Climate change may have led to over 59,000 farmer suicides over the last 30 years in India, argues a research report from the University of California, Berkeley in the US.
Even a 1°C increase in temperature above 20° C in a single day during the crop growing season results in about 70 suicides on average.
The increase in temperature during the cropping season reduces crop yields, resulting in increased suicides, according to a study published in the journal Proceedings of the National Academy of Sciences.
The study was carried out using data for all States and Union Territories.
It has several limitations, though, including the fact that it has not looked at other factors that could have contributed to suicides.
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 between 1967 and 2013 with crop yield and climate data. Data on suicides were collected from the National Crime Records Bureau.
Crop losses due to heat damage cause additional burden on farming households and this at times lead to suicides.
Suicides reported when a single day’s temperature increased by 1°C only during the crop growing season. A similar increase in temperature during other seasons did not result in a rise in suicides.
Crop yield data from 13 States from 1956 to 2000 were compared with climate change data. Dr Carleton found annual yield falling when the temperature was above 20°C during the crop-growing season.
An increase in rainfall by 1 cm during the growing season leads to a decrease of about 0.8 deaths per 100,000, thus lowering the suicide rate by 7% on average.
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 two or three years. Drought apparently does not seem to have any effect on suicide rates, the researcher found.
The study says 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 crop yield is also more negatively affected by higher temperature.
The study did not find any adaptive behaviour to prevent suicides in response to climate change.