Air pollution in India is impacting the productivity of wheat crops, reducing it by almost half, a research paper has said. Noting that India has already been negatively affected by recent climate trends, the paper said the significant decreases in yield could be attributed to two air pollutants - black carbon and ground level ozone. The research paper "Recent Climate and Air Pollution Impacts on Indian Agriculture" that analysed yields of wheat and rice crops for 30 years, found that air pollution caused wheat yields in densely populated states to be 50 per cent lower than 2010. Up to 90 per cent losses were due to the direct effects of short-lived climate pollutants (SLCPs) like smog, the paper authored by Jennifer Burney, an environmental scientist at University of California. The findings have implications for global food security as India is a major rice exporter. The paper further said tropospheric ozone and black carbon have direct effects on crop yields beyond their indirect effects through climate. "Emissions of black carbon and ozone precursors have risen dramatically in India over the past three decades," it added. Scientists examined historical data on crop yields, emissions, and precipitation to draw their conclusions.