An increase in rainfall by 1 cm during the crop growing season leads to on average 7% reduction in the suicide rate.
The increase in temperature during the cropping season reduces crop yields, thus resulting in increased suicides.
Climate change has led to over 59,000 farmer suicides over the last 30 years in India. Even a 1 degree C increase in temperature above 20 degrees C in a single day during the crop growing season in India results in about 70 suicides on average. The increase in temperature during the cropping season reduces crop yields, thus resulting in increased suicides, says a study published in the journal Proceedings of the National Academy of Sciences.
The study was carried out using data for all the 32 States and Union Territories.
Endorsing the temperature-crop yield link, agricultural scientist Prof. M.S. Swaminathan says: “The effect of increased temperature on crop yield is real. In the late 1980s we found that when the temperature increases by 1-1.5 degree C the duration of the crop reduces by one month. Since the duration reduces the yield drops by 300-400 kg.”
Tamma A. Carleton from the University of California, Berkeley and the author of the paper tested the link between climate change, crop yields and suicide by comparing the number of suicides across India during the period 1967 to 2013 with crop yield and climate data. Data on suicides were collected from the National Crime Records Bureau. She found crop loses due to heat damage cause additional burden on farming households and this at times leads to suicides.
Dr. Carleton found suicides reported when a single day’s temperature increased by 1 degree C was seen only during the crop-growing season. Similar increase in temperature during seasons when crops were not grown did not result in increased suicides.
Crop yield data from 13 States from 1956 to 2000 were then compared with climate change data. Dr. Carleton found annual yield falling when the temperature was above 20 degree C during the crop-growing season. “I find that yields mirror suicides in their response to temperature, falling with rising growing season temperatures but reacting minimally to nongrowing season heat,” she writes.
An increase in rainfall by 1 cm during the crop growing season leads to a decrease of about 0.8 deaths per 100,000, thus lowering the suicide rate by 7% on average, she writes.
The effect of climate variation reveals that past growing season temperature strongly influences suicide rates in the following years up to about five years. For instance, when there is abundant rainfall during one growing season, the suicide rates dip for the next 2-3 years. Drought apparently does not seem to have any effect on suicide rates, she found.
The study also finds that South India which is generally hotter has higher farmer suicide rates. Comparing the yields to growing season temperature for 13 States, the author found that States where the yields are more affected by high temperatures are also the States which report higher suicide rates. Maharashtra, Karnataka, Tamil Nadu, and Andhra Pradesh not only show severe suicide responses to temperature but also the crop yield is more negatively affected by higher temperature.
The study did not find any adaptive behaviour to prevent suicides in response to climate change. “We must undertake anticipatory research using genetic checkmating for potential changes in climate such as changes in precipitation, and temperature. Don’t think we have done such research as seriously as we should have,” says Prof. Swaminathan. “Sub-Saharan Africa and South Asia are the most vulnerable regions and we would be the most affected.”
The study has several limitations — it has not looked at other factors that could have contributed to suicides.
India’s average temperature is expected to increase by 3 degree C by 2050. Without investments in adaptations, India might face increased number of lives lost due to suicides, she warns.
Science Chronicle 