the Platte River disappearance of the piping plover on the central Platte can be attributed to harassment caused by human activities, increased predation of nests, and losses of suitable habitat due to the encroachment of vegetation on previously unvegetated shorelines and gravel bars. The committee concluded that current central Platte River habitat conditions adversely affect the likelihood of survival of the piping plover, and, on the basis of available understanding, those conditions have adversely affected the recovery of the piping plover. Changes in habitat along the river—including reductions in open, sandy areas that are not subject to flooding during crucial nesting periods—have been documented through aerial photography since the late 1930s and probably have adversely affected populations of the piping plover. Sandpits and reservoir edges with beaches may, under some circumstances, mitigate the reduction in riverine habitat areas. Because piping plovers are mobile and able to find alternative nesting sites, changes in habitat may not be as severe as they would be otherwise, but no studies have been conducted to support or reject this hypothesis. Primary Sources of Scientific Information: Corn and Armbruster (1993) demonstrated differences (including higher river invertebrate densities and catch rates) in foraging habitat between the river and sand pit sites; this suggests that riverine habitat areas are superior to the sand mines and reservoir beaches for the piping plover. Basic information sources include the listing document and recovery plan. Higgins and Brashier (1993) provide additional information on habitat conditions, survival, and recovery. The committee also considered commentary presented in open sessions and written testimony exemplified by Lingle (G. Lingle, unpublished material, March 22, 2000) and Czaplewski et al. (M.M. Czaplewski et al., Central Platte Natural Resources District, unpublished material, August 22, 2003) that was critical of the research conducted by DOI agencies. 4. Is the current designation of central Platte River habitat as “critical habitat” for the piping plover supported by the existing science? Conclusions: The designation of central Platte habitat as critical habitat for the piping plover is scientifically supportable. Until the last several years, the central Platte supported substantial suitable habitat for the piping plover, including all “primary constituent elements” required for successful reproduction by the species. Accordingly, the central Platte River contributed an average of more than 2 dozen nesting pairs of plovers to the average of more than 100 pairs that nested each year in the Platte River Basin during the 1980s and 1990s. The critical habitat designation for the species explicitly recognizes that not all areas so designated will provide all neces-
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Endangered and Threatened Species of the Platte River sary resources in all years and be continuously suitable for the species. It is also now understood that off-stream sand mines and reservoir beaches are not an adequate substitute for natural riverine habitat. Primary Sources of Scientific Information: Data generated according to standard scientific methods in well-defined and well-executed scientific investigations support the critical habitat designation for the piping plover—including work by Ziewitz et al. (1992), Ducey (1983), and Faanes (1983)—as does the designation in the Federal Register (67:57638 ). The committee also considered commentary presented in open sessions and written testimony exemplified by Lingle (G. Lingle, unpublished material, March 22, 2000) and Czaplewski et al. (M.M. Czaplewski et al., Central Platte Natural Resources District, unpublished materials, August 10, 2001, and August 22, 2003) that was critical of the research conducted by DOI agencies. 5. Do current central Platte habitat conditions affect the likelihood of survival of the interior least tern? Do they limit (adversely affect) its recovery? Conclusions: The committee concluded that current habitat conditions on the central Platte River adversely affect the likelihood of survival of the interior least tern—in much the same fashion as they affect the likelihood of survival of the piping plover—and that on the basis of available information, current habitat conditions on the central Platte River adversely affect the likelihood of recovery of the interior least tern. Reliable population estimates indicate that the total (regional) population of interior least terns was at the recovery goal of 7,000 in 1995, but some breeding areas, including the central Platte River, were not at identified recovery levels. The central Platte subpopulation of least terns declined from 1991 to 2001. The number of terns using the Platte River is about two-thirds of the number needed to reach the interior least tern recovery goal for the Platte. The interior tern is nesting in substantial numbers on the adjacent lower Platte River, but numbers continue to decline on the central Platte, reflecting declining habitat conditions there. The decline in the tern population on the central Platte River has been coincidental with the loss of numerous bare sandbars and beaches along the river. Control of flows and diversion of water from the channel are the causes of these geomorphic changes. Woodland vegetation, unsuitable as tern habitat, has colonized some parts of the central Platte River. Alternative habitats, such as abandoned sand mines or sandy shores of Lake McConaughy, are not suitable substitutes for Platte River habitat because they are susceptible to disturbance by humans and natural predators. The shores of Lake McConaughy are available only at lower stages of the reservoir, and they disappear at high stages.
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Endangered and Threatened Species of the Platte River Primary Sources of Scientific Information: The scientific underpinnings of these conclusions are extensive and substantial, including work by Smith and Renken (1990), Sidle and Kirsch (1993), Ziewitz et al. (1992), and Higgins and Brashier (1993), all of whom used sound, widely accepted, standard scientific methods. The committee also considered commentary presented in open sessions and written testimony exemplified by Lingle (G. Lingle, unpublished material, March 22, 2000) and Czaplewski et al. (M.M. Czaplewski et al., Central Platte Natural Resources District, unpublished material, August 22, 2003) that was critical of the research conducted by DOI agencies. 6. Do current habitat conditions in the lower Platte (below the mouth of the Elkhorn River) affect the likelihood of survival of the pallid sturgeon? Do they limit (adversely affect) its recovery? Conclusions: Current habitat conditions on the lower Platte River (downstream of the mouth of the Elkhorn River) do not adversely affect the likelihood of survival and recovery of the pallid sturgeon because that reach of the river appears to retain several habitat characteristics apparently preferred by the species: a braided channel of shifting sandbars and islands; a sandy substrate; relatively warm, turbid waters; and a flow regime that is similar to conditions that were found in the upper Missouri River and its tributaries before the installation of large dams on the Missouri. Alterations of discharge patterns or channel features that modify those characteristics might irreparably alter this habitat for pallid sturgeon use. In addition, the lower Platte River is connected with a long undammed reach of the Missouri River, which allows access of the pallid sturgeon in the Platte River to other segments of the existing population. Channelization and damming of the Missouri River have depleted pallid sturgeon habitats throughout its former range, so the lower Platte may be even more important for its survival and recovery. The population of pallid sturgeon is so low in numbers, and habitat such as the lower Platte River that replicates the original undisturbed habitat of the species is so rare that the lower Platte River is pivotal in the management and recovery of the species. Primary Sources of Scientific Information: Scientific studies supporting those conclusions are reported in numerous peer-reviewed publications, as exemplified by general research on the habitat of hatchery-derived pallid sturgeon in the lower Platte River by Snook (2001) and Snook et al. (2002). Carlson et al. (1985) and Kallemeyn (1983) provided useful background information. Additional investigations in the Missouri River system by Bramblett (1996) and Bramblett and White (2001) have results that are applicable to the lower Platte River. The committee also considered com-
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Endangered and Threatened Species of the Platte River mentary presented in open sessions and written testimony exemplified by Czaplewski et al. (M.M. Czaplewski et al., Central Platte Natural Resources District, unpublished material, August 22, 2003) that was critical of the research conducted by DOI agencies. 7. Were the processes and methodologies used by the USFWS in developing its central Platte River instream-flow recommendations (i.e., species, annual pulse flows, and peak flows) scientifically valid? Conclusions: The U.S. Fish and Wildlife Service (USFWS) used methods described in an extensive body of scientific and engineering literature. Reports of interagency working groups that addressed instream-flow recommendations cite more than 80 references that were in wide use and generally accepted in the river science and engineering community. The committee reviewed that information, as well as oral and written testimony critical of the research conducted by DOI agencies, and it concluded that the methods used during the calculations in the early 1990s were the most widely accepted at that time. Revisions were made as improved knowledge became available. Although the Instream Flow Incremental Method (IFIM) and Physical Habitat Simulation System (PHABSIM) were the best available science when DOI agencies reached their recommendations regarding instream flows, there are newer developments and approaches, and they should be internalized in DOI’s decision processes for determining instream flows. The new approaches, centered on the river as an ecosystem rather than focused on individual species, are embodied in the concepts of the normative flow regime. Continued credibility of DOI instream-flow recommendations will depend on including the new approach. The instream-flow recommendations rely on empirical and model-based approaches. Surveyed cross sections along the river provided DOI investigators with specific information on the morphology of the river and vegetation associated with the river’s landforms. The portions of the cross sections likely to be inundated by flows of various depths were directly observed. Model calculations to simulate the dynamic interaction of water, geomorphology, and vegetation that formed habitat for species were handled with the prevailing standard software PHABSIM, which has seen wide use in other cases and has been accepted by the scientific community. The software was used by DOI researchers in a specific standard method, IFIM, which permits observations of the results as flow depths are incrementally increased. The continuing DOI model developments, including the emerging SEDVEG model, are needed because of the braided, complex nature of the Platte River—a configuration that is unlike other streams to which existing models are often applied. The committee did not assess the newer models,
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Endangered and Threatened Species of the Platte River because they have not yet been completed or tested, but it recommends that they be explored for their ability to improve decision making. The committee also recognizes that there has been no substantial testing of the predictions resulting from DOI’s previous modeling work,1 and it recommends that calibration of the models be improved. Monitoring of the effects of recommended flows should be built into a continuing program of adaptive management to help to determine whether the recommendations are valid and to indicate further adjustments to the recommendations based on observations. Primary Sources of Scientific Information: The literature used to support USFWS’s methods ranged from basic textbook sources, such as Dunne and Leopold (1978) and Darby and Simon (1999), to specific applications exemplified by Simons & Associates, Inc. (2000) and Schumm (1998). The committee also considered the interagency working reports (Hydrology Work Group 1989; M. Zallen, DOI, unpublished memo, August 11, 1994) and oral and written testimony exemplified by Parsons (2003), Payne (1995; T.R. Payne and Associates, pers. comm., June 19, 2003), Woodward (2003), and Lewis (2003). 8. Are the characteristics described in the USFWS habitat suitability guidelines for the central Platte River supported by the existing science and are they (i.e., the habitat characteristics) essential to the survival of the listed avian species? To the recovery of those species? Are there other Platte River habitats that provide the same values that are essential to the survival of the listed avian species and their recovery? Conclusions: The committee concluded that the habitat characteristics described in USFWS’s habitat suitability guidelines for the central Platte River were supported by the science of the time of the original habitat description during the 1970s and 1980s and were consistent with accepted understanding of how the systems function. New ecological knowledge has since been developed. The new knowledge, largely from information gathered over the last 20 years, has not been systematically applied to the processes of designating or revising critical habitat, and the committee recommends that it be done. The committee also concluded that suitable habitat characteristics along the central Platte River are essential to the survival and recovery of the piping plover and the interior least tern. No alternative habitat exists in the 1 The committee did not consider USGS’s in-progress evaluation of the models and data used by USFWS to set flow recommendations for whooping cranes.
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Endangered and Threatened Species of the Platte River central Platte that provides the same values essential to the survival and recovery of piping plovers and least terns. Although both species use artificial habitat (such as shoreline areas of Lake McConaughy and sandpits), the quality and availability of sites are unpredictable from year to year. The committee further concluded that suitable habitat for the whooping crane along the central Platte River is essential for its survival and recovery because such alternatives as the Rainwater Basin and other, smaller rivers are used only intermittently, are not dependable from one year to the next, and appear to be inferior to habitats offered by the central Platte River. Primary Sources of Scientific Information: The committee relied on the following sources in reaching its conclusions: for whooping cranes, the original listing document, recovery plan, and declaration of critical habitat and Howe (1989), EA Engineering, Science and Technology, Inc. (1985), Austin and Richert (2001), and Lutey (2002); for interior least terns and piping plovers, the original listing documents, recovery plans, and declaration of critical habitat for the piping plover (Fed. Regist. 67 (176): 57638 ), Smith and Renken (1990), Sidle and Kirsch (1993), Ziewitz et al. (1992), Ducey (1983), Faanes (1983), Higgins and Brashier (1993), Corn and Armbruster (1993), and Kirsch and Sidle (1999). The committee also considered commentary presented in open sessions and written testimony exemplified by Lingle (G. Lingle, unpublished material, March 22, 2000) and Czaplewski et al. (M.M. Czaplewski et al., Central Platte Natural Resources District, unpublished material, August 22, 2003) that was critical of the research conducted by DOI agencies. 9. Are the conclusions of the Department of the Interior about the interrelationships of sediment, flow, vegetation, and channel morphology in the central Platte River supported by the existing science? Conclusions: The committee concluded that DOI conclusions about the interrelationships among sediment, flow, vegetation, and channel morphology in the central Platte River were supported by scientific theory, engineering practice, and data available at the time of those decisions. By the early 1990s, when DOI was reaching its conclusions, the community of geomorphologists concerned with dryland rivers had a general understanding of the role of fluctuating discharges in arranging the land forms of the channel, and DOI included this understanding in its conclusions about the river. In the early 1990s, engineering practice, combined with geomorphology and hydrology, commonly used IFIM and PHABSIM to make predictions and recommendations for flow patterns that shaped channels, and this resulted in adjustments in vegetation and habitat. In fact, despite some criticisms, IFIM and PHABSIM are still widely used in the professional
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Endangered and Threatened Species of the Platte River community of river restorationists in 2004. In applying scientific theory and engineering practice, the DOI agencies used the most current data and made additional measurements to bolster the calculations and recommendations. Since the early 1990s, more data have become available, and the USBR has conducted considerable cutting-edge research on a new model (SEDVEG) that should update earlier calculations but is not yet in full operation (and was not reviewed by this committee). Primary Sources of Scientific Information: Murphy et al. (2001) outline the basic understanding of sediment and vegetation dynamics. Sediment data are obtained by sampling sediment concentrations and multiplying the concentrations by discharges and duration. For flow, gaging records on the Platte River are 50 years in duration or longer, and they are in greater density than on many American rivers; the gages provide quality data on water discharge for the Platte River. Murphy and Randle (2003) review the analyses and other sources of knowledge about the flows that provide a sound basis for DOI decisions. In addition to the review by Murphy et al. (2001) concerning vegetation, several studies over the last 20 years have provided an explanation of vegetation dynamics that the committee found to be correct and that is the basis of DOI decisions. Early work by USFWS (1981a) and Currier (1982) set the stage for an evolution of understanding of vegetation change on the river that was later expanded by Johnson (1994). For channel morphology, there is a long history of widely respected research to draw on, including early geomorphologic investigations by Williams (1978) and Eschner et al. (1983), continuing with the reviews by Simons and Associates (2000), and culminating in recent work by Murphy and Randle (2003). The committee also considered commentary presented in open sessions and written testimony exemplified by Parsons (2003) and Lewis (2003) that was critical of the research conducted by DOI agencies. 10. What were the key information and data gaps that the NAS identified in the review? Conclusions: The committee reached its conclusions for the preceding nine questions with reasonable confidence based on the scientific evidence available. However, the committee identified the following gaps in key information related to threatened and endangered species on the central and lower Platte River, and it recommends that they be addressed to provide improved scientific support for decision making. A multiple-species perspective is missing from research and management of threatened and endangered species on the central and lower Platte River. The interactions of the protected species with each other and with
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Endangered and Threatened Species of the Platte River unprotected species are poorly known. Efforts to enhance one species may be detrimental to another species, but these connections remain largely unknown because research has been focused on single species. One approach is to shift from the focus on single species to an ecosystem perspective that emphasizes the integration of biotic and abiotic processes supporting a natural assemblage of species and habitats. There is no systemwide, integrated operation plan or data-collection plan for the combined hydrological system in the North Platte, South Platte, and central Platte Rivers that can inform researchers and managers on issues that underlie threatened and endangered species conservation. Natural and engineered variations in flows in one part of the basin have unknown effects on other parts of the basin, especially with respect to reservoir storage, groundwater storage, and river flows. A lack of a full understanding of the geographic extent of the populations of imperiled species that inhabit the central Platte River and a lack of reliable information on their population sizes and dynamics limit our ability to use demographic models to predict accurately their fates under different land-management and water-use scenarios. Detailed population viability analyses using the most recent data would improve understanding of the dynamics of the populations of at-risk species and would allow managers to explore a variety of options to learn about the probable outcomes of decisions. Continuation of population monitoring of at-risk bird species using the best available techniques, including color-banding of prefledged chicks and application of new telemetry techniques, is recommended. There is no larger regional context for the central and lower Platte River in research and management. Most of the research and decision making regarding threatened and endangered species in the Platte River Basin have restricted analysis to the basin itself, as though species used its habitats in isolation from other habitats outside the basin. There are substantial gaps in integrative scientific understanding of the connections between species that use the habitats of the central and lower Platte River and adjacent habitat areas, such as the Rainwater Basin of southern Nebraska and the Loup, Elkhorn, and Niobrara Rivers and other smaller northern Great Plains rivers. The committee is confident that the central Platte River and lower Platte River are essential for the survival and recovery of the listed bird species and pallid sturgeon. However, in light of the habitat it provides and the perilously low numbers of the species, there is not enough information to assess the exact degree to which the Platte contributes to their survival and recovery. Water-quality data are not integrated into knowledge about species responses to reservoir and groundwater management and are not integrated
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Endangered and Threatened Species of the Platte River into habitat suitability guidelines. Different waters are not necessarily equal, either from a human or a wildlife perspective, but there is little integration of water-quality data with physical or biological understanding of the habitats along the Platte River. The cost effectiveness of conservation actions related to threatened and endangered species on the central and lower Platte River is not well known. Neither the cost effectiveness nor the equitable allocation of measures for the benefit of Platte River species has been evaluated. The ESA does not impose or allow the implementing agencies to impose a cost-benefit test. Listed species must be protected no matter what the cost, unless the Endangered Species Committee grants an exemption. Cost effectiveness, however, is another matter. The ESA permits consideration of relative costs and benefits when choosing recovery actions, for example. USFWS has adopted a policy that calls for minimizing the social and economic costs of recovery actions, that is, of choosing actions that will provide the greatest benefit to the species at the lowest societal cost (Fed. Regist. 59:3472 ). In addition, persons asked to make economic sacrifices for the sake of listed species understandably want assurances that their efforts will provide some tangible benefit. In the Platte, the direct economic costs of measures taken for the benefit of species appear reasonably well understood. The biological benefits are another matter. For example, the costs of channel-clearing and other river-restoration measures are readily estimated. Their precise value for cranes is more difficult to estimate, although their general use is fairly well established. The allocation of conservation costs and responsibility also has not been systematically evaluated. USFWS has concentrated its efforts to protect listed species in the Platte system on federal actions, such as the operation of federal water projects. That focus is understandable. Water projects with a federal nexus account for a large and highly visible proportion of diversions from the system. In addition, those actions may be more readily susceptible to regulatory control than others because they are subject to ESA Section 7 consultation. But some nonfederal actions also affect the species. Water users that depend on irrigation water from the federal projects may well feel that they are being asked to bear an inordinate proportion of the costs of recovering the system. A systematic inventory of all actions contributing to the decline of the species could help the parties to the cooperative agreement channel their recovery efforts efficiently and equitably. The National Research Council committee charged with evaluating ESA actions in the Klamath River Basin recently reached a similar conclusion (NRC 2004a). The effects of prescribed flows on river morphology and riparian vegetation have not been assessed. Adaptive-management principles require that the outcomes of a management strategy be assessed and monitored and
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Endangered and Threatened Species of the Platte River that the strategy be adjusted accordingly, but there has been no reporting of the outcomes of the 2002 prescribed flow, no analysis of vegetation effects of managed flows, no measurement of their geomorphic effects, and no assessment of their economic costs or benefits. The connections between surface water and groundwater are not well accounted for in research or decision making for the central and lower Platte River. The dynamics of and connections between surface water and groundwater remain poorly known, but they are important for understanding river behavior and economic development that uses the groundwater resource. The effects of groundwater pumping, recently accelerated, are unknown but important for understanding river flows. Some of the basic facts of issues regarding threatened and endangered species in the central and lower Platte River are in dispute because of unequal access to research sites. Free access to all data sources is a basic tenet of sound science, but DOI agencies and Nebraska corporations managing water and electric power do not enter discussions about threatened and endangered species on the central and lower Platte River with the same datasets for species and physical environmental characteristics. USFWS personnel are not permitted to collect data on some privately owned lands. As a result, there are substantial gaps between data used by DOI and data used by the companies, and resolution is impossible without improved cooperation and equal access to measurement sites. Important environmental factors are not being monitored. Monitoring, consistent from time to time and place to place, supports good science and good decision making, but monitoring of many aspects of the issues regarding threatened and endangered species on the central and lower Platte River remains haphazard or absent. Important gaps in knowledge result from a lack of adequate monitoring of sediment mobility, the pallid sturgeon population, and movement of listed birds. Responses of channel morphology and vegetation communities to prescribed flows and vegetation removal remain poorly known because the same set of river cross sections is not sampled repeatedly. Groundwater may play an important role in flows, but groundwater pumping is not monitored. Long-term (multidecadal) analysis of climatic influences has not been used to generate a basis for interpretation of short-term change (change over just a few years). The exact interactions between climate and the system are poorly known because only short-term analyses of climate factors have been accomplished so far. In addition, the relative importance of human and climatic controls remains to be explicitly defined by researchers, even though such knowledge is important in planning river restoration for habitat purposes. Direct human influences are likely to be much more important than climate in determining conditions for the threatened and endangered species
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Endangered and Threatened Species of the Platte River of the central and lower Platte River. Potentially important localized controls on habitat for threatened and endangered species on the central and lower Platte River are likely to be related to urbanization, particularly near freeway exits and small cities and towns where housing is replacing other land uses more useful to the species. Off-road vehicle use threatens the nesting sites of piping plovers and interior least terns in many of the sandy reaches of the river. Sandy beaches and bars are inviting to both birds and recreationists. Illegal harvesting has unknown effects on the small remaining population of pallid sturgeon. In each of those cases, additional data are required to define the threats to the listed species. SUMMARY USFWS faces extraordinary challenges in trying to identify the habitat needs and the critical habitat for listed species on the central and lower Platte River. Lack of data, pressures of tight deadlines for research, lack of a well-defined adaptive-management strategy with effective monitoring, and competing uses for the river’s water and landscape resources complicate decision making. Despite those challenges, the science that explains forms and processes of the ecosystems along the central and lower Platte River of Nebraska is sufficient to support many decisions about the management of threatened and endangered species that use the river’s habitats. In all cases, enough is known about the physical environmental processes that control habitat change to make informed decisions for the survival of the whooping crane, piping plover, interior least tern, and pallid sturgeon. Our scientific knowledge is not yet adequate to contribute to decisions regarding the exact role of the central and lower Platte River in the recovery of the whooping crane and pallid sturgeon. Valid science supports critical habitat designations for the piping plover, but the scientific support of critical habitat designation for the whooping crane is weak. Valid science and engineering related to hydrology, geomorphology, sediment transport, and riparian ecology support the DOI instream-flow recommendations and explanations for the river-channel and vegetation changes. The committee found numerous gaps in knowledge that could inform management of threatened and endangered species along the central and lower Platte River, mostly focused on problems of scientific integration, overrestricted scales of analysis, lack of systemwide connections, and lack of standardized procedures for data collection. Land, water, and life in the region surrounding the 100th meridian on the Platte River are highly changeable and precariously balanced. Human manipulations of hydrological conditions and land cover have far-reaching consequences for wildlife populations. Policy based on a desired constant, stable, and predictable set of environmental circumstances is unlikely to be
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Endangered and Threatened Species of the Platte River successful. Policy that relies on scientific knowledge about change through time and over geographic space is the most likely avenue to success in the search for accommodation between economic vitality and diverse and sustainable populations of wildlife that are neither threatened nor endangered.
Representative terms from entire chapter: