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21 result(s) for "Crabb, Benjamin A."
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The effects of electric power lines on the breeding ecology of greater sage-grouse
Anthropogenic infrastructure can negatively affect wildlife through direct mortality and/or displacement behaviors. Some tetranoids (grouse spp.) species are particularly vulnerable to tall anthropogenic structures because they evolved in ecosystems void of vertical structures. In western North America, electric power transmission and distribution lines (power lines) occur in sagebrush (Artemisia spp.) landscapes within the range of the greater sage-grouse (Centrocercus urophasianus; sage-grouse). The U.S. Fish and Wildlife Service recommended using buffer zones near leks to mitigate the potential impacts of power lines on sage-grouse. However, recommended buffer distances are inconsistent across state and federal agencies because data are lacking. To address this, we evaluated the effects of power lines on sage-grouse breeding ecology within Utah, portions of southeastern Idaho, and southwestern Wyoming from 1998-2013. Overall, power lines negatively affected lek trends up to a distance of 2.7 and 2.8 km, respectively. Power lines died not affect lek persistence. Female sage-grouse avoided transmission lines during the nesting and brooding seasons at distances up to 1.1 and 0.8 km, respectively. Nest and brood success were negatively affected by transmission lines up to distances of 2.6 and 1.1 km, respectively. Distribution lines did not appear to affect sage-grouse habitat selection or reproductive fitness. Our analyses demonstrated the value of sagebrush cover in mitigating potential power line impacts. Managers can minimize the effects of new transmission power lines by placing them in existing anthropogenic corridors and/or incorporating buffers at least 2.8 km from active leks. Given the uncertainty we observed in our analyses regarding sage-grouse response to distribution lines coupled with their role in providing electric power service directly to individual consumers, we recommend that buffers for these power lines be considered on a case-by-case basis. Micrositing to avoid important habitats and habitat reclamation may reduce the potential impacts of new power line construction.
Sage-Grouse Breeding and Late Brood-Rearing Habitat Guidelines in Utah
Delineation, protection, and restoration of habitats provide the basis for endangered and threatened species recovery plans. Species recovery plans typically contain guidelines that provide managers with a scientific basis to designate and manage critical habitats. As such, habitat guidelines are best developed using data that capture the full diversity of ecological and environmental conditions that provide habitat across the species’ range. However, when baseline information, which fails to capture habitat diversity, is used to develop guidelines, inconsistencies and problems arise when applying those guidelines to habitats within an ecologically diverse landscape. Greater sage-grouse (Centrocercus urophasianus; sage-grouse) populations in Utah, USA, reflect this scenario—published range-wide habitat guidelines developed through a literature synthesis did not include data from the full range of the species. Although all sage-grouse are considered sagebrush obligates (Artemisia spp.), the species occupies a diversity of sagebrush communities from shrub-dominated semideserts in the southwest to more perennial grass-dominated sagebrush-steppe in the northeast portions of their distribution. Concomitantly, local ecological site and environmental conditions may limit the ability of managers to achieve broader range-wide habitat guidelines. We combined microsite habitat vegetation parameters from radiomarked sage-grouse nest and brood locations with state-wide spatially continuous vegetation, climatic, and elevation data in a cluster analysis to develop empirically based sage-grouse habitat guidelines that encompass the range of ecological and environmental variation across Utah. Using this novel approach, we identified 3 distinct clusters of sage-grouse breeding (i.e., nesting and early brood-rearing) and late brood-rearing habitats in Utah. For each cluster, we identified specific vegetation recommendations that managers can use to assess sage-grouse breeding and late brood-rearing habitat. Our results provide relevant guidelines to Utah’s sage-grouse populations and are feasible given the unique ecological variation found therein. This approach may have application to other species that occupy diverse habitats and physiographic regions.
Seasonal Movements of Greater Sage-grouse Populations in Utah: Implications for Species Conservation
Greater sage-grouse (Centrocercus urophasianus; sage-grouse) is considered an umbrella species for sagebrush (Artemisia spp.) landscapes in western North America. In 2015, the U.S. Fish and Wildlife Service determined sage-grouse unwarranted for protection under the Endangered Species Act (1973) because of conservation actions in priority areas. Understanding seasonal movements is key to delineation and assessment of priority conservation areas. We monitored radiomarked sage-grouse from 1998 to 2013 throughout Utah, USA, to determine seasonal movements. Maximum distances from nearest lek to nesting, summer, and winter locations across all radiomarked grouse averaged 2.20 km (90th percentile = 5.06 km), 3.93 km (90th percentile = 8.45 km), and 3.76 km (90th percentile = 7.15 km), respectively. Maximum movements from nest to summer, nest to winter, and between summer and winter locations across all radiomarked grouse averaged 5.77 km (90th percentile = 13.60 km), 11.77 km (90th percentile = 26.36 km), and 14.75 km (90th percentile = 30.77 km), respectively. Maximum distance from lek of capture to summer locations was greater for males than females, whereas females moved farther than males from lek to winter and summer to winter locations. Adult females moved farther than yearlings from lek to nest and summer to winter areas. The state of Utah’s Sage-Grouse Management Areas included approximately 85% of the radiotelemetry seasonal locations and >95% when weighted by lek counts.Our results suggest that seasonal movements could be facilitated by increasing usable habitat space through management actions, as emphasized in Utah’s sage-grouse plan.
Rare long-distance dispersal of the Island Night Lizard, Xantusia riversiana, maintains high diversity in a fragmented environment
The Island Night Lizard (Xantusia riversiana) is endemic to three of the Channel Islands off the coast of California, USA. Introduced species such as goats, sheep, and cats have profoundly affected the fauna and flora of the islands for over 150 years, but most of these non-native species have been recently removed. We measured the distribution of genetic diversity in Island Night Lizards across San Nicolas Island using DNA microsatellites to assess the impacts of historical habitat change on effective population size, gene flow, and population divergence; to provide baseline data for future monitoring of genetic diversity; and to provide recommendations to inform the restoration of degraded habitat. Despite a history of profound anthropogenic habitat disturbance, genetic diversity was high within sites, and there was no evidence of population bottlenecks. Divergence between sites was extraordinarily high, as expected for this sedentary species. Landscape resistance modeling using circuit theory showed that unsuitable habitat is relatively permeable to gene flow compared to suitable habitat, and yet populations separated by very short geographic distances remain genetically distinct. We found no evidence of a need for short-term intervention such as artificial translocations to maintain genetic diversity. Instead, we suggest that management should focus on maintaining, improving, and increasing habitat, especially in creating patches of habitat to link existing sites.
The effects of federal, state, and private oil and gas ownerships on county wages in the Intermountain West
Advances in drilling technology and increasing resource prices contributed to a boom in oil and natural gas production in the Western U.S. in the first decade of the 2000s. Following the boom, a strain of state-level legislation emerged calling for the transfer of federal lands to the states. A justification for the proposed transfers is the claim that state management will responsibly increase oil and gas production levels currently held back by federal regulations and management. However, a substantial literature indicates that dependence on mineral wealth can be a problematic economic development strategy resulting in slower growth and other undesirable socioeconomic outcomes. Using geological variation in oil and gas abundance in the Intermountain West, this study examined the effects of resource abundance on county wage levels and growth rates over the period 1990 to 2010. Areas of oil and gas abundance were further classified by federal, state, and private surface land ownership to examine institutional ownership effects on wage levels and growth rates. Overall oil and gas abundance was shown to have a positive impact on wage levels and growth rates, while institutional ownerships were found to have significantly differing effects on county wages. State ownership was usually associated with higher wage levels and growth rates than federal ownership, likely due to a lengthy permitting process for drilling on federal lands. Private ownership had insignificant effects on local wages, likely due to absentee ownership. The results provide no evidence of a ‘curse of natural resources’ in the region and lend a modicum of support to state land transfer bills.