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USDA-ARS’ Dr. Lewis Ziska has conducted extensive research on the impact of rising carbon dioxide levels on rice.

Rising carbon dioxide levels will impact crops negatively

Mankind has had to deal with episodes of food insecurity since the beginning of time and into the 20th Century.

Most people who have heard of Dr. Norman Borlaug remember him as a renowned scientist and humanitarian who probably saved millions of lives through his development of disease-resistant wheat varieties.

What’s lesser known is the story of the late scientist’s wife, Margaret Gibson Borlaug. She and her husband were college students in the Depression when the future Mrs. Borlaug dropped out to become a waitress “because she was tired of being hungry all the time.”

It’s impossible to know how that affected Dr. Borlaug’s work, but I thought about that story while listening to a presentation by Dr. Lewis Ziska, physiologist with USDA’s Agricultural Research Service, during a University of Arkansas System Division of Agriculture Food and Agribusiness Webinar. (

“If you don't know who this gentleman is, I would suggest about half of you watching this lecture are only able to do so because of him,” said Ziska, referring to a photograph of Borlaug taken while he worked as a researcher for the Rockefeller Foundation in Mexico.

Speaking on “Climate Change, Carbon Dioxide and Food Security, Challenges and Solutions,” Ziska said mankind has had to deal with episodes of food insecurity since the beginning of time and Into the 20th Century.

The last famine to impact large segments of the population occurred in China in the late 1950s and early 1960s. If you summed up the number of individuals who died from starvation in that event, the total would be about 60 million. (In contrast, about 55 million died during World War II.)

“It’s very difficult if you have never been hungry to know what that feels like,” said Ziska. “There have been times when hunger has been so prevalent that cannibalism has occurred. It’s not something we think about, but it is something that has been an endemic part of civilization since its inception.”

Carrying capacity

As populations were rising in the 1960s and 1970s, scientists began looking at what was called the “carrying capacity” — the number of individuals that can be fed from the earth’s resources. Many people became concerned about the possibility of the population explosion causing a pandemic.

The population has risen to more than 7.6 billion people, so those fears were somewhat unfounded. That’s because scientists like Norman Borlaug found ways to improve the production of wheat, rice and corn, the “Big Three” of the world’s food supply.

“There may be hundreds of thousands of different plant species, but 15 of those cereals supply the bulk of human food,” he said. “The Big Three provide more than 50 percent. When the pandemic was threatening, the obvious thing to do was to add more water and fertilizer to these cereals, which they did. The result was a reduction in yield.”

The plants were becoming so tall and the grain so heavy they fell over, and Borlaug began cross-breeding existing lines of wheat with semi-dwarf types that had a lower center of gravity and didn’t lodge with higher rates of water and fertilizer.

Borlaug’s discoveries helped provide a respite from population problems, “but it didn’t really solve them,” he said. “It put them on hiatus.”

For a while, the increase in world food production exceeded the increase in population. Through the 1970s and 1980s farmers grew more cereals than there were increases in people. In the 1990s and 2000s that began to change.

“We’re starting only to produce as many cereals as there are people,” he said. “Things are becoming tighter, so you cannot rely on the green revolution, per se, to continue to provide sufficient food for the future.”

Instead of increasing by 2 to 2.5 percent, world food production is growing by 1.1 percent. World population growth is also decreasing, fortunately, but production is now barely keeping pace with population growth.

Challenges to food security

“The challenges to food security are already severe,” Ziska said. “And then you have other problems such as climate change. How is that going to impact us?”

For those who doubt the validity of global warming, Ziska notes, consider studies examining the levels of carbon dioxide in the atmosphere. Locations such as Mauna Loa in Hawaii are showing a 30 percent increase in carbon dioxide.

“It’s monitoring at 10,000 feet, and it’s not contaminated by city buses running by the monitors,” he said. “Essentially, during my life time, the amount of carbon dioxide has gone up by almost 30 percent. If you go back in time, the carbon dioxide concentration stayed between 200 and 300 parts per million. Now it’s above 400 per million.”

Why is that? “If you take a source of carbon, which is a source of energy, and oxidize it or burn it, that produces heat and energy. About half of the carbon dioxide, a byproduct of the process, goes in the atmosphere. One-fourth gets reabsorbed by photosynthesis and one-fourth goes into the oceans where it dissolves and is reducing the pH.

“The bottom line is that by the end of the century we anticipate carbon dioxide to be between 600 and as high as 1,000 parts per million.”

Why does that matter? Two reasons, says Ziska. (1) Warmer temperatures due to increased carbon dioxide and water vapor in different concentrations on the earth’s surface, and (2) the effect of increased carbon dioxide on plant and animal life.

“The latter is one that doesn’t get talked about very much, and I think that’s unfortunate,” he said. “When you increase carbon dioxide levels in studies, you find that plants don’t respond the same, and plants like poison ivy, for example, respond more than plants like loblolly pine. From a competitive advantage, the poison ivy will win.”

More plant growth?

Some observers have said increased concentrations of carbon dioxide will simply mean more plant growth and thus, increased crop production. But, as with most things, it isn’t that simple.

An example is the effect of increased carbon dioxide in areas such as bee nutrition. Bees have an innate ability to find sugars — they send signals to other bees through dances they do when they find sources of sugar.

“This isn’t the case so much with protein sources,” says Ziska. “All their protein comes from pollen, and they don’t have the ability to distinguish one pollen source from another. But if protein is being impacted by the rise in carbon dioxide, wouldn’t that also affect bee nutrition?”

Researchers learned that the Smithsonian Natural History Museum in Washington had a collection of goldenrod plants that date back to the 1840s. Assessing the nitrogen levels in the plants going back in time, they were able to determine that as carbon dioxide increases protein levels will go down.

“Is that something that other insects might be seeing?” he asked. “Honestly, I don’t know. But we would be very foolish, I think, to ignore it. We need to find out more about it and other impacts of rising carbon dioxide levels.”

That will be difficult given what’s happening with research activities such as those at USDA’s National Institute of Food and Agriculture and the Agricultural Research Service. In terms of actual dollars, ARS has lost about 25 percent of its budget in recent years.

“I understand the need to spend defense money — you want to be safe,” he said. “We spend on average between $6 and $7 a day for every person in the U.S. We spend 2 cents a day per person on ag research.

“I would argue that investing in public research to sustain and improve agriculture will have benefits in terms of global security, as much as investing in the next weapons system. Not doing so could be asking for a return back to the 20th century famine as an endemic issue.”

TAGS: Wheat Corn
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