As more of the greenhouse gas carbon dioxide enters the atmosphere, leading to climate change, crops might carry fewer nutrients, like zinc and iron. Stanford researchers explored this trend and regions most likely to be hurt by it.

The way we treat the planet has direct consequences on human health. This series of stories explores some of those consequences and what we can do to lessen the risks.

In warmer temperatures suicide rates increase, leading to concerns about an uptick in suicides as the globe continues to warm. But researchers offer some hope if greenhouse gases get under control.

As global temperatures rise, climate change’s impacts on mental health are becoming increasingly evident. Recent research has linked elevated temperatures to an increase in violence, stress and decreased cognitive function leading to impacts such as reduced test scores, lowered worker productivity and impaired decision-making.

Adding to the concern, a Stanford study led by economist Marshall Burke also finds a link between increased temperatures and suicide rates. The research, published in Nature Climate Change, concluded that up to 21,000 additional suicides will occur by 2050 within the United States and Mexico if unmitigated climate change continues to warm the Earth at the current projected rates.

Suicide is one of the top 10 causes of death in the United States. Unlike other leading causes – which include heart disease, cancer, homicide and unintentional injury – suicide rates have increased rather than fallen over time. And, while there has been a noticeable trend of rising suicide rates in warmer months, up to this point it has been difficult to attribute these changes to temperature, as other factors like day length and social patterns also vary.

Burke and team overcame these obstacles by assembling and examining decades worth of temperature and suicide data across thousands of U.S. counties and Mexican municipalities. To complement the data, they also scanned over half a billion Twitter updates or tweets and looked for language signaling a negative state of mind.

They found that hotter than average temperatures increase both suicide rates and the use of depressive language on Twitter. They also concluded that socioeconomic status had little to no impact, meaning wealth does not help insulate populations from suicide risk.

“One claim you often hear is that it’s the socioeconomically disadvantaged that are going to be affected by climate change. Our results suggest that at least in the case of mental health, impacts are going to cut across the income distribution and could affect any of us,” Burke said.

He and his team then used global climate model projections to predict how future temperatures could affect suicide rates. They found climate change could increase suicide rates by 1.4 percent in the United States and 2.3 percent in Mexico by 2050.Excess suicides by 2050 caused by warmer temperatures if greenhouse gas emissions stabilize consistent with Paris Agreement goals (move the slider to the right), or if emissions continue unabated (move the slider to the left). (Image credit: Sam Heft-Neal)

More children die from the indirect impact of armed conflict in Africa than those killed in the crossfire and on the battlefields, according to a new study by Stanford researchers. 

The study is the first comprehensive analysis of the large and lingering effects of armed conflicts — civil wars, rebellions and interstate conflicts — on the health of noncombatants.

The numbers are sobering: 3.1 to 3.5 million infants born within 30 miles of armed conflict died from indirect consequences of battle zones between 1995 and 2005. That number jumps to 5 million deaths of children under 5 in those same conflict zones.

“The indirect effects on children are so much greater than the direct deaths from conflict,” said Stanford Health Policy's Eran Bendavid, senior author of the study published today in The Lancet.

The authors also found evidence of increased mortality risk from armed conflict as far as 60 miles away and for eight years after conflicts. Being born in the same year as a nearby armed conflict is riskiest for young infants, the authors found, with the lingering effects raising the risk of death for infants by over 30 percent.

On the entire continent, the authors wrote, the number of infant deaths related to conflict from 1995 to 2015 were more than three times the number of direct deaths from armed conflict. Further, they demonstrated a strong and stable increase of 7.7 percent in the risk of dying before age 1 among babies born within 30 miles of an armed conflict.

The authors recognize it is not surprising that African children are vulnerable to nearby armed conflict. But they show that this burden is substantially higher than previously indicated. 

“We wanted to understands the effects of war and conflict, and discovered that this was surprisingly poorly understood,” said Bendavid, an associate professor of medicine at Stanford Medicine.  “The most authoritative source, the Global Burden of Disease, only counts the direct deaths from conflict, and those estimates suggest that conflicts are a minuscule cause of death.”

Paul Wise, a professor of pediatrics at Stanford Medicine and a senior fellow at the Freeman Spogli Institute for International Studies, has long argued that lack of health care, vaccines, food, water and shelter kills more civilians than combatants from bombs and bullets. 

This study has now put data behind the theory when it comes to children.

“We hope to redefine what conflict means for civilian populations by showing how enduring and how far-reaching the destructive effects of conflict have on child health,” said Bendavid, an infectious disease physician whose co-authors include Marshall Burke, PhD, an assistant professor of earth systems science and fellow at the Center on Food Security and the Environment.

“Lack of access to key health services or to adequate nutrition are the standard explanations for stubbornly high infant mortality rates in parts of Africa,” said Burke. “But our data suggest that conflict can itself be a key driver of these outcomes, affecting health services and nutritional outcomes hundreds of kilometers away and for nearly a decade after the conflict event”. 

The results suggest efforts to reduce conflict could lead to large health benefits for children.

The Data

The authors matched data on 15,441 armed-conflict events with data on 1.99 million births and subsequent child survival across 35 African countries. Their primary conflict data came from the Uppsala Conflict Data Program Georeferenced Events Dataset, which includes detailed information about the time, location, type and intensity of conflict events from 1946 to 2016. 

The researchers also used all available data from the Demographic and Health Surveys conducted in 35 African countries from 1995 to 2015 as the primary data sources on child mortality in their analysis.

The data, they said, shows that the indirect toll of armed conflict among children is three-to-five times greater than the estimated number of direct casualties in conflict. The indirect toll is likely even higher when considering the effects on women and other vulnerable populations.

Zachary Wagner, a health economist at RAND Corporation and first author of the study, said he knows few are surprised that conflict is bad for child health.

“However, this work shows that the relationship between conflict and child mortality is stronger than previously thought and children in conflict zones remain at risk for many years after the conflict ends.” 

He notes that nearly 7 percent of child deaths in Africa are related to conflict and reiterated the grim fact that child deaths greatly outnumber direct combatant deaths.

“We hope our findings lead to enhanced efforts to reach children in conflict zones with humanitarian interventions,” Wagner said. “But we need more research that studies the reasons for why children in conflict zones have worse outcomes in order to effectively intervene.” 

Another author, Sam Heft-Neal, PhD, is a research fellow at the Center for Food Security and the Environment and in the Department of Earth Systems Science. He, Burke and Bendavid have been working together to identify the impacts of extreme climate events on infant mortality in Africa.

The Freeman Spogli Institute for International Studies (FSI) at Stanford University is pleased to announce that former U.S. Ambassador and World Food Programme (WFP) Executive Director Ertharin Cousin will return for a second year at Stanford. Cousin will serve as the Frank E. and Arthur W. Payne Distinguished Lecturer at FSI and Distinguished Fellow at the Center on Food Security and the Environment and the Center on Democracy, Development and the Rule of Law.

Cousin brings over 30 years of experience addressing hunger and food security strategies on both a national and international scale. As U.S. Ambassador to the United Nations Agencies for Food and Agriculture, she focused on advocating for longer-term solutions to food insecurity and hunger, and at WFP she addressed the challenges of food insecurity in conflict situations.

We caught up with Cousin to ask about her plans for this upcoming school year.

If you had to pick out one thing that most concerns you in the realm of food security, what would it be?

Water access, particularly in terms of smallholder farmer centered irrigation and water management. The development community spent much of the past 10 years working to improve farmers’ access to the right seeds and tools – recognizing the need to increase the quality and quantity of their yields. A significant amount of work has also been performed related to improving private sector investment and to the development of markets including access for smallholder farmers.

Today there are approximately 500 million smallholder farmers in the world. The most vulnerable live and work in places where climate change creates ever more erratic rainy seasons. Particularly, in sub-Saharan Africa where 97 percent of all agriculture remains rain-fed. Too often the short rains don’t come, and the long rains produce insufficient precipitation. Inadequate policy management of diminishing water resources represents a significant problem which we must overcome to make agriculture productive and sustainable for the most vulnerable.

And what work have you been doing to address this issue?

I am working on a number of policy research and development projects. For example, I am co-chairing the Chicago Council on Global Affairs (CCGA) 2019 Global Food Security Symposium’s report exploring the linkages between water management and food security particularly as it relates to nutrition security. The report release will occur March 21, 2019 at the CCGA Food Security Symposium.

Over the past year, you also have been working on a project to encourage the private sector to create sustainable food systems. How is that going?

My work identifying and addressing policy-related challenges impacting private sector partnership and investment in global food system solutions continues. Globally, there is growing recognition that we cannot fix the broken global food system if we do not work to create collaborative efforts between public and private sector, academia, government, non-profits and larger society.

Governments, particularly those in developing countries, often lack both the financial resources and technical capacity required to perform the work and the investment necessary to fix our global food system. Governments and civil society must include private sector as an equal and desired partner. Government policies at the global, state and local level should support and encourage private sector participation.

Using my role here at Stanford as a platform to broker research and information both to private sector as well as to government, has proven quite successful over the past year. In very simple terms, helping global governments understand generating profit does not make the private sector a bad partner.

What successes have you had so far?

I was just in Amsterdam to meet with Royal DSM, a nutrition products manufacturer, with whom I developed a relationship during my tenure at the World Food Programme. In Kigali in Rwanda, DSM and several other partners - including the national government - have developed and are now operating the Africa Improved Foods company, the first European-type baby food manufacturing facility. European-type baby food differs from American products in terms of their lack of sweeteners and conservative use of food preservatives, lack of detectable pesticides (due to farming practices), and their stage-approach: they produce different products for the various stages of baby growth (from birth to 4 years) that cater to the specific nutritional needs of the child. Several farming cooperatives, representing approximately 10,000 Rwandan small farmers, form the sole supply chain for this baby food factory.

WFP serves as a catalyst market for the plant, purchasing the supplemental nutrition product distributed through the region’s targeted nutrition improvement program. The sustainability of the factory is directly related to the partners ability to grow (in addition to WFP) an institutional and a commercial consumer market for this easy-access, nutrient-rich food that is specifically made for children. I am assisting DSM and the government of Rwanda by helping to identify the policy changes required to ensure the sustainability of this public-private partnership. As a proof-of-concept, the success of AIF, will result in new public-private development opportunities. This initiative offers a case study demonstrating how collaboration between the private sector and government actually provides positive benefits for both farmers and nutritious food for consumers.

Why Stanford? How has being here helped your work?

Serving here at Stanford represents my first opportunity to work in academia on a full-time basis. I am a lawyer with over 30 years of experience of working on complicated domestic and global humanitarian and development issues; particularly, hunger related issues. I believe my experience adds value to any academic community. But in many institutions, the value of experience is not readily embraced, particularly because I don't have a PhD and haven’t spent 20 years in a classroom. At Stanford, I discovered collegial faculty, brilliant students and a recognition as well as a respect for my experience-based knowledge. I have received a welcoming response across the campus, collaborating with the law school, colleagues in the medical school, earth system sciences and the business school. The only limit to my participation and partnership with the amazing academic leaders here at Stanford has been time. I am quite looking forward to the opportunities for engagement provided by my additional time on campus.

___________________________________________________________­

The Payne Distinguished Lectureship is awarded to scholars with international reputations as leaders, with an emphasis on visionary thinking, practical problem solving, and the capacity to clearly articulate an important perspective on the global political and social situation. Past Payne Lecturers include Bill Gates, Nobel Laureate Mohamed El Baradei, UNAIDS Executive Director Peter Piot, and novelist Ian McEwan.

The Center on Food Security and the Environment (FSE) addresses critical global issues of hunger, poverty and environmental degradation and is a joint effort of the Freeman Spogli Institute for International Studies and the Stanford Woods Institute for the Environment.

The Center on Democracy, Development and the Rule of Law is an interdisciplinary center for research on development in all of its dimensions:  political, economic, social and legal, and the ways in which these different dimensions interact with one another.

By comparing historical temperature and suicide data, researchers found a strong correlation between warm weather and increased suicides. They estimate climate change could lead to suicide rate increases across the U.S. and Mexico.

Suicide rates are likely to rise as the earth warms, according to new research published July 23 in Nature Climate Change. The study, led by Stanford economist Marshall Burke, finds that projected temperature increases through 2050 could lead to an additional 21,000 suicides in the United States and Mexico.

Researchers have recognized for centuries that suicides tend to peak during warmer months. But, many factors beyond temperature also vary seasonally – such as unemployment rates or the amount of daylight – and up to this point it has been difficult to disentangle the role of temperature from other risk factors.

“Suicide is one of the leading causes of death globally, and suicide rates in the U.S. have risen dramatically over the last 15 years. So better understanding the causes of suicide is a public health priority,” Burke said.

Heat and suicide

To tease out the role of temperature from other factors, the researchers compared historical temperature and suicide data across thousands of U.S. counties and Mexican municipalities over several decades. The team also analyzed the language in over half a billion Twitter updates or tweets to further determine whether hotter temperatures affect mental well-being. They analyzed, for example, whether tweets contain language such as “lonely,” “trapped” or “suicidal” more often during hot spells.

The researchers found strong evidence that hotter weather increases both suicide rates and the use of depressive language on social media.

“Surprisingly, these effects differ very little based on how rich populations are or if they are used to warm weather,” Burke said.

For example, the effects in Texas are some of the highest in the country. Suicide rates have not declined over recent decades, even with the introduction and wide adaptation of air conditioning. If anything, the researchers say, the effect has grown stronger over time.

Effect of climate change

To understand how future climate change might affect suicide rates, the team used projections from global climate models. They calculate that temperature increases by 2050 could increase suicide rates by 1.4 percent in the U.S. and 2.3 percent in Mexico. These effects are roughly as large in size as the influence of economic recessions (which increase the rate) or suicide prevention programs and gun restriction laws (which decrease the rate).

Effects of historical temperature changes on suicide rates are shown for the U.S. and Mexico. (Image credit: Marshall Burke)

Effects of historical temperature changes on suicide rates are shown for the U.S. and Mexico. (Image credit: Marshall Burke)

“We’ve been studying the effects of warming on conflict and violence for years, finding that people fight more when it’s hot. Now we see that in addition to hurting others, some individuals hurt themselves. It appears that heat profoundly affects the human mind and how we decide to inflict harm,” said Solomon Hsiang, study co-author and associate professor at the University of California, Berkeley.

The authors stress that rising temperature and climate change should not be viewed as direct motivations for suicide. Instead, they point out that temperature and climate may increase the risk of suicide by affecting the likelihood that an individual situation leads to an attempt at self-harm.

“Hotter temperatures are clearly not the only, nor the most important, risk factor for suicide,” Burke emphasized. “But our findings suggest that warming can have a surprisingly large impact on suicide risk, and this matters for both our understanding of mental health as well as for what we should expect as temperatures continue to warm.”

Marshall Burke is also a fellow at the Center on Food Security and the Environment, Stanford Woods Institute for the Environment, Freeman Spogli Institute for International Studies, and Stanford Institute for Economic Policy Research. Solomon Hsiang is also a faculty research fellow at the National Bureau of Economic Research. Other Stanford co-authors include Sanjay Basu, assistant professor of medicine, and Sam Heft-Neal, research scholar at the Stanford Center on Food Security and the Environment. Additional co-authors are from Pontificia Universidad Católica de Chile, Vancouver School of Economics, and the University of California, Berkeley. The research was partially supported by the Stanford Woods Institute for the Environment.