Parts Of Colorado Research Articles

Treated water from oil and gas extraction as an unconventional water resource for agriculture in the Anadarko Basin

The energy industry generates large volumes of produced water (PW) as a byproduct of oil and gas extraction. In the central United States, PW disposal occurs through deep well injection, which can increase seismic activity. The treatment of PW for use in agriculture is an alternative to current disposal practices that can also provide supplemental water in regions where limited freshwater sources can affect agricultural production. This paper assesses the potential for developing PW as a water source for agriculture in the Anadarko basin, a major oil and gas field spanning parts of Kansas, Oklahoma, Colorado, and Texas. From 2011 to 2019, assessment of state oil and gas databases indicated that PW generation in the Anadarko Basin averaged 428 million m3/yr. A techno-economic analysis of PW treatment was combined with geographical information on PW availability and composition to assess the costs and energy requirements to recover this PW as a non-conventional water resource for agriculture. The volume of freshwater economically extractable from PW was estimated to be between 58 million m3 per year using reverse osmosis (RO) treatment only and 82 million m3 per year using a combination of RO and mechanical vapor compression to treat higher salinity waters. These volumes could meet 1–2 % and 49–70 % of the irrigation and livestock water demands in the basin, respectively. PW recovery could also modestly contribute to mitigating the decline of the Ogallala aquifer by ~2 %. RO treatment costs and energy requirements, 0.3–1.5 $/m3 and 1.01–2.65 kWh/m3, respectively, are similar to those for deep well injection. Treatment of higher salinity waters increases costs and energy requirements substantially and is likely not economically feasible in most cases. The approach presented here provides a valuable framework for assessing PW as a supplemental water source in regions facing similar challenges.

Range-wide population assessments for subalpine fir indicate widespread disturbance-driven decline

Subalpine forests in western North America are threatened by rapid climate change, increased activity by endemic and exotic insects and diseases, and changing wildfire regimes. The interactive effects of these stressors have resulted in pronounced population declines in many subalpine tree species; however, a systematic assessment of the status and trends of subalpine forests is lacking. Subalpine fir (Abies lasiocarpa) is a widespread species across the western United States, with documented population declines in many parts of its distribution. Here we use subalpine fir as an initial leverage point to build a more complete understanding of subalpine forest baseline conditions and responses to environmental change. Specifically, we leverage the USDA Forest Service Forest Inventory and Analysis (FIA) database to (1) ask how subalpine fir populations are changing across the species’ distribution in the western US, (2) assess the drivers of recent subalpine fir population trends, and (3) explore whether those changes imply generalized species-wide and/or system-wide decline. We found that subalpine fir abundance and basal area are declining concurrently across ∼ 62% of the species’ distribution, and increasing across ∼ 19%. Range-wide, we estimated 25.02 ± 2.74 % subalpine fir mortality between 2000 and 2009 and 2010–2019 FIA inventory periods, with higher mortality concentrated in the eastern Oregon Cascades, central Idaho, and parts of southern Colorado. High regeneration density did not predict positive population trajectories, which were instead associated with higher rates of adult recruitment. While the importance of different mortality agents varied substantially between ecoregions, 83.4% of total range-wide mortality was related to fire or biological disturbance. Declining subalpine fir basal area coincided with declines in the basal area of other co-occurring tree species in 39% of subalpine forest area, and with increases in conspecific basal area in 22% of forest area. Fire disturbance was the single largest cause of subalpine fir mortality; however, even where subalpine fir fire mortality was high, mortality among other species was primarily caused by insects. Our results suggest that subalpine fir declines across large portions of the western United States are driven by forest disturbance, and that declines in subalpine fir populations may be indicative of negative change in subalpine forest systems broadly.

Intense Surface Winds from Gravity Wave Breaking in Simulations of a Destructive Macroburst

Abstract Shortly after 0600 UTC (midnight local time) 9 June 2020, a convective line produced severe winds across parts of northeast Colorado that caused extensive damage, especially in the town of Akron. High-resolution observations showed gusts exceeding 50 m s−1, accompanied by extremely large pressure fluctuations, including a 5-hPa pressure surge in 19 s immediately following the strongest winds and a 15-hPa pressure drop in the following 3 min. Numerical simulations of this event (using the WRF Model) and with horizontally homogeneous initial conditions (using Cloud Model 1) reveal that the severe winds in this event were associated with gravity wave dynamics. In a very stable postfrontal environment, elevated convection initiated and led to a long-lived gravity wave. Strong low-level vertical wind shear supported the amplification and eventual breaking of this wave, resulting in at least two sequential strong downbursts. This wave-breaking mechanism is different from the usual downburst mechanism associated with negative buoyancy resulting from latent cooling. The model output reproduces key features of the high-resolution observations, including similar convective structures, large temperature and pressure fluctuations, and intense near-surface wind speeds. The findings of this study reveal a series of previously unexplored mesoscale and storm-scale processes that can result in destructive winds. Significance Statement Downbursts of intense wind can produce significant damage, as was the case on 9 June 2020 in Akron, Colorado. Past research on downbursts has shown that they occur when raindrops, graupel, and hail in thunderstorms evaporate and melt, cooling the air and causing it to sink rapidly. In this research, we used numerical models of the atmosphere, along with high-resolution observations, to show that the Akron downburst was different. Unlike typical lines of thunderstorms, those responsible for the Akron macroburst produced a wave in the atmosphere, which broke, resulting in rapidly sinking air and severe surface winds.

Legacies of Dust: Land Use and Labor on the Colorado Plains

Legacies of Dust: Land Use and Labor on the Colorado Plains

Verifying Experimental Wet Bulb Globe Temperature Hindcasts Across the United States.

Hot and humid heat exposures challenge the health of outdoor workers engaged in occupations such as construction, agriculture, first response, manufacturing, military, or resource extraction. Therefore, government institutes developed guidelines to prevent heat‐related illnesses and death during high heat exposures. The guidelines use Wet Bulb Globe Temperature (WBGT), which integrates temperature, humidity, solar radiation, and wind speed. However, occupational heat exposure guidelines cannot be readily applied to outdoor work places due to limited WBGT validation studies. In recent years, institutions have started providing experimental WBGT forecasts. These experimental products are continually being refined and have been minimally validated with ground‐based observations. This study evaluated a modified WBGT hindcast using the historical National Digital Forecast Database and the European Centre for Medium‐Range Weather Forecasts Reanalysis v5. We verified the hindcasts with hourly WBGT estimated from ground‐based weather observations. After controlling for geographic attributes and temporal trends, the average difference between the hindcast and in situ data varied from −0.64°C to 1.46°C for different Köppen‐Geiger climate regions, and the average differences are reliable for decision making. However, the results showed statistically significant variances according to geographical features such as aspect, coastal proximity, land use, topographic position index, and Köppen‐Geiger climate categories. The largest absolute difference was observed in the arid desert climates (1.46: 95% CI: 1.45, 1.47), including some parts of Nevada, Arizona, Colorado, and New Mexico. This research investigates geographic factors associated with systematic WBGT differences and points toward ways future forecasts may be statistically adjusted to improve accuracy.

Evgam: An R Package for Generalized Additive Extreme Value Models

This article introduces the R package evgam. The package provides functions for fitting extreme value distributions. These include the generalized extreme value and generalized Pareto distributions. The former can also be fitted through a point process representation. Package evgam supports quantile regression via the asymmetric Laplace distribution, which can be useful for estimating high thresholds, sometimes used to discriminate between extreme and non-extreme values. The main addition of package evgam is to let extreme value distribution parameters have generalized additive model forms, the smoothness of which can be objectively estimated using Laplace's method. Illustrative examples fitting various distributions with various specifications are given. These include daily precipitation accumulations for part of Colorado, US, used to illustrate spatial models, and daily maximum temperatures for Fort Collins, Colorado, US, used to illustrate temporal models.

Geography of Disparity: Connecting COVID-19 Vulnerability and Social Determinants of Health in Colorado

The COVID-19 pandemic has drawn greater attention to social determinants of health and associated health inequities, which disproportionately affect vulnerable populations and places in the U.S. In this study, we explored geographic patterns of local-level COVID-19 vulnerability and associations with social and health determinants across Colorado. To conceptualize social and health determinants and how together they generate risk and exposure, we integrated the concepts of social vulnerability and syndemic to situate COVID-19 vulnerability within a broader hazards of place framework. Using geospatial statistics and GIS, we estimated census tract-level rates of COVID-19, which are not yet available in Colorado, and mapped areas of high and low incidence risk. We also developed composite indices that characterized social and health vulnerabilities to measure multivariate associations with COVID-19 rates. The findings revealed hotspots of persistent risk in mountain communities since the pandemic emerged in Colorado, as well as clusters of risk in the Urban Front Range’s central and southern counties, and across many parts of eastern Colorado. Vulnerability analyses indicate that COVID-19 rates were associated with mental health and chronic conditions along with social determinants that represent inequities in education, income, healthcare access, and race/ethnicity (minority percent of population), which may have disproportionately exposed some communities more than others to infection and severe health outcomes. Overall, the findings provide geographic health information about COVID-19 and vulnerability context, which may better inform local decision-making for interventions and policies that support equity of social determinants of health. Supplemental data for this article is available online at https://doi.org/10.1080/08964289.2021.2021382 .

Dark sky tourism: economic impacts on the Colorado Plateau Economy, USA

Purpose This paper aims to examine the economic impact from dark-sky tourism in national parks in the USA on the Colorado Plateau. The Colorado Plateau is a region encompassing parts of Arizona, Colorado, New Mexico and Utah that is known for its dark, star-filled night skies. Tourists in national parks are increasingly interested in observing this natural recreational amenity – especially considering that it is an ecological amenity that is quickly disappearing from the planet. Using a 10-year forecast of visitors to the national parks and using standard input-output modeling, it is observed that, for the first time anywhere, the value of dark skies to tourism in this area. The authors find that non-local tourists who value dark skies will spend $5.8bn over the next 10 years in the Colorado Plateau. These tourist expenditures will generate $2.4bn in higher wages and create over 10,000 additional jobs each year for the region. Furthermore, as dark skies are even more intense natural amenity in the non-summer months, they have the ability to increase visitor counts to national parks year-round and lead to a more efficient use of local community and tourism-related resources throughout the year. Design/methodology/approach Using a 10-year forecast of visitors to the national parks and using standard input-output modeling, we find that non-local tourists who value dark skies will spend $5.8bn over the next 10 years in the Colorado Plateau. Findings These tourist expenditures will generate $2.4bn in higher wages and create over 10,000 additional jobs each year for the region. Furthermore, as dark skies are even more intense natural amenity in the non-summer months, they have the ability to increase visitor counts to national parks year-round and lead to a more efficient use of local community and tourism-related resources throughout the year. Originality/value To the best of the authors’ knowledge, no other study has attempted to value the environmental amenity of dark skies.

Impact of Low-Income Home Energy-Efficiency Retrofits on Building Air Tightness and Healthy Home Indicators

We studied 226 low-income households as a part of the Colorado Home Energy Efficiency and Respiratory Health (CHEER) study to investigate the relationship between energy-efficiency retrofits (EERs) specific to air sealing of residential building envelopes, annual average infiltration rates (AAIR), and qualitative indicators of “healthy” homes. Blower door tests quantified the leakage area in each home, which was used to estimate the AAIR. Walk-through inspections were used to record observations of air-sealing retrofits conducted as part of Colorado’s Weatherization Assistance Program and indirect indicators of poor indoor environmental quality (IEQ) in the homes, such as visible mold or stains, visible dust on hard surfaces, vapor condensation on windows, dampness, and perceived air quality. Results showed that building characteristics like age and volume affected AAIR more significantly than air-sealing EERs. Among the air-sealing EERs, homes with the air-handler ductwork sealed and windows weather-stripped were found to have significantly lower AAIR compared to the homes without these features. Mold growth, wall stains, notably higher levels of dust, and unacceptable odor levels were more frequently reported in homes with higher AAIR, showing that leakier homes do not necessarily have better IEQ.

Where Renegades Become Saints

Where Renegades Become Saints Ilan Stavans (bio) The Battle of Churubusco: American Rebels in the Mexican-American War Andrea Ferraris Fantagraphics http://www.fantagraphics.com/ 200 Pages; Print, $22.99 I grew up not far from Churubusco in Coyoacán, a borough in the southern part of Mexico City. In my childhood, it still housed a movie studio where some of the Golden Age movies of Mexican cinema with Jorge Negrete, Pedro Infante, and Sara García were produced. The studio was eventually turned into the Cineteca Nacional, a film club where I saw a slew of superb foreign movies by Bergman, Antonioni, and Truffaut. The club was also a depository of archival material. In 1982, the club was destroyed by a tragic explosion: the screen bursts into flames as The Promised Land (1974), a movie by Polish director Andrzej Wajda, was projected. Around 2,000 screenplays went up in flames, as did 9,000 books, paintings by Diego Rivera, and original footage from masters like Manuel Alvarez Bravo and Juan Orol. (I know this because I was supposed to be at the screening. I never made it because I was caught in traffic. Several acquaintances of mine worked at the archives—one of them died.) Maybe this explains why, in part, Churubusco feels like a battlefield. Of course, this piece of land is actually where, on August 20, 1847, the legendary Battle of Churubusco was fought by Mexican soldiers and their supporters against the invading US army in what eventually became a crux in the Mexican-American War of 1846-48. Mexico didn’t just lose the war; it also lost a generous portion of its territory—what today constitutes the “Southwest,” e.g., Texas, California, Nevada, Utah, and parts of Colorado, Arizona, New Mexico and Wyoming. These lands, along with the population in them, were “sold” for $15,000,000 to the Americans. It was a steal whose echoes reverberate across time and have inspired, among others, the Chicano struggle for self-determination as part of the Civil Rights era. What makes the battle poignant is that a number of foreign nationals, including Irish, Italians, and former African-American slaves, switched sides to join the Mexican army against the American invaders. They were part of what came to be known as the San Patricio Battalion. Like the Spanish Civil War almost a century later, when figures like George Orwell, Arthur Koestler, Ernest Hemingway, Pablo Neruda, and others joined forces with the rebellion, the Mexican-American War attracted immense international attention. While the names aren’t as famous—a plaque hangs in the Plaza de San Jacinto, in Mexico City’s San Angel neighborhood, commemorating those soldiers of Irish descent who absconded—many also believed at the time that the fate of humankind as a whole, or at least of neighborly relations in the Americas, was at stake and that they needed to pledge alliance to the weak side in order to push history in what they thought was the right direction. The graphic novel The Battle of Churubusco: American Rebels in the Mexican-American War wants to memorialize its martyrs. It is ambitious in scope and cinematic in execution. Unfortunately, it isn’t very good. Its author, Andrea Ferraris, is an Italian artist who lives in Paris. According to a publisher’s note, she has worked for Disney for a couple of decades and draws Donald Duck for the Danish publisher Egmont. Her affinity for cartoonish characters is clear in these pages. In her style, Ferraris pays homage to Mexican muralist José Clemente Orozco, a Diego Rivera colleague—and sometimes nemesis—whose art decorated a number of important Mexico City buildings and a few more in the United States. Orozco’s depiction of soldiers, priests, merchants, and other revolutionary figures had a pathetic quality to it. He was a committed Communist who campaigned against Mexico’s willingness to welcome Leon Trotsky as he feuded with Joseph Stalin and went into exile. Ferraris’ illustrations, mostly in black and white with an occasional sepia insertion to denote a dreamlike sequence, at times even copy Orozco’s canonical images. Some readers might be...

Two Delphinium ramosum chemotypes, their biogeographical distribution and potential toxicity

Larkspurs (Delphinium, Ranunculaceae) are poisonous plants found on rangelands throughout Western North America. Two main structural groups of norditerpene alkaloids, the N-(methylsuccinimido) anthranoyllycoctonine type (MSAL-type) and the non-MSAL type, are responsible for larkspur-induced poisoning. Information on the alkaloid composition is lacking for a number of Delphinium species, including D. ramosum. Delphinium ramosum grows throughout parts of Colorado and northern New Mexico. The objective of this study was to profile the alkaloid composition of D. ramosum throughout its geographical distribution using both field and herbarium specimens. Two alkaloid profiles were identified, one that contained significantly greater concentrations of the MSAL-type alkaloids than the other. Plants containing each respective alkaloid profile were unique in their geographical distribution. Populations of these two chemotypes will likely differ in their toxic potential and consequently pose different risks of poisoning when grazed by livestock species. This information has important implications in grazing management decisions on D. ramosum-infested rangelands and demonstrates that botanical classification alone is not an adequate indicator of relative risk of toxicity.

Using citizen science monitoring data in species distribution models to inform isotopic assignment of migratory connectivity in wetland birds

Stable isotopes have been used to estimate migratory connectivity in many species. Estimates are often greatly improved when coupled with species distribution models (SDMs), which temper estimates in relation to occurrence. SDMs can be constructed using point locality data from a variety of sources including extensive monitoring data typically collected by citizen scientists. However, one potential issue with SDM is that these data often have sampling bias. To avoid this potential bias, we created SDMs based on marsh bird monitoring program data collected by citizen scientists and other participants following protocols specifically designed to maximize detections of species of interest at locations representative of larger areas of inference. We then used the SDMs to refine isotopic assignments of breeding areas of autumn‐migrating and wintering sora Porzana carolina, Virginia rail Rallus limicola, and yellow rail Coturnicops noveboracensis based on feathers collected from individuals caught at various locations in the United States from Minnesota south to Louisiana and South Carolina. Sora were assigned to an area that included much of the western U.S. and prairie Canada, covering parts of the Pacific, Central, and Mississippi waterfowl Flyways. Yellow rails were assigned to a broad area along Hudson and James Bay in northern Manitoba and Ontario, as well as smaller parts of Québec, Minnesota, Wisconsin, and Michigan, including parts of the Mississippi and Atlantic Flyways. Virginia rails were from several discrete areas, including parts of Colorado, New Mexico, the central valley of California, and southern Saskatchewan and Manitoba in the Pacific and Central Flyways. Our study demonstrates extensive data from organized citizen science monitoring programs are especially useful for improving isotopic assignments of migratory connectivity in birds, which can ultimately lead to better informed management decisions and conservation actions.

The Great Basin Derecho of 31 May 1994

AbstractA significant, convectively induced windstorm known as a derecho occurred over parts of Utah, Wyoming, Idaho, and Colorado on 31 May 1994. The event was unusual in that it occurred not only in an environment of relatively limited moisture, but also one with a thermodynamic profile favorable for dry microbursts in the presence of moderate midtropospheric flow. The development and evolution of the severe wind-producing convective system is described, with emphasis on the synoptic and mesoscale features that may have contributed to its strength and maintenance. A very similar derecho that affected much the same region on 1 June 2002 is more briefly introduced. Questions are raised regarding the unique nature of these events and their potential utility in achieving an increased understanding of the mechanics of derecho-producing convective systems in more moisture-rich environments.

Phylogeography of the walnut twig beetle, Pityophthorus juglandis, the vector of thousand cankers disease in North American walnut trees.

Thousand cankers disease (TCD) of walnut trees (Juglans spp.) results from aggressive feeding in the phloem by the walnut twig beetle (WTB), Pityophthorus juglandis, accompanied by inoculation of its galleries with a pathogenic fungus, Geosmithia morbida. In 1960, WTB was only known from four U.S. counties (in Arizona, California, and New Mexico), but the species has now (2014) invaded over 115 counties, representing much of the western USA, and at least six states in the eastern USA. The eastern expansion places TCD in direct proximity to highly valuable (> $500 billion) native timber stands of eastern black walnut, Juglans nigra. Using mitochondrial DNA sequences, from nearly 1100 individuals, we examined variation among 77 samples of WTB populations across its extended range in the USA, revealing high levels of polymorphism and evidence of two divergent lineages. The highest level of genetic diversity for the different lineages was found in the neighboring Madrean Sky Island and Western New Mexico regions, respectively. Despite their proximity, there was little evidence of mixing between these regions, with only a single migrant detected among 179 beetles tested. Indeed, geographic overlap of the two lineages was only common in parts of Colorado and Utah. Just two haplotypes, from the same lineage, predominated over the vast majority of the recently expanded range. Tests for Wolbachia proved negative suggesting it plays no role in "driving" the spread of particular haplotypes, or in maintaining deep levels of intraspecific divergence in WTB. Genotyping of ribosomal RNA corroborated the mitochondrial lineages, but also revealed evidence of hybridization between them. Hybridization was particularly prevalent in the sympatric areas, also apparent in all invaded areas, but absent from the most haplotype-rich area of each mitochondrial lineage. Hypotheses about the specific status of WTB, its recent expansion, and potential evolutionary origins of TCD are discussed.

Obstetrics-Gynecology Resident Attitudes and Perceptions About Chronic Pelvic Pain: A Targeted Needs Assessment to Aid Curriculum Development

Chronic pelvic pain (CPP) accounts for 10% of gynecologic visits and is a common complaint in university-based and community resident clinics. Resident education about CPP has been inconsistent, and review of the limited literature shows predominantly negative perceptions of patients with CPP. Current literature lacks information regarding obstetrics-gynecology residents' attitudes and acquired knowledge regarding CPP. This targeted needs assessment aims to identify regional obstetrics-gynecology resident attitudes and self-perceived knowledge regarding chronic pelvic pain in order to better address potential educational barriers and look toward placing a greater emphasis on this area in resident training. We conducted a focus group of obstetrics-gynecology residents to identify major themes regarding attitudes about CPP. This informed the development of a survey administered to university-based and community-based obstetrics-gynecology residents (N = 57) in the Colorado part of the Western Mountain Region. Cronbach α was calculated to determine reliability for each theme, and descriptive statistics were calculated for each theme. Independent samples t tests assessed differences between training levels and between university and community training sites. Survey response rate was 72% (41 of 57). Residents consistently reported feeling overwhelmed by CPP patients, perceived a lack of time to see these patients, and indicated a desire to learn more in this area, but they varied in chosen learning methods. No significant differences were found between levels of training or training sites. Most obstetrics-gynecology residents surveyed believe they are inadequately prepared to address the needs of women presenting with CPP.

Natural Hazards Experts Learn First Hand from the Colorado Storm and Flood

The mid‐September deluge of parts of central Colorado—which broke many precipitation records and devastated communities—also personally affected a number of natural hazards experts who live there.

Load-induced subsidence of the Ancestral Rocky Mountains recorded by preservation of Permian landscapes

The Ancestral Rocky Mountains (ARM) formed a system of highlands and adjacent basins that developed during Pennsylvanian–earliest Permian deformation of interior western North America. The cause of this intracratonic deformation remains debated, although many have linked it to far-field compression associated with the Carboniferous–Permian Ouachita-Marathon orogeny of southern North America. The ultimate disappearance of the ARM uplifts has long been attributed to erosional beveling presumed to have prevailed into the Triassic–Jurassic. New observations, however, indicate an abrupt and unusual termination for the largest of the ARM uplifts. Field evidence from paleohighlands in the central ARM of Oklahoma and Colorado indicates that Lower Permian strata onlap Pennsylvanian-aged faults and bury as much as 1000 m of relief atop the paleohighlands. In parts of Oklahoma and Colorado, late Cenozoic partial exhumation of these paleohighlands has revealed landscapes dating from Permian time. These relationships suggest cessation of uplift followed by active subsidence of a broad region that encompassed both basins and uplifted crustal blocks and that commenced in Early Permian time, directly following the Pennsylvanian tectonic apogee of the ARM. Independent from these geological observations, geophysical data reveal a regional-scale mafic load underpinning these paleohighlands, emplaced during Cambrian rifting associated with the southern Oklahoma aulacogen. Geophysical modeling of the effects of such a load in the presence of a horizontal stress field, such as that implied by ARM orogenesis, indicates that the amplitude of flexurally supported features is modulated nonlinearly. This leads to buckling and thrust formation with the application of sufficient compressive stress, and subsidence of topography formed by buckling upon relaxation of the high compressional stresses. We therefore infer that the core ARM highlands subsided owing to the presence of a high-density upper crustal root, and that this subsidence began in the Early Permian owing to relaxation of the in-plane compressional stresses that had accompanied the last phase of the Ouachita-Marathon orogeny of southern and southwestern Laurentia. Our results highlight the importance of tectonic inheritance in intraplate orogenesis and epeirogenesis, including its potential role in hastening the reduction of regional elevation, and enabling the ultimate preservation of paleolandscapes.

Regional analysis of the impacts of climate change on cheatgrass invasion shows potential risk and opportunity

AbstractInteractions between climate change and non‐native invasive species may combine to increase invasion risk to native ecosystems. Changing climate creates risk as new terrain becomes climatically suitable for invasion. However, climate change may also create opportunities for ecosystem restoration on invaded lands that become climatically unsuitable for invasive species. Here, I develop a bioclimatic envelope model for cheatgrass (Bromus tectorum), a non‐native invasive grass in the western US, based on its invaded distribution. The bioclimatic envelope model is based on the Mahalanobis distance using the climate variables that best constrain the species' distribution. Of the precipitation and temperature variables measured, the best predictors of cheatgrass are summer, annual, and spring precipitation, followed by winter temperature. I perform a sensitivity analysis on potential cheatgrass distributions using the projections of 10 commonly used atmosphere–ocean general circulation models (AOGCMs) for 2100. The AOGCM projections for precipitation vary considerably, increasing uncertainty in the assessment of invasion risk. Decreased precipitation, particularly in the summer, causes an expansion of suitable land area by up to 45%, elevating invasion risk in parts of Montana, Wyoming, Utah, and Colorado. Conversely, increased precipitation reduces habitat by as much as 70%, decreasing invasion risk. The strong influence of precipitation conditions on this species' distribution suggests that relying on temperature change alone to project future change in plant distributions may be inadequate. A sensitivity analysis provides a framework for identifying key climate variables that may limit invasion, and for assessing invasion risk and restoration opportunities with climate change.

Predictive Spatial Models for Risk of West Nile Virus Exposure in Eastern and Western Colorado

In the absence of a vaccine for use in humans against West Nile virus (WNV), mosquito control and personal protection against mosquito bites are the only measures available to prevent disease. Improved spatial targeting is desirable for costly mosquito and WNV surveillance and control schemes. We used a multivariate regression modeling approach to develop spatial models predicting high risk of exposure to WNV in western and eastern Colorado based on associations between Geographic Information System-derived environmental data and zip code of residence for 3,659 human WNV disease cases from 2002 to 2006. Models were robust, with user accuracies for correct classification of high risk areas of 67-80%. The importance of selecting a suitable model development area in an ecologically and climatically diverse environment was shown by models based on data from the eastern plains landscape performing poorly in the mountainous western part of Colorado and vice versa.

Combining Mosquito Vector and Human Disease Data for Improved Assessment of Spatial West Nile Virus Disease Risk

Assessments of spatial risk of exposure to vector-borne pathogens that combine vector and human disease data are needed for areas encompassing large tracts of public land with low population bases. We addressed this need for West Nile virus (WNV) disease in the northern Colorado Front Range by developing not only a spatial model for entomological risk of exposure to Culex tarsalis WNV vectors and an epidemiological risk map for WNV disease but also a novel risk-classification index combining data for these independently derived measures of entomological and epidemiological risk. Risk of vector exposure was high in the densely populated eastern plains portion of the Front Range but low in cooler montane areas to the west that are sparsely populated but used heavily for recreation in the summer. The entomological risk model performed well when applied to the western, mountainous part of Colorado and validated against epidemiologic data.