Impacts to grassland and shrubland communities under the various alternatives would be similar; however, the extent and intensity of impacts would vary by alternative. Therefore, discussions for individual alternatives describe impacts to grassland and shrubland communities from surface-disturbing activities, motorized vehicle use, livestock grazing management, special designations, fire management, wildlife management/use, and proactive management actions under the individual alternatives. The following paragraphs generally describe impacts to grassland and shrubland communities regardless of the alternative selected.
Minerals development impacts to grassland and shrubland communities would include long- and short-term impacts, small and localized removal of vegetative surface cover, and larger disturbances covering many acres. There would be surface disturbance from bentonite and gypsum mining under all alternatives, increasing with the area available for locatable mineral entry. Mineral development would alter the distribution and abundance of grassland and shrubland communities and change community structure and diversity. Long-term impacts would mostly be associated with permanent structures and road construction, but some grassland and shrubland communities would not reestablish to pre-disturbance structure and density for more than 20 years. The severity of impacts would depend on the precipitation zone, amount of activity, and the success of reclamation efforts for disturbed areas. The Impacts Common to All Alternatives section under Vegetation Resources describes impacts from other surface-disturbing activities, including ROW development, that would affect grasslands and shrublands.
Motorized vehicle use on public lands may result in adverse short-term and long-term impacts to vegetation in grassland and shrubland communities. A one-time disturbance from off-road motorized vehicle use causes physical damage to vegetation by breaking stems and branches and may disturb the soil surface, depending on soil conditions, slope, and ground cover. With a one-time disturbance, plants and disturbed areas usually recover. However, with repeated use, new trails become established. This results in the long-term reduction of vegetation cover and density, and changes species composition. In areas with significant biological soil crusts, a one-time off-road disturbance can remain visible for many months and is prone to repeated use.
Livestock grazing can cause both adverse and beneficial impacts to vegetation communities. Historically, overgrazing of native perennial grasses has contributed to the spread of nonnative annual grasses (DiTomaso 2000). However, proper grazing in grassland and shrubland communities does not adversely impact rangeland health, and may improve it in certain instances. Manier and Hobbs (2007) found that livestock grazing in sagebrush communities can increase plant species richness and diversity, and Muscha and Hild (2006) found no substantial difference in biological crust cover between areas grazed and areas with light to moderate grazing throughout Wyoming. Improving plant vigor, increasing vegetative cover, and reducing invasive species infestations can occur through removing old growth and decadent vegetation that inhibits new growth. Healthier plant communities are more resistant to the spread of invasive species and other undesirable plant species. Livestock grazing of noxious weeds at crucial points in their life-cycles can decrease the spread of invasive species. Proper livestock grazing management also increases a plant community’s resistance to cheatgrass invasion after a disturbance such as wildland fire (Davies et al. 2009).
Under all of the alternatives, wild horse grazing—if concentrated or localized year-round—within HMAs may result in adverse impacts to grassland and shrubland communities by compacting soils and removing vegetation. Expanding the McCullough Peaks HMA under alternatives B and D may increase the extent of adverse impacts to grasslands and shrublands from concentrated wild horse grazing.
Wildland fire and prescribed fire have both adverse and beneficial impacts to grassland and shrubland communities. In the short term, wildland fires remove vegetation and create an opportunity for the establishment or spread of invasive and noxious weeds. Many invasive species respond rapidly after fire, and can out-compete native species. In areas where invasive species are present, wildland fire increases the likelihood of invasive species expansion. Firefighters and their equipment may also introduce or spread invasive species. Some mechanical control activities disturb the soil surface and remove vegetation, creating an opportunity for invasive species to become established or spread.
In the long term, because of the role fire historically played in these communities, fire would increase vegetative diversity across the landscape, rejuvenate decadent plants, and improve the overall health of these communities. In shrubland communities, impacts from fire usually are long-term and depend on the scale and severity of the disturbance. The potential for sagebrush shrublands to return after fire depends on the acreage burned, the distance to seed sources, and the spread of invasive species, such as cheatgrass, which can increase fire frequency. Limiting or protecting acreage from fire may, in some cases, lessen direct loss of grassland and shrubland communities and reduce the potential spread of invasive species in the short term. However, considering the historic role of fire in maintaining vegetative composition and structure, the lack of fire may decrease the overall health of these communities. Wildlife impacts to vegetation depend on population levels, the distribution of animals, and the ability of animals to move. Crucial winter ranges for mule deer and pronghorn, where shrubs are heavily used, may exhibit vegetation shifts from sagebrush, bitterbrush, and mountain mahogany to conifers, grasses, forbs, and annuals, and in some cases, bare ground. Management actions that prohibit surface-disturbing activities to protect special status species, such as the greater sage-grouse, in grassland and shrubland communities also would benefit vegetation in these areas.
Specific proactive management actions common to all alternatives would benefit grasslands and shrublands to ensure that the selected alternative will meet the goals and objectives for these resource programs. Proactive management actions common to all alternatives include managing vegetative communities in accordance with the Wyoming Standards for Healthy Rangelands (Appendix N) and continuing to use ecological site descriptions; continuing to regularly monitor and evaluate climatic and vegetative data to analyze shifts in rangeland production to implement actions, if necessary, to ensure the long-term productivity of rangeland; and using certified noxious-weed-free vegetation products on all BLM-administered lands. Refer to Chapter 2 for goals, objectives and a complete list of management actions common to all alternatives for grassland and shrubland communities.
Under Alternative A, approximately 105,805 acres of short-term and 13,771 acres of long-term surface disturbance is projected to occur in grassland and shrubland communities, based on the percent cover of these vegetation types in the Planning Area. Under Alternative A, impacts to grassland and shrubland communities associated with surface-disturbing activities would be primarily adverse. Short-term adverse impacts include soil erosion, loss of species diversity, and invasive species spread; however, the relatively small size of individual disturbed areas and the implementing BMPs would minimize these short-term impacts. Long-term impacts from development last longer than 5 years and primarily include a decrease in abundance and distribution of grasslands and shrublands. Table 4-8 lists the acreages of grasslands and shrublands protected from some common surface-disturbing activities (e.g., ROWs and locatable mineral development) under Alternative A.
Routinely seeding, or requiring permittees and operators to seed, disturbed areas with native plant species would encourage native vegetation cover, maintain biological integrity, help shift vegetative communities toward DPC, and reduce the potential for the spread of invasive species. These would be beneficial impacts to grassland and shrubland communities. Conversely, seeding with only native species may reduce reclamation success compared to using the species most likely to restore vegetative cover, whether native or nonnative. Alternative A does not require a reclamation plan, the purpose of which is to incorporate measures to support the return of as much of the disturbed acreage to its predisturbed state as quickly as feasible upon conclusion of operations from a given surface pad. Not requiring comprehensive measures and monitoring to ensure the reclamation of areas following surface disturbance would result in a greater short-term adverse impact. However, reestablishing vegetation cover over disturbed soils within 5 years of initial seeding would encourage native vegetative structure and reduce long-term impacts associated with exposed soils (e.g., establishment and spread of invasive species). These would be beneficial impacts to grassland and shrubland communities.
Under Alternative A, oil, gas, and other minerals development is project to result in 25,390 acres of short-term surface disturbance and 1,130 new oil and gas wells, a portion of which would adversely impact grassland and shrubland communities by contributing to a decline in their abundance, distribution, or health (Appendix T). Most of the Planning Area would remain open to mineral extraction. Alternative A makes available 4,033,195 acres for locatable mineral entry, which would involve long-term surface disturbance in the portion of that acreage where development occurs. Alternative A would result in impacts to grassland and shrubland communities from bentonite and gypsum development. Some of the impacts would be temporary during the life of the operation, with areas of disturbance reclaimed following closure of operations, but some areas may not reestablish pre-disturbance structure and density for more than 20 years.
Invasive species would adversely affect grassland and shrubland communities under Alternative A. The spread of invasive species reduces diversity in grasslands and shrublands and, in the case of cheatgrass spread, alters the fire regime so that fires burn frequently and rapidly. Under Alternative A, the BLM would perform vegetation treatments to control or eradicate invasive species on 2,000 acres. The projected surface disturbance from vegetative treatments under Alternative A would result in short-term adverse impacts, but would benefit grassland and shrubland communities over the long term.
Alternative A would involve the second-most acreage of surface disturbance from pipeline and road development. Pipeline disturbance would be short-term, because reclamation would return herbaceous cover to the disturbance areas following construction. However, grassland and shrublands in low precipitation zones may not return to pre-disturbance cover for more than 20 years. The amount of new road construction in grassland and shrubland communities would impact these areas proportionately through the loss of vegetation and potential spread of invasive species. New roads also would fragment grassland and shrubland communities, which may reduce species diversity.
Motorized vehicle use is limited to existing roads and trails in most of the Planning Area under Alternative A. Even when confined to roads, motorized vehicles increase the potential for invasive species spread and poorly designed or maintained roads may increase erosion and affect adjacent vegetation. Areas with grasslands and shrublands that allow OHV activities, but are further restricted by limiting use to designated roads and trails, include the Absaroka Mountain Foothills SRMA and Bighorn River SRMA. Alternative A allows OHV use in areas with limited travel designations for big game retrieval and dispersed campsite access, which could result in road and trail proliferation that would damage vegetation and impact grasslands and shrublands. Areas where damage from off-road use is most likely include stream crossings, areas with highly erosive soils, steep slopes, areas with important biological soil crusts, and vegetative communities with plants, such as Wyoming big sagebrush, susceptible to physical damage. Motorized vehicle use under Alternative A would result in adverse impacts to grassland and shrubland communities.
Livestock grazing management under Alternative A would have both adverse and beneficial impacts to grassland and shrubland communities (see Table 4-8). Under Alternative A, the BLM emphasizes monitoring on category “I” allotments, treats monitoring on category “M” and “C” allotments as a low priority, and develops and implements AMPs as needed to meet multiple use objectives. By emphasizing monitoring only on higher priority allotments, undesirable conditions in lower priority allotments may not be identified and deterioration or improvement in grassland and shrubland communities may not be realized in a timely manner. However, concentrating monitoring on category “I” allotments would beneficially affect these allotments because undesirable conditions would be identified more quickly. When appropriately managed according to the Wyoming Guidelines for Livestock Grazing Management and other appropriate BMPs, livestock grazing would benefit grasslands and shrublands as described under Impacts Common to All Alternatives.
The BLM requires livestock flushing on a case-by-case basis, allowing for the potential spread of invasive species via livestock to grazed grassland and shrubland communities. However, identifying and flushing potential vector livestock would reduce the threat of invasive species spread in some instances. Rangeland improvements such as reservoirs, pits, pipelines, and wells would involve removing vegetation and may concentrate livestock and increase the potential spread of invasive species. Due to allotment monitoring practices, AMP development, livestock flushing practices, and projected rangeland improvements, livestock grazing under Alternative A would, overall, benefit grasslands and shrublands by continuing to improve these vegetation types in the Planning Area.
Special designations would benefit grasslands and shrublands where the designations protect areas from resource uses or activities that may damage or destroy vegetation or increase the potential for wildfire or invasive species spread. The primary purpose of the Carter Mountain ACEC designated under Alternative A is to protect grassland and shrubland communities. Protective buffers around the Nez Perce (Neeme-poo) NHT and other trails may protect areas of grasslands and shrublands from disturbance. Table 4-8 lists the acreages of grassland and shrubland communities in special designation areas; the designations would limit adverse impacts to these vegetation communities.
The vegetation treatments applied according to the fire and fuels management actions under Alternative A may be inadequate to reduce fuel conditions enough to substantially diminish the risk of catastrophic fire. Most the Planning Area is in FRCC Classes 2 and 3, which have the highest risk of catastrophic fire or of having lost or losing key ecosystem components (see Section 4.3 Fire and Fuels Management). Intense fires in areas where fuels exceed historical levels may destroy the seeds of perennial grasses and shrubs and alter soils to increase the risk of invasive species establishment. The BLM would apply most of the total projected prescribed fire and fuels treatment acreage under Alternative A (70,000 acres) to grassland and shrubland communities not meeting DPC objectives (Appendix T).
Under Alternative A, the BLM utilizes wildland fires to restore fire-adapted ecosystems and to reduce hazardous fuels. Alternative A would involve the second highest level of surface disturbance from prescribed fire and fuels treatments. Prescribed fire would cause a short-term adverse impact to grasslands and shrublands by destroying vegetation, increasing soil erosion, and increasing the potential spread of invasive species. However, the relatively small size of individual treatment areas and the use of BMPs would minimize these short-term impacts. Prescribed fire and fuels treatments would benefit grassland and shrubland communities in the long term by reducing fuels and preventing catastrophic fires. Overall, fire and fuels management under Alternative A would result in long‐term beneficial impacts to shrubland and grassland communities.
Wildlife management actions under Alternative A would indirectly benefit grassland and shrubland communities. Alternative A prohibits domestic sheep grazing on pronghorn crucial winter range, unless adverse impacts can be avoided or mitigated, reducing the potential for increased herbivory that may shift shrubland communities to conifers, grasses, forbs, and annuals. Limiting surface-disturbing activities around greater sage-grouse leks and in winter, nesting, and early brood-rearing habitats would create short-term beneficial impacts to grassland and shrubland communities in these areas. However, if these restrictions prevent vegetation treatments that would improve grassland and shrubland health in the long term, they may adversely impact communities in these areas. The short-term beneficial impacts of preventing vegetation loss from surface disturbance may outweigh potential loss of long-term benefits from vegetation treatments.
Alternative A would result in beneficial long-term impacts to grassland and shrubland health by managing grassland and shrubland communities on 600,000 acres of BLM-administered land toward DPC objectives for watershed protection and livestock grazing. Managing toward DPC objectives improves overall community health, improves plant vigor, reduces the potential for erosion, and improves forage for livestock and wildlife. This active management under Alternative A would benefit a limited portion of the 2,757,959 acres of grassland and shrubland on BLM-administered lands. Because the BLM implements these management actions on a portion of grassland and shrubland communities, Alternative A would create limited long-term beneficial impacts to grasslands and shrublands.
Under Alternative B, approximately 55,256 acres of short-term and 9,538 acres of long-term surface disturbance is projected in grassland and shrubland communities, based on the percent cover of these vegetation types in the Planning Area. Impacts to grassland and shrubland communities associated with surface-disturbing activities would be the least under this alternative. Table 4-8 lists the acreages of grasslands and shrublands protected from some common surface-disturbing activities (e.g., ROWs and locatable mineral development) under this alternative.
Under Alternative B, the BLM analyzes surface-disturbing activities by mapping soils, collecting soil samples for physical and chemical analysis, and evaluating current erosion conditions. Alternative B requires that disturbed areas be reestablished with 50 percent of native vegetative cover within three growing seasons, and 80-percent cover within five growing seasons of initial seeding, based on preexisting conditions. Alternative B also manages disturbed areas to reestablish healthy native plant communities based on preexisting composition or other species, as identified in an approved management plan. Approving reclamation plans before all surface-disturbing activities under this alternative would minimize short-term adverse impacts by requiring project proponents to propose comprehensive measures and monitoring to ensure reclamation of areas following surface disturbance. Reclamation practices under Alternative B increase the chance of successful reestablishment of grasslands and shrublands in disturbed areas. Based on management of reclamation and the amount of long-term disturbance acreage projected under Alternative B, this alternative would result in the least short- and long-term adverse (and greatest beneficial) impacts to grassland and shrubland communities.
Under Alternative B, oil, gas, and other minerals development would result in 17,327 acres of short-term surface disturbance and 509 new oil and gas wells, resulting in impacts similar to those under Alternative A, but to a lesser degree (Appendix T). Alternative B leaves the least area available for locatable mineral entry (3,882,447 acres), which would result in the least long-term surface disturbance compared to the other alternatives. Some of the impacts would be temporary during the life of the operation, with areas of disturbance reclaimed following closure of operations.
Adverse impacts from invasive species would be similar to those under Alternative A, but to a lesser degree. Alternative B would involve the fewest acres of surface disturbance to control or eradicate invasive species. However, due to the projected overall surface disturbance, reclamation practices, and motorized vehicle use restrictions, Alternative B also would involve the smallest area vulnerable to invasive species establishment. Therefore, Alternative B would result in the fewest adverse impacts to grassland and shrubland communities from invasive species.
Alternative B would involve the least acreage of disturbance from pipeline and road development, and the greatest chance of successful reestablishment of grasses and shrubs following construction. Alternative B also would involve the least new road construction. Compared to the other alternatives, projected new roads under Alternative B and management designed to manage for large contiguous blocks of important plant communities along with managing more acreage as ROW avoidance/mitigation and exclusion areas would present the least potential for fragmentation of grasslands and shrublands and associated loss of diversity.
Motorized vehicle use under Alternative B would cause impacts to grasslands and shrublands similar to those under Alternative A, but to a lesser degree. Most of the Planning Area is limited to designated roads and trails, including areas in the West Slope and Badlands areas, limiting impacts to grasslands and shrublands from motorized vehicle use. Alternative B prohibits off-road motorized vehicle use for big game retrieval and dispersed campsites, which would reduce adverse impacts to grasslands and shrublands by preventing road and trail proliferation and vegetation damage. Alternative B would involve more long-term surface disturbance associated with the creation of new roads and trails for recreational purposes than Alternative A, but less than alternatives C and D (Appendix T), with proportional impacts to grasslands and shrublands from vegetation removal. Compared to other alternatives, Alternative B would result in the fewest adverse impacts to grassland and shrubland communities from motorized vehicle use.
Alternative B would result in the most extensive monitoring and grazing management to identify and improve grassland and shrubland conditions in a timely manner. Under Alternative B, the BLM monitors all allotments and develops or revises AMPs for all “I” allotments or allotments not meeting the Wyoming Standards for Healthy Rangelands (Appendix N). The authorized officer can require livestock flushing for up to 72 hours to reduce the threat of invasive species spread via livestock to grassland and shrubland communities. Alternative B would result in the least disturbance acreage from rangeland improvements such as reservoirs, pits, pipelines, and wells (Appendix T), posing the least threat to grasslands and shrublands from invasive species spread and livestock concentration. Conversely, decreasing surface-disturbing rangeland improvement activities may adversely affect some grassland and shrubland communities where problems with livestock distribution cannot be addressed without these projects. Due to allotment monitoring practices, AMP development, livestock flushing practices, and projected rangeland improvements, livestock grazing management under Alternative B would result in the least adverse and most beneficial impacts to grasslands and shrublands.
Under Alternative B, the BLM closes greater sage-grouse Key Habitat Areas and elk and bighorn sheep crucial winter range to livestock grazing (Table 4-8). This management would have a beneficial impact on some grasslands and shrublands by increasing vegetation cover and reducing the chance of soil compaction and invasive species spread. However, a recent land management modeling effort over large areas in eastern Nevada concluded that the proposed removal of livestock grazing alone had little impact on vegetation resiliency, rather, active restoration (e.g., prescribed fire, mechanical and chemical treatments) was required to improve degraded habitats (Provencher et al. 2007). Other research indicates removing grazing will increase woody plant cover and may reduce species richness and diversity (Manier and Hobbs 2007). Any beneficial impacts to grasslands and shrublands in greater sage-grouse Key Habitat Areas and bighorn sheep crucial winter range from the removal of livestock grazing may, therefore, be limited. The removal of livestock grazing would also mean that any beneficial impacts to these areas that would result from properly managed livestock grazing under Alternative A, such as increased resilience to disturbance and removal of decadent vegetation, would not be realized under Alternative B.
Proposed special designations to protect grassland and shrubland communities under Alternative B include the Carter Mountain (existing and expansion areas), Little Mountain (expansion area), Clarks Fork Canyon, Chapman Bench, Rattlesnake Mountain, and Sheep Mountain ACECs. Under Alternative B, the BLM would designated all LWCs as Wild Lands and manage them to protect their naturalness and primitive recreation, and restrict resource uses and activities in these areas that may damage grassland and shrubland vegetation. Alternative B applies the largest buffer around the Heart Mountain Relocation Center National Historic Landmark and the Nez Perce (Neeme-poo) NHT to restrict surface-disturbing activities and motorized vehicle use, which would benefit grassland and shrubland communities in these areas. Table 4-8 lists the acreages of grassland and shrubland communities in special designation areas under Alternative B.
Under Alternative B, the BLM utilizes wildland fires and other vegetation treatments to restore fire-adapted ecosystems and to reduce hazardous fuels. However, Alternative B would result in the least acreage of prescribed fire and fuels treatments (25,000 acres), and therefore the greatest risk of inadequate fuel reductions to substantially reduce the risk of catastrophic fire (Appendix T). This alternative would result in the least long-term beneficial impact from preventing fire that may destroy and permanently alter grassland and shrubland communities, compared to the other alternatives.
Wildlife management actions under Alternative B would indirectly benefit grassland and shrubland communities the most. Alternative B prohibits all new domestic sheep grazing on pronghorn crucial winter range, reducing the potential for overgrazing due to dietary overlap of the two species more than Alternative A. Under Alternative B, the Absaroka Front Management Area, to which the BLM does not apply specific management actions under Alternative A, restricts some resource uses (e.g., mineral leasing and motorized vehicle use) that would remove vegetation or damage grassland and shrubland health on the 56,220 acres of this plant community type in its boundaries. Compared to the other alternatives, Alternative B limits surface disturbance around greater sage-grouse leks and in winter, nesting, and early brood-rearing habitats the most, which would result in a greater beneficial impact. However, Alternative B may also result in the least long-term beneficial impact in these areas by restricting vegetation treatments in areas where the plant community is extremely degraded, especially by the occurrence of noxious weeds, or by the increase in certain conifer species (e.g., juniper). The short-term beneficial impacts of preventing vegetation loss from surface disturbance may outweigh potential loss of long-term benefits from vegetation treatments where they are necessary to restore degraded vegetation communities.
Under Alternative B, the BLM manages to achieve or make progress toward achieving 75 percent or more of Historical Climax Plant Community in all grasslands and shrublands, benefitting these communities by making progress toward improving vegetation conditions. The BLM would also manage to maintain large contiguous blocks of native plant communities, which would result in beneficial impacts to grassland and shrubland communities; however, Alternative B would result in the least acreage of vegetation treatments to improve vegetation conditions (Appendix T).
Under Alternative C, approximately 179,027 acres of short-term and 36,417 acres of long-term surface disturbance is projected in grassland and shrubland communities, based on the percent cover of these vegetation types in the Planning Area. Under Alternative C, the impacts to grassland and shrubland communities associated with surface-disturbing activity is more than any other alternative. Table 4-8 lists the acreages of grasslands and shrublands protected from some common surface-disturbing activities (e.g., ROWs and locatable mineral development) under this alternative.
Under Alternative C, the BLM analyzes surface-disturbing activities by mapping soils, collecting soil samples for physical and chemical analysis, and evaluating current erosion conditions on a case-by-case basis. Alternative C requires that disturbed areas are reestablished with 30 percent of desired vegetative cover within three growing seasons (with no long-term cover requirement) and requires reclamation plans on a case-by-case basis, which would result in a greater beneficial impact from stabilizing soil than Alternative A, but less than alternatives B and D. Allowing the use of approved nonnative seed and reestablishing plant communities to increase commodity production in disturbed areas may result in more immediate soil stabilization in the short term (depending on the species used) than Alternative A, but would also adversely impact disturbed areas by reducing the potential for reestablishing native plant communities in the long term. Based on the reclamation actions under Alternative C and the amount of long-term disturbance acreage projected, this alternative would result in the greatest adverse (and least beneficial) short- and long-term impacts to grassland and shrubland communities.
Under Alternative C, oil and gas and other minerals development would result in 25,771 acres of short-term surface disturbance and 1,257 new oil and gas wells, resulting in impacts similar to those under Alternative A, but to a greater degree (Appendix T). Locatable minerals development under Alternative C would result in similar long-term surface disturbance and associated impacts as those under Alternative A. Overall, minerals development under Alternative C would result in the greatest adverse impacts to grassland and shrubland communities.
Adverse impacts from invasive species would be similar to those under Alternative A, but to a greater degree. Alternative C would result in the most acres of invasive species control or eradication activities. However, Alternative C would also leave the largest area vulnerable to new invasive species establishment due to new surface disturbance (245,783 acres), less rigorous reclamation requirements, and the least restrictive management of motorized vehicle use. Based on these factors, Alternative C would result in the greatest adverse impacts to grassland and shrubland communities from invasive species, relative to the other alternatives.
Alternative C would result in the greatest acreage of disturbance from pipeline and road development and the smallest chance of successful reestablishment of grasses and shrubs following construction. Alternative C also would result in the most new road construction. The projected new roads under Alternative C would result in the greatest potential for fragmentation of grasslands and shrublands and the associated loss of species diversity relative to the other alternatives, particularly since this alternative does not, like Alternative B, manage for large contiguous blocks of important plant communities and manages less acreage as ROW avoidance/mitigation and exclusion areas.
Motorized vehicle use under Alternative C would result in impacts to grasslands and shrublands similar to those under Alternative A, but to a greater degree. Alternative C limits motorized vehicle use to designated roads and trails in more area than Alternative A, but closes less area. Under Alternative C, the BLM also limits motorized vehicle use to designated roads and trails with seasonal closures in the Absaroka Front Management Area, which encompasses 56,220 acres of grasslands and shrublands. Under Alternative C, BLM actions would result in the most long-term surface disturbance from motorized vehicle use, of which a portion would directly impact grasslands and shrublands by removing vegetation. Allowing off-road motorized vehicle use for big game retrieval and dispersed campsites as long as there is no resource damage would put grassland and shrubland communities at greater risk of adverse impacts than Alternative B in this regard. Overall, Alternative C would result in the greatest adverse impacts to grassland and shrubland communities from motorized vehicle use, compared to the other alternatives.
Under Alternative C, the BLM varies the intensity of allotment monitoring, giving priority to category “I” allotments and those not meeting the Wyoming Standards for Healthy Rangelands (Appendix N). By emphasizing monitoring only on higher priority allotments, undesirable conditions in lower priority allotments may not be identified and deterioration or improvement in grassland and shrubland communities may not be realized in a timely manner. Not requiring livestock flushing would result in the greatest risk of invasive species spread to grasslands and shrublands via livestock. Alternative C would result in the most disturbance acreage from rangeland improvements such as reservoirs, pits, pipelines, and wells (Appendix T), posing the greatest threat from invasive species spread—exacerbated due to the lack of livestock flushing—and livestock concentration. Conversely, this alternative has the greatest potential to address some improper livestock distribution-related concentrated herbivory issues that require rangeland improvement projects and, therefore, the beneficial impacts from properly managed livestock grazing, described under Impacts Common to All Alternatives, would also be greatest under this alternative. Under this alternative, the BLM does not manage livestock grazing to enhance other resource values; the BLM would manage grasslands and shrublands at a lower seral stage to increase herbaceous forage production. Potential adverse impacts to grasslands and shrublands from allotment monitoring and grazing management practices, livestock flushing practices, and surface disturbance from projected rangeland improvements would outweigh the potential beneficial impacts from livestock grazing management. Overall, livestock grazing management would result in the greatest adverse impacts to grassland and shrubland communities under Alternative C.
No ACECs, specific to Alternative C, would protect substantial amounts of grasslands and shrublands. Protective buffers around the Nez Perce (Neeme-poo) NHT and Other Historic Trails, of similar size to Alternative A, may protect areas of grasslands and shrublands from disturbance. The BLM also applies a protective buffer around the Heart Mountain Relocation Center National Historic Landmark under this alternative. Table 4-8 lists the acreages of grassland and shrubland communities in special designation areas under Alternative C.
Under Alternative C, the BLM utilizes wildland fires and other vegetation treatments to restore fire-adapted ecosystems, reduce hazardous fuels, and enhance forage for commodity production. Alternative C would result in the most acreage of prescribed fire and fuels treatments (140,000 acres), and therefore the highest probability of adequate fuel reductions to substantially reduce the risk of catastrophic fire (Appendix T). This alternative would result in the most long-term beneficial impact from preventing fire that may destroy and permanently alter grassland and shrubland communities, compared to the other alternatives.
Wildlife management actions under Alternative C would indirectly benefit grassland and shrubland communities the least. Alternative C allows domestic sheep grazing on pronghorn crucial winter range, increasing the potential for overgrazing. Alternative C would allow more resource uses (e.g., oil, gas, and other mineral leasing) in the Absaroka Front Management Area that may result in more adverse impacts to the 56,312 acres of grasslands and shrublands in its boundaries than under Alternative B. Compared to the other alternatives, Alternative C applies the least surface-disturbance restrictions around greater sage-grouse leks and in nesting and early brood-rearing habitats, does not apply restrictions in winter concentration areas, and exempts Oil and Gas Management Areas from discretionary wildlife seasonal stipulations. These management actions would result in the least short-term beneficial impacts by preventing vegetation removal or degradation in these areas, compared to the other alternatives. However, Alternative C allows vegetation treatments over a greater area than the other alternatives, providing a long-term benefit by reducing fuel loads. The short-term adverse impacts of vegetation loss from surface disturbance may outweigh potential long-term benefits from vegetation treatments.
Under Alternative C, the BLM manages to achieve or make progress toward achieving the Wyoming Standards for Healthy Rangelands (Appendix N) for all grasslands and shrublands. Alternative C would result in the most acreage of vegetation treatments to improve vegetation conditions (Appendix T); however, no grasslands and shrublands are managed toward DPC. Alternative C would result in the fewest beneficial impacts from proactive management toward achieving historical community structure and composition. However, the projected area of prescribed burns and vegetation treatments under Alternative C would result in beneficial impacts across the greatest area to achieve rangeland health standards, relative to the other alternatives, in areas needing active restoration due to substantial habitat degradation.
Under Alternative D, approximately 106,997 acres of short-term and 16,166 acres of long-term surface disturbance is projected in grassland and shrubland communities, based on the percent cover of these vegetation types in the Planning Area. Although the BLM projects that Alternative D would result in slightly more surface disturbance than Alternative A, more stringent reclamation and restoration practices may result in fewer long-term adverse impacts from surface disturbance. Table 4-8 lists the acreages of grasslands and shrublands protected from some common surface-disturbing activities (e.g., ROWs and locatable mineral development) under this alternative.
The reclamation and restoration practices under Alternative D would result in similar beneficial impacts to those under Alternative A, but to a greater degree. Incorporating erosion rates and soil stability into soil survey efforts, developing specific objectives and timeframes for reclamation plans in coordination with stakeholders, and beginning interim and final reclamation at the earliest feasible time would result in greater beneficial impacts than alternatives A and C, but less than Alternative B.
Under Alternative D, oil, gas, and other minerals development would result in 24,896 acres of short-term surface disturbance and 1,032 new oil and gas wells, affecting grassland and shrubland communities similar to Alternative A. Locatable minerals development under Alternative D would result in long-term impacts to grasslands and shrublands similar to those under Alternative A. Alternative D closes the second least area in grasslands and shrublands to locatable minerals development and may result in more adverse impacts from long-term surface disturbance than Alternative A. However, the demand for locatable minerals entry, and therefore the level of development and impact, would be similar under all alternatives.
Adverse impacts from invasive species would be similar to those under Alternative A, but to a lesser degree. Alternative D controls or eradicates invasive species on the same amount of land as Alternative A and surface disturbance under Alternative D would leave a similar amount of land vulnerable to invasive species spread. However, the more rigorous reclamation requirements and restrictive management of motorized vehicle use would limit the establishment and spread of invasive species more than Alternative A.
ROW development under Alternative D, including roads and pipelines, would result in impacts similar to those under Alternative A, but to a lesser degree because managing more acreage as ROW avoidance/mitigation or exclusion areas would limit habitat fragmentation more than ROW management under alternatives A and C.
Motorized vehicle use under Alternative D would result in adverse impacts similar to those under Alternative A, but to a lesser degree. Alternative D closes slightly more area to motorized vehicle use than Alternative A, limits motorized vehicle use to designated roads and trails in more area and restricts off-road motorized vehicle use for big game retrieval to within 300 feet of established roads, resulting in less adverse impacts to grasslands and shrublands than alternatives A and C, but more than Alternative B.
Livestock grazing management under Alternative D would result in adverse impacts to grasslands and shrublands similar to Alternative A. However, allowing livestock grazing in areas closed to grazing as a tool to maintain or improve resource conditions may result in more beneficial impacts.
Proposed special designations that would protect grassland and shrubland communities under Alternative D include the Carter Mountain, Little Mountain, Clarks Fork Canyon, and Sheep Mountain ACECs. In addition, the Craig Thomas Little Mountain SMA, Chapman Bench Management Area, and 52,485 acres designated as Wild Lands would limit resource uses and activities that can adversely affect grassland and shrubland communities. Special designations under Alternative D would result in more beneficial impacts to grasslands and shrublands than alternatives A and C, but less than Alternative B.
Fire and fuels management practices and the area treated to reduce fuels under Alternative D would result in impacts similar to those under Alternative A.
Wildlife management actions under Alternative D would result in similar beneficial impacts as those under Alternative A, but to a greater degree. Alternative D prohibits sheep grazing on pronghorn crucial winter range, restricts resource uses in the Absaroka Front Management area, and restricts surface-disturbing activities around greater sage-grouse leks and in winter, nesting, and early brood-rearing habitats more than Alternative A. Restricting surface-disturbing activities may limit vegetation treatments in areas needing restoration where the plant community is extremely degraded; however, the short-term beneficial impacts of preventing vegetation loss from surface disturbance may outweigh potential loss of long-term benefits from vegetation treatments. Overall, wildlife management would result in more indirect beneficial impacts than alternatives A and C, but less than Alternative B.
Proactive management under Alternative D would result in similar beneficial impacts as those under Alternative B, but to a lesser degree. Under Alternative D, the BLM would manage to maintain large contiguous blocks of native plant communities, similar to Alternative B, but would manage grassland and shrubland communities toward achieving 65 percent of Historical Climax Plant Community, compared to 75 percent under Alternative B.