New Research on Crops and CO2 New research into crops and carbon dioxide levels suggests more carbon dioxide may not help plants grow better.
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New Research on Crops and CO2

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New Research on Crops and CO2

New Research on Crops and CO2

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I'm Ira Flatow. This is TALK OF THE NATION: SCIENCE FRIDAY from NPR News.

You know, if there's an upside - if there's a silver lining to the specter of global warming, it's always been the possibility that increased levels of carbon dioxide in the atmosphere might be a good thing, at least for plants and crops, because you know, after all, plants, they eat CO2, they need it to grow. So maybe at least, well - well, global warming might bring greater crop yields in addition to the rising sea levels.

Well, research published this week in the journal Science says that that outlook may be a bit too optimistic, that CO2 may not be as much of a boon to agriculture as those other estimates say.

Joining me now to talk about this is one of the authors of the report, Don Ort. He's professor of plant biology and the research leader of the USDA Agricultural Research Service, Photosynthesis Research Unit, based at the University of Illinois at Urbana-Champaign. Thank you for joining us, Dr. Ort. Sorry, I had to get that long mouthful out.

Professor DONALD ORT (University of Illinois at Champaign-Urbana): You did pretty well. It's pleasure to be here.

FLATOW: But you work with photosynthesis. That's very interesting.

Prof. ORT: Yes, that's correct.

FLATOW: Boy, if we could just harness - how close are we to ever harnessing photosynthesis, to make it really work for us instead of just the plants? Anywhere close to getting that?

Prof. ORT: Well, I think that we are harnessing photosynthesis in many ways. For example, there are things like ethanol that we find in our gasolines that are certainly directly harnessing photosynthesis. For fuels there's bio-diesel.

In terms of artificial systems where we might make electricity directly, I think we're still pretty far from that - probably decades.

FLATOW: Alright, now that I take that journey, let me make a u-turn and bring us back to what we were going to talk about originally and that is, you found that additional - additional carbon dioxide didn't have as big an effect as was thought. Explain to us the theory here and what you found.

Prof. ORT: Well, as many of your listeners may know, CO2 has increased in the atmosphere. Prior to the Industrial Revolution, it was about 260 parts per million. That's increased today to about 380, and by the middle of the century it's projected to be about 550.

And so this CO2 increase brings along with it some factors of global change. One that is well-known is global warming, and the other one that really impacts on agriculture is changing precipitation patterns.

And it had been thought, based on models that have been run, that the two things that are probably bad for agriculture, which is, when averaged across the world, increase in temperature and the changing precipitation patterns, would be cancelled out, or maybe even more than cancelled out, by the beneficial effect of CO2, and CO2 enhances photosynthesis directly in many kinds of plants, and in virtually all kinds of plants it allows them to use water more efficiently.

And what we have shown in this study and our analysis is that the parameterization of these models - that is, the values that have been put into these models to come up with these predictions - have been largely based on studies that have been done in relatively small chambers. And the reason for this is, it's pretty difficult to mimic the atmospheres at 2050 under real field conditions.

FLATOW: S, you mean these studies are done in the closed greenhouse someplace instead of outside on the field?

Prof. ORT: They're not actually greenhouses; they tend to be small chambers that are out in the field, maybe two meters in diameter where CO2 can be elevated, it can be controlled, and they often have open tops. Nonetheless, they're not like the field.

But more recently, there has been technology developed where under field conditions we can mimic the atmospheres in terms of the gas in the atmosphere of 2050 under actual field conditions. These are pretty expensive experiments. They're experiments that have a big land footprint, and so they've only been done on agricultural crops in three different places in the world, Urbana, Illinois being one of them, where we've looked at corn and soybean. Rice and wheat have been looked at - or rice has been looked at in Japan. Wheat and sorghum have been looked at in Arizona.

FLATOW: And you found?

Prof. ORT: And we found - after all that - we found that when you look under true field conditions in the real world, the stimulation that you see in yield is roughly half of that that was projected from the chamber studies.

And so, one of the big take-home messages of our study and our analysis is that the projections based on these higher, more optimistic values in terms of what world food supply will be in 2050, are probably significantly overly optimistic, and that because of that, areas that were considered to essentially balance out, areas, for instance, in the Tropics, that the CO2 effect would balance out the deleterious effects. In all likelihood, it won't.

And in temperate areas where we expected an enhancement of yield, in all likelihood, that enhancement of yield is going to be substantially smaller, perhaps half as large as what was anticipated.

FLATOW: So there's really no good news then about...

Prof. ORT: Well, there's no good news from the standpoint of projecting forward with what we know now. I think that there is good news from the standpoint that this probably says that the feeling that agriculture would take care of itself during this global change scenario over the next half-century probably is not true.

And so it needs to move higher up on the priority list of things that we worry about and things that we do something about.

FLATOW: Could you genetically engineer better crops to survive under this more intense CO2?

Prof. ORT: Well, that's exactly what I was getting at. The upside of this is that we do have the understanding and we do have the tools in place that we know, in principle, the kinds of things that would need to be changed in order for plants to respond more robustly to this elevated CO2, take more advantage of the elevated CO2 in terms of stimulating photosynthesis.

And then, on the other hand, to engineer crops that can also withstand the higher temperatures and, perhaps, the drought that's going to exist in various parts of the world. So there is an upside.

FLATOW: Yeah. Is there any way to predict, with any accuracy, where the food will be growing? You know, as the climate changes, where the food - the breadbaskets of the world will be moving as the climate changes.

Prof. ORT: Well, I mean, that there is a general feeling that there will be a migration away from the equator, so things will, in this hemisphere, tend to go further north. But one has to remember that there are two other things that are required in agriculture. One is you actually have to have the land area and the quality soils in order to have a breadbasket.

And the second thing that won't change with global climate change is the length of the day. And so the further you go north, the amount of sunlight that you get during those growing season days is smaller. And so that's going to feed back in terms of this migration of the so-called breadbaskets away from the equator.

FLATOW: Mm hmm. Well, thank you very much for taking time to talk with us. This was quite fascinating, Don.

Prof. ORT: Well, it's been my pleasure.

FLATOW: Have a good weekend. Don Ort is professor of plant biology and the research leader of the USDA/Agricultural Research Service Photosynthesis Research Unit - and we say that with all respect - based at the University of Illinois at Urbana-Champaign.

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