100th Meridian Research Articles

All Dried Out: How Responses to Drought Make Droughts Worse

Water usage is governed through a variety of mechanisms, including government administration and market tools. In 2006-2008 Barcelona’s region, a water scarce area, suffered a drought comparable to the one faced today by the US West. This article surveys a variety of techniques which were or could have been used to address these scarcity challenges. Spanish water regulations established water markets in 1999 but neither the design, nor its implementation were optimal. In addition to the design and implementation flaws, the response to the 2006-2008 drought crisis shows how emergency measures highjack water markets as a viable solution to water scarcity. Emergency responses bail out urban voters while no structural solutions to make water use in the agricultural sector more efficient are adopted. Neither the urban suppliers nor the agricultural sector has, thus, incentives to participate in a water market and droughts are to be managed using ad hoc solutions. Lessons for the US West can be drawn because that crisis’ responses are no different than the ones that could be undertaken by states west of the 100th meridian to tackle the current drought.

Streetscape Environmentalism: Floods, Social Justice, and Political Power in San Antonio, 1921–1974

Streetscape Environmentalism: Floods, Social Justice, and Political Power in San Antonio, 1921–1974 Char Miller (bio) Click for larger view View full resolution Map of prominent water features of San Antonio’s west side. Map by Charles D. Grear. [End Page 158] You can locate Zarzamora Creek on the map: type in its coordinates on Google Earth—N 29°31, W 98°34—and you will have pinpointed its cartographical location. But that digital representation will tell you little about its environmental significance or its cultural meaning to the city of San Antonio. Often bone-dry, the Zarzamora is an eight-mile dusty channel that falls away from the Hill Country to the northwest of the urban core. The creek first twists and turns in a south-westerly direction, breaks south and east before flowing into a retention pond known as Elmendorf Lake, merging there with Apache Creek. Their combined stream flow then presses into San Pedro Creek a mile or so above its confluence with the San Antonio River. The Zarzamora is thus a small part of the San Antonio’s 4,180 square-mile drainage system. Perhaps the Zarzamora’s frequent dryness and small size are why the Spanish, who gave the creek its name, neglected to demarcate its presence in their eighteenth-century maps of this sprawling watershed, which made arable the river valley where they sited five religious missions, built a civilian community and a presidio, and irrigated innumerable farms and [End Page 159] ranches. For these colonists, like most modern-day San Antonians, Zarzamora Creek left an almost-invisible mark on the South Texas landscape. But the Zarzamora has a habit of becoming quite noticeable when it rains. Then, what appears unimportant and practically indecipherable becomes overwhelming in significance and force. To account for this startling transformation, start with the confluence of meteorology and topography. San Antonio lies just east of the 100th meridian, long identified as the break point between the humid East and arid West. But this meteorological boundary is not as fixed as the meridian appears on a map, and depending on whether the Pacific Ocean is in an El Niño or La Niña cycle, San Antonio oscillates between deluge and drought. The amount of rain that can fall is startling: the prevailing southeasterly breezes pull supersaturated air up from the Gulf of Mexico that rises as it reaches San Antonio and the Hill Country. Should this uplift collide with a wall of high-pressure air or a cold front pushing down from the north, the resultant storms can produce lightning and earthshaking thunder, and can quickly drench and race across parched ground. In late June and early July 2002, for instance, upwards of thirty-five inches fell in seven days, and the two major rivers that cut through the city, the San Antonio and the Medina, registered record heights; tragically, twelve people lost their lives. On October 17–18, 1998, the same scenario had occurred after a cold front slammed into the region’s high humidity, which then was supercharged by “a plume of moist mid- and high-level air . . . streaming across the area from Hurricane Madeline off the west coast of Mexico.” More than twenty inches of rain fell in twenty-four hours, killing eleven.1 The problem was not solely how much precipitation slanted down as where and how it landed. The Hill Country, and the larger Edwards Plateau of which it is a part, serve as an elevated catchment basin; as rainwater hits and cascades down its slopes, it is funneled into channels that over the millennia have been carved into the limestone terrain. From Austin to San Antonio, a series of rivulets, creeks, and streams carry these turbulent floodwaters to the flatlands, where they power into the Little Colorado or San Marcos, Guadalupe or San Antonio Rivers, which carry the churning flow south and east into the Gulf of Mexico. This complex combination of weather patterns, geological structures, and riparian systems, along with the killer surges they regularly produce, has led the National Weather Service to dub south-central Texas “Flash-Flood Alley.”2 Zarzamora Creek has contributed its share to that...

Estimating the spatial distribution of wintering little brown bat populations in the eastern United States.

Depicting the spatial distribution of wildlife species is an important first step in developing management and conservation programs for particular species. Accurate representation of a species distribution is important for predicting the effects of climate change, land-use change, management activities, disease, and other landscape-level processes on wildlife populations. We developed models to estimate the spatial distribution of little brown bat (Myotis lucifugus) wintering populations in the United States east of the 100th meridian, based on known hibernacula locations. From this data, we developed several scenarios of wintering population counts per county that incorporated uncertainty in the spatial distribution of the hibernacula as well as uncertainty in the size of the current little brown bat population. We assessed the variability in our results resulting from effects of uncertainty. Despite considerable uncertainty in the known locations of overwintering little brown bats in the eastern United States, we believe that models accurately depicting the effects of the uncertainty are useful for making management decisions as these models are a coherent organization of the best available information.

An integrated approach to grazingland ecological assessments and management interpretations

In the United States, grazinglands have been separated into categories such as rangelands and pasturelands and have traditionally been assessed using different methods and indicators. The term grazingland refers to areas producing forage from native or introduced plants and harvested directly by animals without reference to land tenure or other land uses (Allen et al. 2011). The largest area of grazingland in the United States occurs west of the 100th meridian, in water-limited rangelands (Briske 2011). The eastern portion of the country, where water is not a limiting factor, contains substantial areas of improved pastures (Sanderson et al. 2012). Together, these grazinglands represent a substantial proportion, nearly 22% (Jin et al. 2013), of agricultural lands in the United States (figure 1) and contribute many ecosystem goods and services that help support human well-being (Nelson et al. 2012). When taking into account the dichotomy in grazingland terminology, it is important to note that for some parts of the United States, and many parts of the world, the difference between pasturelands and grazinglands is less clear and land considered a pasture to some might be considered an intensively managed rangeland to others. Here we follow the Allen et al. (2011) definitions for…

Geographic coincidence of richness, mass, conservation value, and response to climate of U.S. land birds.

Distributional patterns across the United States of five avian community breeding-season characteristics--community biomass, richness, constituent species' vulnerability to extirpation, percentage of constituent species' global abundance present in the community (conservation index, CI), and the community's position along the ecological gradient underlying species composition (principal curve ordination score, PC--were described, their covariation was analyzed, and projected effects of climate change on the characteristics and their covariation were modeled. Higher values of biomass, richness, and CI were generally preferred from a conservation perspective. However, higher values of these characteristics often did not coincide geographically; thus regions of the United States would differ in their value for conservation depending on which characteristic was chosen for setting conservation priorities. For instance, correlation patterns between characteristics differed among Landscape Conservation Cooperatives. Among the five characteristics, community richness and the ecological gradient underlying community composition (PC) had the highest correlations with longitude, with richness declining from east to west across the contiguous United States. The ecological gradient underlying composition exhibited a demarcation near the 100th meridian, separating the contiguous United States grossly into two similar-sized avian ecological provinces. The combined score (CS), a measure of species' threat of decline or extirpation, exhibited the strongest latitudinal pattern, declining from south to north. Over -75% of the lower United States, projected changes in June temperature and precipitation to year 2080 were associated with decreased averaged values of richness, biomass, and CI, implying decreased conservation value for birds. The two ecological provinces demarcated near the 100th meridian diverged from each other, with projected changes in June temperatures and precipitation from the year 2000 to 2080 suggesting increased ecological dissimilarity between the eastern and western halves of the lower United States with changing climate. Anticipated climate-related changes in the five characteristics by 2080 were more weakly correlated with latitude or longitude then the responses themselves, indicating less distinct geographic patterns of characteristic change than in the characteristics themselves. Climate changes projected for 2080 included geographic shifts in avian biomass, CS, and PC values, a moderate overall decline in CI, and general decline in species richness per site.

Testing Hybridization Hypotheses with Morphometry: the Case of Eastern American Arctic Species of <I>Potentilla</I> sect. <I>Niveae</I> (Rosaceae)

Abstract Asexual reproduction, polyploidy and hybridization are well-known sources of taxonomic complexity in angiosperms. All these processes are believed to occur in Potentilla sect. Niveae (Rosaceae). Although it has been assumed that hybridization is common in section Niveae, this hypothesis has not been tested and recent studies suggest that phenotypic plasticity may sometimes better explain morphological intermediates in nature. To clarify the role of hybridization in the evolution of section Niveae, we tested two hybridization hypotheses for its eastern American Arctic species. The first is a potential hybrid between Potentilla nivea and Potentilla arenosa, and the second between Potentilla arenosa and Potentilla vahliana sensu lato. Twenty-four quantitative and 12 qualitative morphological characters were scored on specimens sampled from a representative range of the parental species and putative hybrids in the American Arctic east of the 100th meridian. Multivariate analyses showed that these two...

Determinants of homestead claims and the expansion of Western settlement

This article examines the impact economic variables had on the rate of settlement, measured by original homestead claims, in the Western United States. Our results from the estimated panel regressions indicate that the underlying rationale for the Homestead Act, namely that economic factors were important for settlement, was justified. The two most important economic variables, output prices, measured by real wheat prices, and the cost of capital, measured by real interest rates, were statistically significant in explaining the change in the original homestead claims. Furthermore, contrary to previous studies, railroad mileage was not found to be significant. This study also reveals that the location of a homestead relative to the 100th meridian, the traditional boundary of humid and sub-humid areas, had little effect on the response of homesteaders to economic variables.

Nationwide Assessment of Nonpoint Source Threats to Water Quality

Water quality is a continuing national concern, in part because the containment of pollution from nonpoint (diffuse) sources remains a challenge. We examine the spatial distribution of nonpoint-source threats to water quality. On the basis of comprehensive data sets for a series of watershed stressors, the relative risk of water-quality impairment was estimated for the over 15,000 fifth-level watersheds in the contiguous United States. A broad division emerged at about the 100th meridian, with eastern areas typically under higher stress than western areas, reflecting the generally higher housing, road, and agriculture densities and higher levels of atmospheric deposition in the eastern division. Recent trends in some stressors are encouraging, but the prospect of further substantial population growth indicates continued pressure on water quality, suggesting that renewed focus on controlling nonpoint-source pollution will be needed if the goals of the Clean Water Act are to be attained.

The 100th Meridian Initiative at the Lake Mead National Recreation Area, NV, USA: Differences between boater behaviors before and after a quagga mussel, Driessena rostiformis bugensis, invasion

The 100 th Meridian Initiative was developed to help prevent the spread of aquatic nuisance species (ANS) through boater education and research on boater movement patterns and behaviors. Surveys employing these elements were conducted at Lake Mead National Recreation Area (LMNRA) in 2002-2003 before the discovery of the quagga mussel (Dreissena rostiformis bugensis Andrusov 1897) and in 2007-2008 after an established population of quagga mussels was found in the Lake. Boaters were asked questions in a personal interview or a mail-in survey regarding what body of water they had previously launched their watercraft in, where they were planning to launch next, if they cleaned their watercraft between each launch, and if they were aware of quagga mussels or other ANS. Results from the personal interviews and mail-in surveys indicated a significant increase in mussel awareness between the pre- and post- mussel invasion groups. Cleaning habits between the study periods for both interviews and mail-in surveys did not differ significantly. Boat trailer states of registration were also documented in both study periods in the parking lots of LMNRA. In 2002-2003, 0.6% of the trailers documented were from states with known zebra or quagga mussel populations, whereas in 2007-2008, 98.2% of states documented had known zebra or quagga mussel populations. Increased boater awareness will help prevent the spread of aquatic invasive species and the 100 th Meridian Initiative is a helpful way to educate boaters and collect relevant data on future mussel invasions. The preservation of natural waters is vital for the conservation of native species and the prevention of zebra and quagga mussel invasions will assist in this preservation. Further efforts should be directed toward educating boaters on effective cleaning methods.

The 100th Meridian, Ecological Boundaries, and the Problem of Reification

Fuzzy and investigative ecological boundaries are reconstituted as absolute and tangible when used to inform natural resource management policies. The process of treating symbolic representations of ecological discontinuities as if they were authentic reflections of reality represents a process of reification and may lead to inappropriate policy provisions with adverse local ecological and social consequences. This essay describes how the United States Department of Agriculture's Conservation Reserve Program takes the 100th meridian—a simplified representation of the ambiguous gradient between the non-arid East from the arid West—and hardens it into a concrete boundary where farmers follow different rules depending on what side of the boundary they reside.

Field and climate‐based model for predicting the density of host‐seeking nymphal Ixodes scapularis, an important vector of tick‐borne disease agents in the eastern United States

ABSTRACTAim Ixodes scapularis is the most important vector of human tick‐borne pathogens in the United States, which include the agents of Lyme disease, human babesiosis and human anaplasmosis, among others. The density of host‐seeking I. scapularis nymphs is an important component of human risk for acquiring Borrelia burgdorferi, the aetiological agent of Lyme disease. In this study we used climate and field sampling data to generate a predictive map of the density of host‐seeking I. scapularis nymphs that can be used by the public, physicians and public health agencies to assist with the diagnosis and reporting of disease, and to better target disease prevention and control efforts.Location Eastern United States of America.Methods We sampled host‐seeking I. scapularis nymphs in 304 locations uniformly distributed east of the 100th meridian between 2004 and 2006. Between May and September, 1000 m2 were drag sampled three to six times per site. We developed a zero‐inflated negative binomial model to predict the density of host‐seeking I. scapularis nymphs based on altitude, interpolated weather station and remotely sensed data.Results Variables that had the strongest relationship with nymphal density were altitude, monthly mean vapour pressure deficit and spatial autocorrelation. Forest fragmentation and soil texture were not predictive. The best‐fit model identified two main foci – the north‐east and upper Midwest – and predicted the presence and absence of I. scapularis nymphs with 82% accuracy, with 89% sensitivity and 82% specificity. Areas of concordance and discordance with previous studies were discussed. Areas with high predicted but low observed densities of host‐seeking nymphs were identified as potential expansion fronts.Main conclusions This model is unique in its extensive and unbiased field sampling effort, allowing for an accurate delineation of the density of host‐seeking I. scapularis nymphs, an important component of human risk of infection for B. burgdorferi and other I. scapularis‐borne pathogens.

Revisiting the life and scientific reputation of Ferdinand Vandeveer Hayden

Profiles of Rocky Mountain Geologists – a continuing series Hayden annoyed almost everyone he knew at one time or another; he thrived on spiteful controversy. —Mike Foster, 1994, p. 351 At the period of his greatest success Hayden was always the same unpretentious and enthusiastic seeker for knowledge. —Edward Drinker Cope, 1888 Had Congress created the United States Geological Survey (USGS) in 1877, rather than a year later, Ferdinand Vandeveer Hayden (Fig. 1) would likely have become the first director. He was the favorite. If this had happened, Hayden's reputation and prominence today would be completely different. Figure 1. F. V. Hayden, about the time of his directorship of the U.S. Geological Survey of the Territories, 1870. Courtesy of U.S. Geological Survey Photographic Library. By many accounts, Hayden was the most qualified of the principal candidates for the USGS directorship, a group that included Clarence King, John Wesley Powell, and George Montague Wheeler. Congressional support for Hayden's U.S. Geological and Geographical Survey of the Territories, and for Hayden as its leader, was greater than that for the Geological Exploration of the Fortieth Parallel (the King Survey), the Geographical Survey West of the 100th Meridian (under Wheeler, of the U.S. Army's Corps of Engineers), or the Geographical and Geological Survey of the Rocky Mountain Region (the Powell Survey). At the time, from his published studies and newspaper stories, Hayden was well known and respected both in the U.S. and in Europe. He managed many people and projects, and he raised the money to keep people in the field and in offices writing their reports, the publication for which he also arranged. During the 25 years or so of his exploration in the American West—up to about 1878—Hayden's publications exceeded in number and were frequently equal to or superior in quality to those …

First record of Orconectes rusticus (Girard, 1852) (Decapoda, Cambaridae) west of the Great Continental Divide in North America

Orconectes rusticus (Girard, 1852), known as the rusty crayfish, have spread over the last 50 years from their historical range in the Ohio River drainage, United States, to waters throughout much of 18 additional eastern and central states, provinces of Ontario and Qu?bec in Canada, and the Laurentian Great Lakes (Hobbs et al., 1989; Olden et al., 2006; Taylor et al., 2007). O. rusticus are omni vores and aggressive, resulting in numerous ecological and evolutionary impacts manifested across entire food webs. The invasion of this species has been associ ated with negative effects on aquatic plants, invertebrates, snails, and fishes (e.g., Olsen et al., 1991; Lodge et al., 1994; McCarthy et al., 2006), in addition to dis placing and hybridizing with native crayfish (e.g., Perry et al., 2001). The most westward reported occurrences of O. rusticus are the North Platte River near Dou glas, Wyoming (where the population is believed to have been successfully eradi cated) and Conchas Lake in north-east New Mexico (Bouchard, 1977). Preventing the westward spread of aquatic nuisance species from eastern North America is a primary goal of the 100th Meridian Initiative (http://www.100thmeridian.org). Here we are the first to document the presence of O. rusticus west of the Continental Divide in North America, separating watersheds that drain into the Pacific Ocean from those river systems that drain into the Atlantic Ocean. On 19 July 2005, a field survey conducted by the Xerces Society for Invertebrate Conservation and the Confederated Tribes of Warm Springs Reservation of Oregon revealed the occurrence of a non-native Orconectes sp. crayfish in the upper

Israel Cook Russell--explorer, geomorphologist, geographer, educator

Profiles of Rocky Mountain Geologists – a continuing series Israel Cook Russell (1852–1906) is best known for his geomorphic studies of the Great Basin region and Cascade Arc during the latter half of the 19th Century. As a long–time U. S. Geological Survey (USGS) geologist and close associate of John Wesley Powell (1834–1902) and Grove Karl Gilbert (1843–1918), Russell was one of the foremost contributors to the science of Quaternary geology in the American West. Rabbitt (1980, p. 163) notes that Russell “endured rather than enjoyed the comforts of civilization” and was enthusiastic about fieldwork, especially in the American West. My purpose is to provide a review of his professional career with a focus on his contributions to geology. Russell (Fig. 1) was born in upstate New York in 1852. He graduated with degrees in Bachelor of Science and Civil Engineering from the University of the City of New York in 1872, and Master of Science in 1875 (Lombard and D'Ooge, 1906). He also undertook graduate studies at the Columbia University School of Mines. He visited New Zealand in 1874 as a member of the U. S. Transit of Venus Expedition , and returned to Columbia University as an assistant professor of geology in 1875. As no provision was made for work in natural history on this expedition, Russell obtained an appointment as ‘photographer' (Gilbert, 1906) and acquired the necessary skills in a hurried course under physicist Ernest Rutherford (1871–1937). These skills were put to extensive use for the remainder of his life and account for the majority of photographs in his publications. Figure 1. Portrait of Israel Cook Russell (USGS photo archives). In 1878 Russell was hired as an assistant geologist on George Montague Wheeler's (1842–1905) U. S. Geographical Survey West of the 100th Meridian working in Colorado and …

The Assignment of Property Rights on the Western Frontier: Lessons for Contemporary Environmental and Resource Policy

I examine the assignment of private property rights during the nineteenth and early twentieth centuries to five natural resources on federal lands in the Far West. Assigning property rights required adaptation from established, eastern practices. The resulting property rights and their long-term welfare effects inform over-fishing, excessive air pollution, and other natural resource and environmental problems. Allocations based on local conditions, prior use, and unconstrained by outside government mandates were most effective in both addressing the immediate threat of open-access and providing a longer-term basis for production, investment, and trade. Initial faulty property allocations and path dependencies are discussed.This is what stretched westward from the 100th meridian, this complex, misunderstood two fifths of the continental United States where men had come before law arrived and where before there were adequate maps there were warring interests, white against Indian, cattleman against sheepman and both against nester, open range notions against the use of the newly invented barbed wire, Gentile against Mormon, land rights against water rights, appropriation rights to water against riparian rights to water, legitimate small settler against speculator and land-grabber. The public domain as Powell knew it was all of these, its only unity the unity of little rain.Wallace StegnerStegner, Beyond the 100th Meridian, p. 218.

Nostalgia, goodness and ethical paradox

We research in Saskatchewan, in the Dry Land elucidated by Trevor Herriot (2001). We start with his notion that `those of us who live west of the 100th meridian have been using nostalgia to construct a romance fiction out of our history… there is no denying the power of nostalgia' (p. 2). Our landscape shapes us as we in turn shape it, we feel obligated to be sensitive to the glamours of nostalgia. Our prairie landscape evokes questions: What does it mean to research ethically in this space? What are the possible foci of our nostalgia? And, how do we navigate the ethical paradoxes in which we find ourselves? This article argues that research pushed by cultural norms creates double-binds around notions of `good' and `R/right'. By juxtaposing nostalgia and goodness, we examine ethical paradoxes facing us as academics in renegotiating these double-binds.

Forecasting the Expansion of Zebra Mussels in the United States

Because zebra mussels spread rapidly throughout the eastern United States in the late 1980s and early 1990s, their spread to the western United States has been expected. Overland dispersal into inland lakes and reservoirs, however, has occurred at a much slower rate than earlier spread via connected, navigable waterways. We forecasted the potential western spread of zebra mussels by predicting the overland movement of recreational boaters with a production-constrained gravity model. We also predicted the potential abundance of zebra mussels in two western reservoirs by comparing their water chemistry characteristics with those of water bodies with known abundances of zebra mussels. Most boats coming from waters infested with zebra mussels were taken to areas that already had zebra mussels, but a small proportion of such boats did travel west of the 100th meridian. If zebra mussels do establish in western U.S. water bodies, we predict that population densities could achieve similar levels to those in the Midwestern United States, where zebra mussels have caused considerable economic and ecological impacts. Our analyses suggest that the dispersal of zebra mussels to the western United States is an event of low probability but potentially high impact on native biodiversity and human infrastructure. Combining these results with economic analyses could help determine appropriate investment levels in prevention and control strategies.

Spatiotemporal Patterns of Host-Seeking Ixodes scapularis Nymphs (Acari: Ixodidae) in the United States

Abstract The risk of Lyme disease for humans in the eastern United States is dependent on the density of host-seeking Ixodes scapularis Say nymphal stage ticks infected with Borrelia burgdorferi. Although many local and regional studies have estimated Lyme disease risk using these parameters, this is the first large-scale study using a standardized methodology. Density of host-seeking I. scapularis nymphs was measured by drag sampling of closed canopy deciduous forest habitats in 95 locations spaced among 2° quadrants covering the entire United States east of the 100th meridian. Sampling was done in five standardized transects at each site and repeated three to six times during the summer of 2004. The total number of adults and nymphs of the seven tick species collected was 17,972, with 1,405 nymphal I. scapularis collected in 31 of the 95 sites. Peak global spatial autocorrelation values were found at the smallest lag distance (300 km) and decreased significantly after 1,000 km. Local autocorrelation statistics identified two significant high-density clusters around endemic areas in the northeast and upper Midwest and a low-density cluster in sites south of the 39th parallel, where only 21 nymphs were collected. Peak nymphal host-seeking density occurred earlier in the southern than in the most northern sites. Spatiotemporal density patterns will be combined with Borrelia prevalence data as part of a 4-yr survey to generate a nationwide spatial risk model for I. scapularis-borne Borrelia, which will improve targeting of disease prevention efforts.

Spatiotemporal Patterns of Host-Seeking <I>Ixodes scapularis</I> Nymphs (Acari: Ixodidae) in the United States

The risk of Lyme disease for humans in the eastern United States is dependent on the density of host-seeking Ixodes scapularis Say nymphal stage ticks infected with Borrelia burgdorferi. Although many local and regional studies have estimated Lyme disease risk using these parameters, this is the first large-scale study using a standardized methodology. Density of host-seeking I. scapularis nymphs was measured by drag sampling of closed canopy deciduous forest habitats in 95 locations spaced among 2 degrees quadrants covering the entire United States east of the 100th meridian. Sampling was done in five standardized transects at each site and repeated three to six times during the summer of 2004. The total number of adults and nymphs of the seven tick species collected was 17,972, with 1,405 nymphal I. scapularis collected in 31 of the 95 sites. Peak global spatial autocorrelation values were found at the smallest lag distance (300 km) and decreased significantly after 1,000 km. Local auto-correlation statistics identified two significant high-density clusters around endemic areas in the northeast and upper Midwest and a low-density cluster in sites south of the 39th parallel, where only 21 nymphs were collected. Peak nymphal host-seeking density occurred earlier in the southern than in the most northern sites. Spatiotemporal density patterns will be combined with Borrelia prevalence data as part of a 4-yr survey to generate a nationwide spatial risk model for I. scapularis-borne Borrelia, which will improve targeting of disease prevention efforts.

The Impact of Global Warming on U.S. Agriculture: An Econometric Analysis of Optimal Growing Conditions

We link farmland values to climatic, soil, and socioeconomic variables for counties east of the 100th meridian, the historic boundary of agriculture not primarily dependent on irrigation. Degree days, a non-linear transformation of the climatic variables suggested by agronomic experiments as more relevant to crop yield gives an improved fit and increased robustness. Estimated coefficients are consistent with the experimental results. The model is employed to estimate the potential impacts on farmland values for a range of recent warming scenarios. The predictions are very robust and more than 75% of the counties in our sample show a statistically significant effect, ranging from moderate gains to large losses, with losses in the aggregate that can become quite large under scenarios involving sustained heavy use of fossil fuels.