More than taking the heat: crops and global change

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Grain production per unit of land will need to more than double over this century to address rising population and demand. This at a time when the procedures that have delivered increased yields over the past 50 years may have reached their ceiling for some of the world's most important crops. Rising global temperature and more frequent droughts will act to drive down yields. The projected rise in atmospheric [CO2] by mid-century could in theory increase crop photosynthesis by over 30%, but this is not realized in grain yields in current C3 cultivars in the field. Emerging understanding of gene networks controlling responses to these environmental changes indicates biotechnological opportunities for adaptation. Considerably more basic research, particularly under realistic field conditions, is critical before these opportunities can be adequately understood and validated. Given the time needed between discovery in a model plant species and translation to traits or stacked changes in a commercial grain crop cultivar, there is an urgent need to vigorously pursue and develop these opportunities now.

Section snippets

An impending grain drain?

Nothing is more important to humanity and the stability of societies, than a reliable and affordable supply of food. Climate change will clearly alter where crops can be grown and their productivity, the extent to which this will affect global food supply remains controversial. The Intergovernmental Panel on Climate Change (IPCC) concluded that despite climate change and increasing world population, crop surpluses at the global level would continue resulting in a ‘small decline in real world

Taking the heat

The accumulation of greenhouse gases in the atmosphere is driving a warming trend that is projected to continue throughout this century. Decreases in agricultural yield are already linked to increases in growing season temperatures [4]. For example, an increase of 1.5–2°C is projected for the US during the next 50 years and 3–6°C by the end of the century [5]. Increase in average temperature could result in longer potential growing seasons at high latitudes, and often shorter seasons at low

Drying out

Water availability dominates global crop yields [21]. The water holding capacity of air, or in effect its drying power, increases exponentially with temperature. Therefore, even with no change in precipitation, increased evapotranspiration driven by higher air temperature will increase drought incidence. An analysis of the northeastern U.S. predicts increased growing season soil water deficits even with little or no change in annual precipitation [22]. The IPCC projected that the land area

Carbonating the atmosphere

Rising atmospheric [CO2] is the largest single driver of global warming, but as a limiting substrate for photosynthesis it also directly increases plant production. Before the Industrial Revolution, the concentration was about 270 μmol mol−1. It has risen at an ever increasing rate since then, reaching 387 μmol mol−1 in 2009 and projected to increase to 550 μmol mol−1 by mid-century and possibly 800 μmol mol−1 by 2100. The one positive of global change for food production has appeared to be rising

Conclusion

While debate continues around whether climate change will cause global grain shortages or not, on the precautionary principle the world needs to be prepared. The cost of undertaking the basic research and precommercial development to achieve adaptations to rising temperature, drought incidence and [CO2] will be small compared to the social and economic disruptions, not to mention the human cost, of serious grain shortages. While we have outlined some targets above, these are only scraping the

References and recommended reading

Papers of particular interest published within the period of review have been highlighted as:

  • • of special interest

  • •• of outstanding interest

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