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Growth rates in aggregate crop productivity to 2050 will continue to be mainly driven by technological and agronomic improvements, just as they have for the past century. Even in the most pessimistic scenarios, it is highly unlikely that climate change would result in a net decline in global yields. Instead, the relevant question at the global scale is how much of a headwind climate change could present in the perpetual race to keep productivity growing as fast as demand. Overall, the net effect of climate change and CO2 on global average supply of calories is likely to be fairly close to zero over the next few decades, but it could be as large as 20% to 30% of overall yield trends. Of course, this global picture hides many changes at smaller scales that could be of great relevance to food security, even if global production is maintained (Easterling et al., 2007).

To reduce uncertainties in global impacts, better estimates of rates of global warming and responsiveness of crop yields to warming and CO2 (and their combination) would be particularly useful. We note that the responsiveness of yields will depend partly on the crops themselves, including any genetic improvements made to reduce sensitivity to T or improve responsiveness to CO2, as well as adaptive management changes by farmers in choosing what, when, where, and how to grow their crops. The effects of changes in O3 are currently much less understood but could also represent a significant impact at the global scale.

It will never be possible to unambiguously measure the effect of changes in climate, CO2, and O3, given the scale of global food production and the fact that agriculture is always changing in multiple ways. However, the best available science related to climate change and crop physiology indicates that climate change represents a credible threat to sustaining global productivity growth at rates necessary to keep up with demand. Increasing the scale of investments in crop improvement, and increasing the emphasis of these investments on global change factors, will help to sustain yield growth over the next few decades.

 

vía  American Society of Plant Biologists.

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