Global Warming: Carbon Dioxide and Nutrient Collapse

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David Wallace-Wells is determined to relieve us of any delusions about the changes being wrought by human-created climate change.  He collects what are the known-knowns and the known unknowns and scares us with suggested unknown-unknowns in his book The Uninhabitable Earth: Life After Warming.  Complacency is no longer an option.  These are his opening words.

Carbon dioxide is a plant nutrient.  Just as our bodies respond to a change in nutrient levels so do those of plants.  What higher carbon dioxide levels do, at least to some critical food sources, is increase the levels of carbohydrates produced at the expense of proteins, minerals, and vitamins.  Not only will our warming earth make the production of crops more difficult, the crops produced will be of less nutritious (“more like junk food”) for reasons we hadn’t anticipated.  Helena Bottemiller Evich provides a concise summary of how scientists, ever so slowly, became aware of this unknown-unknown in The great nutrient collapse. 

Evich tells the story of Irakli Loladze, a mathematician with an abiding interest in biology.  Loladze was introduced to a biological paradox as a graduate student in 1998.

“Zooplankton are microscopic animals that float in the world’s oceans and lakes, and for food they rely on algae, which are essentially tiny plants. Scientists found that they could make algae grow faster by shining more light onto them—increasing the food supply for the zooplankton, which should have flourished. But it didn’t work out that way. When the researchers shined more light on the algae, the algae grew faster, and the tiny animals had lots and lots to eat—but at a certain point they started struggling to survive. This was a paradox. More food should lead to more growth. How could more algae be a problem?”

“The biologists had an idea of what was going on: The increased light was making the algae grow faster, but they ended up containing fewer of the nutrients the zooplankton needed to thrive. By speeding up their growth, the researchers had essentially turned the algae into junk food. The zooplankton had plenty to eat, but their food was less nutritious, and so they were starving.”

Loladze knew that accelerated growth of algae could also be caused by increasing the level of carbon dioxide available.  Would the same effect be observed in that case?  If so, a similar effect would be occurring planet wide as levels of carbon dioxide continued to rise.  He discovered that there was very little data available to address this hypothesis, but what there was suggested that it was true.  However, the relevant scientific community had not even raised the concern.  It would fall on him, as a sideline to his main work, to push the issue.

What was known was that the nutritional quality of many of our crops had declined over the time between 1950 and 1999.  In 2004 a study of this data was published detailing this decline: Changes in USDA food composition data for 43 garden crops, 1950 to 1999.  It included this summary.

“As a group, the 43 foods show apparent, statistically reliable declines (R

These investigators assumed that these degradations could be explained by the agricultural market shifting to higher yield varieties of plants that produced fewer nutrients.  This conclusion could not rule out a role for carbon dioxide in the process, and Loladze kept pushing the issue, finally exciting the interest of other researchers.  One of the approaches was to examine the evolution of a wild plant that was unaffected by man-made decisions.

“Goldenrod, a wildflower many consider a weed, is extremely important to bees. It flowers late in the season, and its pollen provides an important source of protein for bees as they head into the harshness of winter. Since goldenrod is wild and humans haven’t bred it into new strains, it hasn’t changed over time as much as, say, corn or wheat. And the Smithsonian Institution also happens to have hundreds of samples of goldenrod, dating back to 1842, in its massive historical archive…”

“They found that the protein content of goldenrod pollen has declined by a third since the industrial revolution—and the change closely tracks with the rise in CO2.”

Carbon dioxide as a cause of nutrient collapse can now be studied more directly after researchers developed what is called the FACE technique.

“Researchers use a technique that essentially turns an entire field into a lab. The current gold standard for this type of research is called a FACE experiment (for “free-air carbon dioxide enrichment”), in which researchers create large open-air structures that blow CO2 onto the plants in a given area. Small sensors keep track of the CO2 levels. When too much CO2 escapes the perimeter, the contraption puffs more into the air to keep the levels stable. Scientists can then compare those plants directly to others growing in normal air nearby.”

If nutrient collapse was occurring because of rising CO2 levels, the most affected would be people possessing limited food security where malnutrition is a constant threat.  Many such people depend on rice as the main food source.  FACE studies were performed on rice varieties to determine what effect a CO2 level consistent with what might be reached in the next few decades would have on nutrition: Carbon dioxide (CO2) levels this century will alter the protein, micronutrients, and vitamin content of rice grains with potential health consequences for the poorest rice-dependent countries.

“As of 2013, approximately 600 million individuals, primarily in Southeast Asia [the countries of Bangladesh, Cambodia, Indonesia, Lao People’s Democratic Republic (PDR), Madagascar, Myanmar, and Vietnam], consume ≥50% of their per capita dietary energy and/or protein directly from rice…”

“When grown under field conditions at these anticipated [CO2] a significant reduction (an average of −10.3%) in protein relative to current [CO2] was observed for all rice cultivars…Similarly, significant reductions in iron (Fe) and zinc (Zn) were also observed (−8.0 and −5.1%, respectively) among all rice cultivars tested…”

These degradations will be on top of the loss of nutrients already caused at our current CO2 levels.  As usual, the wealthy produce climate change, and the poor will be the first to suffer the consequences.

Evich summarizes the results of studies beginning to emerge as these issues attain a higher priority and more data becomes available.

“Earlier this summer [2017], a group of researchers published the first studies attempting to estimate what these shifts could mean for the global population. Plants are a crucial source of protein for people in the developing world, and by 2050, they estimate, 150 million people could be put at risk of protein deficiency, particularly in countries like India and Bangladesh. Researchers found a loss of zinc, which is particularly essential for maternal and infant health, could put 138 million people at risk. They also estimated that more than 1 billion mothers and 354 million children live in countries where dietary iron is projected to drop significantly, which could exacerbate the already widespread public health problem of anemia.”

These conclusions result from an effect once deemed too small to be of interest.  Is this the extent of the effect, or are we considering the tip of an iceberg?  Remember the tale of the zooplankton; bad things can happen when one plays with nutrition levels.  And how many other unexamined effects and feedback loops will be excited as the climate warms and changes?

Let us recall Wallace-Wells’ initial warning.