scholarly journals Introduction to the Population Ecology of North American Caribou

Rangifer ◽  
1996 ◽  
Vol 16 (4) ◽  
pp. 11
Author(s):  
Dale R. Seip ◽  
Kent Brown
Keyword(s):  
North America ◽  
Population Ecology ◽  
North American ◽  
Canis Lupus ◽  
General Model ◽  
Competition For Food ◽  
The Impact

Bergerud has discussed how major differences in caribou density across North America appear to be related to the impact of wolf (Canis lupus) predation, and the strategies used by caribou to avoid wolves. Caribou living in areas without wolves usually occur at high densities and are regulated by competition for food. In this session, we asked the presenters to discuss the population ecology of different caribou herds in North America and to evaluate if they fit the general model.

scholarly journals A Link between the Hiatus in Global Warming and North American Drought

2015 ◽  
Vol 28 (9) ◽  
pp. 3834-3845 ◽  
Author(s):  
Thomas L. Delworth ◽  
Fanrong Zeng ◽  
Anthony Rosati ◽  
Gabriel A. Vecchi ◽  
Andrew T. Wittenberg
Keyword(s):  
Global Warming ◽  
North America ◽  
Surface Temperature ◽  
North American ◽  
Radiative Forcing ◽  
Tropical Pacific ◽  
Global Warming Hiatus ◽  
Warming Hiatus ◽  
The Impact ◽  
The Tropical Pacific

Abstract Portions of western North America have experienced prolonged drought over the last decade. This drought has occurred at the same time as the global warming hiatus—a decadal period with little increase in global mean surface temperature. Climate models and observational analyses are used to clarify the dual role of recent tropical Pacific changes in driving both the global warming hiatus and North American drought. When observed tropical Pacific wind stress anomalies are inserted into coupled models, the simulations produce persistent negative sea surface temperature anomalies in the eastern tropical Pacific, a hiatus in global warming, and drought over North America driven by SST-induced atmospheric circulation anomalies. In the simulations herein the tropical wind anomalies account for 92% of the simulated North American drought during the recent decade, with 8% from anthropogenic radiative forcing changes. This suggests that anthropogenic radiative forcing is not the dominant driver of the current drought, unless the wind changes themselves are driven by anthropogenic radiative forcing. The anomalous tropical winds could also originate from coupled interactions in the tropical Pacific or from forcing outside the tropical Pacific. The model experiments suggest that if the tropical winds were to return to climatological conditions, then the recent tendency toward North American drought would diminish. Alternatively, if the anomalous tropical winds were to persist, then the impact on North American drought would continue; however, the impact of the enhanced Pacific easterlies on global temperature diminishes after a decade or two due to a surface reemergence of warmer water that was initially subducted into the ocean interior.

scholarly journals Novel Highly Pathogenic Avian A(H5N2) and A(H5N8) Influenza Viruses of Clade 2.3.4.4 from North America Have Limited Capacity for Replication and Transmission in Mammals

mSphere ◽  
2016 ◽  
Vol 1 (2) ◽  
Author(s):  
Bryan S. Kaplan ◽  
Marion Russier ◽  
Trushar Jeevan ◽  
Bindumadhav Marathe ◽  
Elena A. Govorkova ◽  
...  
Keyword(s):  
North America ◽  
Avian Influenza ◽  
North American ◽  
Influenza Viruses ◽  
Morbidity And Mortality ◽  
Avian Influenza Viruses ◽  
Highly Pathogenic ◽  
The North ◽  
Domestic Poultry ◽  
The Impact

ABSTRACT Highly pathogenic H5 influenza viruses have been introduced into North America from Asia, causing extensive morbidity and mortality in domestic poultry. The introduced viruses have reassorted with North American avian influenza viruses, generating viral genotypes not seen on other continents. The experiments and analyses presented here were designed to assess the impact of this genetic diversification on viral phenotypes, particularly as regards mammalian hosts, by comparing the North American viruses with their Eurasian precursor viruses. Highly pathogenic influenza A(H5N8) viruses from clade 2.3.4.4 were introduced to North America by migratory birds in the fall of 2014. Reassortment of A(H5N8) viruses with avian viruses of North American lineage resulted in the generation of novel A(H5N2) viruses with novel genotypes. Through sequencing of recent avian influenza viruses, we identified PB1 and NP gene segments very similar to those in the viruses isolated from North American waterfowl prior to the introduction of A(H5N8) to North America, highlighting these bird species in the origin of reassortant A(H5N2) viruses. While they were highly virulent and transmissible in poultry, we found A(H5N2) viruses to be low pathogenic in mice and ferrets, and replication was limited in both hosts compared with those of recent highly pathogenic avian influenza (HPAI) H5N1 viruses. Molecular characterization of the hemagglutinin protein from A(H5N2) viruses showed that the receptor binding preference, cleavage, and pH of activation were highly adapted for replication in avian species and similar to those of other 2.3.4.4 viruses. In addition, North American and Eurasian clade 2.3.4.4 H5NX viruses replicated to significantly lower titers in differentiated normal human bronchial epithelial cells than did seasonal human A(H1N1) and highly pathogenic A(H5N1) viruses isolated from a human case. Thus, despite their having a high impact on poultry, our findings suggest that the recently emerging North American A(H5N2) viruses are not expected to pose a substantial threat to humans and other mammals without further reassortment and/or adaptation and that reassortment with North American viruses has not had a major impact on viral phenotype. IMPORTANCE Highly pathogenic H5 influenza viruses have been introduced into North America from Asia, causing extensive morbidity and mortality in domestic poultry. The introduced viruses have reassorted with North American avian influenza viruses, generating viral genotypes not seen on other continents. The experiments and analyses presented here were designed to assess the impact of this genetic diversification on viral phenotypes, particularly as regards mammalian hosts, by comparing the North American viruses with their Eurasian precursor viruses.

scholarly journals The impact of evangelical revivals on global mission: The case of North American evangelicals in Brazil in the nineteenth and twentieth centuries

2010 ◽  
Vol 31 (1) ◽  
Author(s):  
Edward L. Smither
Keyword(s):  
Nineteenth Century ◽  
Latin America ◽  
North America ◽  
North American ◽  
Roman Catholic ◽  
Global Missions ◽  
Global Mission ◽  
Current Article ◽  
Evangelical Identity ◽  
The Impact

The aim of the current article is to show that an important element behind the establishment of evangelical missions to Brazil � particularly during the pioneering stages � was evangelical revival, especially that which occurred in North America during the nineteenth century. Following a brief introduction to the general relationship between eighteenth- and nineteenth century revivals and evangelical missions, I shall endeavour to support historically the commonly accepted, yet often unsubstantiated, correlation between such movements of revival and mission. Firstly, I will show the significant paradigm shift in missional thinking, which took place in the nineteenth century, as North American evangelicals began to regard Roman Catholic countries in Latin America as mission fields. Secondly, I shall argue that the influence of nineteenth-century revivalist evangelicalism (particularly that sourced in North America) on missions to Brazil and Latin America can best be observed in the Brazilian evangelical identity that emerged in the twentieth century, which has, in turn, propelled the Brazilian evangelical church into its own significant involvement in global missions (Noll 2009:10).

Ecogeography and the Great American Interchange

Paleobiology ◽  
1991 ◽  
Vol 17 (3) ◽  
pp. 266-280 ◽  
Author(s):  
S. David Webb
Keyword(s):  
North America ◽  
South America ◽  
North American ◽  
Mammalian Fauna ◽  
The South ◽  
Land Bridge ◽  
Southern Mexico ◽  
The North ◽  
Land Mammal ◽  
The Impact

When the isthmian land bridge triggered the Great American Interchange, a large majority of land-mammal families crossed reciprocally between North and South America at about 2.5 Ma (i.e., Late Pliocene). Initially land-mammal dynamics proceeded as predicted by equilibrium theory, with roughly equal reciprocal mingling on both continents. Also as predicted, the impact of the interchange faded in North America after about 1 m.y. In South America, contrary to such predictions, the interchange became decidedly unbalanced: during the Pleistocene, groups of North American origin continued to diversify at exponential rates. Whereas only about 10% of North American genera are derived from southern immigrants, more than half of the modern mammalian fauna of South America, measured at the generic level, stems from northern immigrants. In addition, extinctions more severely decimated interchange taxa in North America, where six families were lost, than in South America, where only two immigrant families became extinct.This paper presents a two-phase ecogeographic model to explain the asymmetrical results of the land-mammal interchange. During the humid interglacial phase, the tropics were dominated by rain forests, and the principal biotic movement was from Amazonia to Central America and southern Mexico. During the more arid glacial phase, savanna habitats extended broadly right through tropical latitudes. Because the source area in the temperate north was six times as large as that in the south, immigrants from the north outnumbered those from the south. One prediction of this hypothesis is that immigrants from the north generally should reach higher latitudes in South America than the opposing contingent of land-mammal taxa in North America. Another prediction is that successful interchange families from the north should experience much of their phylogenetic diversification in low latitudes of North America before the interchange. Insofar as these predictions can be tested, they appear to be upheld.

scholarly journals Impact of the El Niño type and PDO on the winter sub-seasonal North American zonal temperature dipole via the variability of positive PNA patterns

2021 ◽  
Author(s):  
Yao Ge ◽  
Dehai Luo
Keyword(s):  
North America ◽  
North American ◽  
El Niño ◽  
El Nino ◽  
Hadley Cell ◽  
Height Anomaly ◽  
Central Pacific ◽  
The West ◽  
Anticyclonic Anomaly ◽  
The Impact

Abstract In recent years, the winter (from December to February, DJF) North American surface air temperature (SAT) anomaly in midlatitudes shows a “warm west/cold east” (WWCE) dipole pattern. To some extent, the winter WWCE dipole can be considered as being a result of the winter mean of sub-seasonal WWCE events. In this paper, the Pacific SST condition linked to the sub-seasonal WWCE SAT dipole is investigated. It is found that while the sub-seasonal WWCE dipole is related to the positive Pacific North American (PNA+) pattern, the impact of the PNA+ on the WWCE dipole depends on the El Niño SST type and the phase of Pacific decadal Oscillation (PDO). For a central-Pacific (CP) type El Niño, the positive (negative) height anomaly center of PNA+ is located in the west (east) part of North America to result in an intensified WWCE dipole, though the positive PDO favors the WWCE dipole. In contrast, the WWCE dipole is suppressed under an Eastern-Pacific (EP) type El Niño because the PNA+ anticyclonic anomaly dominates the whole North America.Moreover, the physical cause of why the type of El Niño influences the PNA+ is further examined. It is found that the type of El Niño can significantly influence the location of PNA+ through changing North Pacific midlatitude westerly winds (NPWWs). For the CP-type El Niño, the eastward migration of PNA+ is suppressed to favor its anticyclonic (cyclonic) anomaly appearing in the west (east) region of North American owing to reduced NPWWs. But for the EP-type El Niño, NPWWs are intensified to cause the appearance of the PNA+ anticyclonic anomaly over the whole North America due to enhanced Hadley cell and Ferrell cell.

scholarly journals The Impact of Large-Scale Orography on Northern Hemisphere Winter Synoptic Temperature Variability

2019 ◽  
Vol 32 (18) ◽  
pp. 5799-5814 ◽  
Author(s):  
Nicholas J. Lutsko ◽  
Jane Wilson Baldwin ◽  
Timothy W. Cronin
Keyword(s):  
North America ◽  
Northern Hemisphere ◽  
North American ◽  
Large Scale ◽  
Temperature Variability ◽  
Temperature Gradients ◽  
Northwest Pacific ◽  
Near Surface ◽  
The North ◽  
The Impact

Abstract The impact of large-scale orography on wintertime near-surface (850 hPa) temperature variability on daily and synoptic time scales (from days to weeks) in the Northern Hemisphere is investigated. Using a combination of theory, idealized modeling work, and simulations with a comprehensive climate model, it is shown that large-scale orography reduces upstream temperature gradients, in turn reducing upstream temperature variability, and enhances downstream temperature gradients, enhancing downstream temperature variability. Hence, the presence of the Rockies on the western edge of the North American continent increases temperature gradients over North America and, consequently, increases North American temperature variability. By contrast, the presence of the Tibetan Plateau and the Himalayas on the eastern edge of the Eurasian continent damps temperature variability over most of Eurasia. However, Tibet and the Himalayas also interfere with the downstream development of storms in the North Pacific storm track, and thus damp temperature variability over North America, by approximately as much as the Rockies enhance it. Large-scale orography is also shown to impact the skewness of downstream temperature distributions, as temperatures to the north of the enhanced temperature gradients are more positively skewed while temperatures to the south are more negatively skewed. This effect is most clearly seen in the northwest Pacific, off the east coast of Japan.

scholarly journals Postcranial diversity and recent ecomorphic impoverishment of North American gray wolves

2018 ◽  
Vol 14 (1) ◽  
pp. 20170613 ◽  
Author(s):  
Susumu Tomiya ◽  
Julie A. Meachen
Keyword(s):  
North America ◽  
North American ◽  
Canis Lupus ◽  
Late Quaternary ◽  
Gray Wolf ◽  
Evolutionary Potential ◽  
The Holocene ◽  
Gray Wolves ◽  
The Usa ◽  
Northwestern North America

Recent advances in genomics and palaeontology have begun to unravel the complex evolutionary history of the gray wolf, Canis lupus . Still, much of their phenotypic variation across time and space remains to be documented. We examined the limb morphology of the fossil and modern North American gray wolves from the late Quaternary (< ca 70 ka) to better understand their postcranial diversity through time. We found that the late-Pleistocene gray wolves were characterized by short-leggedness on both sides of the Cordilleran–Laurentide ice sheets, and that this trait survived well into the Holocene despite the collapse of Pleistocene megafauna and disappearance of the ‘Beringian wolf' from Alaska. By contrast, extant populations in the Midwestern USA and northwestern North America are distinguished by their elongate limbs with long distal segments, which appear to have evolved during the Holocene possibly in response to a new level or type of prey depletion. One of the consequences of recent extirpation of the Plains ( Canis lupus nubilus ) and Mexican wolves ( C. l. baileyi ) from much of the USA is an unprecedented loss of postcranial diversity through removal of short-legged forms. Conservation of these wolves is thus critical to restoration of the ecophenotypic diversity and evolutionary potential of gray wolves in North America.

The impact of ecosystem change on dust emission in North America

2020 ◽  
Author(s):  
Mark Hennen ◽  
Nicholas Webb ◽  
Adrian Chappell
Keyword(s):  
North America ◽  
North American ◽  
Surface Wind ◽  
Dust Emission ◽  
Soil Surface ◽  
Ecosystem Change ◽  
Management Options ◽  
Subjective Analysis ◽  
Disturbance Regimes ◽  
The Impact

&lt;p&gt;An estimated 50 Mt yr&lt;sup&gt;-1&lt;/sup&gt; of dust is emitted from North American landscapes, with profound regional impacts (Shao et al., 2011). Dust emission flux in North America is controlled by wind speed and land surface (aerodynamic) roughness that are variable in both space and time. Vegetation growth, form and spatial distribution characterise different ecosystem regimes and protect the soil surface from the shearing stress of the wind. In the dry western US, diverse land use and management drivers create disturbance regimes that produce diverse ecosystem responses that could be drastically impacting rates of wind erosion and dust emission (Ravi et al., 2010). Resolving the impacts of ecosystem change on aeolian processes is needed to quantify anthropogenic-induced dust loads and identify management options as environmental solutions (Webb and Pierre, 2018).&lt;/p&gt;&lt;p&gt;Currently, erosion surfaces in North America are derived from satellite imagery, either by spatial analysis of mean aerosol optical depth concentrations (e.g. Ginoux et al., 2012) or point source identification through subjective analysis of individual daily multispectral images (e.g. Lee et al., 2012; Kandakji et al., 2020). In either approach, the results are subjected to spatial and temporal bias caused by a lag in emission-to-observation period and loss of data during cloudy (dust and meteorological) periods. To complement these approaches we produced the first moderate (500 m) resolution daily maps of dust emission across the dry western United States. These maps were based on estimates of soil surface wind friction velocity (u&lt;sub&gt;s*&lt;/sub&gt;) derived from MODIS albedo data (Chappell and Webb 2016) using a commonly applied model (Marticorena and Bergammetti, 1995).&lt;/p&gt;&lt;p&gt;The North American dust emission climatology from 2001-2018 was compared with the u&lt;sub&gt;s*&lt;/sub&gt; data volume to identify the spatio-temporal occurrence of three key disturbance regimes: i) land clearing for energy infrastructure, ii) invasion of shrublands by exotic annual grasses that alter fire regimes, and iii) replacement of grasslands by invasive shrub species. Against this background we examine the state and transition of ecosystem change across these landscapes to understand the impact on current dust emission. We use these findings to comment on the implications for future dust emission and to encourage the development of this modelling approach in Earth System Models. &amp;#160;&amp;#160;&amp;#160;&lt;/p&gt;

scholarly journals Case studies of ozone transport between North America and Europe in summer 2000

2005 ◽  
Vol 5 (4) ◽  
pp. 6127-6184 ◽  
Author(s):  
G. Guerova ◽  
I. Bey ◽  
J.-L. Attié ◽  
R. V. Martin
Keyword(s):  
North America ◽  
North American ◽  
North Atlantic Ocean ◽  
Conveyor Belt ◽  
Tropospheric Chemistry ◽  
Pollution Transport ◽  
The North ◽  
Range Transport ◽  
European Mountain ◽  
The Impact

Abstract. This paper reports on Long Range Transport (LRT) of ozone and related species over the North Atlantic ocean and its impact on Europe. Measurements of NO2 and O3 columns from the GOME and MOPITT satellite instruments are first used in conjunction with the GEOS-CHEM global model of transport and tropospheric chemistry to identify the major events of LRT that reach Europe over the course of the summer 2000. Model simulations are then used to examine surface O3 observations at a European mountain site and O3 vertical profiles over several European cities to quantify the impact of the LRT events on the European ozone distributions. Over the course of summer 2000, we identified nine major episodes of pollution transport between North America and Europe, which are in majority associated with WCB/post-frontal outflow (7 events) and zonal transport (2 events). We find that on average three episodes occur per month with the strongest ones being in June. The number and frequency of LRT events that reach Europe after leaving North America is strongly driven by the position and strength of the Azores anticyclone. After leaving North America, the plumes can either i) travel in the North American cyclones, mostly in the Warm Conveyor Belt (WCB), tracking poleward and thus reach Europe at high latitudes; ii) be transported zonally between 40° and 55° N directly to Europe; iii) be incorporated into the Azores anticyclone and reach Europe at mid-latitudes. Based on model sensitivity simulation it can be concluded that on average the North American sources of ozone contribute between 2–8 ppb in PBL and 10–13 ppb in FT. During particular episodes the North American sources resulted in O3 enhancement up to 25–28 ppb in the layer between 800–600 hPa and 10–12 ppb in PBL. For some episodes a substantial North American contribution (30% or higher) does not translate into a well marked enhancement of the total O3.

scholarly journals Predation and caribou populations

Rangifer ◽  
1991 ◽  
Vol 11 (4) ◽  
pp. 46 ◽  
Author(s):  
Dale R. Seip
Keyword(s):  
North America ◽  
Canis Lupus ◽  
Predator Avoidance ◽  
Rangifer Tarandus ◽  
Food Resources ◽  
Numerical Response ◽  
Population Differences ◽  
Annual Increment ◽  
Wolf Predation ◽  
The Impact

Predation, especially wolf (Canis lupus) predation, limits many North American caribou (Rangifer tarandus) populations below the density that food resources could sustain. The impact of predation depends on the parameters for the functional and numerical response of the wolves, relative to the potential annual increment of the caribou population. Differences in predator-avoidance strategies largely explain the major differences in caribou densities that occur naturally in North America. Caribou migrations that spatially separate caribou from wolves allow relatively high densities of caribou to survive. Non-migratory caribou that live in areas where wolf populations are sustained by alternate prey can be eliminated by wolf predation.

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