Summary

Since 1971, the Bureau of Land Management (BLM) of the U.S. Department of the Interior has been responsible for managing the majority of free-ranging horses and burros on arid federal public lands in the western United States. In the Wild Free-Roaming Horses and Burros Act of 1971 (P.L. 92-195), the U.S. Congress charged BLM with the “protection, management, and control of wild free-roaming horses and burros on public lands.” However, the agency is also tasked with managing the land for multiple uses. Public lands provide habitat for horses and burros, but they are also used for recreation, mining, forestry, grazing for livestock, and habitat for wild ungulates and other species. Therefore, although the act stipulated that free-ranging horses and burros were “an integral part of the natural system of the public lands,” it limited their range to “their known territorial limits” in 1971. The land was to be “devoted principally but not exclusively to their welfare in keeping with the multiple-use management concept of public lands.” Horses and burros were to be managed at “the minimal feasible level.” In addition, management was to “achieve and maintain a thriving natural ecological balance on the public lands,” protect wildlife habitat, and prevent range deterioration.

The goal of managing free-ranging horses and burros to achieve the vaguely defined thriving natural ecological balance within the multiple-use mandate for public lands has challenged BLM’s Wild Horse and Burro Program since its inception. When BLM commissioned the National Research Council to conduct a study of the program in 2011, budget costs for managing the animals were mounting. To sustain healthy populations on healthy rangeland and to maintain a thriving natural ecological balance, BLM attempts to manage herds within population-size ranges that it deems appropriate management levels (AMLs) for designated regions known as Herd Management Areas (HMAs). However, because there are human-created barriers to dispersal and movement and no substantial predator pressure, maintaining a herd within an AML requires removing animals in roundups, also known as gathers. Adoption demand does not balance the number of animals removed, and there is no political support for culling unadopted animals. Therefore, BLM pays for animals removed from the range to live in long-term holding pastures for the remainder



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Summary S ince 1971, the Bureau of Land Management (BLM) of the U.S. Department of the ­Interior has been responsible for managing the majority of free-ranging horses and burros on arid federal public lands in the western United States. In the Wild Free-Roaming Horses and Burros Act of 1971 (P.L. 92-195), the U.S. Congress charged BLM with the “protec- tion, management, and control of wild free-roaming horses and burros on public lands.” However, the agency is also tasked with managing the land for multiple uses. Public lands provide habitat for horses and burros, but they are also used for recreation, mining, forestry, grazing for livestock, and habitat for wild ungulates and other species. Therefore, although the act stipulated that free-ranging horses and burros were “an integral part of the natural system of the public lands,” it limited their range to “their known territorial limits” in 1971. The land was to be “devoted principally but not exclusively to their welfare in keeping with the multiple-use management concept of public lands.” Horses and burros were to ­ be managed at “the minimal feasible level.” In addition, management was to “achieve and maintain a thriving natural ecological balance on the public lands,” protect wildlife habitat, and prevent range deterioration. The goal of managing free-ranging horses and burros to achieve the vaguely defined thriving natural ecological balance within the multiple-use mandate for public lands has challenged BLM’s Wild Horse and Burro Program since its inception. When BLM commis- sioned the National Research Council to conduct a study of the program in 2011, budget costs for managing the animals were mounting. To sustain healthy populations on healthy rangeland and to maintain a thriving natural ecological balance, BLM attempts to manage herds within population-size ranges that it deems appropriate management levels (AMLs) for designated regions known as Herd Management Areas (HMAs). However, because there are human-created barriers to dispersal and movement and no substantial predator pressure, maintaining a herd within an AML requires removing animals in roundups, also known as gathers. Adoption demand does not balance the number of animals removed, and there is no political support for culling unadopted animals. Therefore, BLM pays for animals removed from the range to live in long-term holding pastures for the remainder 1

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2 USING SCIENCE TO IMPROVE THE BLM WILD HORSE AND BURRO PROGRAM of their lives. At the time the committee’s report was prepared, long-term holding costs consumed about half the Wild Horse and Burro Program’s budget. BLM is subject to ardent criticism from various stakeholders regarding its approach to management of free-ranging equids. Some parties express concern that the health of the range and the condition of other species that inhabit the land are adversely affected by pop- ulations of horses and burros that often exceed AMLs. Other members of the public think that horses and burros are unfairly restricted and are concerned that AMLs are too low to maintain genetically healthy herds and that horses and burros are confined to too little public land. They are also concerned about the stress placed on animals during ­gathers and in holding facilities. To improve the sustainability and public acceptance of the program, BLM asked the National Research Council Committee to Review the Bureau of Land Management Wild Horse and Burro Management Program to build on previous Research Council reports on BOX S-1 Statement of Task At the request of the Bureau of Land Management (BLM), the National Research Council (NRC) will conduct an independent, technical evaluation of the science, methodology, and technical decision-making approaches of the Wild Horse and Burro Management Program. In evaluating the program, the study will build on findings of three prior reports prepared by the NRC in 1980, 1982, and 1991 and summarize additional, relevant research completed since the three earlier reports were prepared. Relying on informa- tion about the program provided by BLM and on field data collected by BLM and others, the analysis will address the following key scientific challenges and questions: 1. Estimates of the wild horse and burro populations: Given available information and methods, how accu­ ately can wild horse and burro populations on BLM land designated for wild horse and burro use r be estimated? What are the most accurate methods to estimate wild horse and burro herd numbers and what is the margin of error in those methods? Are there better techniques than BLM currently uses to estimate population numbers? For example, could genetics or remote sensing using unmanned aircraft be used to estimate wild horse and burro population size and distribution? 2. Population modeling: Evaluate the strengths and limitations of models for predicting impacts on wild horse populations given various stochastic factors and management alternatives. What types of deci- sions are most appropriately supported using the WinEquus model? Are there additional models BLM should consider for future uses? 3. Genetic diversity in wild horse and burro herds: What does information available on wild horse and burro herds’ genetic diversity indicate about long-term herd health, from a biological and genetic per- spective? Is there an optimal level of genetic diversity within a herd to manage for? What management actions can be undertaken to achieve an optimal level of genetic diversity if it is too low? 4. Annual rates of wild horse and burro population growth: Evaluate estimates of the annual rates of i ­ncrease in wild horse and burro herds, including factors affecting the accuracy of and uncertainty related to the estimates. Is there compensatory reproduction as a result of population-size control (e.g., fertility control or removal from herd management areas)? Would wild horse and burro populations self-limit if they were not controlled, and if so, what indicators (rangeland condition, animal condition, health, etc.) would be present at the point of self-limitation?

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SUMMARY 3 the program and to provide BLM with a scientific evaluation of the program’s pressing chal- lenges (Box S-1). KEY FINDINGS FINDING: Management of free-ranging horses and burros is not based on rigor- ous population-monitoring procedures. At the time of the committee’s review, most HMAs did not use inventory methods or statistical tools common to modern wildlife management. Survey methods used to obtain sequential counts of populations on HMAs were often inconsistent and poorly documented and did not quantify uncertainty related to estimates. The committee concluded that many methodological flaws identified in previous reviews of the program have persisted. 5. Predator impact on wild horse and burro population growth: Evaluate information relative to the abundance of predators and their impact on wild horse and burro populations. Although predator management is the responsibility of the U.S. Fish and Wildlife Service or State wildlife agencies and given the constraints in existing federal law, is there evidence that predators alone could effectively control wild horse and burro population size on BLM land designated for wild horse and burro use? 6. Population control: What scientific factors should be considered when making population control deci- sions (roundups, fertility control, sterilization of either males or females, sex ratio adjustments to favor males, and other population control measures) relative to the effectiveness of control approach, herd health, genetic diversity, social behavior, and animal well-being? 7. Fertility control of wild horses: Evaluate information related to the effectiveness of fertility control m ­ ethods to prevent pregnancies and reduce herd populations. 8. Managing a portion of a population as nonreproducing: What scientific and technical factors should BLM consider when managing for wild horse and burro herds with a reproducing and nonreproducing population of animals (i.e., a portion of the population is a breeding population and the remainder is nonreproducing males or females)? When managing a herd with reproducing and nonreproducing animals, which options should be considered: geldings, vasectomized males, ovariectomized mares, or other interventions? Is there credible evidence to indicate that geldings or vasectomized stallions in a herd would be effective in decreasing annual population growth rates, or are there other methods BLM should consider for managing stallions in a herd that would be effective in tangibly suppressing population growth? 9. Appropriate Management Level (AML) establishment or adjustment: Evaluate BLM’s approach to estab- lishing or adjusting AML as described in the 4700-1 Wild Horses and Burros Management Handbook. Based upon scientific and technical considerations, are there other approaches to establishing or adjust- ing AML BLM should consider? How might BLM improve its ability to validate AML? 10. Societal considerations: What are some options available to BLM to address the widely divergent and conflicting perspectives about wild horse and burro management and to consider stakeholder concerns while using the best available science to protect land and animal health? 11. Additional research needs: Identify research needs and opportunities related to the topics listed above. What research should be the highest priority for BLM to fill information and data gaps, reduce uncer- tainty, and improve decision-making and management?

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4 USING SCIENCE TO IMPROVE THE BLM WILD HORSE AND BURRO PROGRAM However, improvements in population monitoring have been implemented in recent years, and the committee supports these efforts. Aggregating neighboring HMAs, on which free movement of horses or burros is known or likely, into HMA complexes to coordinate population surveys, removals, and other management actions can improve data quality and interpretation and enhance population management (Figure S-1). The committee com- mends the partnership between BLM and the U.S. Geological Survey to develop rigorous, practical, and cost-effective survey methods that account for imperfect detection of animals. The committee strongly encourages continuing this collaborative research effort to develop a suite of survey methods effective for the variety of landscapes occupied by free-ranging equids. Transferring this knowledge to managers responsible for monitoring populations is essential if the reforms are to be institutionalized. BLM should develop protocols for how frequently surveys are to be conducted and ensure that the resources are available to field personnel to maintain a standardized survey schedule. Consideration should be given to identifying sentinel populations in a subset of HMAs that represent the diverse ecological settings throughout western rangelands. Detailed, annual demographic studies of sentinel populations could be used to improve assessment of population dynamics and responses to changes in animal den- sity, management interventions, seasonal weather, and climate. Record-keeping needs to be substantially improved; the committee recommends the development of a uniform FIGURE S-1  Herd Management Areas managed together or with Wild Horse (or Burro) Territories as complexes. NOTE: Blank Herd Management Areas are not managed as part of a complex. DATA SOURCE: Mapping data and complex information provided by the Bureau of Land Management.

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SUMMARY 5 relational database that is accessible to and used by all field offices for recording all pertinent population survey data. FINDING: On the basis of the information provided to the committee, the statis- tics on the national population size cannot be considered scientifically rigorous. The links between the statistics on the national population size and actual population surveys, which are the foundational data of all estimates, are obscure. The procedures used for developing annual HMA population-size estimates from counts are not standardized and often not documented. Therefore, it seems that the national statistics are the product of hundreds of subjective, probably independent, judgments and assumptions by range managers and administrators about the proportion of animals counted during surveys, population growth rates, effects of management interventions, and potential animal move- ments between HMAs. Development and use of a uniform and centralized relational database, which captures all inventory and removal data generated at the level of the field offices and animal pro- cessing and holding facilities, to generate annual program-wide statistics would provide a clear connection between the data collected and the reported statistics. The committee also suggests that the survey data at the HMA level and procedures used to modify the survey data to generate population estimates be made readily available to the public to improve transparency and public trust in the management program. In the committee’s judgment, the reported annual population statistics are probably underestimates of the actual number of equids on the range inasmuch as most of the indi- vidual HMA population estimates are based on the assumption that all animals are detected and counted in population surveys. A large body of scientific literature on techniques for inventorying horses and other large mammals clearly refutes that assumption and suggests that the proportion of animals missed on surveys ranges from 10 to 50 percent. An earlier National Research Council committee and the Government Accountability Office also con- cluded that reported statistics were underestimates. FINDING: Horse populations are growing at 15-20 percent a year. The committee concluded that the age-structure data on horses removed from the range can provide a reasonable assessment of the general growth rate of the free-ranging horse populations in the western United States. The population growth rate index derived from those data is generally consistent with the herd-specific population growth rates reported in the literature. On the basis of the published literature and the additional management data reviewed by the committee, the committee concluded that most free-ranging horse populations managed by BLM are probably growing at 15-20 percent a year. FINDING: Management practices are facilitating high horse population growth rates. Free-ranging horse populations are growing at high rates because their numbers are held below levels affected by food limitation and density dependence. In population ecol- ogy, density dependence refers to the influence of density on such population processes as population growth, age-specific survival, and natality. Effects of increased population den- sity are manifested through such changes as reductions in pregnancy, fecundity, percentage of females lactating, young-to-female ratios, and survival rates. Regularly removing horses

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6 USING SCIENCE TO IMPROVE THE BLM WILD HORSE AND BURRO PROGRAM holds population levels below food-limited carrying capacity. Thus, population growth rate could be increased by removals through compensatory population growth from decreased competition for forage. As a result, the number of animals processed through holding facili- ties is probably increased by management. FINDING: The primary way that equid populations self-limit is through ­increased competition for forage at higher densities, which results in smaller quantities of forage available per animal, poorer body condition, and decreased natality and survival. Density dependence, due to food limitation, will reduce population growth rates in equids and other large herbivores through reduced fecundity and survival. Case studies show that animal responses to density dependence will include increased numbers of ani- mals that are in poor body condition and are dying from starvation. Rangeland health is also affected by density dependence. Equids invariably affect veg- etation abundance and composition. Reduced vegetation cover, shifts in species composi- tion, and increased erosion rates often occur on rangelands occupied by equids. However, no case study has reported that the changed vegetation cannot persist over a long period of time or that complete loss of vegetation cover is an inevitable outcome. The results are consistent with theoretical predictions that when a herbivore population is introduced, vegetation cover will initially change and productivity will often be reduced by herbivory. In some environments, however, moderate levels of herbivory have little adverse effect or even have favorable effects on plant production. Vegetation production may decline, but it may stabilize at a lower level as herbivore populations come into quasiequilibrium with the altered vegetation. Whether such a system can persist over the long term is unknown. FINDING: Predation will not typically control population growth rates of free- ranging horses. A large predator, when abundant, can influence the dynamics of free-ranging ­ungulates. However, the potential for predators to affect free-ranging horse populations is limited by the absence of abundance of such predators as mountain lions and wolves on HMAs. Mountain lions are ambush predators and require habitats that have broken topography and tree cover, whereas equids favor habitats that have more extensive viewsheds. Wolves are capable of chasing prey across open, flat topography and have substantial effects on a few horse populations on other continents and certain areas in Canada. Despite evidence that wolves prey on equids elsewhere, the committee was unable to identify any examples of wolf predation on free-ranging equids in the United States. The distribution of wolves in the western United States has been severely reduced by humans, and few habitats of free- ranging horses were occupied by wolves at the time the report was prepared; in addition, there had been little study of the overlap between burros and predators. FINDING: The most promising fertility-control methods for application to free- ranging horses or burros are porcine zona pellucida (PZP) vaccines, GonaCon™ vaccine, and chemical vasectomy. The criteria most important in selecting promising fertility-control methods for free- ranging equids are the delivery method, availability, efficacy, duration of effect, and ­potential physiological and behavioral side effects. Considering those criteria, the methods judged

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SUMMARY 7 most promising are PZP and GonaCon vaccination of females and chemical vasectomy in males. Each method has advantages and disadvantages (Table S-1). Of the PZP vaccines, PZP-22 and SpayVac® seem most appropriate and practical because of their longer dura- tion of effect. GonaCon can be used and has been tested in males, and its effects are similar to those of chemical castration. Preserving natural behaviors is important, so GonaCon seems more appropriate for use in females in that some research has suggested that female sexual behavior continues. However, further studies on behavioral effects of this product are needed. Chemical vasectomy is promising as an alternative to or in combination with treating females. The effects of surgical vasectomy, and presumably of chemical vasectomy, on sexual behavior closely parallel those of the PZP vaccines and possibly of GonaCon. No method that does not affect physiology or behavior has been developed. The most appropriate comparison in assessing the effects of any fertility-control method is with gath- ering. That is, to what extent does the prospective method affect health, herd structure, and TABLE S-1  Advantages and Disadvantages of the Most Promising Fertility-Control Methods Method Advantages Disadvantages PZP-22 and Research and application in both Capture needed for hand injection of PZP-22 SpayVac®a captive and free-ranging horses Allows estrous cycles to continue so Extended breeding season requires males to natural behaviors are maintained defend females longer High efficacy With repeated use, return to fertility becomes less predictable Can be administered during pregnancy Out-of-season births are possible or lactation Chemical Simpler than surgical vasectomy Requires handling and light anesthesia Vasectomy Permanent Permanent No side effects expected Only surgical vasectomy has been studied in horses, so side effects of the chemical agent are unknown Normal male behaviors maintained Extended breeding season requires males to defend females longer and may result in late- season foals if remaining fertile males mate Should have high efficacy Only surgical vasectomy has been studied in horses, so efficacy rate is unknown GonaCon™ Capture may be needed for hand injection of for Females initial vaccine and any boosters Effective for multiple years Lower efficacy than PZP-vaccine products, especially after first year Sexual behavior exhibited Sexual behavior may not be cyclic, inasmuch as ovulation appears to be blocked Social behaviors not affected in the Should not be administered during early single field study pregnancy because abortion could occur Few data on horses aPZP-22 and SpayVac® are formulated for longer efficacy and require further documentation of continued efficacy and of rate of unexpected effects.

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8 USING SCIENCE TO IMPROVE THE BLM WILD HORSE AND BURRO PROGRAM the expression of natural behaviors compared with the effects of gathering? The selected methods are considered the most promising because they have the fewest and least serious effects on those parameters. Their application requires handling the animals (gathering), but this process is no more disruptive than the current method for controlling numbers and does not entail the further disruption of removal and relocation to long-term holding facilities. Considering all the current options, these three methods, either alone or in com- bination, offer the most acceptable alternative for managing population numbers. FINDING: Management of equids as a metapopulation is necessary for the long- term genetic health of horses and burros at the HMA or HMA-complex level. The committee reviewed the results of genetic studies of 102 horse HMAs that were based on samples collected during 2000-2012 and found that the reported levels in genetic diversity for most populations were similar to those in healthy mammalian populations, although that could change in time. Little is known about the genetic health of burros; the few studies that have been conducted reported low genetic diversity compared with that in domestic donkeys. Management actions to achieve optimal genetic diversity may ­nvolvei intensive management of individual animals in HMAs, translocations of free-ranging horses and burros among HMAs or holding areas to effect genetic restoration, or some combination of these. The committee recommends routine monitoring at all gathers and the collection and analysis of a sufficient number of samples to detect losses of diversity. The committee also recommends that BLM consider at least some animals on different HMAs as a single population and use the principles of metapopulation theory to direct management activi- ties that attain and maintain the level of genetic diversity needed for continued survival, reproduction, and adaptation to changing environmental conditions. Although there is no minimum viable population size above which a population can be considered forever viable, studies suggest that thousands of animals will be needed for long-term viability and maintenance of genetic diversity. Few HMAs are large enough to buffer the effects of genetic drift and herd sizes must be maintained at prescribed AMLs, so managing HMAs as a metapopulation will reduce the rate of reduction of genetic diversity over the long term. Movement of individual animals among HMAs to maintain genetic diversity will need to be guided by genetic, demographic, behavioral, and logistical factors. FINDING: Phenotypic data have not been recorded and integrated into genetic management of free-ranging populations. Recording the occurrence of diseases and clinical signs and the ages and sexes of the affected animals would allow BLM to monitor the distribution and prevalence of genetic conditions that have direct effects on population health. Ten or 11 conditions in horses are known to be caused by genetic mutations. Some are not lethal, so it is possible for the mutations to increase in frequency in HMAs, especially if inbreeding occurs. Few conditions present clinical signs that would be unambiguous and readily discernible during a gather. However, because many of the conditions can be diagnosed via genetic screening of blood or hair samples, surveillance of the genetic muta- tions underlying them is possible in HMAs. Screening samples from gathered horses could generate frequencies of the alleles involved in the disorders, and the frequencies could be monitored during later gathers to determine whether a particular HMA has a higher occur- rence of a given mutation that might affect the fitness of the herd. Although there are no known clinical issues in burros, the committee recommends that BLM routinely monitor

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SUMMARY 9 and record any morphological anomalies in burros that may indicate the deleterious e ­ ffects of inbreeding. FINDING: Input parameters used in the WinEquus model are not transparent, and it is unclear whether or how results are used in management decisions. BLM includes results of WinEquus population modeling in its gather plans and envi­ ronmental assessments of horse HMAs. WinEquus uses an individual-based approach (each animal is tracked individually as opposed to the use of aggregated age-sex or life- stage classes) to simulate population dynamics and management of free-ranging horses in the framework of age-structured and sex-structured population models. Given appropri- ate data, it can incorporate the effects of environmental and demographic stochasticities, density dependence, and management actions and can simulate population dynamics for up to 20 years. There are no similar modeling studies of burros. The committee found that, given appropriate data, WinEquus can adequately simulate horse population dynamics under alternative management actions (no treatment, removal, female fertility control, and the combination of removal and fertility control). However, the WinEquus results depend heavily on values of input parameters and on the WinEquus o ­ ptions selected by the user when setting up the simulations. Values of input parameters and data used to estimate the values were rarely provided, and the WinEquus options selected often were not described. Most gather plans and environmental assessments sim- ply copied and pasted WinEquus output and gave no explanation or interpretation of the results. Those results cannot be adequately interpreted without knowledge of the input parameter values and WinEquus options selected by the user. It appeared that one of the default datasets was used to model population dynamics of most or all HMAs or HMA complexes. It is therefore not surprising that most plans and assessments arrived at identical conclusions regarding the potential effects of the manage- ment alternatives considered. The majority of gather plans conveyed nothing about whether or how results of popu- lation modeling were used to make management decisions, so the committee could not determine with certitude whether or how BLM uses WinEquus results. Specifically, it was difficult to determine whether results were used to make management decisions or were offered as justification for management decisions that were made independently of model­ ing results. Furthermore, in the absence of at least some site-specific data and relevant information regarding input parameters and WinEquus options, model results would be difficult for a critical reader to accept as pertinent and meaningful. A clear description of input parameters, including those needed for various management alternatives, and a detailed description of various WinEquus options selected by the user would help the gen- eral public to determine the reliability of WinEquus modeling results. In addition, a clear explanation of whether or how results of population modeling were used would improve transparency with the public. FINDING: A more comprehensive model or suite of models could help BLM to address and adapt to challenges related to management of horses and burros on the range, management of animals in holding facilities, and program costs. The adequacy of a population model depends on how (and for what purpose) BLM plans to use it, characteristics and processes included in it, management alternatives to be simulated, and availability of data to assign values to parameters of the model. If BLM

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10 USING SCIENCE TO IMPROVE THE BLM WILD HORSE AND BURRO PROGRAM plans to use a population model for short-term horse population projection and to evaluate potential effects of such management alternatives as female fertility control, removal, or a combination of the two, WinEquus is probably sufficient. However, a suitable modeling framework could inform short-term and long-term man- agement plans. Such a framework would simulate life history, social behavior, mating system, genetics, forage limitation, use of habitat, climate variation, and effects of alterna- tive management actions throughout horse or burro life spans. The usefulness of the infor- mation obtained from population modeling is directly related to the reliability of the data used to assign values to parameters and depends on how adequately the model structure reflects life history of the study organisms and whether and to what extent deterministic, stochastic, and management actions that affect the study population are considered. The committee recognizes that HMA managers often do not have adequate input information to estimate model parameter values for most HMAs. Therefore, efforts should be made to ensure that future modeling exercises use data from the target HMA or HMA complex or a sentinel population that closely resembles the target population being modeled. A comprehensive modeling study that evaluates the population dynamics of horses or burros in the western rangelands and in short-term and long-term holding facilities and the costs and consequences of management alternatives, including those not yet available to BLM, would help in evaluating whether and to what extent stated management objectives are achievable under current or projected funding situations. Such a study could help to identify the most effective or cost-effective management options to achieve the objectives or the achievable goals given available funding and policy constraints. FINDING: The Wild Horses and Burros Management Handbook lacks the speci- ficity necessary to guide managers adequately in establishing and adjusting appropriate management levels. The Wild Horses and Burros Management Handbook, issued by BLM in 2010, provides some degree of consistency in goals, forage allocation, and general habitat considerations and should help to improve consistency in how AMLs are set. However, it does not pro- vide detail related to monitoring and assessment methods. The resulting flexibility allows managers to decide what specific approaches fit local environmental conditions and admin- istrative capacity but makes it difficult to review the program’s on-the-ground methods. The handbook would be more informative if it provided guidelines on how to conduct various kinds of assessments (even if there were a variety of appropriate methods avail- able) or referenced appropriate sources, linking them to particular settings or situations. The handbook lacks clear protocols for evaluating habitat components other than forage availability. Without clear protocols specific enough to ensure repeatability, the monitoring organization cannot determine whether observed change is due to changes in condition or to changes in methods. Protocols should also include establishment of controls when the goal is to distinguish treatment or management effects from other causes of change. FINDING: The handbook does not clarify the vague legal definitions related to implementing and assessing management strategies for free-ranging equids. Managing equid populations as free-ranging with the minimal management called for in the legislation entails conceptual challenges associated with defining what constitutes land deterioration or health, thriving natural ecological balance, and rangeland condition. For example, the concept of a thriving natural ecological balance does not provide guidance

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SUMMARY 11 for determining how to allocate forage and other resources among multiple uses, which ecosystem components should be included and monitored in the “balance,” or how to decide when a system is out of “balance.” It brings up arguments over whether such a bal- ance exists in nature or is even possible. Furthermore, it is easily conflated with the forage allocation process, which is a policy decision. Similarly, rangeland health and setting of land health standards may be seen as a problem of developing specific ecological measure- ments and standards or as a matter of arriving at a consensus about how rangelands should be maintained. Without precise definitions, those concepts are uninformed by science and open to multiple interpretations. The handbook does not provide assistance in dealing with this dilemma. An alternative approach for setting AMLs would address the challenge of defining terms used as management criteria, including appropriate, thriving, natural, in balance, healthy, and deteriorated. The approach would involve the development of a conceptual model for ecosystem functioning relative to management objectives and of indicators to measure the degree of departure from a scientifically informed conceptual model of an “appropriately” functioning free-ranging equid ecosystem. FINDING: How AMLs are established, monitored, and adjusted is not transpar- ent to stakeholders, supported by scientific information, or amenable to adapta- tion with new information and environmental and social change. AMLs are a focal point of controversy between BLM and the public. It is therefore necessary to develop and maintain standards for transparency, quality, and equity in AML establishment, adjustment, and monitoring. Research suggests that transparency is an im- portant contributor to the development of trust between agencies and stakeholders. The public should be able to understand the methods used and how they are implemented and should be able to access the data used to make decisions. Transparency will also encour- age high quality in data acquisition and use. Data and methods used to inform decisions must be scientifically defensible. Resources are allocated to horses or burros in a context of contending uses for BLM lands, all of which have some standing in the agency’s charge for multiple-use management. Environmental variability and change, changes in social values, and the discovery of new information require that AMLs be adaptable. Adaptive management, an itera- tive ­ ecision-making process, can incorporate development of management objectives, d actions to address these objectives, monitoring of results, and repeated adaptation of management to achieve desired results. A key tenet of adaptive management is treating m ­ anagement ­ ctions as testable hypotheses. Maximizing long-term knowledge of the a system and thereby improving management hinge on several fundamental tenets of research and monitoring design, including the use of controls and replication and con- trolling for variability over time. Uncertainty should be explicitly incorporated into estimated measures (such as herd size or utilization rate on an HMA). The committee concludes that the above principles could be more thoroughly integrated into the Wild Horse and Burro Program to increase the defensibility and scientific validity of manage- ment actions. FINDING: Resolving conflicts with polarized values and opinions regarding land management rests on the principles of transparency and community-based public participation and engagement in decision-making. Decisions of scien- tific content will have greater support if they are reached through collaborative,

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12 USING SCIENCE TO IMPROVE THE BLM WILD HORSE AND BURRO PROGRAM broadly based, integrated, and iterative analytic-deliberative processes that i ­ nvolve both the agency and the public. There are several well-developed processes for encouraging public participation in public-lands decision-making and management. To reduce conflict and improve the trans- parency and quality of decisions, the committee suggests using the analytic-deliberative approach to public participation. Participatory decision-making processes foster the devel- opment of a shared understanding of the ecosystem, an appreciation for others’ viewpoints, and the development of good working relationships. Thus, BLM should engage with the public in ways that allow public input to influence agency decisions, develop an iterative process between public deliberation and scientific discovery, and codesign the participa- tory process with representatives of the public. Finding ways to involve citizens in data- gathering or other scientific practices may help to build relationships and understanding. Because there are also concerns about horses and burros among the national—not just the local and regional—public, it would be appropriate for BLM to support research that uses survey methods that go beyond opinion polls to capture tradeoffs in public concerns to improve understanding of perceptions, values, and preferences regarding horse and burro management, as was recommended by the National Research Council in 1980 and 1982. FINDING: Tools already exist for BLM to use in addressing challenges faced by its Wild Horse and Burro Program. The continuation of “business-as-usual” practices will be expensive and unproductive for BLM. Because compelling evidence exists that there are more horses on public range- lands than reported at the national level and that horse population growth rates are high, unmanaged populations would probably double in about 4 years. If populations were not actively managed for even a short time, the abundance of horses on public rangelands would increase until animals became food-limited. Food-limited horse populations would affect forage and water resources for all other animals on shared rangelands and potentially conflict with the multiple-use policy of public rangelands and the legislative mandate to maintain a thriving natural ecological balance. Fertility-control agents have been pursued to enhance efficacy of population management, with the potential to reduce population growth rates and hence the number of animals added to the national population each year. The potential effects of fertility control, however, are limited by the number and propor- tion of animals that must be effectively treated with contraceptive agents. The committee’s conclusions that there are considerably more horses and possibly burros on public lands than reported and that population growth rates are high suggest that the effects of fertility intervention, although potentially substantial, may not completely alleviate the challenges BLM faces in the future in effectively managing the nation’s free-ranging equid popula- tions, given legislative and budgetary constraints. However, the tools already exist for BLM to address many challenges. Given the na- ture of the situation, a satisfactory resolution will take time, resources, and dedication to a combination of strategies underpinned by science. In the short term, intensive management of free-ranging horses and burros would be expensive, but addressing the problem imme- diately with a long-term view is probably a more affordable and satisfactory answer than continuing to remove animals to long-term holding facilities. Investing in science-based management approaches would not solve the problem instantly, but it could lead the Wild Horse and Burro Program to a more financially sustainable path that manages healthy horses and burros with greater public confidence.