Measuring and mitigating agricultural greenhouse gas production in the US Great Plains, 1870-2000.

The Great Plains region of the United States is an agricultural production center for the global market and, as such, an important source of greenhouse gas (GHG) emissions. This article uses historical agricultural census data and ecosystem models to estimate the magnitude of annual GHG fluxes from all agricultural sources (e.g., cropping, livestock raising, irrigation, fertilizer production, tractor use) in the Great Plains from 1870 to 2000. Here, we show that carbon (C) released during the plow-out of native grasslands was the largest source of GHG emissions before 1930, whereas livestock production, direct energy use, and soil nitrous oxide emissions are currently the largest sources. Climatic factors mediate these emissions, with cool and wet weather promoting C sequestration and hot and dry weather increasing GHG release. This analysis demonstrates the long-term ecosystem consequences of both historical and current agricultural activities, but also indicates that adoption of available alternative management practices could substantially mitigate agricultural GHG fluxes, ranging from a 34% reduction with a 25% adoption rate to as much as complete elimination with possible net sequestration of C when a greater proportion of farmers adopt new agricultural practices.

Impact of historical land-use changes on greenhouse gas exchange in the U.S. Great Plains, 1883-2003.

European settlement of North America has involved monumental environmental change. From the late 19th century to the present, agricultural practices in the Great Plains of the United States have dramatically reduced soil organic carbon (C) levels and increased greenhouse gas (GHG) fluxes in this region. This paper details the development of an innovative method to assess these processes. Detailed land-use data sets that specify complete agricultural histories for 21 representative Great Plains counties reflect historical changes in agricultural practices and drive the biogeochemical model, DAYCENT, to simulate 120 years of cropping and related ecosystem consequences. Model outputs include yields of all major crops, soil and system C levels, soil trace-gas fluxes (N2O emissions and CH4 consumption), and soil nitrogen mineralization rates. Comparisons between simulated and observed yields allowed us to adjust and refine model inputs, and then to verify and validate the results. These verification and validation exercises produced measures of model fit that indicated the appropriateness of this approach for estimating historical changes in crop yield. Initial cultivation of native grass and continued farming produced a significant loss of soil C over decades, and declining soil fertility led to reduced crop yields. This process was accompanied by a large GHG release, which subsided as soil fertility decreased. Later, irrigation, nitrogen-fertilizer application, and reduced cultivation intensity restored soil fertility and increased crop yields, but led to increased N2O emissions that reversed the decline in net GHG release. By drawing on both historical evidence of land-use change and scientific models that estimate the environmental consequences of those changes, this paper offers an improved way to understand the short- and long-term ecosystem effects of 120 years of cropping in the Great Plains.

The limits of autonomy: the Belmont Report and the history of childhood.

This article examines the National Commission for the Protection of Human Subjects of Biomedical and Behavioral Research recommendations on children as research subjects in the context of the history of American childhood. The Commission's deliberations took place during the post-World War II period of rapid changes in understandings of childhood and adolescence, brought on in part by school children's highly visible roles as risk-taking protagonists in the polio vaccine trials and the civil rights movement; by the children's rights movement and court decisions granting children and adolescents greater autonomy in divorce cases and in delinquency and mental health hearings, among other rights; and finally by a renewed movement for child protection led by parents of disabled children and by polio survivors themselves. The National Commission's final recommendations emphasized the need for parents to approve, for children above age seven to assent to research, and for children in special care (either medical, psychiatric, or because they were orphans or had committed juvenile crimes) generally to be subjects of research only if there was some direct connection between the reasons for their special care and the objectives of the research. Ultimately, in these recommendations, the National Commission charted a middle ground between the children's rights movement, which advocated enhanced self-determination for children, and the disability rights movement, which urged greater protection for children.

Household and farm transitions in environmental context.

Recent debate in the literature on population, environment, and land use questions the applicability of theory that patterns of farm extensification and intensification correspond to the life course of farmers and to the life cycle of farm families. This paper extends the debate to the agricultural development of the United States Great Plains region, using unique data from 1875 to 1930 that link families to farms over time in 25 environmentally diverse Kansas townships. Results of multilevel statistical modeling indicate that farmer's age, household size, and household structure are simultaneously related to both the extent of farm operations and the intensity of land use, taking into account local environmental conditions and time trends as Kansas was settled and developed. These findings validate farm- and life cycle theories and offer support for intergenerational motivations for farm development that include both daughters and sons. Environmental variation in aridity was a key driver of farm structure.

Katrina in Historical Context: Environment and Migration in the U.S.

The massive publicity surrounding the exodus of residents from New Orleans spurred by Hurricane Katrina has encouraged interest in the ways that past migration in the U.S. has been shaped by environmental factors. So has Timothy Egan's exciting book, The Worst Hard Time: The Untold Story of those who survived the Great American Dust Bowl. This paper places those dramatic stories into a much less exciting context, demonstrating that the kinds of environmental factors exemplified by Katrina and the Dust Bowl are dwarfed in importance and frequency by the other ways that environment has both impeded and assisted the forces of migration. We accomplish this goal by enumerating four types of environmental influence on migration in the U.S.: 1) environmental calamities, including floods, hurricanes, earthquakes, and tornadoes, 2) environmental hardships and their obverse, short-term environmental benefits, including both drought and short periods of favorable weather, 3) environmental amenities, including warmth, sun, and proximity to water or mountains, and 4) environmental barriers and their management, including heat, air conditioning, flood control, drainage, and irrigation. In U.S. history, all four of these have driven migration flows in one direction or another. Placing Katrina into this historical context is an important task, both because the environmental calamities of which Katrina is an example are relatively rare and have not had a wide impact, and because focusing on them defers interest from the other kinds of environmental impacts, whose effect on migration may have been stronger and more persistent, though less dramatic.

Beyond Social Science History: Population and Environment in the US Great Plains.

This essay advocates for broadening social science history to include an even larger horizon, in order to reach a new level of understanding of human society in the past. It builds on and shares insights from twenty years of research that integrates environmental knowledge and environmental science into a history of social change, while simultaneously trying to understand in detail how people changed the environment. The focus of the research is the demographic, social, agricultural, and environmental history of the U.S. Great Plains, from the 1870s to the end of the twentieth century. Beyond supporting the argument for a broader interdisciplinary vision of history, the essay shows how the Great Plains environment was changed by human action, and the ways that the environment shaped human behavior in turn. The history of the Plains shows that the impact of human action on the land was dramatic and unmistakable. People radically changed land cover, but their actions were only one factor in causing events like the Dust Bowl, and only one part of the measurable increase in greenhouse gases. At the same time, the environment also constrained and shaped human behavior, even though it had less to do with family organization than broad trends in social change in the late nineteenth and early twentieth centuries. The environment's most dramatic contribution was to spur out-migration in the 1930s when drought caused wide-spread agricultural failure, further confirmation of the importance of going beyond purely social factors to understand how people lived in the past.

"Big data" in economic history.

Big data is an exciting prospect for the field of economic history, which has long depended on the acquisition, keying, and cleaning of scarce numerical information about the past. This article examines two areas in which economic historians are already using big data - population and environment - discussing ways in which increased frequency of observation, denser samples, and smaller geographic units allow us to analyze the past with greater precision and often to track individuals, places, and phenomena across time. We also explore promising new sources of big data: organically created economic data, high resolution images, and textual corpora.

Immigrants, their children, and theories of assimilation: family structure in the United States, 1880-1970.

This research employs United States census data from 1880 to 1970 to assess the influence of ethnicity and generation on the family structure of Mexican, Irish, Swedish, Italian, Polish, and native white children. Using evidence for three generations, it tests two theories, linear assimilation and segmented assimilation. Assimilation theory makes no special claims for ethnic effects, but segmented assimilation proposes that ethnicity influences the incorporation of immigrant-origin children into American society. We find few consistent ethnic effects on the probability of family type. Our principal finding is that migration itself, common to all groups, has similar consequences for all; these are revealed in generational changes in family structure. The historical periods of open immigration do differ from the contemporary period, which implies that immigration policy affects family structure. The results disconfirm segmented assimilation theory's emphasis on ethnicity in family structure, and confirm aspects of linear assimilation theory. They point to the salience of structural factors resulting from migration experience and policy, rather than ethnicity, in the evolution of family form among immigrant-origin persons.

Migration in the 1930s: Beyond the Dust Bowl.

This paper analyzes in detail the role of environmental and economic shocks in the migration of the 1930s. The 1940 U.S. Census of Population asked every inhabitant where they lived five years earlier, a unique source for understanding migration flows and networks. Earlier research documented migrant origins and destinations, but we will show how short term and annual weather conditions at sending locations in the 1930s explain those flows, and how they operated through agricultural success. Beyond demographic data, we use data about temperature and precipitation, plus data about agricultural production from the agricultural census. The widely known migration literature for the 1930s describes an era of relatively low migration, with much of the migration that did occur outward from the Dust Bowl region and the cotton South. Our work about the complete U.S. will provide a fuller examination of migration in this socially and economically important era.

Land Use and Family Formation in the Settlement of the U.S. Great Plains.

In agricultural settings, environment shapes patterns of settlement and land use. Using the Great Plains of the United States during the period of its initial Euro-American settlement (1880-1940) as an analytical lens, this article explores whether the same environmental factors that determine settlement timing and land use-those that indicate suitability for crop-based agriculture-also shape initial family formation, resulting in fewer and smaller families in areas that are more conducive to livestock raising than to cropping. The connection between family size and agricultural land availability is now well known, but the role of the environment has not previously been explicitly tested. Descriptive analysis offers initial support for a distinctive pattern of family formation in the western Great Plains, where precipitation is too low to support intensive cropping. However, multivariate analysis using county-level data at 10-year intervals offers only partial support to the hypothesis that environmental characteristics produce these differences. Rather, this analysis has found that the region was also subject to the same long-term social and demographic changes sweeping the rest of the country during this period.

Emptying the nest: older men in the United States, 1880-2000.

Between 1880 and 2000, the percentage of married men 60 and older living only with their wives in empty nest households rose from 19 percent to 78 percent. Data drawn from the US census show that more than half of this transformation occurred in the 30-year period from 1940 to 1970, bookended by moderate increases between 1880 and 1940 and very modest increases after 1970. Two literatures have presented demographic, cultural, and economic explanations for the decline in elderly co-residence with their children, but none adequately accounts for a sharp change in the mid-twentieth century. Both aggregate comparisons and multivariate analysis of factors influencing the living arrangements of elderly men suggest that economic advances for all age groups in the critical 30-year period, along with trends in fertility and immigration, best explain the three-stage shift that made the empty nest the dominant household form for older men by the beginning of the twenty-first century.

Confidentiality and spatially explicit data: concerns and challenges.

Recent theoretical, methodological, and technological advances in the spatial sciences create an opportunity for social scientists to address questions about the reciprocal relationship between context (spatial organization, environment, etc.) and individual behavior. This emerging research community has yet to adequately address the new threats to the confidentiality of respondent data in spatially explicit social survey or census data files, however. This paper presents four sometimes conflicting principles for the conduct of ethical and high-quality science using such data: protection of confidentiality, the social-spatial linkage, data sharing, and data preservation. The conflict among these four principles is particularly evident in the display of spatially explicit data through maps combined with the sharing of tabular data files. This paper reviews these two research activities and shows how current practices favor one of the principles over the others and do not satisfactorily resolve the conflict among them. Maps are indispensable for the display of results but also reveal information on the location of respondents and sampling clusters that can then be used in combination with shared data files to identify respondents. The current practice of sharing modified or incomplete data sets or using data enclaves is not ideal for either the advancement of science or the protection of confidentiality. Further basic research and open debate are needed to advance both understanding of and solutions to this dilemma.