CO2 hits crop protein

12 Apr, 2014 04:00 AM
These field results are consistent with findings from previous laboratory studies

AS carbon dioxide levels in the atmosphere hit their highest level for possibly three million years, researchers have determined that the gas is changing the nutritional quality of food crops.

The effect of rising CO2 levels is already evident across the world’s crops, say researchers from the University of California, Davis, and could reduce the amount of plant protein available globally by three per cent over the next few decades.

The assimilation of nitrogen plays a key role in a plant's growth and productivity. In food crops, it is especially important because plants use nitrogen to produce the proteins that are vital for human nutrition.

Wheat alone provides nearly one-fourth of all protein in the global human diet.

Laboratory studies had demonstrated that elevated levels of carbon dioxide inhibit plants’ assimilation of nitrate into proteins, but there had been no verification of this process in field-grown plants.

A team led by Arnold Bloom, a professor in the UC Davis Department of Plant Sciences, examined samples of wheat that had been grown in 1996 and 1997 in the Maricopa Agricultural Center near Phoenix, Arizona.

While the wheat was being grown, carbon dioxide-enriched air was released in the fields, creating an elevated level of atmospheric carbon at the test plots, similar to what is now expected to be present in the next few decades.

Control plantings of wheat were also grown in the ambient, untreated level of carbon dioxide.

Leaf material harvested from the various wheat tests plots was immediately placed on ice, and then oven dried and stored in vacuum-sealed containers to minimize changes over time.

When Dr Bloom and his team pulled out the preserved leaf material, they were able to do analyses not available when the plants were harvested.

"These field results are consistent with findings from previous laboratory studies, which showed that there are several physiological mechanisms responsible for carbon dioxide's inhibition of nitrate assimilation in leaves," Dr Bloom said.

Other studies have shown that protein concentrations in the grain of wheat, rice and barley, and in potato tubers, can decline by up to eight per cent under elevated levels of atmospheric carbon dioxide.

"When this decline is factored into the respective portion of dietary protein that humans derive from these various crops, it becomes clear that the overall amount of protein available for human consumption may drop by about three per cent as atmospheric carbon dioxide reaches the levels anticipated to occur during the next few decades," Dr Bloom said.

Heavy nitrogen fertilisation could partially compensate for this decline in food quality, but it would also mean higher costs, more nitrate leaching into groundwater and increased emissions of nitrous oxide, a potent greenhouse gas.

Concentrations of CO2 in the atmosphere passed 400 parts per million (ppm) for the first time since recordings began in 2013. Before the 20th century, CO2 levels hadn’t exceeded 300 ppm for at least 800,000 years, according to studies of air trapped in Antarctic ice cores.

The last time CO2 levels passed 400 ppm was probably in the Pliocene Epoch, between 2.6 and 5.3 million years ago, when the planet was about 3-4 degrees warmer than it was in the 19th Century, before the current warming phase began.

Findings from the UC Davis study have been reported in the journal Nature Climate Change.

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13/04/2014 7:16:30 AM

What!! CO2 is not really a fertiliser after all!! Gee, Golly Gosh, who would have thought that that the scientists were right after all??
Bruce C
14/04/2014 9:01:38 AM

They could try an alternative source of protein known as BEEF.
14/04/2014 9:16:29 AM

I think its important to note that the lab results could not be reproduced in the field- so really the findings are irrelevant.
practical farmer
14/04/2014 9:39:12 AM

It all sounds convincing until they say that the world was 3-4 degress warmer when CO2 levels were last at 400ppm than the 19th century. The 19th century included the end of the Little Ice Age, which was several degrees cooler than the Mediaeval Warm Period 400 years before, when it was warmer than now without elevated CO2. They also don't mention the increased volume of plant material grown with elevated CO2, only the lowwering of protein levels. I just wish we could get the whole picture sometimes.
14/04/2014 11:46:26 AM

If the " Global Warming / Climate Change" story had been handled TRUTHFULLY in the beginning we wouldn't have this ongoing debate now. Remember Tim saying it was not going to rain again in outback NSW ? The lies and half truths go on and on because someone can see a job = money in it. SOLUTION ? Learn to adapt--------as we have always done.
14/04/2014 12:42:02 PM

You miss the point, rosco. The research team stated "These field results are consistent with findings from previous laboratory studies". Many research projects, in the field and in the laboratory, show that different types of plants have different results under enhanced CO2. The endlessly repeated claim "CO2 is plant food" is a gross over-simplification. The whole picture is available, practical farmer, if you take the trouble to read the research results. See e.g.: owledge/library/effects-of-rising -atmospheric-concentrations-of-ca rbon-13254108
14/04/2014 1:58:33 PM

Count that with the increase in grain protein (due to breeding and other management practices) over the last few decades.
14/04/2014 2:56:56 PM

The 400 ppm figure rings an alarm bell for me. When I was at school in the 1960s we were taught that the atmosphere is made up of 78% nitrogen, 21% oxygen, .03% carbon dioxide, and the rest was rare gases like argon, freon, etc. The rise from .03% to .04% in 50 years is pretty drastic, and the implications for protein production are worrying. No, Bruce C, beef can't replace grain as a protein source because of the scale needed and the resources needed to produce the meat, and get it to hungry mouths in good condition. Grain keeps and travels better, and also provides carbs, fibre etc.
14/04/2014 8:33:06 PM

Sounds like another load of unsubstantiated fear mongering from the climate nutters and deceivers.
15/04/2014 12:39:29 PM

argis. Standard CC spin, protein is limited by nitrogen. Increase CO2 with out increasing nitrogen and you get more plant material with the same overall protein (or less protein/gram of plant material) However increase nitrogen fertilizer, in line with CO2 (standard greenhouse management) and you get more plant material, AND more protein.
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Can't you boys find another playground to occupy? Same old punters, same old tired barbs and
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He might well be a decent bloke Chick, however Jock is right on the money regarding Sterles