Over 1,900 farm suicides were triggered every year over the last 30 years in India by warming related to climate change, says a new study published in the Proceedings of the National Academy of Sciences (PNAS) of the United States of America.
The study, ‘Crop-damaging temperatures increase suicide rates in India’, by University of California, Berkeley researcher Tamma Carleton, finds that temperature during India’s main agricultural season has a “strong positive effect” on annual suicide rates. Also, southern India witnesses the most prominent spikes in suicide rates for a given change in temperature. Four states — Maharashtra, Karnataka, Tamil Nadu, and Andhra Pradesh — that have been at the centre of public debates on agricultural influences on suicide “not only have severe suicide responses to temperature, but also exhibit large negative impacts of temperature on yield”, the study states.
“Warming over the last 30 years is responsible for 59,300 suicides in India, accounting for 6.8% of the total upward trend,” according to the study. “These results deliver large-scale quantitative evidence linking climate and agricultural income to self-harm in a developing country.”
The study calculates that “warming a single day by 1 degree Celsius during India’s agricultural growing season leads to roughly 65 suicides across the country, whenever that day’s temperature is above 20 degrees Celsius”. Warming a day by 5 degrees Celsius has five times that effect.
Carleton analysed the relationship between annual suicide rates, measured for each of India’s states and Union Territories, and cumulative exposure to temperature and rainfall using a regression model. The study relies on data from the National Crime Records Bureau, “which contains the universe of reported suicides in the country from 1967 to 2013”.
However, Carleton points to two key empirical concerns. First, a study of the relationship between suicide rates and climatic variables has very little precedent in existing literature. “I therefore use a flexible nonlinear model and show robustness of my results to alternative functional form assumptions.”
Second, the channels through which adverse climate conditions may affect suicide rates are not immediately discernible, yet are of central policy relevance. “To this end, I distinguish between climate conditions that damage crops and those that have no effect on agricultural yields. I do so by estimating differential impacts of climate during growing and nongrowing seasons, using the arrival and departure of the southwest summer monsoon to define seasonality.”
According to the study, “the differential response of suicide to temperature in the growing and nongrowing seasons is consistent with an agricultural channel in which heat damages crops”. This places economic pressure on farming households, which may lead to suicides.