Climate change stunts nutritional needs

Buck Reed picking out avocados at Whole Foods in Tucson. A new study expects staple crops to lose some nutritional value as CO2 emissions continue to rise. Photo by: J.D. Molinary for Arizona Sonora News.

Because of climate change, you might be getting less in what you eat and not even realize.

According to a study published in August by the journal Nature Climate Change, rising carbon dioxide emissions in the atmosphere could cause a decrease in certain plant nutrients by mid-century.

Protein, iron and zinc in certain crops is expected to fall as more CO2 pours into the atmosphere.

Iron is a mineral that assists red blood cells in carrying oxygen through the body. According to the Centers for Disease Control (CDC), iron aids children’s capacity to learn. Zinc is important to the immune system, child development and the body’s ability to heal properly. It’s even essential to make DNA in cells. Protein is also necessary for childhood development, but it’s also found in much of the body. Bones, muscles, skin, hair, nails and internal organs consist of substantial amounts of protein.

This news goes hand-in-hand with a report released last week by the United Nations, which said climate change could be wreaking havoc on the planet and its inhabitants in little over a decade with worsening fires, floods and famine.

In the Nature Climate Change study, crops were grown under CO2 levels of 550 parts per millions, or ppm, and had less nutritional value than crops produced under present levels. These crops lost protein, iron and zinc contents by 3–17 percent under CO2 conditions of 550 ppm.

The most consistent climate models anticipate atmospheric CO2 will reach 550 ppm between 2050 and 2100. However, these models, used in this study, predict CO2 levels could rise to about 940 ppm by the end of the century.

Data from the National Oceanic & Atmospheric Administration (NOAA) shows that in January 1979 atmospheric CO2 was about 336 ppm, but by January 2016 it had increased to an average of just above 400 ppm.

Parts per million means for every million particles in the air, 400 of them are carbon dioxide particles. These levels fluctuate somewhat, but this number represents an average global concentration of CO2 in the atmosphere.

Previous studies examined the effect of carbon dioxide on crop nutrients, but these were done in greenhouses and growing chambers on a small scale, said Samuel Myers, director of the Planetary Health Alliance, principle research scientist at the Harvard School of Public Health and lead author of “Impact of anthropogenic CO2 emissions on global human nutrition.” The results, Myers said, weren’t large enough to generalize with scientific conclusions.

“We grew 41 cultivars of six food crops on seven locations on three continents over 10 years and got a much, much bigger sample size,” Myers said.

This study produced a large set of reliable data. It concluded that as atmospheric CO2 rises, crops will lose significant amounts of key nutrients if nothing is done to mitigate the problem.

Myers said they were surprised with these results.

“I mean we don’t really understand why it’s happening,” he said, “and it’s not something we necessarily would have anticipated.”

The majority of humans around the world acquire the bulk of their nutrients from plants. So, while a loss of nutrients may not be immediately felt by those in regions of the world where food is readily available, relatively inexpensive and diverse in choice, it could have a devastating effect in regions already at risk — poor nations and poor communities.

Worldwide, 1 in 3 people are malnourished. If there aren’t significant improvements, that number is expected to increase to about 2 in 3 people by 2030, according to the Committee on World Food Security.

As staple crops become less nutritious, more and more people will become susceptible to nutrient deficiencies, and this will expose populations to heightened risk of anemia and related diseases.

Myers said that populations in developed countries are more insulated from this problem because of generally richer diets with more food diversity.

However, he said, even though it wasn’t the focus of their study, he’s worried about possible increase in heart disease and stroke in developed countries because of the increase of carbohydrates in these crops.

Even with the robust diversity in food in places like the United States, there are still worries about nutrition deficiencies.

“Iron particularly for (premenopausal) women can be of concern because … they have a higher iron requirement than men do,” said Kelly Jackson, a registered dietitian nutritionist and assistant professor of practice in Nutritional Sciences at the University of Arizona. “So, we do see iron deficiency anemia … in women; that’s certainly not uncommon in women in the U.S.”

While rising CO2 is expected to negatively impact plant nutrition, it also affects plant growth in other ways.

Some research has shown that higher levels of CO2 could increase yields in some crops. A study done by NASA concluded that heightened CO2 allowed some crops to retain more water and increased photosynthesis, thus increasing yields, but this study did not evaluate nutritional value changes in the crops.

However, Gary Nabhan, a research scientist at the University of Arizona’s Southwest Center and the Kellogg Endowed Chair in Southwestern Borderlands Food and Water Security, said it’s more feasible that crop yields will decline as climate change becomes more pronounced.

“If you’re having heat stress and water stress you don’t achieve those yields under higher (CO2) conditions,” Nabhan said.

According to the NOAA, the increase of CO2 has been meteoric compared to the natural buildups of the past. The web page about atmospheric carbon dioxide on states, “The annual rate of increase in atmospheric carbon dioxide over the past 60 years is about 100 times faster than previous natural increases, such as those that occurred at the end of the last ice age 11,000-17,000 years ago.”

To put that into perspective, the last time atmospheric CO2 was above 400 ppm was millions of years ago, long before humans were around. And the rise to over 900 ppm could lead to drastic changes in the environment.

“There were palm trees growing in the arctic,” Myers said, “and sea level was about 100 meters higher than it is right now and there were crocodiles wandering around in Wyoming.”

The sharp rise in atmospheric CO2 is mostly due to anthropogenic emissions, which are emissions caused by human activities such as burning fossil fuels and even agriculture itself,  according to the United Nations’ Intergovernmental Panel on Climate Change (IPCC).

Agriculture actually plays a major role in anthropogenic greenhouse gas emissions. Data analyzed by IPCC shows agriculture, forestry and other land use account for about 24 percent of global greenhouse gas emissions. This is mostly due to emissions from livestock and soil and nutrient management, as well as deforestation.

Of all the greenhouse gases, CO2 is reportedly the largest contributor to the warming of the planet. According to the NOAA, carbon dioxide absorbs heat, similar to other greenhouse gases, but there is more CO2 present in the atmosphere and it will remain in the atmosphere longer than other gases. This warming is causing global temperatures to surge.

The State of the Climate report from last year noted that Earth’s surface temperature has warmed 1.3 – 1.6 Fahrenheit at a per century rate since 1901. However, since 1975 this warming has about doubled to 2.7 – 3.2 Fahrenheit at a per century rate. The rapid warming of the planet is shifting what crops can be grown where.

The USDA Plant Hardiness Zone map shows significant changes between the 1990 version of the map and the most recent update in 2012. The Plant Hardiness Zone map is produced by the USDA to help farmers and gardeners decide what can be best grown in their regions. The changes show the zones shifting north, meaning crops that used to thrive in certain regions are slowly being pushed north by this warming.

Another factor creating uncertainty in food systems, especially here in the Southwest, is rainfall patterns.

George Frisvold, a professor in Agricultural and Resource Economics at the University of Arizona, said there is a lot more of a consensus on the models predicting future temperature than on models predicting rainfall patterns.

In places like the Southwest, where water is already scarce and infrastructure is built around current farmlands and rainfall patterns, this could lead to serious problems. Where today’s irrigation infrastructure delivers water to specific areas, that system may not be as useful if lands suitable for farming shift severely.

“Basically the whole irrigation infrastructure system was built to move water to the most productive croplands,” Frisvold said. “So if temperatures change, the best places to grow crops may change. (And) if you don’t have that irrigation infrastructure that follows with it, then it might be harder to produce some of those crops.”

Myer’s study explains possible solutions to this problem. Breeding cultivars of certain crops, such as rice and legumes, may have the potential to retain more of their nutritional density, even with rising CO2. This process, called  biofortification, is “breeding crops that are just richer in particular nutrients,” Myers said, and could help produce nutrients at current or near-current levels.

Because some areas are over reliant on certain crops, efforts to diversify food systems in regions susceptible to malnutrition is another solution in some places, according to Myers.

Jackson said fortification programs — which add nutrients to foods, such as adding iodine to salt — could focus on vulnerable groups and help reduce the chance of deficiencies in parts of the world. Fortification allows people to meet their nutritional needs even with a minimal or restricted diet.

These methods may help at-risk people avoid malnutrition and its side effects, but won’t slow CO2 emissions.

“It would probably be more of a Band-aid on the issue, but we have seen fortification be beneficial in certain cases,” Jackson said.

Myers said facing climate change and focusing on policies to lower emissions should be the main approach to solving this problem.

“The most obvious thing we can do is reduce our carbon dioxide emissions, which we need to do aggressively anyway to address climate change and also ocean acidification,” Myers said.

J.D. Molinary is a reporter for Arizona Sonora News, a service from the School of Journalism with the University of Arizona. Contact J.D. at

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