Scientists gauge risk of protein deficiency caused by carbon dioxide emissions

Human-caused carbon dioxide emissions lower the nutritional value of staple crops, increasing the risk for dietary deficiencies among the world’s most vulnerable people.

A just-published American study provides further evidence for the need to curb human-caused CO2 emissions.

According to new findings from Harvard T.H. Chan School of Public Health in Boston, if CO2 levels continue to rise as projected, the populations of 18 countries may lose more than 5% of their dietary protein by 2050 due to a decline in the nutritional value of rice, wheat, and other staple crops.

The researchers estimate that roughly an additional 150 million people may be placed at risk of protein deficiency because of elevated levels of CO2 in the atmosphere. This is the first study to quantify this risk.

“This study highlights the need for countries that are most at risk to actively monitor their populations’ nutritional sufficiency, and, more fundamentally, the need for countries to curb human-caused CO2 emissions,” said Samuel Myers, senior research scientist in the Department of Environmental Health.

The study will be published online today in Environmental Health Perspectives.

Globally, 76% of the population derives most of their daily protein from plants. To estimate their current and future risk of protein deficiency, the researchers combined data from experiments in which crops were exposed to high concentrations of CO2 with global dietary information from the United Nations and measures of income inequality and demographics.

They found that under elevated CO2 concentrations, the protein contents of rice, wheat, barley, and potatoes decreased by 7.6%, 7.8%, 14.1%, and 6.4%, respectively. The results suggested continuing challenges for Sub Saharan Africa, where millions already experience protein deficiency, and growing challenges for South Asian countries, including India, where rice and wheat supply a large portion of daily protein. The researchers found that India may lose 5.3% of protein from a standard diet, putting a predicted 53 million people at new risk of protein deficiency.

A companion paper co-authored by Myers, which will be published as an Early View article August 2, 2017 in GeoHealth, found that CO2-related reductions in iron content in staple food crops are likely to also exacerbate the already significant problem of iron deficiency worldwide. Those most at risk include 354 million children under 5 and 1.06 billion women of childbearing age–predominantly in South Asia and North Africa–who live in countries already experiencing high rates of anemia and who are expected to lose more than 3.8% of dietary iron as a result of this CO2 effect.

These two studies, taken alongside a 2015 study co-authored by Myers showing that elevated CO2 emissions are also likely to drive roughly 200 million people into zinc deficiency, quantify the significant nutritional toll expected to arise from human-caused CO2 emissions.

“Strategies to maintain adequate diets need to focus on the most vulnerable countries and populations, and thought must be given to reducing vulnerability to nutrient deficiencies through supporting more diverse and nutritious diets, enriching the nutritional content of staple crops, and breeding crops less sensitive to these CO2 effects. And, of course, we need to dramatically reduce global CO2 emissions as quickly as possible,” Myers said.

Funding for the study was provided by the Bill & Melinda Gates Foundation and by the Winslow Foundation.

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“Estimated Effects of Future Atmospheric CO2 Concentrations on Protein Intake and the Risk of Protein Deficiency by Country and Region,” Danielle E. Medek, Joel Schwartz, and Samuel S. Myers, Environmental Health Perspectives, online August 2, 2017, doi: 10.1289/EHP41

“Potential rise in iron deficiency due to future anthropogenic carbon dioxide emissions,” M. R. Smith, C. D. Golden, and S. S. Myers, GeoHealth, Early View article, August 2, 2017, doi: 10.1002/2016GH000018

 

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Wounded plants send out alarms to warn their neighbors

Uh, oh. How sensitive will you be to the feelings of the grass when you next mow the lawn – and how will vegans respond to the news?

University of Delaware studies of Arabidopsis thaliana, also known as mustard weed, have found that when a leaf was nicked, the injured plant sent out an emergency alert to neighboring plants which began beefing up their defenses.

A wounded plant will warn its neighbors of danger, says Harsh Bais, an associate professor of plant and soil sciences in UD’s College of Agriculture and Natural Resources.

“It doesn’t shout or text, but it gets the message across. The communication signals are in the form of airborne chemicals released mainly from the leaves.”

Connor Sweeney, a high school student, delved into work in Bais’s lab at the Delaware Biotechnology Institute after school, on weekends and during summer breaks, culturing an estimated thousand Arabidopsis plants for experiments. Seeds were placed in Petri plates and test tubes containing agar, a gelatinous growing medium.

Each batch of seeds would germinate after about six days, transforming into delicate-stemmed three-inch plants with bright-green leaves.

One day in the lab, Sweeney put two plants a few centimeters apart on the same Petri plate and made two small cuts on the leaf of one to simulate an insect’s attack.

What happened next, as Sweeney says, was “an unexpected surprise.”

The next day, the roots on the uninjured neighbour plant had grown noticeably longer and more robust–with more lateral roots poking out from the primary root.

“It was crazy–I didn’t believe it at first,” Bais says. “I would have expected the injured plant to put more resources into growing roots. But we didn’t see that.”

Bais asked Sweeney to repeat the experiment multiple times, partitioning the plants to rule out any communication between the root systems. In previous research, Bais had shown how soil bacteria living among the roots can signal leaf pores, called stomata, to close up to keep invasive pathogens out.

“The reason why the uninjured plant is putting out more roots is to forage and acquire more nutrients to strengthen its defenses,” Bais says. “So we began looking for compounds that trigger root growth.”

Sweeney measured auxin, a key plant growth hormone, and found more of this gene expressed in neighboring plants when an injured plant was around. He also confirmed that neighbour plants of injured plants express a gene that corresponds to a malate transporter (ALMT-1). Malate attracts beneficial soil microbes, including Bacillus subtilis, which Bais and his colleagues discovered several years ago.

Apparently, uninjured plants that are in close proximity to injured ones and that have increased malate transporter associate more with these microbes. These beneficials bond with the roots of the uninjured plants to boost their defenses.

“So the injured plant is sending signals through the air. It’s not releasing these chemicals to help itself, but to alert its plant neighbors,” Bais said.

What are these mysterious concoctions, known scientifically as volatile organic compounds, and how long do they persist in the atmosphere or in soil for that matter–is it like a spritz of perfume or the lingering aroma of fresh-cooked popcorn?

“We don’t know yet,” says Bais, who has already started this next leg of the research. “But if you go through a field of grass after it’s been mowed or a crop field after harvesting, you’ll smell these compounds.”

Sweeney first visited the Delaware Biotechnology Institute as an eighth grader, for a boot camp on basic laboratory procedures, which sparked his interest in research. He has since won the 2016 Delaware BioGENEius Challenge, was a 2016 international BioGENEius Challenge finalist and was named a semifinalist in the 2017 Regeneron Science Talent Search. Later this year he will head off to MIT, double-majoring in economics and biological engineering.

He is interested in looking at the agricultural side of science, saying it may not sound sexy, but everybody needs to eat. So if you can use cutting-edge technologies in genomics that feed more people while lessening the environmental footprint, “that’s where I want to be”.