Carbon Dioxide and Crop Yield in China Climate and Society, EESC V1003.001 Alexandra DiPalma Charlotte Chiang

Two Sides of One Issue: Will CO2 Positively Affect Agricultural Production? We examine this topic as it relates to rice production in China, and how the combined effects of global warming, foremost of which is atmospheric carbon dioxide growth, will affect the future of global food security.

Why China? Why Rice? Over one-fifth of the world’s population depends on the crop yielded in China; the staple crop is rice China is a rapidly industrializing country; between 1992 and 2002, China’s carbon emission increased by 33%, and the mean surface temperature is expected to rise 2.2 oC within the next 50 years

Carbon Dioxide and Human-induced Global Warming Global warming over the past 150 years has correlated strongly with human activity Foremost amongst its effects has been an increase in atmospheric CO2 levels, which is expected to grow to ~550ppm by the year 2050

Theory 1: Positive Effect of Increased CO2 on Crop Yield Increased CO2 = greater photosynthetic efficiency Laboratory experiments predict that 550 ppm will result in a 38% increase in rice crop productivity Free-air concentration enrichment (FACE) models, developed in recent years, show this statistic to be closer to 13% - this can be attributed to the ability of FACE to better simulate real-life crop-growing circumstances

Theory 2: Net Effect of Global Warming is Decreased Crop Yield Records of crop yield over the past 50 years show that rice production has not grown, in spite of technological advancements & other factors This stagnation in production can be explained by three factors associated with global warming: temperature increase, rise in tropospheric ozone Precipitation unpredictability

Political & Economic Implications In 2006, China’s food price inflation accounted for 85% of total inflation By 2050, China’s demand for cereals will double, while actual cereal consumption per capita will decline by 18-35% To combat these issues, China has expanded its agricultural investment and implemented policies to control food prices – these steps have been taken with the hope of ensuring food security both domestically and internationally

Possible Solutions Crop-breeding will create new crops with high yield and resistance Improving rainfall-use efficiency (through fertilizer and greater rooting depth) will maximize rainfall transpired by the crop and minimize loss from soil and weeds Eco-farming will increase crop resilience to weather change by considering environmental factors (ie: landscape, livestock) as farmers decide which crops to grow

Conclusions While CO2 increase does, in isolation, have a positive effect on crop yield, it cannot be seen as a solution to the negative effects that other climate change factors have on crop yield Many studies indicating that CO2 will be the “silver-lining” of global warming with regards to crop yield have not been realistic in their simulations of nature, and also do not account for associated effects of global warming that will decrease it