Climate change’s impacts are already being felt around the world – from more intense wildfires, hurricanes, floods, hail and wind, and droughts. The National Oceanographic and Atmospheric Administration reported there were 16 disaster events that cost more than $1 billion in the United States, with a total cost of $306.2 billion, making 2017 the most costly year for disasters on record.  

In the agriculture sector, no region of the country was spared from extreme events, ranging from frosts affecting the southern states, numerous hail and wind events in the Northeast, Midwest, Great Plains and western wildfires.  From oranges to wine to cattle – the costs of these disasters to producers have been enormous.

But what’s less discussed is how the long-term impacts of rising levels of greenhouse gases and increased temperatures will impact nutrition in crops.  There is a growing body of research that should sound alarm bells for policymakers, farmers, and eaters.  It paints a grim picture, one where climate change will not only cause greater uncertainty for producers but severely impact the nutrition of crops in unexpected ways. That’s bad news for a population that’s expected to hit 9.8 billion by 2050.

Atmospheric levels of carbon dioxide (CO2) are at higher levels than at any point in human history, recorded at over 400 ppm in 2016.  Under a ‘business as usual’ scenario, the level of CO2 in the atmosphere is expected to surpass 550 ppm by mid-century.  A growing body of research has demonstrated that rising levels of CO2 reduce key nutrients for human health, including zinc, iron and protein in a wide variety of cereal and legume crops. Deficiency in these nutrients can cause a host of health and developmental issues, including stunted growth and lower IQ.

A large, multi-site analysis of the effects of rising CO2 on staple crops was conducted in 2014.  Using seven research sites worldwide, researchers tested the effects of rising CO2 on zinc, iron, and protein levels in rice, wheat, maize, soybeans, field peas, and sorghum.  The researchers found that increases in CO2 were associated with a decrease of anywhere between 3 and 17 percent in zinc in the tested crops. The notable exception was maize and sorghum, whose nutrients are less affected by rising levels of CO2.   In most of the poorest countries of the world, these six staple crops make up the majority of diets.  

Using these 2014 findings, researchers at Harvard projected the effects of diminishing zinc and iron in staple crops on human nutrition in both high income countries as well as low income countries.  Published in Nature Climate Change on Monday, August 27, the researchers found that projected increases in CO2 levels could cause 175 million people (1.9 percent) to become deficient in zinc, and an additional 122 million people (1.3 percent) to become deficient in protein. For iron, it is expected that 1.4 billion women of child-bearing age and young children (representing 57 percent of these groups) will be at high risk for iron deficiency as a result of increased atmospheric CO2.

The risk for nutritional deficiency is highest in regions -- [primarily India, South Asia, Sub-Saharan Africa, North Africa, the Middle East, and Southeast Asia] -- where the diet is comprised mainly of these staple crops. Poor regions that rely heavily on maize, millet and sorghum, such as regions of South and Central America, Central and Western Africa, will be less affected by expected nutrient deficiencies.  

While global diets have been shifting, largely due to growing income levels in certain regions, the authors note that malnutrition has been particularly persistent or worsening in some regions, such as India and Sub-Saharan Africa.  

The mechanism that causes certain crops to be less nutritious with elevated levels of atmospheric CO2 are still not understood.  The researchers point out that research for breeding CO2 tolerant crop strains, biofortification and supplementation can help address the problem and will be important to combating deficiencies in vulnerable regions.


For more information see: