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Bureau of Land Management

governmentWashington D.C., District of Columbia, United States

Research output, citation impact, and the most-cited recent papers from Bureau of Land Management (United States). Aggregated across the NobleBlocks index of 300M+ scholarly works.

Total works
2.9K
Citations
71.7K
h-index
113
i10-index
1.2K
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Bureau of Land Management

Top-cited papers from Bureau of Land Management

Pacific Salmon at the Crossroads: Stocks at Risk from California, Oregon, Idaho, and Washington
Willa Nehlsen, Jack E. Williams, James A. Lichatowich
1991· Fisheries963doi:10.1577/1548-8446(1991)016<0004:psatcs>2.0.co;2

The American Fisheries Society herein provides a list of depleted Pacific salmon, steelhead, and sea-run cutthroat stocks from California, Oregon, Idaho, and Washington, to accompany the list of rare inland fishes reported by Williams et al. (1989). The list includes 214 native naturally-spawning stocks: 101 at high risk of extinction, 58 at moderate risk of extinction, 54 of special concern, and one classified as threatened under the Endangered Species Act of 1973 and as endangered by the state of California. The decline in native salmon, steelhead, and sea-run cutthroat populations has resulted from habitat loss and damage, and inadequate passage and flows caused by hydropower, agriculture, logging, and other developments; overfishing, primarily of weaker stocks in mixed-stock fisheries; and negative interactions with other fishes, including nonnative hatchery salmon and steelhead. While some attempts at remedying these threats have been made, they have not been enough to prevent the broad decline of stocks along the West Coast. A new paradigm that advances habitat restoration and ecosystem function rather than hatchery production is needed for many of these stocks to survive and prosper into the next century.

Biodiversity of Stream Insects: Variation at Local, Basin, and Regional Scales
Mark R. Vinson, Charles P. Hawkins
1998· Annual Review of Entomology537doi:10.1146/annurev.ento.43.1.271

We review the major conceptual developments that have occurred over the last 50 years concerning the factors that influence insect biodiversity in streams and examine how well empirical descriptions and theory match. Stream insects appear to respond to both spatial and temporal variation in physical heterogeneity. At all spatial scales, the data largely support the idea that physical complexity promotes biological richness, although exceptions to this relationship were found. These exceptions may be related to how we measure habitat complexity at finer spatial scales and to factors that influence regional richness, such as biogeographic history, at broader spatial scales. However, the degree to which local stream insect assemblages are influenced by regional processes is largely unknown.

Extinctions of North American Fishes During the past Century
Robert Rush Miller, James D. Williams, Jack E. Williams
1989· Fisheries490doi:10.1577/1548-8446(1989)014<0022:eonafd>2.0.co;2

Extinctions of 3 genera, 27 species, and 13 subspecies of fishes from North America are documented during the past 100 years. Extinctions are recorded from all areas except northern Canada and Alaska. Regions suffering the greatest loss are the Great Lakes, Great Basin, Rio Grande, Valley of Mexico, and Parras Valley in Mexico. More than one factor contributed to the decline and extinction of 82% of the fishes. Physical habitat alteration was the most frequently cited causal factor (73%). Detrimental effects of introduced species also were cited in 68% of the extinctions. Chemical habitat alteration (including pollution) and hybridization each were cited in 38% of the extinctions, and overharvesting adversely affected 15% of the fishes. This unfortunate and unprecedented rate of loss of the fishery resource is expected to increase as more of the native fauna of North America becomes endangered or threatened.

Predicted responses of arctic and alpine ecosystems to altered seasonality under climate change
Jessica G. Ernakovich, Kelly A. Hopping, Aaron B. Berdanier, Rodney T. Simpson +3 more
2014· Global Change Biology424doi:10.1111/gcb.12568

Global climate change is already having significant impacts on arctic and alpine ecosystems, and ongoing increases in temperature and altered precipitation patterns will affect the strong seasonal patterns that characterize these temperature-limited systems. The length of the potential growing season in these tundra environments is increasing due to warmer temperatures and earlier spring snow melt. Here, we compare current and projected climate and ecological data from 20 Northern Hemisphere sites to identify how seasonal changes in the physical environment due to climate change will alter the seasonality of arctic and alpine ecosystems. We find that although arctic and alpine ecosystems appear similar under historical climate conditions, climate change will lead to divergent responses, particularly in the spring and fall shoulder seasons. As seasonality changes in the Arctic, plants will advance the timing of spring phenological events, which could increase plant nutrient uptake, production, and ecosystem carbon (C) gain. In alpine regions, photoperiod will constrain spring plant phenology, limiting the extent to which the growing season can lengthen, especially if decreased water availability from earlier snow melt and warmer summer temperatures lead to earlier senescence. The result could be a shorter growing season with decreased production and increased nutrient loss. These contrasting alpine and arctic ecosystem responses will have cascading effects on ecosystems, affecting community structure, biotic interactions, and biogeochemistry.

Effect of thinning and prescribed burning on crown fire severity in ponderosa pine forests
Jolie Pollet, Philip N. Omi
2002· International Journal of Wildland Fire417doi:10.1071/wf01045

Fire exclusion policies have affected stand structure and wildfire hazard in north American ponderosa pine forests. Wildfires are becoming more severe in stands where trees are densely stocked with shade-tolerant understory trees. Although forest managers have been employing fuel treatment techniques to reduce wildfire hazard for decades, little scientific evidence documents the success of treatments in reducing fire severity. Our research quantitatively examined fire effects in treated and untreated stands in western United States national forests. Four ponderosa pine sites in Montana, Washington, California and Arizona were selected for study. Fuel treatments studied include: prescribed fire only, whole-tree thinning, and thinning followed by prescribed fire. On-the-ground fire effects were measured in adjacent treated and untreated forests. We developed post facto fire severity and stand structure measurement techniques to complete field data collection. We found that crown fire severity was mitigated in stands that had some type of fuel treatment compared to stands without any treatment. At all four of the sites, the fire severity and crown scorch were significantly lower at the treated sites. Results from this research indicate that fuel treatments, which remove small diameter trees, may be beneficial for reducing crown fire hazard in ponderosa pine sites.

Multidimensional evaluation of managed relocation
David M. Richardson, Jessica J. Hellmann, J. S. McLachlan, Dov F. Sax +4 more
2009· Proceedings of the National Academy of Sciences381doi:10.1073/pnas.0902327106

Managed relocation (MR) has rapidly emerged as a potential intervention strategy in the toolbox of biodiversity management under climate change. Previous authors have suggested that MR (also referred to as assisted colonization, assisted migration, or assisted translocation) could be a last-alternative option after interrogating a linear decision tree. We argue that numerous interacting and value-laden considerations demand a more inclusive strategy for evaluating MR. The pace of modern climate change demands decision making with imperfect information, and tools that elucidate this uncertainty and integrate scientific information and social values are urgently needed. We present a heuristic tool that incorporates both ecological and social criteria in a multidimensional decision-making framework. For visualization purposes, we collapse these criteria into 4 classes that can be depicted in graphical 2-D space. This framework offers a pragmatic approach for summarizing key dimensions of MR: capturing uncertainty in the evaluation criteria, creating transparency in the evaluation process, and recognizing the inherent tradeoffs that different stakeholders bring to evaluation of MR and its alternatives.

Alaska’s changing fire regime — implications for the vulnerability of its boreal forestsThis article is one of a selection of papers from The Dynamics of Change in Alaska’s Boreal Forests: Resilience and Vulnerability in Response to Climate Warming.
Eric S. Kasischke, David L. Verbyla, T. Scott Rupp, A. D. McGuire +4 more
2010· Canadian Journal of Forest Research380doi:10.1139/x10-098

A synthesis was carried out to examine Alaska’s boreal forest fire regime. During the 2000s, an average of 767 000 ha·year –1 burned, 50% higher than in any previous decade since the 1940s. Over the past 60 years, there was a decrease in the number of lightning-ignited fires, an increase in extreme lightning-ignited fire events, an increase in human-ignited fires, and a decrease in the number of extreme human-ignited fire events. The fraction of area burned from human-ignited fires fell from 26% for the 1950s and 1960s to 5% for the 1990s and 2000s, a result from the change in fire policy that gave the highest suppression priorities to fire events that occurred near human settlements. The amount of area burned during late-season fires increased over the past two decades. Deeper burning of surface organic layers in black spruce ( Picea mariana (Mill.) BSP) forests occurred during late-growing-season fires and on more well-drained sites. These trends all point to black spruce forests becoming increasingly vulnerable to the combined changes of key characteristics of Alaska’s fire regime, except on poorly drained sites, which are resistant to deep burning. The implications of these fire regime changes to the vulnerability and resilience of Alaska’s boreal forests and land and fire management are discussed.

Fishes of North America Endangered, Threatened, or of Special Concern: 1989
Jack E. Williams, James E. Johnson, Dean A. Hendrickson, Salvador Contreras-Balderas +4 more
1989· Fisheries368doi:10.1577/1548-8446(1989)014<0002:fonaet>2.0.co;2

The American Fisheries Society herein provides an update of their now decade-old list of rare North American fishes. The 1989 list adds 139 new taxa to the list developed by Deacon et al. (1979) of 251 fishes and removes 26 for a total of 364 fishes in Canada, United States, and Mexico that warrant protection because of their rarity. The 26 taxa removed from the 1979 list include 16 removed because of better information on their taxonomy or status and 10 because they have become extinct. Not a single fish warranted removal from the list because of successful recovery efforts. In addition, 49 fishes have changed in status but remain on the list: 7 have improved in status, 24 have declined, and 18 have been reclassified because new information revealed that they were either more common or rarer than was earlier believed and, therefore, were incorrectly classified in 1979. Comparison of the 1979 and 1989 lists indicates that recovery efforts have been locally effective for some species, but are clearly lagging behind deterioration of the overall fish fauna. The health of aquatic habitats in North America continues to decay. A major commitment to conservation of entire ecosystems, rather than the inconsistent recovery efforts for individual species, is needed to reverse this trend.

Changes in forest productivity across Alaska consistent with biome shift
Pieter S. A. Beck, Glenn P. Juday, Claire Alix, Valerie Barber +4 more
2011· Ecology Letters352doi:10.1111/j.1461-0248.2011.01598.x

Global vegetation models predict that boreal forests are particularly sensitive to a biome shift during the 21st century. This shift would manifest itself first at the biome's margins, with evergreen forest expanding into current tundra while being replaced by grasslands or temperate forest at the biome's southern edge. We evaluated changes in forest productivity since 1982 across boreal Alaska by linking satellite estimates of primary productivity and a large tree-ring data set. Trends in both records show consistent growth increases at the boreal-tundra ecotones that contrast with drought-induced productivity declines throughout interior Alaska. These patterns support the hypothesized effects of an initiating biome shift. Ultimately, tree dispersal rates, habitat availability and the rate of future climate change, and how it changes disturbance regimes, are expected to determine where the boreal biome will undergo a gradual geographic range shift, and where a more rapid decline.

Comparison of Soil Bacterial Communities in Rhizospheres of Three Plant Species and the Interspaces in an Arid Grassland
Cheryl R. Kuske, Lawrence O. Ticknor, Mark E. Miller, John Dunbar +3 more
2002· Applied and Environmental Microbiology344doi:10.1128/aem.68.4.1854-1863.2002

Soil bacteria are important contributors to primary productivity and nutrient cycling in arid land ecosystems, and their populations may be greatly affected by changes in environmental conditions. In parallel studies, the composition of the total bacterial community and of members of the Acidobacterium division were assessed in arid grassland soils using terminal restriction fragment length polymorphism (TRF, also known as T-RFLP) analysis of 16S rRNA genes amplified from soil DNA. Bacterial communities associated with the rhizospheres of the native bunchgrasses Stipa hymenoides and Hilaria jamesii, the invading annual grass Bromus tectorum, and the interspaces colonized by cyanobacterial soil crusts were compared at three depths. When used in a replicated field-scale study, TRF analysis was useful for identifying broad-scale, consistent differences in the bacterial communities in different soil locations, over the natural microscale heterogeneity of the soil. The compositions of the total bacterial community and Acidobacterium division in the soil crust interspaces were significantly different from those of the plant rhizospheres. Major differences were also observed in the rhizospheres of the three plant species and were most apparent with analysis of the Acidobacterium division. The total bacterial community and the Acidobacterium division bacteria were affected by soil depth in both the interspaces and plant rhizospheres. This study provides a baseline for monitoring bacterial community structure and dynamics with changes in plant cover and environmental conditions in the arid grasslands.

DISTRIBUTION OF SAGE-GROUSE IN NORTH AMERICA
Michael A. Schroeder, Cameron L. Aldridge, Anthony D. Apa, Joseph R. Bohne +4 more
2004· Ornithological Applications325doi:10.1650/7425

We revised distribution maps of potential presettlement habitat and current populations for Greater Sage-Grouse (Centrocercus urophasianus) and Gunnison Sage- Grouse (C. minimus) in North America. The revised map of potential presettlement habitat included some areas omitted from previously published maps such as the San Luis Valley of Colorado and Jackson area of Wyoming. Areas excluded from the revised maps were those dominated by barren, alpine, and forest habitats. The resulting presettlement distribution of potential habitat for Greater Sage-Grouse encompassed 1 200 483 km2, with the species' current range 668 412 km2. The distribution of potential Gunnison Sage-Grouse habitat encompassed 46 521 km2, with the current range 4787 km2. The dramatic differences between the potential presettlement and current distributions appear related to habitat alteration and degradation, including the adverse effects of cultivation, fragmentation, reduction of sagebrush and native herbaceous cover, development, introduction and expansion of invasive plant species, encroachment by trees, and issues related to livestock grazing. Distribución de Centrocercus spp. en América del Norte Resumen. Revisamos los mapas de distribución potencial precolombino y de poblaciones actuales de Centrocerus urophasianus y C. minimus en América del Norte. El mapa modificado de hábitat potencial precolombino incluyó algunas áreas omitidas de mapas anteriormente publicados, como el Valle San Luis de Colorado y el área de Jackson, Wyoming. Las áreas excluídas de los mapas modificados fueron las dominadas por hábitats forestales, alpinos y estériles. La distribución precolombina resultante para C. urophasianus abarcó 1 200 483 km2, con un territorio actual de 668 412 km2. La distribución de habitat potencial para C. minimus abarcó 46 521 km2, con un territorio actual de 4787 km2. Estos contrastes tan marcados parecen estar relacionados con la modificación y degradación del hábitat, incluyendo los efectos nocivos de la agricultura, la fragmentación de hábitat, la disminución de Artemisia spp. y otras coberturas herbáceas nativas, el desarollo, la introducción y la expansión de especies de plantas invasoras, la invasión de árboles y cuestiones relacionadas con pastoreo de ganado.

Cadmium Sorption and Transport in Variable Charge Soils: A Review
Ravi Naidu, Rai S. Kookana, M. E. Sumner, Robert D. Harter +1 more
1997· Journal of Environmental Quality324doi:10.2134/jeq1997.00472425002600030004x

Abstract Alfisols, Entisols, Inceptisols, Ultisols, Vertisols, and Oxisols are all commonly found in tropical and subtropical regions receiving more than 500 mm mean annual rainfall. Landscapes throughout the tropics and subtropics are, however, dominated by Oxisols and Ultisols occupying extensive areas of potentially highly productive soils. The mineral fractions of these soils consist primarily of low‐activity clays having variable surface charge that differs from high activity clays in the origin of that charge. Low activity clays are dominated by iron (Fe) and aluminium (Al) oxyhydroxides and 1:1 layer silicates (kaolin). Much research has been conducted on the effects of pH, organic matter (OM), and cation composition of the soil solution on the surface charge characteristics of variable charge soils from the tropics. In general, net negative surface charge increases with increasing soil pH and OM content. Adsorption of metal ions by variable charge soils and minerals also increases as their pH, clay, and OM contents increase. Although the precise mechanisms for the change in net negative charge of soil and mineral surfaces with increasing pH are not fully understood, the generation of negative charge either through dissociation of H + ions from surfaces or consumption of OH − ions by soils is generally accepted. In soils dominated by permanent charge surfaces, heavy metals are not mobile but in variable charge soils, the low surface charge density creates conditions conducive to increased mobility. Consequently, the adsorption of heavy metals, in particular, cadmium (Cd) by strongly weathered soils in relation to the effects of inorganic and organic ligands and the implications for metal transport are reviewed.

Biological activities of bovine glycomacropeptide
Ernest P. Brody
2000· British Journal Of Nutrition309doi:10.1017/s0007114500002233

Biological activity of bovine kappa-caseino glycomacropeptide (GMP) has received much attention in recent years. Research has focused on the ability of GMP to bind cholera and Escherichia coli enterotoxins, inhibit bacterial and viral adhesion, suppress gastric secretions, promote bifidobacterial growth and modulate immune system responses. Of these, protection against toxins, bacteria, and viruses and modulation of the immune system are the most promising applications.

Engaging Recreational Fishers in Management and Conservation: Global Case Studies
Elise F. Granek, Elizabeth M. P. Madin, Matthew Brown, Will F. Figueira +4 more
2008· Conservation Biology295doi:10.1111/j.1523-1739.2008.00977.x

Globally, the number of recreational fishers is sizeable and increasing in many countries. Associated with this trend is the potential for negative impacts on fish stocks through exploitation or management measures such as stocking and introduction of non-native fishes. Nevertheless, recreational fishers can be instrumental in successful fisheries conservation through active involvement in, or initiation of, conservation projects to reduce both direct and external stressors contributing to fishery declines. Understanding fishers' concerns for sustained access to the resource and developing methods for their meaningful participation can have positive impacts on conservation efforts. We examined a suite of case studies that demonstrate successful involvement of recreational fishers in conservation and management activities that span developed and developing countries, temperate and tropical regions, marine and freshwater systems, and open- and closed-access fisheries. To illustrate potential benefits and challenges of involving recreational fishers in fisheries management and conservation, we examined the socioeconomic and ecological contexts of each case study. We devised a conceptual framework for the engagement of recreational fishers that targets particular types of involvement (enforcement, advocacy, conservation, management design [type and location], research, and monitoring) on the basis of degree of stakeholder stewardship, scale of the fishery, and source of impacts (internal or external). These activities can be enhanced by incorporating local knowledge and traditions, taking advantage of leadership and regional networks, and creating collaborations among various stakeholder groups, scientists, and agencies to maximize the probability of recreational fisher involvement and project success.

Lethal Aggression in Mobile Forager Bands and Implications for the Origins of War
Douglas P. Fry, Patrik Söderberg
2013· Science292doi:10.1126/science.1235675

It has been argued that warfare evolved as a component of early human behavior within foraging band societies. We investigated lethal aggression in a sample of 21 mobile forager band societies (MFBS) derived systematically from the standard cross-cultural sample. We hypothesized, on the basis of mobile forager ethnography, that most lethal events would stem from personal disputes rather than coalitionary aggression against other groups (war). More than half of the lethal aggression events were perpetrated by lone individuals, and almost two-thirds resulted from accidents, interfamilial disputes, within-group executions, or interpersonal motives such as competition over a particular woman. Overall, the findings suggest that most incidents of lethal aggression among MFBS may be classified as homicides, a few others as feuds, and a minority as war.

Rangeland Health Attributes and Indicators for Qualitative Assessment
David A. Pyke, Jeffrey E. Herrick, Patrick L. Shaver, Mike Pellant
2002· Journal of Range Management265doi:10.2307/4004002

David A. Pyke, Jeffrey E. Herrick, Patrick Shaver, Mike Pellant, Rangeland Health Attributes and Indicators for Qualitative Assessment, Journal of Range Management, Vol. 55, No. 6 (Nov., 2002), pp. 584-597

Development and Use of State-and-Transition Models for Rangelands
Brandon T. Bestelmeyer, Joel R. Brown, Kris M. Havstad, Robert R. Alexander +2 more
2003· Journal of Range Management263doi:10.2307/4003894

Brandon T. Bestelmeyer, Joel R. Brown, Kris M. Havstad, Robert Alexander, George Chavez, Jeffrey E. Herrick, Development and Use of State-and-Transition Models for Rangelands, Journal of Range Management, Vol. 56, No. 2 (Mar., 2003), pp. 114-126

Relationships between structure and function in streams contrasting in temperature
Nikolai Friberg, John Bøhme Dybkjær, Jón S. Ólafsson, Gísli Már Gíslason +2 more
2009· Freshwater Biology257doi:10.1111/j.1365-2427.2009.02234.x

Summary 1. We studied 10 first‐order Icelandic streams differing in geothermal influence in separate catchments. Summer temperature (August–September) ranged between 6 and 23 °C. 2. Macroinvertebrate evenness and species overlap decreased significantly with temperature whereas taxon richness showed no response. In total, 35 macroinvertebrate species were found with Chironomidae the dominant taxonomic group. Macroinvertebrate density increased significantly with temperature. Dominant species in the warm streams were Lymnaea peregra and Simulium vittatum . Algal biomass, macrophyte cover and richness were unrelated to temperature. Densities of trout ( Salmo trutta ), the only fish species present, reflected habitat conditions and to a lesser degree temperature. 3. Density of filter‐feeders increased significantly with temperature whereas scraper density, the other dominant functional feeding group, was unrelated to temperature. Stable isotope analysis revealed a positive relationship between δ 15 N and temperature across several trophic levels. No pattern was found with regard to δ 13 C and temperature. 4. Leaf litter decomposition in both fine and coarse mesh leaf bags were significantly correlated to temperature. In coarse mesh leaf packs breakdown rates were almost doubled compared with fine mesh, ranging between 0.5 and 1.3 g DW 28 days −1 . Nutrient diffusion substrates showed that the streams were primarily nitrogen limited across the temperature gradient while a significant additional effect of phosphorous was found with increasing temperature. 5. Structural and functional attributes gave complementary information which all indicated a change with temperature similar to what is found in moderately polluted streams. Our results therefore suggest that lotic ecosystems could be degraded by global warming.

Clovis Age Western Stemmed Projectile Points and Human Coprolites at the Paisley Caves
Dennis L. Jenkins, Loren G. Davis, Thomas W. Stafford, Paula F. Campos +4 more
2012· Science246doi:10.1126/science.1218443

The Paisley Caves in Oregon record the oldest directly dated human remains (DNA) in the Western Hemisphere. More than 100 high-precision radiocarbon dates show that deposits containing artifacts and coprolites ranging in age from 12,450 to 2295 (14)C years ago are well stratified. Western Stemmed projectile points were recovered in deposits dated to 11,070 to 11,340 (14)C years ago, a time contemporaneous with or preceding the Clovis technology. There is no evidence of diagnostic Clovis technology at the site. These two distinct technologies were parallel developments, not the product of a unilinear technological evolution. "Blind testing" analysis of coprolites by an independent laboratory confirms the presence of human DNA in specimens of pre-Clovis age. The colonization of the Americas involved multiple technologically divergent, and possibly genetically divergent, founding groups.

Distribution of Sage-Grouse in North America
Michael A. Schroeder, Cameron L. Aldridge, Anthony D. Apa, Joseph R. Bohne +4 more
2004· Ornithological Applications234doi:10.1093/condor/106.2.363

Abstract We revised distribution maps of potential presettlement habitat and current populations for Greater Sage-Grouse (Centrocercus urophasianus) and Gunnison Sage- Grouse (C. minimus) in North America. The revised map of potential presettlement habitat included some areas omitted from previously published maps such as the San Luis Valley of Colorado and Jackson area of Wyoming. Areas excluded from the revised maps were those dominated by barren, alpine, and forest habitats. The resulting presettlement distribution of potential habitat for Greater Sage-Grouse encompassed 1 200 483 km2, with the species' current range 668 412 km2. The distribution of potential Gunnison Sage-Grouse habitat encompassed 46 521 km2, with the current range 4787 km2. The dramatic differences between the potential presettlement and current distributions appear related to habitat alteration and degradation, including the adverse effects of cultivation, fragmentation, reduction of sagebrush and native herbaceous cover, development, introduction and expansion of invasive plant species, encroachment by trees, and issues related to livestock grazing. Distribución de Centrocercus spp. en América del Norte Resumen. Revisamos los mapas de distribución potencial precolombino y de poblaciones actuales de Centrocerus urophasianus y C. minimus en América del Norte. El mapa modificado de hábitat potencial precolombino incluyó algunas áreas omitidas de mapas anteriormente publicados, como el Valle San Luis de Colorado y el área de Jackson, Wyoming. Las áreas excluídas de los mapas modificados fueron las dominadas por hábitats forestales, alpinos y estériles. La distribución precolombina resultante para C. urophasianus abarcó 1 200 483 km2, con un territorio actual de 668 412 km2. La distribución de habitat potencial para C. minimus abarcó 46 521 km2, con un territorio actual de 4787 km2. Estos contrastes tan marcados parecen estar relacionados con la modificación y degradación del hábitat, incluyendo los efectos nocivos de la agricultura, la fragmentación de hábitat, la disminución de Artemisia spp. y otras coberturas herbáceas nativas, el desarollo, la introducción y la expansión de especies de plantas invasoras, la invasión de árboles y cuestiones relacionadas con pastoreo de ganado.