Tag Archives: Woodrow Wilson School

Model anticipates ecological impacts of human responses to climate (Conservation Biology)

A Princeton University research team has created a readily transferable method for conservation planners trying to anticipate how agriculture will be affected by such adaptations. The tested their model by studying wheat and maize production in South Africa. (Image source: WWS)

A Princeton University research team has created a readily transferable method for conservation planners trying to anticipate how agriculture will be affected by such adaptations. The tested their model by studying wheat and maize production in South Africa. (Image source: WWS)

By B. Rose Huber, Woodrow Wilson School of Public and International Affairs

Throughout history, humans have responded to climate.

Take, for example, the Mayans, who, throughout the eighth and 10th centuries, were forced to move away from their major ceremonial centers after a series of multi-year droughts, bringing about agricultural expansion in Mesoamerica, and a clearing of forests. Much later, in the late 20th century, frequent droughts caused the people of Burkina Faso in West Africa to migrate from the dry north to the wetter south where they have transformed forests to croplands and cut the nation’s area of natural vegetation in half.

Such land transformations, while necessary to ensure future crop productivity, can themselves have large ecological impacts, but few studies have examined their effects. To that end, a Princeton University research team has created a model to evaluate how a human response to climate change may alter the agricultural utility of land. The study, featured in Conservation Biology, provides a readily transferable method for conservation planners trying to anticipate how agriculture will be affected by such adaptations.

“Humans can transform an ecosystem much more rapidly and completely than it can be altered by shifting temperature and precipitation patterns,” said Lyndon Estes, lead author and associate research scholar in the Woodrow Wilson School of International and Public Affairs. “This model provides an initial approach for understanding how agricultural land-use might shift under climate change, and therefore which currently natural areas might be converted to farming.”

Under the direction of faculty members Michael Oppenheimer and David Wilcove, both from the Wilson School’s Program in Science, Technology and Policy, and with the help of visiting student research collaborator Lydie-Line Paroz from ETH Zurich and colleagues from several other institutions, Estes studied South Africa, an area projected to be vulnerable to climate change where wheat and maize are the dominant crops.

Before determining how climate change could impact the crops, the team first needed to determine which areas have been or might be farmed for maize and wheat. They created a land-use model based on an area’s potential crop output and simulated how much of each crop was grown from 1979 to 1999 – the two decades for which historical weather data was available. They also calculated the ruggedness of each area of land, which is related to the cost of farming it. Taking all factors into account, the model provides an estimate of whether the land is likely to be profitable or unprofitable for farming.

To investigate any climate-change impacts, the team then examined the production of wheat and maize under 36 different climate-response scenarios. Many possible future climates were taken into account as well as how the crops might respond to rising levels of carbon dioxide. Based on their land-use model, the researchers calculated how the climate-induced productivity changes alter a land’s agricultural utility. In their analysis, they included only conservation lands – current nature reserves and those that South African conservation officials plan to acquire – that contained land suitable for growing one of the two crops either currently or in the future. However, Estes said the model could be adapted to assess whether land under other types of uses (besides conservation) are likely to be profitable or unprofitable for future farming.

They found that most conservation lands currently have low agricultural utility because of their rugged terrain, which makes them difficult to farm, and that they are likely to stay that way under future climate-change scenarios. The researchers did pinpoint several areas that could become more valuable for farming in the future, putting them at greater risk of conversion. However, some areas were predicted to decrease value for farming, which could make them easier to protect and conserve.

“While studying the direct response of species to climatic shifts is important, it’s only one piece of a complicated puzzle. A big part of that puzzle relates to how humans will react, and history suggests you don’t need much to trigger a change in the way land is used that has a fairly long-lasting impact. ” said Estes. “We hope that conservation planners can use this approach to start thinking about human climate change adaptation and how it will affect areas needing protection.”

Other researchers involved in the study include: Lydie-Line Paroz, Swiss Federal Institute of Technology; Bethany A. Bradley, University of Massachusetts; Jonathan Green, STEP; David G. Hole, Conservation International; Stephen Holness, Centre for African Conservation Ecology; and Guy Ziv, University of Leeds.

The work was funded by the Princeton Environmental Institute‘s Grand Challenges Program.

Read the abstract.

Estes LD, Paroz LL, Bradley BA, Green JM, Hole DG, Holness S, Ziv G, Oppenheimer MG, Wilcove DS. Using Changes in Agricultural Utility to Quantify Future Climate-Induced Risk to Conservation Conservation Biology (2013). First published online Dec. 26, 2013.

Death of an adult son increases depressive symptoms in mothers, but not fathers (Social Science and Medicine)

Sad mother picture

A study by researchers at Princeton and Georgetown Universities found that Taiwanese mothers – but not fathers – experience depressive symptoms after an adult son’s death, while the death of a daughter had no such effect on either parent.

By B. Rose Huber, Woodrow Wilson School of Public and International Affairs

Mothers – but not fathers – exhibited symptoms of depression and experienced declines in overall health after the death of an adult son, while the death of a daughter had no such effect on either parent, according to one of the first studies to examine the impacts of the death of an adult child on parents aged 65 and older.

In East Asian cultures, an adult son’s role in the family is crucial to the wellbeing and financial stability of his parents, the researchers suggest. Therefore, a traumatic event, like the death of a son, could place quite a strain on elderly parents living in these cultures – particularly women, especially if the deceased son is the eldest or only son.

The researchers, from the Office of Population Research in Princeton University’s Woodrow Wilson School, published their findings in the journal Social Science & Medicine based on data from the Taiwanese Longitudinal Study of Aging, a nationally representative survey designed to assess the health of older people in Taiwan.

“In East Asian cultures like Taiwan, sons hold the primary responsibility for providing financial and instrumental assistance to their elderly parents,” said lead author Chioun Lee, a Princeton postdoctoral research associate. “Older women who have had particularly few educational and occupational opportunities are more likely to rely on their sons for support. Therefore, a traumatic event, like a son’s death, could place quite a strain on a mother’s health.”

Along with study coauthor Noreen Goldman, the Hughes-Rogers Professor of Demography and Public Affairs at WWS, and researchers from Georgetown University, Lee used data collected for the Taiwanese Longitudinal Study of Aging from 1996 to 2007, which included approximately 4,200 participants.

To evaluate parental wellbeing, they used two self-reported measures: one for overall health and another for depressive symptoms. Each respondent’s health was assessed based on the following question: “Regarding your current state of health, do you feel it is excellent, good, average, not so good, or poor?” The items were coded on a one-to-five-point scale with higher scores indicating better health. Past studies have indicated that this measure is a strong predictor of mortality.

Depressive symptoms were measured with an eight-item subset of the Center for Epidemiological Studies Depression Scale, which asks participants to report how often they’ve experienced various situations or feelings in the past week. Possible answers range from “0,” which means rarely or none of the time, to “3,” which is most or all of the time. Higher scores for the eight items indicate more frequent depressive symptoms.

The researchers controlled for parental wellbeing prior to the death of a child and analyzed the data in two stages. First, they tested the extent to which a child’s death affected a parent’s health and then whether that varied by the parent’s sex. Finally, they determined the influence of a deceased child’s sex on parental wellbeing.

They found that women who lost a son scored, on average, 2.4 points higher on levels of depressive symptoms than those who did not lose a child. For men, there were no significant differences. There was no evidence to suggest that either mothers or fathers were significantly affected by depressive symptoms or declines in reports of overall health following the death of a daughter. Lee explains that while finances are a concern, there may be other factors at play.

“I also think that various attributes of deceased children, such as birth order, affective bonds with their parents or cause of death, might influence parental wellbeing,” said Lee, who is a native of Korea and observed son preference and gender inequality throughout her childhood.

According to Goldman, these findings underscore the continued gender inequality in Taiwan.

“Despite large advances in women’s labor market participation and educational attainment in recent years – for example, women in Taiwan are now more likely than men to hold a higher education degree – son preference persists, affecting various aspects of women’s well-being,” Goldman said.

Read the abstract.

Lee, C., et al., Death of a child and parental wellbeing in old age: Evidence from Taiwan, Social Science & Medicine (2013), http://dx.doi.org/10.1016/jsocscimed.2013.08.007

The work was funded by the Demography and Epidemiology Unit of the Division of Behavioral and Social Research at the National Institute on Aging and the Eunice Kennedy Shriver National Institute of Child Health and Human Development.

More or less equal? How men factor into the reproductive equation (Gender & Society)

A new study calls attention to the role of men’s behavior and health in reproductive outcomes, such as fetal health, birth defects and childhood diseases. (Image credit: CDC/Amanda Mills)

A new study calls attention to the role of men’s behavior and health in reproductive outcomes, such as fetal health, birth defects and childhood diseases. (Image credit: CDC/Amanda Mills)

By Bess Connolly Martell, Office of Public Affairs and Communications, Yale University

Researchers know a lot about how women’s bodily health affects their fertility, but less is known about how men’s health affects reproductive outcomes. Yale University researcher Rene Almeling and co-author Miranda Waggoner of Princeton University address this discrepancy in an article published Tuesday, Dec. 3, in the journal Gender & Society.

In the period before conception, family health history and current health behaviors matter for women and men alike, say the researchers, adding that more clinical research needs to be done on how men’s bodily health affects their sperm, and in turn, reproductive health outcomes.

“The lack of attention to men in research on reproduction leaves open many important questions, including how men’s reproductive contributions are understood,” say Almeling, an assistant professor of sociology at Yale, and Waggoner, a postdoctoral researcher in the Office of Population Research in the Woodrow Wilson School of Public and International Affairs at Princeton.

The vast majority of medical and social science research on reproduction focuses on women. It wasn’t until recently that scientists began studying the role that men’s behavior and men’s health play in reproductive outcomes, such as fetal health, birth defects and childhood diseases.

The stereotypical association of women with family and men with work has led to a focus on women’s bodies in reproduction, leaving the question of how men’s health contributes to reproduction unanswered.

“What kinds of advice, if any, do men receive about preparing their bodies for reproduction?” ask the researchers. “Men should be empowered with information about how their age, health history and unhealthy behaviors can affect pregnancy outcomes.”

The sperm bank is one of the few places where men’s reproductive health takes center stage, the researchers note. At sperm banks, men are counseled on healthy eating, avoiding stress and reducing alcohol consumption. Not adhering to this advice can and does lead to lower sperm counts, suggesting that this kind of guidance might be more broadly useful for men trying to conceive children with their partners.

There are also associated policy implications. The Affordable Care Act stipulates that women with private insurance are no longer required to pay for preconception health appointments, but excluding men from such coverage continues to obscure their role in reproduction, say Almeling and Waggoner. “Paying attention to how reproductive equations influence policy can suggest new and different avenues for improving public health,” say the sociologists. They add, “Recent public health initiatives devoted to preconception care offer at least the possibility that men’s reproductive contributions will be considered alongside women’s.”

Read the abstract.

Almeling, Rene and Miranda R. Waggoner. More and Less than Equal: How Men Factor in the Reproductive Equation. Gender & Society December 2013 27: 821-842, first published on April 25, 2013 doi:10.1177/0891243213484510.

Both authors received funding from the National Science Foundation (Almeling grant #0602871 and Waggoner grant #1029087), and Miranda Waggoner also received support from the National Institutes of Health (T32 HD007163).

Princeton researchers use mobile phones to measure happiness (Demography)

By Tara Thean, Science-Writing Intern, Office of the Dean for Research

World map

Locations of study subjects on world map (Source: Demography)

Researchers at Princeton University are developing ways to use mobile phones to explore how one’s environment influences one’s sense of well-being.

In a study involving volunteers who agreed to provide information about their feelings and locations, the researchers found that cell phones can efficiently capture information that is otherwise difficult to record, given today’s on-the-go lifestyle. This is important, according to the researchers, because feelings recorded “in the moment” are likely to be more accurate than feelings jotted down after the fact.

To conduct the study, the team created an application for the Android operating system that documented each person’s location and periodically sent the question, “How happy are you?”

The investigators invited people to download the app, and over a three-week period, collected information from 270 volunteers in 13 countries who were asked to rate their happiness on a scale of 0 to 5. From the information collected, the researchers created and fine-tuned methods that could lead to a better understanding of how our environments influence emotional well-being. The study was published in the June issue of Demography.

The mobile phone method could help overcome some of the limitations that come with surveys conducted at people’s homes, according to the researchers. Census measurements tie people to specific areas — the census tracts in which they live — that are usually not the only areas that people actually frequent.

“People spend a significant amount of time outside their census tracks,” said John Palmer, a graduate student in the Woodrow Wilson School of Public and International Affairs and the paper’s lead author. “If we want to get more precise findings of contextual measurements we need to use techniques like this.”

Palmer teamed up with Thomas Espenshade, professor of sociology emeritus, and Frederic Bartumeus, a specialist in movement ecology at the Center for Advanced Studies of Blanes in Spain, along with Princeton’s Chang Chung, a statistical programmer and data archivist in the Office of Population Research; Necati Ozgencil, a former Professional Specialist at Princeton; and Kathleen Li, who earned her undergraduate degree in computer science from Princeton in 2010, to design the free, open source application for the Android platform that would record participants’ locations at various intervals based on either GPS satellites or cellular tower signals.

Though many of the volunteers lived in the United States, some were in Australia, Canada, China, France, Germany, Israel, Japan, Norway, South Korea, Spain, Sweden and the United Kingdom.

Palmer noted that the team’s focus at this stage was not on generalizable conclusions about the link between environment and happiness, but rather on learning more about the mobile phone’s capabilities for data collection. “I’d be hesitant to try to extend our substantive findings beyond those people who volunteered.” he said.

However, the team did obtain some preliminary results regarding happiness: for example, male subjects tended to describe themselves as less happy when they were further from their homes, whereas females did not demonstrate a particular trend with regards to emotions and distance.

“One of the limitations of the study is that it is not representative of all people,” Palmer said. Participants had to have smartphones and be Internet users. It is also possible that people who were happy were more likely to respond to the survey. However, Palmer said, the study demonstrates the potential for mobile phone research to reach groups of people that may be less accessible by paper surveys or interviews.

Palmer’s doctoral dissertation will expand on this research, and his adviser Marta Tienda, the Maurice P. During Professor in Demographic Studies, said she was excited to see how it will impact the academic community. “His applied research promises to redefine how social scientists understand intergroup relations on many levels,” she said.

This study involved contributions from the Center for Information Technology Policy at Princeton University, with institutional support from the National Institutes of Health Training Grant T32HD07163 and Infrastructure Grant R24HD047879.

Read the abstract.

Palmer, John R. B., Thomas J. Espenshade, Frederic Bartumeus, Chang Y. Chung, Necati Ercan Ozgencil and Kathleen Li. 2013. New Approaches to Human Mobility: Using Mobile Phones for Demographic Research. Demography 50:1105–1128. DOI 10.1007/s13524-012-0175-z

How will crops fare under climate change? Depends on how you ask (Global Change Biology)

Research image

Mechanistic (top row) and empirical (bottom row) simulations compared recent, or “baseline,” maize production in South Africa (1979-99) to projected future production under climate change (2046-65). While both models showed a reduction in output, the third column shows that the empirical model estimated a widespread yield loss of around 10 percent (in yellow), while the mechanistic model showed several areas of increased production (in green). (Image by Lyndon Estes)

Research image 2

For wheat, the mechanistic model (top row) projected greater wheat yields, while the empirical model (bottom row) suggested that wheat-growing areas would expand by almost 50 percent. (Image by Lyndon Estes)

By Morgan Kelly, Office of Communications

The damage scientists expect climate change to do to crop yields can differ greatly depending on which type of model was used to make those projections, according to research based at Princeton University. The problem is that the most dire scenarios can loom large in the minds of the public and policymakers, yet neither audience is usually aware of how the model itself influenced the outcome, the researchers said.

The report in the journal Global Change Biology is one of the first to compare the agricultural projections generated by empirical models — which rely largely on field observations — to those by mechanistic models, which draw on an understanding of how crop growth and development are affected by the environment. Building on similar studies from ecology, the researchers found yet more evidence that empirical models may show greater losses as a result of climate change, while mechanistic models may be overly optimistic.

The researchers ran an empirical and a mechanistic model to see how maize and wheat crops in South Africa — the world’s ninth largest maize producer, and sub-Saharan Africa’s second largest source of wheat — would fare under climate change in the years 2046 to 2065. Under the hotter, wetter conditions projected by the climate scenarios they used, the empirical model estimated that maize production could drop by 3.6 percent, while wheat output could increase by 6.2 percent. Meanwhile, the mechanistic model calculated that maize and wheat yields might go up by 6.5 and 15.2 percent, respectively.

In addition, the empirical model estimated that suitable land for growing wheat would drop by 10 percent, while the mechanistic model found that it would expand by 9 percent. The empirical model projected a 48 percent expansion in wheat-growing areas, but the mechanistic reported only 20 percent growth. In regions where the two models overlapped, the empirical model showed declining yields while the mechanistic model showed increases. These wheat models were less accurate, but still indicative of the vastly different estimates empirical and mechanistic can produce, the researchers wrote.

Disparities such as these aren’t just a concern for climate-change researchers, said first author Lyndon Estes, an associate research scholar in the Program in Science, Technology and Environmental Policy in Princeton’s Woodrow Wilson School of Public and International Affairs. Impact projections are crucial as people and governments work to understand and address climate change, but it also is important that people understand how they are generated and the biases inherent in them, Estes said. The researchers cite previous studies that suggest climate change will reduce South African maize and wheat yields by 28 to 30 percent — according to empirical studies. Mechanistic models project a more modest 10 to 19 percent loss. What’s a farmer or government minister to believe?

“A yield projection based only on empirical models is likely to show larger yield losses than one made only with mechanistic models. Neither should be considered more right or wrong, but people should be aware of these differences,” Estes said. “People who are interested in climate-change science should be aware of all the sources of uncertainty inherent in projections, and should be aware that scenarios based on a single model — or single class of models — are not accounting for one of the major sources of uncertainty.”

The researchers’ work relates to a broader effort in recent years to examine the biases introduced into climate estimates by the models and data scientists use, Estes said. For instance, a paper posted Aug. 7 by Global Change Biology — and includes second author and 2011 Princeton graduate Ryan Huynh — challenges predictions that higher global temperatures will result in the widespread extinction of cold-blooded forest creatures, particularly lizards. These researchers say that a finer temperature scale than existing projections use suggests that many cold-blooded species would indeed thrive on a hotter Earth.

Scientists are aware of the differences between empirical and mechanistic models, said Estes, who was prompted by a similar comparison that showed an empirical-mechanistic divergence in tree-growth models. Yet, only one empirical-to-mechanistic comparison (of which Estes also was first author) has been published in relation to agriculture — and it didn’t even examine the impact of climate change.

The solution would be to use both model classes so that researchers could identify each class’s biases and correct for it, Estes said. Each model has different strengths and weaknesses that can be complementary when combined.

Simply put, empirical models are built by finding the relationship between observed crop yields and historical environmental conditions, while mechanistic models are built on the physiological understanding of how the plant grows and reproduces in response to a range of conditions. Empirical models, which are simpler and require fewer inputs, are a staple in studying the possible effects of climate change on ecological systems, where the data and knowledge about most species is largely unavailable. Mechanistic models are more common in studying agriculture because there is a much greater wealth of data and knowledge that has accumulated over several thousand years of agricultural development, Estes said.

“These two model classes characterize different portions of the environmental space, or niche, that crops and other species occupy,” Estes said. “Using them together gives us a better sense of the range of uncertainty in the projections and where the errors and limitations are in the data and models. Because the two model classes have such different structures and assumptions, they also can improve our confidence in scenarios where their findings agree.”

Read the abstract.

Estes, Lyndon D., Hein Beukes, Bethany A. Bradley, Stephanie R. Debats, Michael Oppenheimer, Alex C. Ruane, Roland Schulze and Mark Tadross. 2013. Projected climate impacts to South African maize and wheat production in 2055: A comparison of empirical and mechanistic modeling approaches. Global Change Biology. Accepted, unedited article first published online: July 17, 2013. DOI: 10.1111/gcb.12325

The work was funded by the Princeton Environmental Institute‘s Grand Challenges Program.