When temperatures rise to levels that damage crops, suicides go up: Tamma Carleton

The general finding that temperature appears more significant than rainfall in determining suicide rates, is consistent with work from other parts of the world, where agricultural yields are shown to be more affected by temperature than they are by rainfall.

Written by Sowmiya Ashok | Updated: August 3, 2017 7:33 pm
farm suicide, India farmer suicide rate, National Academy of Sciences (PNAS), University of California As per a study, over 1,900 farm suicides were triggered every year over the last 30 years in India by warming related to climate change.

What led you to study the links between temperature rise and farmer suicides? 

First, in my research, I spend a lot of time thinking about and studying the many ways that the climate impacts global economic and social stability. While some aspects of climate impacts are relatively easy to observe and measure, such as crop yields or national GDP, other key indicators of human wellbeing are harder to quantify, yet essential to consider as we plan for and create policy around a future under climate change.

Second, the suicide epidemic in India has received an exceptional amount of attention in the media, yet little quantitative research existed to inform any policy. I wanted to use data and careful statistics to test this hypothesis and provide measurable answers for policymakers seeking to enact an effective suicide prevention policy in India.

What are the main findings of the study, and its shortcomings? 

Many have argued that increasing risks faced by farmers have caused periods of economic destitution in which some individuals will cope by committing suicide. Often, these claims involve climate events, which damage crops and push many into poverty. I use data to test the hypothesis that climate change has played a role in elevating the risk of suicide in India. I show that when temperatures rise to levels that damage crops, suicide rates also go up. It appears that crop losses are the key culprits linking self-harm to hot temperatures.

Given the limited availability of data, this study cannot directly speak to particular policy solutions that are actively being debated in India. For example, I cannot trace changes in the climate to individuals who incur debt, and show evidence that debt relief programmes or access to low interest loans could mitigate rising suicide rates. I also cannot identify whether a suicide victim had access to crop insurance or not, and whether that insurance made suicide a less likely outcome in light of a warming climate. Therefore, while my findings are suggestive that such policies may be fruitful, it is left to future research to focus on specific policy solutions to the tragic deaths we see as a result of climate change.

What factors could potentially confound your estimation? 

Suicide is an incredibly complex phenomenon with many contributing factors. I isolate the role of climate in determining suicides from all other possible contributing factors by following the same population within India as it experiences a different climate at different points in time. So we can think about observing a population during a hot growing season, in which temperatures get to levels that damage crops. Then we observe that same population in a year where growing season temperatures are cooler, remaining at levels optimal for crop growth. We can compare the suicide rate in this location in the year with a hot growing season and to the suicide rate during the year with a cooler growing season. After controlling for other regional trends, this allows me to isolate the role of the climate from all other drivers of suicide. It’s important to note that this is not a deterministic relationship between temperature and suicide.

You say “suicide rates fall as growing season rainfall increases — although the relationship is statistically insignificant”. Could you explain? 

The general finding that temperature appears more significant than rainfall in determining suicide rates, is consistent with work from other parts of the world, where agricultural yields are shown to be more affected by temperature than they are by rainfall. I look both at temperature and rainfall, key variables that influence agricultural yields in India and elsewhere. I find that while both temperature and rainfall affect suicide rates, temperature is the dominant climatic variable.

To investigate this further, I estimate an alternative statistical method, which allows me to measure the impacts of longer-run trends in climate, as opposed to comparing one year of rainfall in a given location to another year in that same location. This alternative approach demonstrates a substantial negative effect of growing season rainfall on suicide rates, which is statistically significant. Under this approach, I find that increasing growing season rainfall by 1 cm lowers the suicide rate by 7%, on average.

What have India’s economic growth and improvements in agricultural yields impacted suicides over the study period? 

Households with more economic resources may be able to invest in heat-tolerant seeds, pay the upfront costs of irrigation technologies, or take up crop insurance. Increases in average crop yields could have weakened the link between temperature and suicide by providing agricultural households with more savings. However, I found that these forms of adaptation were not taking place, as the effect of temperature on suicide is virtually identical in recent years as it was over 40 years ago. This is not inconsistent with the broader literature on climate impacts, where researchers have found little evidence of adaptation in other regions of the world and for other types of climate damage.

The study finds no evidence to suggest that communities acclimatize to high temperatures or become more resilient as they get richer. Why do you think this is the case?

TC: There are many possible impediments to adaptation that keep communities from being able to reduce the impacts of temperature as the climate warms. I find no evidence that populations within India have been able to successfully adapt to a warming climate. The relationship between temperature and suicide is the same across different populations within India, and at different points in time, suggesting that even as India has gradually warmed while experiencing robust economic growth, people appear no better able to cope with high temperatures. Without substantial investments in adaptive technologies and behaviors, this finding means that it’s likely we will see a sustained rise in suicide rates as climate change continues to unfold in India.

The study mentions that the findings are crucial since it could cause ripple effects throughout the Indian economy? What would some of these effects be?

TC: Damages to agricultural yields can permeate throughout the economy, as food prices may rise and the demand for agricultural laborers may fall. This could lead to distress both within the farming community, as well as for those whose incomes and necessary expenditures indirectly depend on crop yields. The damages to the overall Indian economy from these climatic shifts are currently undocumented; I look forward to future research that can help quantify the magnitude of these monetary damages, as these were not the focus of the present study.

Tamma Carleton is a PhD student of Agricultural & Resource Economics at UC Berkeley, specialising in problems at the intersection of environment and development.
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