SWCA Environmental Consultants
SWCA Environmental Consultants
Brunelle A.,University of Utah |
Minckley T.A.,University of Wyoming |
Lips E.,Great Basin |
Burnett P.,SWCA Environmental Consultants
Journal of Quaternary Science | Year: 2013
Records of past vegetation and fire history can be complicated by changes in the depositional environment of a sampling location. However, these changes can alternatively be used as a measure of climate variability. Our study site, ca. 18.0cal. ka BP record from Little Brooklyn Lake, Wyoming, located near the crest of the Snowy Range, records three moisture states. Initially, the lake was likely a glacier-fed pond indicated by the presence of Pediastrum algae colonies. Around 13.0 cal. ka BP this pond transitioned to a meadow environment, suggested by the loss of Pediastrum algae colonies and slow sedimentation rates. Meadow conditions were maintained until ca. 5.0 cal. ka BP when Pediastrum algae colony abundance increased, indicating the formation of a shallow lake. From 18.0 to ca. 5.0 cal. ka BP, the pollen record is suggestive of alpine vegetation conditions with relatively high spruce and herbaceous taxa. Low charcoal influx also characterizes the period between 18.0 and 5.0 cal. ka BP. After 5.0 cal. ka BP, the coincidence of the formation of shallow lake and pollen data, indicating a shift to a spruce and fir forest, suggests an increase in effective moisture. Fire remained rare in this basin over the entire record, however, once the lake established sedimentation rates and charcoal influx increased. © 2013 John Wiley & Sons, Ltd.
Plentovich S.,University of Hawaii at Manoa |
Eijzenga J.,SWCA Environmental Consultants |
Eijzenga H.,Bishop Museum
Biological Invasions | Year: 2011
Invasive species eradication and control are considered vital components of the conservation, restoration, and management of many native ecosystems. Invasive ants, which are notoriously difficult to eradicate, can cause catastrophic changes in ecosystems and are aggressive colonists. Here we report the eradication and control of two widely distributed invasive ants and subsequent unanticipated effects on arthropod and avian communities. We used a paired experimental design that included 1 year of baseline data collection, to test the effects of the formicide hydramethylnon on abundances of two ant species on two pairs of offshore islets. Pheidole megacephala was eradicated from the treated islet in pair 1 and was not detected during 2003-2008. On pair 2 Solenopsis geminata numbers declined, but the species remained present. Target ant densities remained high on untreated islets. Application of hydramethylnon reduced numbers of alien cockroaches (Order: Blattaria), but we did not detect effects on other non-target arthropods. The eradication of P. megacephala was followed by dynamic compositional changes in the ant community, including the apparent colonization by three species (S. geminata, Tetramorium bicarinatum and Anoplolepis gracilipes) previously undetected on the islet. One of these, A. gracilipes, underwent a rapid range expansion during 2006-2008 which corresponded with reduced seabird nesting success. We conclude that hydramethylnon can be used effectively to eradicate P. megacephala. However, ant eradications can have detrimental effects on ecosystems and the potential for subsequent colonization of sites by other ant species that may be more harmful and more difficult to eradicate needs to be considered. © 2010 Springer Science+Business Media B.V.
Chimera C.G.,Pacific Cooperative Studies Unit |
Buddenhagen C.E.,SWCA Environmental Consultants |
Clifford P.M.,Pacific Cooperative Studies Unit |
Clifford P.M.,University of Hawaii at Manoa
Biofuels | Year: 2010
Biofuel crops are increasingly promoted as environmental and economical solutions to global energy needs, but actual benefits versus costs may be less favorable than advocates claim. Among the risks associated with their cultivation is the potential to exacerbate the invasive species problem. Evidence is growing that many proposed biofuel crops are ideally suited to become successful invaders. We compared actual and candidate terrestrial biofuel crops suitable for temperate and tropical climates with introduced, nonbiofuel species, and demonstrated that biofuel species are almost three-times more likely to naturalize and over twice as likely to be invasive as nonbiofuel crops in both climatic conditions. Similar potential may exist for algae biofuels. The risks could be mitigated, and unintended environmental costs avoided, by implementing precautions including assessing and removing the worst invaders from consideration, selecting lower risk species for widespread cultivation, and actively controlling the spread of crops from cultivated areas. © 2010 Future Science Ltd.
Stumpf K.J.,Northland College |
Theimer T.C.,Northern Arizona University |
McLeod M.A.,SWCA Environmental Consultants |
Koronkiewicz T.J.,SWCA Environmental Consultants
Journal of Wildlife Management | Year: 2012
The southwestern willow flycatcher (Empidonax traillii extimus) is a federally endangered subspecies that breeds in increasingly fragmented and threatened habitat. We examined whether temporal and habitat characteristics were associated with risk of predation and probability of brood parasitism by brown-headed cowbirds (Molothrus ater) on flycatcher nests at 6 sites in southern Nevada and northwestern Arizona, USA. For nest predation, we found the most support for a model that included date and an interaction between parasitism status and nesting stage. Daily nest survival decreased from 0.87 (95% CI = 0.81-0.93) to 0.78 (95% CI = 0.72-0.84) through the season for parasitized nests but remained relatively constant for unparasitized nests (0.93, 95% CI = 0.91-0.95 to 0.92, 95% CI = 0.91-93). Parasitized nests had lower survival than non-parasitized nests during the incubation (0.85, 95% CI = 0.84-0.86 vs. 0.92, CI = 0.91-0.93) and nestling (0.79, 95% CI = 0.77-0.81 vs. 0.91, 95% CI = 0.90-0.92) stages. Of the variables included in our parasitism candidate models, model-averaged coefficients and odds ratios supported only distance to habitat edge; odds of parasitism decreased 1% for every 1 m from the habitat edge. Nests greater than 100 m from an edge were 50% less likely to be parasitized as those on an edge, however, only 52 of 233 nests (22%) were found at this distance. Where management and conservation goals include reducing nest losses due to parasitism, we recommend restoration of habitat patches that minimize edge and maximize breeding habitat further from edges. At sites where cowbirds have been documented as important nest predators, controlling cowbirds may be one option, but further study of the link between parasitism and nest predation and the identification of major nest predators at specific sites is warranted. © 2011 The Wildlife Society.
Widmer A.M.,SWCA Environmental Consultants |
Fluder J.J.,SWCA Environmental Consultants |
Kehmeier J.W.,SWCA Environmental Consultants |
Medley C.N.,New Mexico Interstate Stream Commission |
And 2 more authors.
River Research and Applications | Year: 2012
Long-distance drift of eggs and larvae has been identified as a possible cause of downstream displacement and poor recruitment of the endangered Rio Grande silvery minnow (Hybognathus amarus; silvery minnow). Seven experiments were conducted using artificial eggs to estimate silvery minnow egg drift and retention in the Albuquerque and Isleta reaches of the regulated Middle Rio Grande, New Mexico, USA over a range of flows during expected spawning times. Bead retention varied by reach, discharge, and shape of the hydrograph. Highest retention (6.9 and 9.7% per km in the Albuquerque and Isleta reaches, respectively) occurred on the ascending limb of a high flow in areas where there was substantial floodplain inundation. Retention was maximized at different flows in each reach (97 and 140m 3/s, respectively), possibly associated with reach-specific floodplain inundation thresholds. Lowest retention in each reach (2.1 and 1.7%, respectively) occurred on the descending limb of low and high flows, respectively. Of the silvery minnow eggs produced in the combined Albuquerque and Isleta reaches in 2005, 8-14% are predicted to have been retained in the Albuquerque Reach (67km) and 49-83% in the Isleta Reach (86km) based on the distribution of adult fish and measured bead retention rates. Although silvery minnow propagules are capable of drifting long distances, our study suggests that considerable retention occurs in the Middle Rio Grande. Habitat restoration to increase channel habitat complexity, and flow management to promote floodplain inundation should help to retain a greater proportion of propagules in upstream reaches. © 2010 John Wiley & Sons, Ltd.
Ansari S.,SWCA Environmental Consultants |
Daehler C.C.,University of Hawaii at Manoa
Biological Invasions | Year: 2010
Few studies have examined the life history of temperate plant invaders in the tropics. Temperate invaders that utilize seasonal cues to influence their life histories may be expected to behave differently in the tropics. This study examined variation in life history in an invading temperate weed, Verbascum thapsus, across an elevation gradient (1,690-2,720 m) along the montane and subalpine slopes of Mauna Kea, Hawaii. Over 7,000 seedlings were marked and monitored over a period of 3 years. Germination, survival, growth, and reproduction in V. thapsus varied among sites along the elevational gradient. Compared to plants at lower elevations, those at higher elevation sites (>2,000 m) had lower early seedling survival, higher established rosette survival, higher vegetative growth rates, higher threshold sizes for flowering, and commonly lived more than 3 years before flowering. The abundance of competing vegetation generally decreased with elevation, and this may drive variation in V. thapsus survival and growth. Size-dependent survival appears to play a major role in the selection for smaller size at first flowering and shorter generation time at lower elevations. This pattern is opposite to that reported in temperate mountains where high elevation plants flower sooner and at smaller size, but both patterns appear consistent with general life history theory for biennials. Due to novel biotic and climatic interactions in the tropics, predictions of growth patterns and invasion dynamics for temperate weeds in the tropics can be misleading when based on the plant's behavior in temperate systems. © 2010 Springer Science+Business Media B.V.
Mata S.A.,University of Southern California |
Corsetti C.L.,SWCA Environmental Consultants |
Corsetti F.A.,University of Southern California |
Awramik S.M.,University of California at Santa Barbara |
Bottjer D.J.,University of Southern California
Palaios | Year: 2012
Large (up to 7 cm in diameter) and deep-penetrating (up to 30 cm) vertical burrows are described from the lower Cambrian Wood Canyon Formation of the Death Valley region, United States, and their paleoenvironmental and paleoecological implications are addressed. Trace fossils occur as dense populations that precede the earliest occurrences of Skolithos pipe rock in the region. These trace fossils are assigned to the ichnogenera Bergaueria, Conichnus, and Dolopichnus, and each represents the burrowing behavior of an anemone-like organism. These ichnotaxa occur within oolitic and sandy dolostones of a flood-tidal delta and lagoonal environment, respectively, and burrow fill is dominated by echinoderm ossicles. Ichnofabric indices of 4-5 and a tidally influenced position place these ichnotaxa within the same nearshore locus of bioturbation as Skolithos pipe rock; however, unlike Skolithos pipe rock, the tracemaker of these trace fossils can be identified. This study reveals that anemone-like animals were responsible for extensive modification of the marine substrate and this style of deep-penetrating bioturbation appears first in nearshore environments. This is in accord with the observation that many evolutionary novelties originate in nearshore environments, and specifically that deep-penetrating bioturbation originated nearshore before expanding offshore. This study also provides insight into the paleoecology of earliest Cambrian noncalcified cnidarians and their behavior and paleoenvironmental distribution during the Cambrian radiation. Copyright © 2012 SEPM (Society for Sedimentary Geology).
Guezou A.,Charles Darwin Foundation |
Trueman M.,Charles Darwin Foundation |
Trueman M.,University of Western Australia |
Buddenhagen C.E.,SWCA Environmental Consultants |
And 4 more authors.
PLoS ONE | Year: 2010
Background: Plant invasions are causing habitat degradation in Galapagos. Problems are concentrated on the four inhabited islands. Plants introduced to rural areas in the humid highlands and urban areas on the arid coast act as foci for invasion of the surrounding Galapagos National Park. Methodology/Principal Findings: Here we present results of the most comprehensive inventory to date of alien vascular plants in the inhabited areas of Galapagos. The survey was conducted between 2002 and 2007, in 6031 properties (97% of the total) on Floreana, Isabela, San Cristobal and Santa Cruz Islands. In total 754 alien vascular plant taxa were recorded, representing 468 genera in 123 families. Dicotyledons represented 554 taxa, monocotyledons 183, there were 7 gymnosperms and 10 pteridophytes. Almost half (363) of the taxa were herbaceous. The most represented families were Fabaceae (sensu lato), Asteraceae and Poaceae. The three most recorded species in the humid rural areas were Psidium guajava, Passiflora edulis and Bryophyllum pinnatum, and in the dry urban areas, Aloe vera, Portulaca oleracea and Carica papaya. In total, 264 (35%) taxa were recorded as naturalized. The most common use for taxa was ornamental (52%). Conclusions/Significance: This extensive survey has increased the known alien vascular flora of Galapagos by 257 species, giving a ratio of alien to native taxa of 1.57:1. It provides a crucial baseline for plant invasion management in the archipelago and contributes data for meta analyses of invasion processes worldwide. A repeat of the survey in the future would act as an effective early detection tool to help avoid further invasion of the Galapagos National Park. © 2010 Guézou et al.
McLeod M.A.,SWCA Environmental Consultants |
Koronkiewicz T.J.,SWCA Environmental Consultants
Wildlife Society Bulletin | Year: 2014
Control of brown-headed cowbirds (Molothrus ater) is often advocated to reduce parasitism and improve nesting success of sensitive populations of passerine birds, but little information is available in the literature concerning the relative effectiveness of different types of cowbird traps or the effects of these traps on non-target species. We used portable traps to capture cowbirds in 2003-2007 at 3 study areas in southern Nevada and western Arizona. We compared the effectiveness of traps with flat tops versus funnel-shaped tops in 2005 and compared entrance slots of 2 different widths in 2006-2007. Traps with funnel-shaped tops had higher cowbird capture rates and lower escape rates than did flat-topped traps. Funnel-topped traps also had a higher capture rate of non-target species. Funnel-topped traps with a 3.8-cm-wide entrance slot had a higher capture rate for male cowbirds than did identical traps with a 3.2-cm-wide entrance slot. Capture rates for female cowbirds did not differ between slot sizes, nor did escape rates for either males or females. Capture rates for non-target species did not differ between slot widths, but wider slots captured larger bodied species (e.g., white-winged dove [Zenaida asiatica] and great-tailed grackle [Quiscalus mexicanus]) that were not seen in the traps with narrower slots in the years when both slot widths were tested. Cowbird traps with a funnel-topped design should be used to maximize the number of cowbirds captured and removed from a site. A slot width of 3.2cm may minimize non-target captures, particularly of larger bodied species, while still allowing effective removal of female cowbirds. © 2014 The Wildlife Society.
Ong L.,SWCA Environmental Consultants |
Holland K.N.,Hawaii Institute of Marine Biology
Marine Biology | Year: 2010
Parrotfishes can be significant bioeroders and sediment producers on coral reefs. We quantified the bioerosion rates of two similarly sized Hawaiian parrotfishes with two different feeding modes (Scarus rubroviolaceus-a scraper and Chlorurus perspicillatus-an excavator). The results showed that feeding modes did not affect bioerosion rates but that bioerosion rates were size dependent, with largest individuals (S. rubroviolaceus 45-54 cm FL) bioeroding up to 380 ± 67 kg ind-1 year-1. The size for onset of bioerosion capabilities for both species was 15 cm. Grazing by the two species consumed 60% of the carbonate production of the fore reef area, suggesting that large parrotfishes in Hawaii are ecologically important bioeroders. As individual large S. rubroviolaceus contributed disproportionately more to bioerosion and sediment production than the equivalent biomass of smaller conspecifics, management strategies designed to retain normal reef bioerosion rates should seek to preserve the historical size structure of S. rubroviolaceus populations and to especially protect the larger size classes. © 2010 Springer-Verlag.